IMPORTANT UPDATE: I did some more efficiency tests in the spring using the outgoing air and it seems that my HRV is actually around 60% efficient (which is still pretty good), not 85%. I wanted to make a video about this but I ended up having to put it on the back burner because I went through the process of selling my house. When making this video, I made the mistake of testing efficiency using the incoming fresh air. I think that heat generated by the fans skewed the results. Here’s a formula I used for a corrected efficiency test using the outgoing air instead: × = (T_room - T_outgoingAir) / (T_room - _outdoors) An example of one of my test runs (Fahrenheit): 60.5%=(70-44)/(70-27) So yeah, it is less efficient than I initially thought. That being said, it still worked quite well. I want to address some questions I’ve seen: I do think that almost all of the air is flowing through the core. The filters were quite dirty when I dismantled this HRV, and in order for them to have gotten like that, I do believe air must have passed through them/the core. I don’t think there is very much leakage in the chambers. I sealed them very thoroughly with hot glue and weather stripping, and did leakage tests. I acknowledge that there could be some leakage, but not that I could find. Next point, to the couple people who quoted Egon Spengler at me: no, I don’t believe I’m “crossing the streams” (intake/exhaust air streams mixing). After this video came out, I installed elbow duct attachments to the indoor supply and outdoor exhaust to the direct the air streams away from the intakes 🙂 Potential reasons I didn’t run into condensation issues: lower HRV efficiency combined with the low dew points in my house (from ventilation with dry, cold air + no humidification). I only used this HRV during the late fall, winter, and early spring when the air is very dry. I’m too worried about mold growth when it gets humid. Though less efficient than I initially thought, it still worked great! If you're curious about how this DIY HRV performed long-term, check out this video of mine: th-cam.com/video/LiptsaKmq80/w-d-xo.htmlsi=bsEbBQ9pKLKozY4u
60% is good for crossflow HE in these materials. And filters get dirty much faster than we think ;) It's not uncommon to send a reserve filter set with a new AHU.
How would you deal with moisture condensing inside the core? If you turned the box on its side, moisure could run out of the core channels. EDIT: I see you do address this, kinda. However, it’s still true that this is a no-go for any climate that has to deal with condensation.
@@stcredzero great question. I’m also concerned about ventilating using an HRV (even a factory made unit) during humid months. ERVs are better for ventilating humid air. I’m currently making a video explaining how to install an ERV one’s self (even for those who don’t live in a ducted home!). That might prove useful to you when it comes out.
I really love the idea. Things like this have crossed my mind quite some times in the last couple of years. But please help me as I'm trying to wrap my head around the calculations. Wouldn't it be much more accurate if you measured the temperaturr of the in the four ducts for your calculations? And perhaps als the airflow? (Especially flowing from inside out) I'm thinking of: DeltaT_,OutsideIn = T_Inlet_OutsideIn - T_Outlet_OutsideIn DeltaT_,InsideOut = T_Inlet_InsideOut = T_Outlet_InsideOut = Delta_T = DeltaT_,InsideOut - DeltaT_,OutsideIn Gain = Delta_T * Air_HeatCapacity * Airflow_OutsideIn (I'm probably missing some details here 😉) And then there's this thing about air particles. Do you have any measurements from before then installation of the installation and how do they compare to the new figures? I'm having some Ikea air quality sensors and about 99% of time they all show no polution or just a little bit.
For better efficiency (if you even need it) you need a bigger and more elongated core. To all the naysayers, this guy built a system extremely similar to a professionally manufactured one. Many manufacturers also use plastic cores, and even plastic fiber cloth cores (with moisture wicking effect)
As an HVAC guy i can say your design although unconventional and bulky is just fine, your fans you use for circulation would benefit from the coandâ effect to increase air flow. Also those efficiency rating the big companies use are totally skewed so your system is probably working better than off the shelf systems thanks to that massive core you built
@@Geoff9001 I’ve only used mine during colder, drier seasons. I definitely would avoid using an HRV in your climate, especially during warmer months. An ERV (combined with a dehumidifier) would be a safer ventilation option for your region.
@@HealthyHomeGuide have you seen any decent homemade ERVs online? This is the first homemade hrv I've seen online and it looks great, although a little big
@macthemec can you elaborate on how one would use box fan to achieve a Coanda effect? Where is the effect happening? Is the idea to get the air flow from the fan to follow to the walls, or floor, and thus travel further than it would had it not? Is it perhaps fashioning a shroud or cowl to affix to the box fan, one which would create a Coanda effect? I really can’t imagine how this would work?
Dude you are brilliant, it never would have occurred to me to use the natural tunnels inside of coroplast board! That's legit mate. You've managed to achieve very near the efficiency of commercial units that cost thousands of dollars. This is such a great idea, you've given me all kinds of ideas for my own apartment.
as an actual HVAC Technician i think that is pretty neat. the physics is the right way around and from the numbers i can tell it works. the only way to improve would be a more conductive material to get the usual 90-98% efficiency but apparently its conductive enough.
@@JordieG8 i have no explanation for this. i dont remember why i said 90-98 i guess i meant max. just goes to show take everything with a grain of salt or something
New subscriber here!! This is the best design I have seen on the Tubes my friend!!!!!I am starting a gourmet and medicinal mushroom growing business in Delaware with my best friend/business partner and I have been researching ways to reclaim heat and use alternative methods of heating and cooling. I developed a device that collects and. inverts electrostatic electricity from the atmosphere and converts it into usable dynamic electricity. I need one part to finish the design but it works . I am designing ot so that it can work with off the shelf transformers and such . The last part I need it a triggered spark gap and to buy one is expensive. I bought a lathe but there is a learning curve on it....
Honestly making this from plastic is pretty dope in terms of cost. However you could make it MUCH smaller. I have a lot of those plastic sheets lying around for different purposes. Also you're using layers of plastic in 2 directions, which might lower the performance because it has not amazing heat conductivity. Just one set with gaps would be perfect. This is high static pressure application, so in this case, it would be best to get 2 centrifugal (radial) fans, not axial ones. It would also make sense to make the heat exchanger much longer, and thinner, to get full heat extraction. Great video though. Nice design.
@@HealthyHomeGuide I will probably make one for balcony, where it has to fit into square drain channel. With centrifugal fans you could theoritically add cyclone filtering to get rid of heavier stuff.
Definitely going to do this now, didn’t know that the diy actually worked so well and with testing to back it up! Thats all I needed! This will definitely help with my parents cold basement and spare second story room if I hooked it up to the previous improperly installed furnace air return. Thanks
Man I'm absolutely blown away. You did an amazing job. Well done on your research and execution. I have a whole new view on heat recovery systems now. In HVAC, these items are extremely expensive. I don't often get to specify these due to clients not having the budget for it. After seeing your results though, I think I can come up with something affordable and efficient on a commercial scale. I feel efficiency can be improved with a quick material study. Thanks for your video. I'm very impressed and appreciative for you helping me see how simple this system can really be.
This is unbelievably cool, even with the potentially lower efficiency number. I just bought a house and have a 1990s furnace that I want to keep running as long as possible. Currently in the process of cleaning and sealing the duct system and trying to DIY as much as possible. The furnace uses a long insulated flex duct to allow unfiltered cold Canadian air into the furnace room for combustion. I feel it’s very inefficient (and dirty) to have a clear line of outdoor air entering my home. Your system seems like the perfect DIY method to address this problem. Just found your channel and looking forward to seeing what other ideas you have.
I applaud the initiative. This is certainly the future & I love it. Some things to consider... 1) CO2 "cannot" be affected by the unit, as the CO2 level is whatever you are drawing out of the air coming in from outside (usually about 400 unless something weird is going on. Plants like it when we "talk to them" because we are breathing CO2 at them. CO2 builds up in a house because of "us". 2) I would be greatly concerned about the VOCs coming off all that plastic, adhesive and other chemicals from 3-D printing. It's gonna off-gas, a LOT! Funny your comment, "insane!", right after, cause..., yeh. 3) There is an actual Metric they use, CFM/watt, to quantify how much actual work is being done. It's used to measure performance. Measuring the Factual temps of the airstreams is of great interest also. 4) Tape the edges of the filters or there is bypass (sneaking around the filtration, around corners). HEPA has no "bypass". 5) Measuring the air pressures will tell you the static resistance various parts of the system are causing - core, filters, vents. Cool experiment, but don't mislead people with hyperbole instead of data. Maintain integrity. Do no harm. Cheers.
There is more things to consider: 1) The heat exchanger is not going to be very efficient, because it does not have perfect counter-flow. In the 2 corners at the border between inside and outside, there will be heat exchange between the hottest part of your system and the coldest part. A simple system of two (long enough) concentric pipes is going to perform better. 2) In winter, condensation in the outstream will boost efficiency even further. In summer, condensation will occur on the instream, making this system unusable. 3) Indoors, it is much better to have air intake and outlet in opposite parts of the house, so the clean air will spread without the need for additional fans. Outdoors, outlet and intake can be closer together, and should probably be pointing in the same direction in order not to get drafts when it's windy.
Bro, you would put a little greenhouse lean-to against a southern wall of the house outside the window to actually heat your house on sunny winter days. Also, you could just skip the return fan and suck air in and make your house “positive pressure so that you leak a little air outside rather than allowing dirty air from outside to find its way into the house
If your HRV actually is 85% efficient you should get a lot of condensation when outdoor temperature is below freezing. You can figure out the dew point of your indoor air, and unless that is as low or lower than the expected temperature of the exhaust air there should be condensation. The "fresh air" you get is definitely a mix of fresh air and indoor air that leaked into the fresh air stream, possibly not in the core, but definitely in the giga-supersized chambers outside the core. Also you need to make sure the flows doesn't mix outside to get an measurement of the actual efficiency. If you measure the temperature that leaves the house, on the outside, instead of the mixed airflow, and compare that to indoor and outdoor temperatures you can find out the actual efficiency. The actual efficiency is definitely not anywhere near 85%. Aluminium conducts heat around a thousand times better than most plastics, and you can make aluminium much thinner, which also improves heat transfer compared to plastics. You even have two layers of plastic, and a layer of adhesive, and possibly areas with air too. And no way those fans can force hundreds of CFM through that core, a powerful leaf blower might be able to do that.
Thanks very much for your comment! So, I did some more efficiency tests in the spring using the outgoing air and it seems that my HRV is actually around 60% efficient, not 85%. I wanted to make a video about this but I ended up having to put it on the back burner because I dismantled this HRV when the warmer weather came and went through the process of selling my house. When making this video, I made the mistake of testing efficiency using the incoming fresh air. I think that heat generated by the fans skewed the results. Here's a formula I used for a corrected efficiency test using the outgoing air instead: × = (T_room - T_outgoing Air) / (T_room - _outdoors) An example of one of my test runs (Fahrenheit): 60.5%=(70-44)/(70-27) So yeah, it is less efficient than I initially thought. I want to address some other points: I do think that almost all of the air is flowing through the core. The filters were quite dirty when I dismantled this HRV, and in order for them to have gotten like that, I do believe air must have passed through them/the core. I don’t think there is very much leakage in the chambers. I sealed them very thoroughly with hot glue and weather stripping, and conducted leakage tests. I acknowledge that there could be some leakage, but not that I could find. I also don’t believe the intake/exhaust air streams are mixing very much. I installed elbow duct attachments to the indoor supply and outdoor exhaust to the direct the air streams away from the intakes. Lastly, dew point in my house is quite low in the winter. I don’t use humidifiers and this HRV brought in plenty of fresh, dry air. Again, thanks for your insightful comment.
An aluminium heat exchanger can be 'too efficient', you still need the effective insulation factor between the two sides (internal and external), and clarity of where any condensation should (and should not) occur.
@@hhkk6155 could still probably get good results with a water loop design. Would also allow you to separate where the intake and exhaust is going. Like one widow has an intake with an aluminum heat exchanger and the other window has an exhaust with a heat exchanger. No mixing of air and probably make it more compact. Hell you could have the exhaust on the other end of the house if you wanted. Could also eliminate the exhaust filter he has and opt for a real heat exchanger cleaner when needed since it isn't plastic.
This is exactly what I was looking for!!!! I have a Resin printer that I want to exhaust out of the room, but I don’t want to lose all the heat or cool air in the winter/summer. I hope this works for me! I don’t need to change much air, just a little bit, so I bet a 4” fan set to low would be enough for my application. Great job!
Great design bro! This should work damn well for your money! As an engineer, I am pleased to hear competent technical reasoning accompanied by such a simple but ingenious design.Bravo. Physics does not work on the loud brand and price of equipment, but on the principle. You inspired me not only to make a similar device for myself, but also to think about the serial creation of cheaper systems.Where I live, such systems are not financially available at all. Everyone deserves to breathe clean air.
Amen to that, and well said! Everyone does deserve to breathe clean air. Even people who aren’t rich. Even people who don’t live in homes with duct systems, people who rent, or people in areas where HRVs/ERVs aren’t accessible.
Wow! Your did great! You did a great job! And so efficient too! I live in a very small home in CT, a 200 yr old home, I renovated 20 yrs ago. Our home is 24x22, with basement, 1st flr, 2nd flr, and walk up attic. It's a post and beam kinda house. I installed ductwork, and Air handlers, one in the attic to service the 2nd flr, and one in basement to service the 1st flr. I have a boiler for heat, so it is a hydronic system. Each AHU has a hot water coil, that way I can also temper the discharge temp. So I think about 5 yrs ago, I added a Fan tech ERV to my 2nd flr setup. I added external filter boxes, with I think Merv 12 filters it came with, cause you need to keep that core clean as well as the air we are gonna be breathing. This was the lowest price unit at the time, and the enthalpy core is same product you used, but not as nice as yours, mine is not very efficient, so on really cold days, I don't use it. But a year later I bought a HRV for the basement I spent a little more and got one a bit more efficient. [I'm not rolling in $] I have seen some really high efficient EVR's but big $. I'm fortunate I inject the "make up" air into my air handling system. I also have UV-C lights in the AHU's. I have my 2nd floor ERV set up so when I run it, a relay turns on the FAN mode on my t-stat, so the AHU is running to distribute the air when the ERV runs. I have a Timer so 2nd floor runs at night [bedrooms all on 2nd flr] but also another timer called an Air cycler. This means it will run say from 6pm to 8am, but the air cycler runs the system 15 mins every hour. Then if someone hits the Exh fan switch for the bathroom, it turns on. [The stale exhaust air, get sucked out through the bathroom registers]. Anyway the results are great! I eventually will improve the ERV with a more efficient one in the future. The indoor air can be so bad, plus I'm try to learn about "static" pressure in the house. So when I turn on the range hood on highest setting 600cfm, where the make up air? or air coming in? Do we pull a negative pressure bringing in more bad stuff through the chimney?? Or cracks around the doors?? So an intentional conditioned make up air system is so important, especially weather when you cannot open windows. So thank you for sharing your project! So cool! [sorry to be so long winded here, but I get excited about this stuff! ] God bless! AL from CT
Thanks for your comment, Al! And thank you for sharing your HVAC experience. It sounds like you’ve had quite the ventilation journey. I’m actually thinking about make-up air a lot right now. And absolutely, if you don’t have a dedicated make-up air system, it’s very likely that the range hood (especially at the highest setting) is pulling air from hazardous places, or at the very least potentially causing moisture to build up in the cracks that the air gets sucked through. Unfortunately, my kitchen actually doesn’t have an exhaust system at all! I’m now planning on putting one in. My next video is going to be about this! Tune in if you’re interested. It should be out within the next few days.
You probably want to insulate the intake and exhaust pipes on the outside end of the HRV - those have cold (in winter)/hot (in summer) air that is going to lead to undesirable heat transfer to your indoor air.
This is great! I wake up every morning and my bedroom smells like crap.. Sinuses and nose at winter are always kinda gunked up ... Every time i get ill in the winter months is always the same symptoms, sinuses , nose and throat full of awful fluids that i have to spit out.....I think all the bad fluids wanting to go out from our lungs and throat is way of our body to clear and flush all that crap out.. Im 100% sure that air quality plays a massive role in that respiratory system. I dont mind opening window for a fresh air multiple times a day but at winter its kind of waste energy and also when it gets cold outside air is crap to! Cause here in Serbia a good bunch of houses still uses wood and coal to heat their homes... here the market is so terrbile that small home HRV's are basicly non existant and the big comercial stuff is to expensive.. Your build rly goot me thinking, looks simple to make and i could put it on my attic and duct it down in the house like a cealing vent. Curious to see whats next .. Would like to see how you tested efficiency , what was the indoor temp and intake temp of the fresh air and stuff like that. Greets from Serbia.
Thank you so much for your comment! My heart goes out to you. I too have woken up many mornings with terrible sinus and throat problems, and even other health problems, especially since I bought the house I'm currently living in. There is something toxic in our homes that I think we don't yet fully understand. So many people are posting online about experiencing these symptoms. At 6:44 in the video, I shared one of the efficiency test results. Here's another result from a different day: outside temp: 40.0F, Inside room temp: 68.4F, fresh air intake temp: 64.2F = 85% efficiency. By the way, people burn wood and oil here too, and the byproducts are really unpleasant to breathe. Not coal in the state I live in, fortunately. I hope you're able to solve your air quality issues! Reach out any time!
To improve upon your design ; if you suck the air close to the floor in your basement you'll also get Radon out of your home. Intake/exhaust on each side should be seperated by about 6feet. You could install a ceiling fan instead of the box fan that on the chair. Great work!
Thanks That's a really good design. I've been thinking about how to build something like this for our home. I'd not considering using coroplast, but it's almost made for the job !
Absolutely! Coroplast is an amazing material - polypropylene is the safest plastic, I feel. No BPA, no VOCs. I think that my HRV core is pretty laborious to build though. I’m in the process of trying to find a cheap source for replacement HRV cores, so we DIYers can just build a simple HRV housing for a pre-made core. Stay tuned!
Love it, considering buiilding one of these for my home too! You could have used half the correx by using double sided foam tape to create the core, with one channel being formed by taping two sheets together. (using tape with a thickness similar to the height of the plastic sheets) this has the advantage of also reducing the thickness of plastic seperating the air channels, so heat transfer should be more efficient. (as it would be one layer of plastic rather than two layers plus glue) Also a dual core design could improve efficeny by doubling the surface area for heat transfer.
@@Mavrik9000 Mainly just because it reduces the amount of material needed for the core, so in theory you could create a dual core confgiuration with the same material plus tape!
I disagree. Dust filters are weak. Oddly, they don’t filter out 100% of large particles like dust. According to the EPA, dust filters remove less than 20% of large particles (3-10 microns). A better filter will protect the core more effectively, for longer. Also, I wanted to use the same filter on the intake and exhaust so the pressures were balanced.
Mitsubishi sell these. They are called lossnay units. Reasonable instantaneous efficiency results, for more reliable figures use loggers and gather more data points at changing operating conditions.
Condensation within the unit will be a problem in most climates and when heating or cooling the incoming air. Over time the heat transfer plates will grow a biomass that can (in extreme cases) include dear old Legionella - the bane of commercial air con units. So a unit will need a means to drain condensate to a waste, and a way to periodically (say annually) disinfect / clean the core.
A low tech "defrost mode" method is to just redirect the two outdoor ports together so the core warms up to room temperature eventually. By measuring the output temperature and only going into defrost mode when the output goes below freezing can make it automatic.
For a simpler low tech defrost, you could just put it on a timer. If the unit is in the house, you could turn it off for a few hours and it would naturally warm up and defrost. That is even more low tech.
This is amazing. I now think my son should have this in the little room he sleeps in with the door closed all night. He'd be freezing with the window always open, but he has allergies and could use the filter. Plus I can imagine that CO2 levels rise in a tightly-sealed, unventilated small room with someone breathing all night. Hmm. You have me really thinking. I need to get your recommendations for the right instruments to measure air quality. Oh, and you really are sounding less allergic. Nice!
Thank you so much! You’re spot on with your thinking. Sleeping in a tightly sealed, small room with no ventilation can cause CO2 to rise to unhealthy levels. I slept in a room like that for a while and woke up oddly groggy every day. Yes, opening a window is a bad solution due to cold of course, but mainly because small particles like car exhaust and byproducts from peoples’ heating systems can drift in in unhealthy quantities. Not to mention allergenic particles, which tend to be larger and less systemically harmful. If you’re interested in good instruments to measure air quality, check the bottom of the description of this video for the ones I used :) Thanks again!
A known problem with the above coroplast heat exchanger design is it can only transfer heat to the incoming air theoretically maximally by 50% because of Laws of Thermodynamics,. A consequence is room gets chilly, if indeed not quite as cold as as a naked open window would make it. There are also designs which use a pipe within a pipe, and a different mechanism at the window to exchange heat, I believe by merely mixing and not separating in and out air streams. It can be piped further into the building to the isolated spaces needing air. When it gets there its room temperature warm. There are small round through wall units for sale, which by principle of operation, when placed across the house or large room from each other will conspire to coordinate taking turns breathing out while other breathes in @ 15 minute intervals (configurable), reducing cold island effect. Don't want little Johnny to miss skool becuz of the sniffles.
Nice build. Anyway next time consider brushless centrifugal fans and also damper to allow the unit work in "circulation mode", in mine, is also built-in cheap AC unit, so mu unit can also cool and heat...
Thanks! I’ve tried to find centrifugal fans but I’m not able to find one that is reasonably priced, well-made, and also delivers a good amount of airflow while being speed adjustable (for quiet operation if needed). Let me know if you find one. The AC infinity fans I use are actually mixed flow fans, so they’re basically a combination of axial and centrifugal, which I find to be great for a DIY application like this.
Dude. You’re an awesome enthusiastic presenter of your creations. I’m thinking of something like this for my large garage. Maybe not quite this big tho
I appreciate that you like my presentation style! If I could do this HRV project again, I’d build it smaller. Maybe with 2” thick filters instead of 4” thick. And with more powerful fans.
@@ww-pw6di I appreciate that question. I haven’t used this HRV since the spring because I’m too afraid of mold growth to run it during more warm/humid seasons. During the warmer months this past year, I used my DIY fresh air intake for ventilation, but there were limitations to how much I could use it during warmer, more humid stretches. I’m now using an ERV for year-round ventilation (+ a whole house dehumidifier in the warmer months). I’m actually working on an ERV installation video (for those of us who don’t have ducted homes). For the record, I still think my DIY HRV could be a great budget option in colder, drier months.
@@HealthyHomeGuide Thanks for the reply! Was the mold concern in regards to the box or the core getting moldy or rather the humidity causing mold growth elsewhere in the house?
@@ww-pw6di You ask very smart questions. I was concerned about both, to be honest. I’ve learned hard lessons about how careful I have to be with introducing humid air into my living space. Because I’m very sensitive to mold.
Absolutely. I’m actually working on a video where I do a DIY installation of an ERV. I didn’t build the ERV, but I built a system to retrofit it into a window. Stay tuned.
It would be nice to see examples of external house wall holes that pass permit inspection. Hole covering would include everything needed to simply unplug whatever DIY HRV solution you have in place to easily sell your home.
Thanks for your videos! I don't sub often, but you've earned it 100%. Also, noticed a rebounder/Cellerciser in your living room...just wanted to confirm it's an actual Cellerciser! They're great aren't they? Any tips or tricks you've noticed while using it? Thanks
I love to hear that, thank you! It is indeed a Cellerciser - such a good quality product. I like to swing my arms forward and backward while bouncing to get the lymph circulating.
@@HealthyHomeGuide do you know how well this would work for hot and humid Texas summers? I know an ERV is what I need, just didn't know if that poly might work well for that or if I needed something like an aluminum core. Thanks!
@@Slipperypuffin Yup, an ERV (as opposed to an HRV) would absolutely be the way to go for the specific reason of ensuring your home didn’t pull in too much moisture from the humid Texas outdoors. If you have the budget and space, I’d recommend buying an ERV, because I’m not sure how to actually build one. If you want to try an HRV instead (which won’t get rid of humidity) coroplast could certainly work because coroplast is moisture resistant. Based on what I’ve seen, a coroplast core should do fine at cooling the incoming air in the summer, you’d just probably need some sort of condensation drain.
Great project, even if the efficiency did not quite measure up. I would argue however that anybody building one to install in an older home should dive deep into already existing air infiltration issues. Just a few poorly sealed holes in the framing can cause a hidden issue through the entire home, even through interior walls over crawlspace construction. The pocket hole doors originally built into my home permitted an absolute blast of air through them when the house was pressurized, much of it likely coming from the crawlspace. (I sealed the pocket doors in entirely.) Even the catch on the jamb for a door latch became an obvious breach that a little caulk easily fixed.
If you're chasing every last % of efficiency you could make your own fine channel aluminum heat exchange core. Get two or three Fiskars 9340 paper crimpers with metal crimp rollers. The rollers are the parts you'll want, to put together end to end on a common shaft because they're only 6.5" long. Might need to double up on the crimpers if only one roller in them is aluminum. You'd have to build a custom frame to hold them and add a long hand crank. For metal, whatever thickness is used for offset printing plates would probably be ideal for the corrugated channel sheets. To separate the corrugated sheets use heavy foil, the thickness used for single use turkey roasting pans ought to do. I'd expect thinner to be better for heat transfer. Can't go too thin on the corrugated sheets gauge because the core would need rigid plates on the sides and a way to compress it to ensure good contact between the corrugated and flat sheets to block bleeding of air between in and out paths. It would have to be more efficient with heat only having to cross one very thin, highly heat conductive sheet of heavy aluminum foil VS two layers of plastic that don't transfer heat anywhere near as well as aluminum. Any bet it'd be over 90% efficient at heat transfer? Fiskars makes a wavy version of the crimper, model 9341. Wavy channels would make the air slower, with a longer path through the core, but those crimpers look like the crimp rollers are all plastic.
This is quite honestly a brilliant idea. Thank you! I did some corrected efficiency tests and my HRV actually turned out not to be 85% efficient. It’s more like 60% efficient. See my pinned comment for more details!
Clever to recognize coroplast as a useful material! Its thermal conductivity would suck compared to metal, but if the dwell time of the air inside then heat exchanger is long enough, that will compensate: Half the conductivity? Just double the dwell time. 1/4 => 4x, etc, etc. It seems the duct fans are working fine for you, but a cheaper and potentially better solution could be a used squirrel-cage blower from an HVAC system, with the speed adjusted via either a cheap A/C speed controller (triad plus noise filter) or by putting a small motor on it, running it via a timing-belt setup (the kind of timing belts used for 3D printers. Squirrel cage blowers are great when dealing with back-pressure from filters or the stack itself.
Amen! Great points. I did indeed make the core larger to increase dwell time. I had never heard of squirrel cage blowers, and that sounds like a fascinating idea. I guess they’re a high static pressure blower?
@@HealthyHomeGuide Exactly. They use them in HVAC systems to overcome the static pressure from the filter and all the ducting, registers, etc.I don't know the details of relative efficiency, etc, but you'll find them any time there's higher static pressure. (The rotor/impeller is an open-ended drum with angled slots around its periphery. The name comes from looking like something a squirrel (or hamster?) would use to exercise in :-) The blower from a home HVAC system would be grossly overpowered for your application (and probably too big as well), but any time a furnace/air-handler is being changed out because an HVAC system is being completely redone for some reason, chances are the blower will still be good; I don't know if I've ever seen one wear out and have to be replaced; at least not in any houses I've lived in or owned. You'll find smaller ones inside air conditioners and dehumidifiers that might be more size-appropriate for your use, but it might be a wrestle to get one out of a junked unit because they're not built for easy replacement.
@@DaveEtchells This is absolutely fascinating. I think I’ve seen the type of blower you’re referring to. I’ll put this on my list of investigational projects. Gotta see if I can find a smaller one - I suspect that one of these blowers might groan if I used an A/C speed controller to try to dial it down. I tried using an A/C speed controller on a very powerful duct fan and it wasn’t pretty haha. Lots of electrical moaning.
That's an interesting design. I've actually seen a very similar design (using coroplast) from an HVAC company that fleeced me thousands of dollars some years ago for an HVAC design that included one of their custom ERVs. I got suspicious after seeing that they didn't have a test in HVI database, and after seeing the docs that they sent me, it literally showed 0% humidity recovery for their "ERV". Which made sense, since this type of design is non permeable and cannot recover humidity, making it an HRV only solution. Didn't have the time nor energy to try and get my money back.
Damn, that’s absolutely insane that that company had the audacity to sell an ERV with 0% humidity recovery. That’s laughable. It’s like selling a car that gets 0% gas mileage.
@@HealthyHomeGuide Yeah... the person in charge previously worked for ASHRAE in a fairly high ranking position too, which made me not as suspicious as I should have been initially, so it took too long to figure out that I'm being essentially scammed. By the way, and I might have missed this in the video, you should consider using ECM 0-10v blowers as they're much more efficient, quieter, and easier to control using industry standard means. Makes balancing easier too.
@@HealthyHomeGuide Yeah the company is still in business too, continuing to sell what I think they call a "polymer fixed plate" core "ERVs". Oh well. Yeah if you're already using EC inline fans that you can easily vary speeds on, then it's already all good. Planning on ducting it by any chance? Exhaust from kitchen and bathrooms, fresh air supply to bedrooms and living and all that. Don't need to use large duct either, I think Zehnder for example uses only 3" ducts. Then you can do more neat stuff like set up boost modes for a limited amount of time when cooking and such, though you'd optimally want a recirculating hood there, but that's a separate subject hehe.
Chloroplast may work, and you appear to have built this one sufficently large to get fairly good efficency at the rate of air exchange. But, know this. Plastic is inefficientl at moving heat across a given surface area. Your heat exchanger could get comparable efficency with a smaller design if the core were made of sheets of aluminum seperated by small three or four spacers each layer. Or you could achieve significantly higher efficency with an aluminum core built to to your existing core size.
Thanks for this video! I think that you could make that box into a vertical version if you used plywood for the largest sides. It would not need to be more than 3/8" thick to support that core. Probably 3/16" would do. I bet masonite or "bath-board" (which has a nice finish on one side) would work very well. Adding some 1/2"x1/2" wood pieces in certain corners to further stiffen the housing would help as well. (even if using your current materials for the walls) I think that you might get more efficient airflow if you used some internal ducting to reduce turbulence between the air inlets and the filters and the air outlets and the core. (The shape of the chambers the air passes through is probably causing a lot of turbulence) A piece of thin poster board could be formed into a cone that is the diameter of the inlet at one end. The other end could be creased into a square to fit the filter or core. (the circumference of the filter/core end should be equal to or slightly larger than the perimeter of the filter/core in order to fit) That would give you a custom duct for very little in the way of expense and effort. Another good material for this would be a used printing-press plate. They are usually aluminium and can be gotten at any place that prints posters etc on a lithographic press. A layer of radiant-barrier material (like ArmaFoil from EnergyEfficientSolutions d0t c0m) over the block in the window and on the inside of the walls of the housing of the HRV would insulate the system and increase the efficiency a little more without adding much bulk or weight. You could also make the core out of the lithographic plates I mentioned above. Just cut out a rectangle whose long side is longer than the short side by twice the distance you want between plates. Then fold the edges of each of the short sides down by the distance you want between plates; so the profile is like a very wide staple or 'u' shape.(if you cut them out and folded them right; they should be square now) Then you stack them alternating the sides that are closed by taping the folded edges to the unfolded edges on the next plate. You could use hvac foil tape for this to get maximum efficiency. This setup has three advantages over the current core design: The first is that aluminium transfers heat much more efficiently than plastic. The second is that the single layer walls would be more efficient. The third is that there would be better airflow through the core because of the undivided center of each layer. (A tip for cutting lithographic plates is to use an xacto knife and a straight edge. You do not need to cut all the way through. Just score it well and then bend it at the score lines and it will snap)
Glad you enjoyed it! To be clear, this is an HRV, not an ERV. I’m not sure how one would go about making a DIY ERV, but if you find out, do let me know!
I think the main thing stopping you from having better efficiency is the cross-flow. Your two airflows are perpendicular to each other, and you can get better heat transfer by having contraflow instead, where the airflows are in opposite directions. However, that makes construction slightly more tricky, and probably can't be done with the materials you are using, as the airflow needs to change direction in the middle of the core, and the core needs to be longer to have that contraflow section in the middle. I'm considering making a unit with (very cheap) aluminium foil, but I'm not 100% sure it is durable enough.
You’re absolutely right. I want to make a counterflow core eventually for that exact reason. Do you know how you’re going to mold the aluminum foil into channels and make it rigid enough to hold its shape?
It would be nice if there was a good filament that could 3D print a large 300 x 300 x 300 mm core. Maybe a filament that can easily be coated in copper later?
Filtering the fresh air isn't a bad idea. I apply herbicides all day, but stop near evening because of the inversions carrying the product to unwanted places. I live near the field and wouldn't mind having something like this. Pretty big though.
Yup, temperature inversions are really disconcerting. If I were to build this device again, I’d do it with 2” thick filters instead of 4” thick filters, and I’d make the housing smaller.
Thank you for sharing this, truly. Definitely a thumbs up! Sharing knowledge and experience like this this is the internet at its best. Also nice to give credit to your sources at the end. Question 1: High effective is 85% as compared to a commercial system? I could do my own research of course but in case somebody knows already ... Question 2: Did you consider alternatives to spray adhesive for laminating the plastic heat exchanger stack? I am thinking it is an unnecessary source of VOC’s? Are there “healthier” adhesive options or am I being overly concerned? Question 3: Would efficiency increase with a heat exchange filter material of greater thermal conductivity like copper or aluminum? A am pretty sure moisture build up would be an issue if installed “properly” with outgoing air coming from high air moisture areas like bathroom, kitchen and laundry rooms however. But in any case really cool build!
What I need an HRV/ERV for is to lower the CO2 levels in our very air tight 1100sq/ft home with propane cook surface, 2 adults and 2, 80lb dogs. The CO2 levels quickly rise to over 2000 PPM without exhaust fan running and periodic use of the whole house fan with doors open. High CO2 levels cause headaches, drowsiness and other health problems. I bought a quality Ambient Weather indoor AQI monitor which tracks 2.5micron and 10micron particles as well as CO2 levels with reasonable accurance and was shocked at the dangerous CO2 levels we were living with.
Your thinking is spot on. In a tight house with that amount of occupants, CO2 levels can certainly rise to unhealthy levels. What is even more important for health than CO2 is VOC levels, which recent research has shown are up to 100x higher indoors than outdoors. That’s why it’s even more important to dilute your indoor air with outdoor air.
8:52 Condensation needs much less air movement. You always deliver fresh energy, to evaporate the condensate. This is a great factor for efficiency at large temperature differences, but what can you do🤗
Very cool. I’d love to see a full build video with parts and dimensions. I’m already wondering if I could fit this in the top of my entry closet. It’d require drilling holes in my exterior wall and the closet wall, but it’d solve the obstruction and looks issues here. Also curious to see the process of changing the filters. If you have to open the top for maintenance then this install location might not work (though I guess you could put it on the floor of the closet instead).
Thanks! I like the idea of putting it in a closet. To give you a rough idea, the housing is 36"x30"x14.25". I do indeed have to open the top cover to change the filters. It's fairly simple; I just secure them in place with a couple strips of tape. I put weather stripping around where the housing contacts the top cover and then secure the top cover down with clear, low VOC tape.
Very cool to see the concept in action. If the plastic transfers heat so well, wouldn't you need another material to insulate the connection to the window?
Great question! I am using weather-sealing tape to ensure that cold air doesn’t blow through small cracks at the edges of the window insert. As for the plastic insert itself, coroplast has a 4 mm layer of air in between its two plastic layers. The air acts as an insulator. Also, the plastic isn’t actually that fantastic at heat transfer compared to something like aluminum. The coroplast insert doesn’t seem to get that cold.
PS: for heat recovery and fans, I decicded to go with commercial solution which was in just about 600€, so I added only control, dampers for circulation mode and AC unit for cooling and heating😂
Congratulations and thanks for sharing. May i suggest you change your filter with 3M by example. Filter buy are not good filter. go see the Consumer Reports tests. A lot of merv 13 filters are actually not real good. 3M, Nordic Pure and Air Handler are good choices, to name a few
Very cool. 🤔 I like the idea of a charcoal filter, but I'm clueless where you would put it in the system. I'm building my retirement home in Arizona (a cute little hacienda style cottager) and I want to incorporate as many DIY solutions, and revive as much ancient technology as possible. Thick adobe walls will go a long way towards providing the thermal mass I'll need in the desert to moderate temperature swings. I think instead of the plastic body you could use ducting sheetmetal or the smooth fibreglass boards used in commercial kitchens, hospitals, etc. Both materials would give the same smoothness, but would be a lot more robust. Mine is NOT going to be proudly displayed in the living room! Sorry, although I'm now retired, you can take the girl out of the interior design business but... I plan to properly tuck it away in a conditioned attic space and cleverly vent the clean, temperature-moderated air throughout the house in inconspicuous or decorative ways. Can't wait to binge-watch some of your other videos.
Thanks Linda! I ended up using two 2” thick activated carbon filters that look similar to the filters I showed in this video, they’re just black. There are two available spots against the core where they can rest, in the same manner as the MERV-13 filters shown in this video. I deeply appreciate your philosophy when it comes reviving ancient technology. I’ve been learning about Terra Preta recently - very cool ancient tech. I used coroplast for the body because it’s very easy to cut, lightweight, non-toxic (polypropylene is BPA-free and does not off-gas at all), durable, moisture-resistant, recyclable (polypropylene is a thermoplastic that can be recycled), and CHEAP. I wanted to build it all from one cheap material, but I appreciate your point about the robustness. Your interior design-friendly plan sounds amazing. If you end up doing that, I’d be happy to make a video featuring you on this channel if you’d like. Good luck!
@@HealthyHomeGuide 🥰 That you're a gardener. My favorite terra preta video is by David the Good th-cam.com/video/DnTaWiO5Eso/w-d-xo.htmlsi=xiT9K3iHJjA2ySeZ. I'll save you the suspense: it worked great, but David moved to new land and it petered out in a year. My theory: the deposit he created was only 3' deep. The deposits in the Amazon are frequently 60' deep, and were renewed annually for centuries. I think David's on to something, but I also think that it needs renewal every year for many years to become self sustaining. Enjoy!
@@mikemotorbike4283 Yeah. That makes sense. But it's only a "sheet"? Huh. I didn't know that, I thought it was like the air filter, about 2 inches thick and approximately the same size as the Merv filter, just black. Interesting. Thanks for the info!
I'm looking into this myself as I'm struggling with keeping the cat litter smell at bay now that I have two cats, and great to see that this design with the plastic actually works well. I would have figured it would not have enough thermal conductivity. I might have to experiment with this and see if it will help. Right now I'm just opening the windows but that won't exactly be an option in the dead of winter!
Thanks for bringing this up! Ventilating is a great way to keep odors like cat litter at bay, but also comes with its risks if not done properly. If you haven’t seen my latest video yet, I think it’d actually be really relevant to your situation: th-cam.com/video/80r9qwJPcTI/w-d-xo.html
The thermal capacity of air is so low compared to most solids that the conductivity is not too much of an issue. Conceptually, if you think of the HRV in a steady state of operation, there is a thermal gradient along each of the channels constantly re-enforced by the air passing through at almost the same temperature. The transfer of heat between the channel wall and the air is likely far more limited than the transfer of heat through the thin plastic wall. I built my own DIY HRV just using a BIG pair of concentric plastic pipes connected up to ducting. Primarily for ventilation, but why wouldn't you want some heat recovery? Capable of higher rates of ventilation as the airflow has little restriction, but better heat recovery at lower speed.
Drainage - I don't believe that you need a big slope to ensure that water will drain. You may need to balance the wetting of the surface with the size of the passages so that the droplet sizes (should they form) don't block the flow. And just because the exchanger flow may pass the dew point, doesn't mean that there is energy exchange available to cover the latent heat part. You'll need to try it in a shower room (warm wet air) with exchange to a cold wet rainy exterior....
this is one of those (awesome!) things that works in specific climates. Another example is a swamp cooler. If i used this where i live my house interior would be covered in slime mold, too humid. Same with a swamp cooler. 😞
You’re absolutely right. I only used this HRV in the late fall, winter, and early spring when it’s not too humid. I took it down once the humidity came. The last thing I want is mold growth because I’m really sensitive to it.
Don't use carbon filters, they only absorb to equilibrium, then they re-emit when they get any warmer than that. The only way to make them work for a length of time requires periodic desorption cycles like a desiccant based dehumidifier.
Impressive and inspiring, thank you. For someone interested in trying this, why coroplast, other than it comes pre-corrugated for maximum surface area? Wouldn't metal plates work better at transferring heat? (but much more time-consuming to pleat by hand). Maybe the fins from old A/C and HVAC equipment can be repurposed for this. Amazing effort and spirit, blessings and apprecation.
I appreciate that, thank you for commenting! Good question. I used coroplast because it’s very easy to cut, lightweight, non-toxic (polypropylene is BPA-free and does not off-gas at all), durable, moisture-resistant, recyclable (polypropylene is a thermoplastic that can be recycled), and CHEAP. I wanted to build it all from one cheap material. Coroplast transfers heat pretty well. Some commercial units built today actually use corrugated plastic for their cores! I also don’t know how to cut metal, bond it properly, clean it right, and work with it safely in general (especially with old potentially rusty parts). For someone with expertise there, it could be cool! Thanks again for your great question!
I have an existing HRV that is starting to show it's age (getting noisy) and replacing the fans would be something like 1200-1500€ so I am thinking about getting a new one. Doing some DIY work on it with third party fans is something I have been thinking about, but the original fans are custom built and I have been unable to find duct fans that I can properly control. The originals are radial fans and built specifically for the HRV...
Thank you for asking! I’ve posted the tools and materials list at the bottom of the video description. The fan is on that list. Let me know if you have further questions.
Well done and nice and cheap. I well remember last century, pre internet, someone had constructed a very efficient HR unit out of pleated paper! Large pieces of paper, folded about every half inch or centimeter and laid cross ways like your core flute and connected just the same as yours. The paper being thin, had excellent heat transfer properties and low impedance to air flow. Question would be, how would it go in high humidity? Maybe spraying with a mixture of something non toxic but hydrophobic would be the answer. Plant wax? I'd say your set up would suffer losses because if the poor heat transfer of the double layers of coreflute. I have seen single sided stuff around. That would improve efficiency. Maybe single sided corrugated cardboard would be the go?
You’re welcome! The videos I linked in the description are very helpful for demonstrating how to build a core. The one by Designed by Instinct is particularly useful.
Now that your video is 6 months old have you inspected and cleaned the cleaned the HRV and particularly the core yet? One of the biggest hidden dangers of HRVs is that they require maintenance which could easily be skipped and result not just in decreased performance, but also mould growth in the core which would negate your efforts to improve air quality. You stated that your core is horizontal and hence is not able to be drained and that you didn't expect any difficulties due to your climate which may be a correct assumption, however the only way to know this is empirically. I would be very interested in the results of an inspection. Thank you very much and all the best.
Good question. I inspected and cleaned it when I took it down at the end of the spring when the hot/humid weather came. The filters were very dirty and the core was clean. Still, I gave it a soap bath to kill any invisible mold spores/particulate. The air is dry in northern Vermont in the winter, so condensation wasn’t an issue in the core, likely because coroplast doesn’t become as cold as, say, metal. There were times when the metal ducts developed condensation, but nothing major, and nothing that caused mold growth. I didn’t use my HRV during warmer weather because I’m too afraid of mold growth. Instead, I used a MERV-16 fresh air intake that I built (I have a video on it). This winter, I’m probably going to install an ERV in my window. Stay tuned for an installation video.
@@HealthyHomeGuide Very interesting. I am no HVAC engineer though I have some college HVAC knowledge, which leads me to think that the biggest contribution to high moisture in the core would actually come during the winter when moist warm indoor air would have the temperature reduced enough in the core for condensation to form (ie this air would reach its dew point). I look forward to your future videos.
Thank you again! In the interest of full disclosure, I just posted a pinned comment in which I discuss some corrected efficiency tests that I did. My HRV turned out not to be 85% efficient. It’s actually 60% efficient. See the comment for more info!
Great work! I'd place in the attic or at least that is what I planned to do with mine. I assume you saw the Hackaday HRV and maybe also my comments there and his youtube videos. I bought a few rolls, and even got some for free, of aluminum window screen. The thought was at some time 3D printing or maybe CNC in wood a tool and die to stamp like a linear ridge zig zag stamp so to increase the surface area of the alternating layers. I also found an old hair iron crip wave thing that is close, though small. I plan to only space the one path of flow and use corrugate on the other path. The spaced path that would use two other maybe three strip of one width corrugate tubes would have the zig zag aluminum mesh. I left off wondering how to plastic weld both sides into the full sheet of corrugate. The other thought was just ironing into both side of the corrugate the aluminum screen. That might work suitable as well and just then placing the zig zag screen into contact. I probably should work on again since I have now another size of corrugate material, 4mm, and not only the cutout 12x12 inch larger thickness 10mm corrugate. What thickness corrugate did you use? Thanks for sharing. Great to see more of these designs being made successfully and cost effectively.
@@HealthyHomeGuide I'll remember when I do and try to report back. I'm sure I'll post something on here as well. Your welcome and thank you! Very inspiring and yet creative.
Hey. Nice video. I have a few questions if you don't mind fielding them. I also have a few tips. I use a similar Panasonic unit, but I made modifications to it (some similar to what you made). 1. It looked like you had a filter for your exhaust air (right before the air entered the heat exchanger core). Was that to prevent dust from getting into the core and clogging it up when the walls of the tubes got damp? 2. I either missed it or you didn't say. Did you lay the sheets of corrugated plastic at alternating right angles to each other as you stacked up that core? Cool idea. For tips, you should DEFINTELY separate the intakes and exhaust vents as soon as you can - especially for the inside outlets. I'm sure you're immediately dumping a fair bit of your newly pumped in fresh air. As soon as you can spread those apart, do it. If you have a radon issue in your house, consider grabbing the air to exhaust from down in the lowest part of your house. If you have any occasional smoke (like from a fireplace), consider grabbing air to exhaust from up high where smoky air rises to. Overly humid bathroom would be a good place to collect waste air too. You get the idea. Consider dumping fresh air where you want things to dry out. Mine dumps over my kitchen sink where I do dishes. The dishes dry in no time. That wasn't planned ahead of time, but it's appreciated. Those fans are awesome by the way. I use those for venting air all over the place. I use that exact 6" model for running hot air under my concrete floors to warm them like old Roman baths used to. Very reliable. Great video. Thx for sharing!
Thanks for watching! Yes, I filtered the exhaust airstream before the core to prevent particulate (mostly dust) from building up in the core. Factory made units generally do this too. Yup, I laid sheets of coroplast at alternating right angles to form the core. Agreed. After this video came out, I installed elbow duct attachments to the indoor supply and outdoor exhaust to the direct the air streams away from the intakes 🙂 Thanks for the tips! Using fans for indoor air circulation works for drying as well. That’s good to know that you find those fans reliable! Thanks so much for your support.
Don't thank me for watching your videos, thank YOU for taking the time to make them. As a fellow TH-cam creator, I know we don't make much on most of our videos. Although with 66K views, that's got to be adding up to at least something, but still generally (for me anyhow) less than I'd make if I were doing a normal job at minimum wage. Making videos is def more fun though! @@HealthyHomeGuide
@@PraxisPrepper I actually just got monetized this week, so I won’t make anything on the $66k views I had racked up before monetization unfortunately. I’d love to make TH-cam my main career eventually because it’s so fun. I’m hopeful!
Best luck in that endeavor. I'm definitely no expert at it, but I can share a few bits of advice from someone who's been doing it for a bit. 1. In my last 3 months, my channel had 57k views and that resulted in $275. So that's a bit of a ballpark. 2. Not all videos seem to be treated the same when it comes to payments for ads. I've had many videos with pretty much the same views and numbers of ads per video get wildly different revenue amounts. So just be aware of that. 3. TH-cam is definitely serious about pulling down one's channel's ad impressions (which are what lead to views) if one does things that aren't popular at the time. I also run a channel that's all about different language learning for kids (alphabets, counting, simple math, colors, etc.) Some of the lessons that I've posted in the past have been in languages like English, Spanish, Italian, German, Russian, Chinese, etc. Those were all very cool with TH-cam until recently when I posted a video teaching the Russian alphabet and that day my channel got pretty much shut down (meaning going from consistent thousands of views per day to consistently just a few dozen views per day). I guess Russian anything (even the alphabet) is taboo now. I've experienced similar things during covid in regard to items such as back when the official public word was that it wasn't airborne and I openly spoke about how I thought it very likely was actually airborne (given that it was a type of coronavirus and those are commonly spread through the air). It's hard to predict (for me anyhow) but sticking to truthful things or reality isn't a shield for your channel. Where you do a lot of videos about health-related topics, just be aware that if you make a video about something that's totally 100% true, but that truth becomes controversial (like cold viruses being airborne), it can create a big issue in terms of growing your channel. Again, I can't offer any specific advice, but I share that reality with you so if it ever happens to you, you'll understand what's going on and won't think you're alone in your treatment. 4. Last, I recently found out that TH-cam has a blacklist of videos that (for undisclosed reasons) they don't send ad impressions out for. I recently created a short video (the vertical TH-cam Short style) and it had a 100% CTR, an average viewing duration of 250%, and 100% likes. But after more than a month, TH-cam had only given it 22 ad impressions (several tens of thousands is more what I'm used to). I was on with a TH-cam tech for about an hour (using it as a case study) to try to understand why that video wasn't being shared at all. They refused to give specifics, but told me that TH-cam keeps a list of videos that are deemed "ineligible" for ad impressions. I still to this day have no idea why. It was just some silly short about an AI image Id created that looked weird in how it came out. Totes vanilla content. Anyhow... welcome to the wild world of TH-cam creating!@@HealthyHomeGuide
@@PraxisPrepper Thank you for that. Hearing about the nuances of your experience is really helpful. I’ll be on the lookout for all those things. My first observation is that since being monetized on October 16th, my views have gone down significantly. Like, a stark difference. Night and day. Before monetization, I was getting 1500 views per day consistently, and after monetization, I’m getting 500.
You would get better heat transfer if you only used a full sheet of coroplast every other layer. The intermediate layers would just use a strip of coroplast at the edge for a separator. Of course the downside is that it would unbalanced.
I disagree for two reasons: Firstly, I measured CO2 levels with and without the HRV to ensure fresh air is being brought in, and it is. Data for that is in the video. Secondly, one of the ducts extends further externally than the other. So one extends 2 feet outside and the other extends 1 foot, which helps them avoid exchanging air. It's difficult to see in the video because the longer outside duct curves downward. Internally, since I released this video, I actually put a curve in the supply outlet, so it blows in a different direction that the return (exhaust).
@@HealthyHomeGuide To be fair to Beny, it is difficult to tell the extensions of your intake/exhausts from the presentation. Given that, one addition that you should check is the distance of the intake to any other exhausts on that side of the house (and this includes windows-unless they are never to be opened again). Normally, 5' seems to be the magic number. Good job on the rest.
Great job! I've seen a similar design on "build it solar" website before, but good to actually see a working prototype. One question: do you get condensation inside your core? Some HRV design includes a heating element to combat the condensation.
Thanks so much! I used this HRV only when it was dry outside in the late fall, winter, and early spring. So I didn’t run into condensation issues. I’m too paranoid about mold growth to use it in the more humid months. But I am working on a DIY ERV installation video for year-round ventilation. To be clear: I’m not making the ERV myself, I’m installing it myself.
I built the unit you saw on Build it Solar back in about 1988 or so. The painted plywood enclosure was around four feet square, as I recall, and about one foot deep. The core was a stack of coroplast sheets siliconed together. I had no way of measuring its performance at the time but it worked very well in our small cottage. All these years later, I'm thinking about doing it again for our off-grid home. Yes, it IS do-able for the do-it-yourselfer!
Very interesting, but we need a better way to warm air and cool air in the opposing seasons. Have you had any such thoughts for folks who want/need to have highly efficient homes as far as energy consumption and insulation goes?
As far as year-round ventilation goes, ERVs are the way to go. I’m actually working on a DIY ERV installation video. To be clear: I’m not making the ERV myself, I’m installing it myself.
IMPORTANT UPDATE: I did some more efficiency tests in the spring using the outgoing air and it seems that my HRV is actually around 60% efficient (which is still pretty good), not 85%. I wanted to make a video about this but I ended up having to put it on the back burner because I went through the process of selling my house.
When making this video, I made the mistake of testing efficiency using the incoming fresh air. I think that heat generated by the fans skewed the results.
Here’s a formula I used for a corrected efficiency test using the outgoing air instead:
× = (T_room - T_outgoingAir) / (T_room - _outdoors)
An example of one of my test runs (Fahrenheit):
60.5%=(70-44)/(70-27)
So yeah, it is less efficient than I initially thought. That being said, it still worked quite well.
I want to address some questions I’ve seen:
I do think that almost all of the air is flowing through the core. The filters were quite dirty when I dismantled this HRV, and in order for them to have gotten like that, I do believe air must have passed through them/the core.
I don’t think there is very much leakage in the chambers. I sealed them very thoroughly with hot glue and weather stripping, and did leakage tests. I acknowledge that there could be some leakage, but not that I could find.
Next point, to the couple people who quoted Egon Spengler at me: no, I don’t believe I’m “crossing the streams” (intake/exhaust air streams mixing). After this video came out, I installed elbow duct attachments to the indoor supply and outdoor exhaust to the direct the air streams away from the intakes 🙂
Potential reasons I didn’t run into condensation issues: lower HRV efficiency combined with the low dew points in my house (from ventilation with dry, cold air + no humidification).
I only used this HRV during the late fall, winter, and early spring when the air is very dry. I’m too worried about mold growth when it gets humid. Though less efficient than I initially thought, it still worked great!
If you're curious about how this DIY HRV performed long-term, check out this video of mine: th-cam.com/video/LiptsaKmq80/w-d-xo.htmlsi=bsEbBQ9pKLKozY4u
60% is good for crossflow HE in these materials. And filters get dirty much faster than we think ;) It's not uncommon to send a reserve filter set with a new AHU.
How would you deal with moisture condensing inside the core? If you turned the box on its side, moisure could run out of the core channels. EDIT: I see you do address this, kinda. However, it’s still true that this is a no-go for any climate that has to deal with condensation.
@@stcredzero great question. I’m also concerned about ventilating using an HRV (even a factory made unit) during humid months. ERVs are better for ventilating humid air. I’m currently making a video explaining how to install an ERV one’s self (even for those who don’t live in a ducted home!). That might prove useful to you when it comes out.
I really love the idea. Things like this have crossed my mind quite some times in the last couple of years.
But please help me as I'm trying to wrap my head around the calculations. Wouldn't it be much more accurate if you measured the temperaturr of the in the four ducts for your calculations? And perhaps als the airflow? (Especially flowing from inside out)
I'm thinking of:
DeltaT_,OutsideIn = T_Inlet_OutsideIn - T_Outlet_OutsideIn
DeltaT_,InsideOut = T_Inlet_InsideOut = T_Outlet_InsideOut =
Delta_T = DeltaT_,InsideOut - DeltaT_,OutsideIn
Gain = Delta_T * Air_HeatCapacity * Airflow_OutsideIn (I'm probably missing some details here 😉)
And then there's this thing about air particles. Do you have any measurements from before then installation of the installation and how do they compare to the new figures?
I'm having some Ikea air quality sensors and about 99% of time they all show no polution or just a little bit.
For better efficiency (if you even need it) you need a bigger and more elongated core.
To all the naysayers, this guy built a system extremely similar to a professionally manufactured one. Many manufacturers also use plastic cores, and even plastic fiber cloth cores (with moisture wicking effect)
As an HVAC guy i can say your design although unconventional and bulky is just fine, your fans you use for circulation would benefit from the coandâ effect to increase air flow. Also those efficiency rating the big companies use are totally skewed so your system is probably working better than off the shelf systems thanks to that massive core you built
I appreciate the encouragement! And thank you for that Coanda effect idea - I’m gonna tweak the locations of my circulating fans to capitalize on it.
How would one deal with condensation for something like this? Curious if this would work as well during Texas summers!!
@@Geoff9001 I’ve only used mine during colder, drier seasons. I definitely would avoid using an HRV in your climate, especially during warmer months. An ERV (combined with a dehumidifier) would be a safer ventilation option for your region.
@@HealthyHomeGuide have you seen any decent homemade ERVs online? This is the first homemade hrv I've seen online and it looks great, although a little big
@macthemec can you elaborate on how one would use box fan to achieve a Coanda effect? Where is the effect happening? Is the idea to get the air flow from the fan to follow to the walls, or floor, and thus travel further than it would had it not? Is it perhaps fashioning a shroud or cowl to affix to the box fan, one which would create a Coanda effect? I really can’t imagine how this would work?
Dude you are brilliant, it never would have occurred to me to use the natural tunnels inside of coroplast board! That's legit mate. You've managed to achieve very near the efficiency of commercial units that cost thousands of dollars. This is such a great idea, you've given me all kinds of ideas for my own apartment.
Aw, that’s very kind! Thank you so much. Feel free to let me know if you have any questions or want to show me your future designs.
what do you think of using corrugated cardboard?@@HealthyHomeGuide
as an actual HVAC Technician i think that is pretty neat. the physics is the right way around and from the numbers i can tell it works. the only way to improve would be a more conductive material to get the usual 90-98% efficiency but apparently its conductive enough.
That’s very kind, thank you! That means even more coming from you, as a legitimate HVAC tech
90-98 is definitely not the “usual” efficiency rating for HRV/ERV’s. That would be on the extremely high end.
@@JordieG8 agreed.
@@JordieG8 i have no explanation for this. i dont remember why i said 90-98 i guess i meant max. just goes to show take everything with a grain of salt or something
@@steffankaizer all good dude, I thought you maybe got it confused with high efficiency furnaces or something. Lol
New subscriber here!! This is the best design I have seen on the Tubes my friend!!!!!I am starting a gourmet and medicinal mushroom growing business in Delaware with my best friend/business partner and I have been researching ways to reclaim heat and use alternative methods of heating and cooling. I developed a device that collects and. inverts electrostatic electricity from the atmosphere and converts it into usable dynamic electricity. I need one part to finish the design but it works . I am designing ot so that it can work with off the shelf transformers and such . The last part I need it a triggered spark gap and to buy one is expensive. I bought a lathe but there is a learning curve on it....
Honestly making this from plastic is pretty dope in terms of cost.
However you could make it MUCH smaller.
I have a lot of those plastic sheets lying around for different purposes.
Also you're using layers of plastic in 2 directions, which might lower the performance because it has not amazing heat conductivity. Just one set with gaps would be perfect.
This is high static pressure application, so in this case, it would be best to get 2 centrifugal (radial) fans, not axial ones.
It would also make sense to make the heat exchanger much longer, and thinner, to get full heat extraction.
Great video though.
Nice design.
I fully agree with all those tips!
@@HealthyHomeGuide I will probably make one for balcony, where it has to fit into square drain channel.
With centrifugal fans you could theoritically add cyclone filtering to get rid of heavier stuff.
Definitely going to do this now, didn’t know that the diy actually worked so well and with testing to back it up! Thats all I needed! This will definitely help with my parents cold basement and spare second story room if I hooked it up to the previous improperly installed furnace air return. Thanks
Great! You’re super lucky that you have ducts already in place in your house, even if they’re not properly installed. Good luck!
Stunningly simple, cheap and effective. Well done man!
Glad you like it!
Man I'm absolutely blown away. You did an amazing job. Well done on your research and execution. I have a whole new view on heat recovery systems now. In HVAC, these items are extremely expensive. I don't often get to specify these due to clients not having the budget for it. After seeing your results though, I think I can come up with something affordable and efficient on a commercial scale. I feel efficiency can be improved with a quick material study. Thanks for your video. I'm very impressed and appreciative for you helping me see how simple this system can really be.
Man, this is one of the best comments I’ve gotten! I really appreciate that. So glad I was able to inspire you.
This is unbelievably cool, even with the potentially lower efficiency number. I just bought a house and have a 1990s furnace that I want to keep running as long as possible. Currently in the process of cleaning and sealing the duct system and trying to DIY as much as possible. The furnace uses a long insulated flex duct to allow unfiltered cold Canadian air into the furnace room for combustion. I feel it’s very inefficient (and dirty) to have a clear line of outdoor air entering my home. Your system seems like the perfect DIY method to address this problem. Just found your channel and looking forward to seeing what other ideas you have.
Thanks so much! I think you’re smart to pick up on the fact that your furnace situation may not be the best. Most people ignore those things. Not us!
"Never cross the streams." Dr. Egon Spengler
I applaud the initiative. This is certainly the future & I love it. Some things to consider...
1) CO2 "cannot" be affected by the unit, as the CO2 level is whatever you are drawing out of the air coming in from outside (usually about 400 unless something weird is going on. Plants like it when we "talk to them" because we are breathing CO2 at them. CO2 builds up in a house because of "us".
2) I would be greatly concerned about the VOCs coming off all that plastic, adhesive and other chemicals from 3-D printing. It's gonna off-gas, a LOT! Funny your comment, "insane!", right after, cause..., yeh.
3) There is an actual Metric they use, CFM/watt, to quantify how much actual work is being done. It's used to measure performance. Measuring the Factual temps of the airstreams is of great interest also.
4) Tape the edges of the filters or there is bypass (sneaking around the filtration, around corners). HEPA has no "bypass".
5) Measuring the air pressures will tell you the static resistance various parts of the system are causing - core, filters, vents.
Cool experiment, but don't mislead people with hyperbole instead of data. Maintain integrity. Do no harm. Cheers.
There is more things to consider:
1) The heat exchanger is not going to be very efficient, because it does not have perfect counter-flow. In the 2 corners at the border between inside and outside, there will be heat exchange between the hottest part of your system and the coldest part. A simple system of two (long enough) concentric pipes is going to perform better.
2) In winter, condensation in the outstream will boost efficiency even further. In summer, condensation will occur on the instream, making this system unusable.
3) Indoors, it is much better to have air intake and outlet in opposite parts of the house, so the clean air will spread without the need for additional fans. Outdoors, outlet and intake can be closer together, and should probably be pointing in the same direction in order not to get drafts when it's windy.
Bro, you would put a little greenhouse lean-to against a southern wall of the house outside the window to actually heat your house on sunny winter days.
Also, you could just skip the return fan and suck air in and make your house “positive pressure so that you leak a little air outside rather than allowing dirty air from outside to find its way into the house
If your HRV actually is 85% efficient you should get a lot of condensation when outdoor temperature is below freezing. You can figure out the dew point of your indoor air, and unless that is as low or lower than the expected temperature of the exhaust air there should be condensation. The "fresh air" you get is definitely a mix of fresh air and indoor air that leaked into the fresh air stream, possibly not in the core, but definitely in the giga-supersized chambers outside the core. Also you need to make sure the flows doesn't mix outside to get an measurement of the actual efficiency. If you measure the temperature that leaves the house, on the outside, instead of the mixed airflow, and compare that to indoor and outdoor temperatures you can find out the actual efficiency. The actual efficiency is definitely not anywhere near 85%.
Aluminium conducts heat around a thousand times better than most plastics, and you can make aluminium much thinner, which also improves heat transfer compared to plastics. You even have two layers of plastic, and a layer of adhesive, and possibly areas with air too. And no way those fans can force hundreds of CFM through that core, a powerful leaf blower might be able to do that.
Thanks very much for your comment! So, I did some more efficiency tests in the spring using the outgoing air and it seems that my HRV is actually around 60% efficient, not 85%. I wanted to make a video about this but I ended up having to put it on the back burner because I dismantled this HRV when the warmer weather came and went through the process of selling my house.
When making this video, I made the mistake of testing efficiency using the incoming fresh air. I think that heat generated by the fans skewed the results.
Here's a formula I used for a corrected efficiency test using the outgoing air instead:
× = (T_room - T_outgoing Air) / (T_room - _outdoors)
An example of one of my test runs (Fahrenheit):
60.5%=(70-44)/(70-27)
So yeah, it is less efficient than I initially thought.
I want to address some other points:
I do think that almost all of the air is flowing through the core. The filters were quite dirty when I dismantled this HRV, and in order for them to have gotten like that, I do believe air must have passed through them/the core.
I don’t think there is very much leakage in the chambers. I sealed them very thoroughly with hot glue and weather stripping, and conducted leakage tests. I acknowledge that there could be some leakage, but not that I could find.
I also don’t believe the intake/exhaust air streams are mixing very much. I installed elbow duct attachments to the indoor supply and outdoor exhaust to the direct the air streams away from the intakes.
Lastly, dew point in my house is quite low in the winter. I don’t use humidifiers and this HRV brought in plenty of fresh, dry air.
Again, thanks for your insightful comment.
That’s a well regarded reply. Maybe when you get a chance just do an edit update including these findings.
An aluminium heat exchanger can be 'too efficient', you still need the effective insulation factor between the two sides (internal and external), and clarity of where any condensation should (and should not) occur.
The real world heat conduction is also a function of thickness, and in thin material plastic is as good as aluminum in case of HRVs
@@hhkk6155 could still probably get good results with a water loop design. Would also allow you to separate where the intake and exhaust is going. Like one widow has an intake with an aluminum heat exchanger and the other window has an exhaust with a heat exchanger. No mixing of air and probably make it more compact. Hell you could have the exhaust on the other end of the house if you wanted. Could also eliminate the exhaust filter he has and opt for a real heat exchanger cleaner when needed since it isn't plastic.
This is exactly what I was looking for!!!! I have a Resin printer that I want to exhaust out of the room, but I don’t want to lose all the heat or cool air in the winter/summer. I hope this works for me! I don’t need to change much air, just a little bit, so I bet a 4” fan set to low would be enough for my application. Great job!
Glad I could help!
i built one in spokane in 85, using plastic sheeting and bathroom exhaust fans. i like your design.
Damn, you were one of the OGs. Thanks for watching!
Excellent video. Really good build quality and very well explained.
Thanks so much!
Great design bro! This should work damn well for your money! As an engineer, I am pleased to hear competent technical reasoning accompanied by such a simple but ingenious design.Bravo. Physics does not work on the loud brand and price of equipment, but on the principle. You inspired me not only to make a similar device for myself, but also to think about the serial creation of cheaper systems.Where I live, such systems are not financially available at all. Everyone deserves to breathe clean air.
Amen to that, and well said! Everyone does deserve to breathe clean air. Even people who aren’t rich. Even people who don’t live in homes with duct systems, people who rent, or people in areas where HRVs/ERVs aren’t accessible.
Wow! Your did great! You did a great job! And so efficient too! I live in a very small home in CT, a 200 yr old home, I renovated 20 yrs ago. Our home is 24x22, with basement, 1st flr, 2nd flr, and walk up attic. It's a post and beam kinda house. I installed ductwork, and Air handlers, one in the attic to service the 2nd flr, and one in basement to service the 1st flr. I have a boiler for heat, so it is a hydronic system. Each AHU has a hot water coil, that way I can also temper the discharge temp. So I think about 5 yrs ago, I added a Fan tech ERV to my 2nd flr setup. I added external filter boxes, with I think Merv 12 filters it came with, cause you need to keep that core clean as well as the air we are gonna be breathing. This was the lowest price unit at the time, and the enthalpy core is same product you used, but not as nice as yours, mine is not very efficient, so on really cold days, I don't use it. But a year later I bought a HRV for the basement I spent a little more and got one a bit more efficient. [I'm not rolling in $] I have seen some really high efficient EVR's but big $. I'm fortunate I inject the "make up" air into my air handling system. I also have UV-C lights in the AHU's. I have my 2nd floor ERV set up so when I run it, a relay turns on the FAN mode on my t-stat, so the AHU is running to distribute the air when the ERV runs. I have a Timer so 2nd floor runs at night [bedrooms all on 2nd flr] but also another timer called an Air cycler. This means it will run say from 6pm to 8am, but the air cycler runs the system 15 mins every hour. Then if someone hits the Exh fan switch for the bathroom, it turns on. [The stale exhaust air, get sucked out through the bathroom registers]. Anyway the results are great! I eventually will improve the ERV with a more efficient one in the future. The indoor air can be so bad, plus I'm try to learn about "static" pressure in the house. So when I turn on the range hood on highest setting 600cfm, where the make up air? or air coming in? Do we pull a negative pressure bringing in more bad stuff through the chimney?? Or cracks around the doors?? So an intentional conditioned make up air system is so important, especially weather when you cannot open windows. So thank you for sharing your project! So cool! [sorry to be so long winded here, but I get excited about this stuff! ] God bless! AL from CT
Thanks for your comment, Al! And thank you for sharing your HVAC experience. It sounds like you’ve had quite the ventilation journey. I’m actually thinking about make-up air a lot right now. And absolutely, if you don’t have a dedicated make-up air system, it’s very likely that the range hood (especially at the highest setting) is pulling air from hazardous places, or at the very least potentially causing moisture to build up in the cracks that the air gets sucked through.
Unfortunately, my kitchen actually doesn’t have an exhaust system at all! I’m now planning on putting one in. My next video is going to be about this! Tune in if you’re interested. It should be out within the next few days.
One of the best channels on YT.
Thank you!!!
You probably want to insulate the intake and exhaust pipes on the outside end of the HRV - those have cold (in winter)/hot (in summer) air that is going to lead to undesirable heat transfer to your indoor air.
I like that suggestion! Thanks.
Keep it up. Love the facts and your delivery.
Thanks so much! That’s very kind.
Subscribed man. I'm not sure how I've come by your channel, but I am very grateful and have learned so much. Thank you for taking the time to post!
I’m grateful to the algorithm for bringing you here!
This is great! I wake up every morning and my bedroom smells like crap.. Sinuses and nose at winter are always kinda gunked up ... Every time i get ill in the winter months is always the same symptoms, sinuses , nose and throat full of awful fluids that i have to spit out.....I think all the bad fluids wanting to go out from our lungs and throat is way of our body to clear and flush all that crap out.. Im 100% sure that air quality plays a massive role in that respiratory system. I dont mind opening window for a fresh air multiple times a day but at winter its kind of waste energy and also when it gets cold outside air is crap to! Cause here in Serbia a good bunch of houses still uses wood and coal to heat their homes... here the market is so terrbile that small home HRV's are basicly non existant and the big comercial stuff is to expensive.. Your build rly goot me thinking, looks simple to make and i could put it on my attic and duct it down in the house like a cealing vent. Curious to see whats next .. Would like to see how you tested efficiency , what was the indoor temp and intake temp of the fresh air and stuff like that. Greets from Serbia.
Thank you so much for your comment! My heart goes out to you. I too have woken up many mornings with terrible sinus and throat problems, and even other health problems, especially since I bought the house I'm currently living in. There is something toxic in our homes that I think we don't yet fully understand. So many people are posting online about experiencing these symptoms.
At 6:44 in the video, I shared one of the efficiency test results. Here's another result from a different day: outside temp: 40.0F, Inside room temp: 68.4F, fresh air intake temp: 64.2F = 85% efficiency.
By the way, people burn wood and oil here too, and the byproducts are really unpleasant to breathe. Not coal in the state I live in, fortunately.
I hope you're able to solve your air quality issues! Reach out any time!
To improve upon your design ; if you suck the air close to the floor in your basement you'll also get Radon out of your home. Intake/exhaust on each side should be seperated by about 6feet.
You could install a ceiling fan instead of the box fan that on the chair.
Great work!
Thanks for the suggestions! You might be interested in seeing my DIY ERV installation (newer video). I made some of the improvements you mentioned.
Thanks That's a really good design. I've been thinking about how to build something like this for our home. I'd not considering using coroplast, but it's almost made for the job !
Absolutely! Coroplast is an amazing material - polypropylene is the safest plastic, I feel. No BPA, no VOCs. I think that my HRV core is pretty laborious to build though. I’m in the process of trying to find a cheap source for replacement HRV cores, so we DIYers can just build a simple HRV housing for a pre-made core. Stay tuned!
Great job!! You SHOULD be proud of it. it looks NO different than the expensive Panasonic one. Thank you for the inspiration!!
That’s very kind! If you end up making it, could you let me know how it turns out?
I've seen a dehumidifier use similar looking plastic heat exchanger to pre-cool incoming air with the cold condensate water.
Love it, considering buiilding one of these for my home too!
You could have used half the correx by using double sided foam tape to create the core, with one channel being formed by taping two sheets together. (using tape with a thickness similar to the height of the plastic sheets) this has the advantage of also reducing the thickness of plastic seperating the air channels, so heat transfer should be more efficient. (as it would be one layer of plastic rather than two layers plus glue)
Also a dual core design could improve efficeny by doubling the surface area for heat transfer.
Please describe differently. The advantage other than more direct contact of the layers is unclear.
@@Mavrik9000 Mainly just because it reduces the amount of material needed for the core, so in theory you could create a dual core confgiuration with the same material plus tape!
@@Chriz.What I mean by "describe differently" is the physical layout. I don't understand how the configuration you have described is assembled.
The stale air only needs a dust filter to keep the core clean, not a m13
I disagree. Dust filters are weak. Oddly, they don’t filter out 100% of large particles like dust. According to the EPA, dust filters remove less than 20% of large particles (3-10 microns). A better filter will protect the core more effectively, for longer.
Also, I wanted to use the same filter on the intake and exhaust so the pressures were balanced.
You are the TH-cam MVP on this subject💪🏻
Hahah thank you
Mitsubishi sell these. They are called lossnay units.
Reasonable instantaneous efficiency results, for more reliable figures use loggers and gather more data points at changing operating conditions.
Fascinating! I’ll have to check them out.
Condensation within the unit will be a problem in most climates and when heating or cooling the incoming air. Over time the heat transfer plates will grow a biomass that can (in extreme cases) include dear old Legionella - the bane of commercial air con units. So a unit will need a means to drain condensate to a waste, and a way to periodically (say annually) disinfect / clean the core.
I agree. I only use this HRV in the late fall, winter, and early spring.
I am so making a MEME from you saying “absolutely”!
Hahaha. I ABSOLUTELY love that.
Awesome! You inspired me to build one. I’ll try brazing aluminum flashing for better conduction.
Glad I inspired you! Hope you build something awesome.
A low tech "defrost mode" method is to just redirect the two outdoor ports together so the core warms up to room temperature eventually. By measuring the output temperature and only going into defrost mode when the output goes below freezing can make it automatic.
That’s fascinating, I love the idea!
For a simpler low tech defrost, you could just put it on a timer. If the unit is in the house, you could turn it off for a few hours and it would naturally warm up and defrost. That is even more low tech.
This is amazing. I now think my son should have this in the little room he sleeps in with the door closed all night. He'd be freezing with the window always open, but he has allergies and could use the filter. Plus I can imagine that CO2 levels rise in a tightly-sealed, unventilated small room with someone breathing all night. Hmm. You have me really thinking. I need to get your recommendations for the right instruments to measure air quality.
Oh, and you really are sounding less allergic. Nice!
Thank you so much! You’re spot on with your thinking. Sleeping in a tightly sealed, small room with no ventilation can cause CO2 to rise to unhealthy levels. I slept in a room like that for a while and woke up oddly groggy every day.
Yes, opening a window is a bad solution due to cold of course, but mainly because small particles like car exhaust and byproducts from peoples’ heating systems can drift in in unhealthy quantities. Not to mention allergenic particles, which tend to be larger and less systemically harmful.
If you’re interested in good instruments to measure air quality, check the bottom of the description of this video for the ones I used :) Thanks again!
A known problem with the above coroplast heat exchanger design is it can only transfer heat to the incoming air theoretically maximally by 50% because of Laws of Thermodynamics,. A consequence is room gets chilly, if indeed not quite as cold as as a naked open window would make it.
There are also designs which use a pipe within a pipe, and a different mechanism at the window to exchange heat, I believe by merely mixing and not separating in and out air streams. It can be piped further into the building to the isolated spaces needing air. When it gets there its room temperature warm.
There are small round through wall units for sale, which by principle of operation, when placed across the house or large room from each other will conspire to coordinate taking turns breathing out while other breathes in @ 15 minute intervals (configurable), reducing cold island effect. Don't want little Johnny to miss skool becuz of the sniffles.
Nice build. Anyway next time consider brushless centrifugal fans and also damper to allow the unit work in "circulation mode", in mine, is also built-in cheap AC unit, so mu unit can also cool and heat...
Thanks! I’ve tried to find centrifugal fans but I’m not able to find one that is reasonably priced, well-made, and also delivers a good amount of airflow while being speed adjustable (for quiet operation if needed). Let me know if you find one.
The AC infinity fans I use are actually mixed flow fans, so they’re basically a combination of axial and centrifugal, which I find to be great for a DIY application like this.
you can use the air gradient system to measure your co2 and pm ratings
Dude. You’re an awesome enthusiastic presenter of your creations. I’m thinking of something like this for my large garage. Maybe not quite this big tho
I appreciate that you like my presentation style! If I could do this HRV project again, I’d build it smaller. Maybe with 2” thick filters instead of 4” thick. And with more powerful fans.
@@HealthyHomeGuide In your newer videos you don't seem to be using this design. Is there a reason? Thanks
@@ww-pw6di I appreciate that question. I haven’t used this HRV since the spring because I’m too afraid of mold growth to run it during more warm/humid seasons. During the warmer months this past year, I used my DIY fresh air intake for ventilation, but there were limitations to how much I could use it during warmer, more humid stretches.
I’m now using an ERV for year-round ventilation (+ a whole house dehumidifier in the warmer months). I’m actually working on an ERV installation video (for those of us who don’t have ducted homes).
For the record, I still think my DIY HRV could be a great budget option in colder, drier months.
@@HealthyHomeGuide Thanks for the reply! Was the mold concern in regards to the box or the core getting moldy or rather the humidity causing mold growth elsewhere in the house?
@@ww-pw6di You ask very smart questions. I was concerned about both, to be honest. I’ve learned hard lessons about how careful I have to be with introducing humid air into my living space. Because I’m very sensitive to mold.
It would so nice to recover moisture also!
Absolutely. I’m actually working on a video where I do a DIY installation of an ERV. I didn’t build the ERV, but I built a system to retrofit it into a window. Stay tuned.
It would be nice to see examples of external house wall holes that pass permit inspection. Hole covering would include everything needed to simply unplug whatever DIY HRV solution you have in place to easily sell your home.
I like that idea. I think I’ll eventually look into that.
Thanks for your videos! I don't sub often, but you've earned it 100%. Also, noticed a rebounder/Cellerciser in your living room...just wanted to confirm it's an actual Cellerciser! They're great aren't they? Any tips or tricks you've noticed while using it? Thanks
I love to hear that, thank you! It is indeed a Cellerciser - such a good quality product. I like to swing my arms forward and backward while bouncing to get the lymph circulating.
Wow! Excellent job, I'm definitely going to build something similar
Thank you! And good luck! Let me know if you have any questions.
@@HealthyHomeGuide do you know how well this would work for hot and humid Texas summers? I know an ERV is what I need, just didn't know if that poly might work well for that or if I needed something like an aluminum core. Thanks!
@@Slipperypuffin Yup, an ERV (as opposed to an HRV) would absolutely be the way to go for the specific reason of ensuring your home didn’t pull in too much moisture from the humid Texas outdoors. If you have the budget and space, I’d recommend buying an ERV, because I’m not sure how to actually build one.
If you want to try an HRV instead (which won’t get rid of humidity) coroplast could certainly work because coroplast is moisture resistant. Based on what I’ve seen, a coroplast core should do fine at cooling the incoming air in the summer, you’d just probably need some sort of condensation drain.
Now add a solar preheater to the inlet and crank that efficiency up.
Great project, even if the efficiency did not quite measure up. I would argue however that anybody building one to install in an older home should dive deep into already existing air infiltration issues. Just a few poorly sealed holes in the framing can cause a hidden issue through the entire home, even through interior walls over crawlspace construction. The pocket hole doors originally built into my home permitted an absolute blast of air through them when the house was pressurized, much of it likely coming from the crawlspace. (I sealed the pocket doors in entirely.) Even the catch on the jamb for a door latch became an obvious breach that a little caulk easily fixed.
If you're chasing every last % of efficiency you could make your own fine channel aluminum heat exchange core. Get two or three Fiskars 9340 paper crimpers with metal crimp rollers. The rollers are the parts you'll want, to put together end to end on a common shaft because they're only 6.5" long. Might need to double up on the crimpers if only one roller in them is aluminum. You'd have to build a custom frame to hold them and add a long hand crank. For metal, whatever thickness is used for offset printing plates would probably be ideal for the corrugated channel sheets. To separate the corrugated sheets use heavy foil, the thickness used for single use turkey roasting pans ought to do. I'd expect thinner to be better for heat transfer. Can't go too thin on the corrugated sheets gauge because the core would need rigid plates on the sides and a way to compress it to ensure good contact between the corrugated and flat sheets to block bleeding of air between in and out paths.
It would have to be more efficient with heat only having to cross one very thin, highly heat conductive sheet of heavy aluminum foil VS two layers of plastic that don't transfer heat anywhere near as well as aluminum. Any bet it'd be over 90% efficient at heat transfer?
Fiskars makes a wavy version of the crimper, model 9341. Wavy channels would make the air slower, with a longer path through the core, but those crimpers look like the crimp rollers are all plastic.
This is quite honestly a brilliant idea. Thank you! I did some corrected efficiency tests and my HRV actually turned out not to be 85% efficient. It’s more like 60% efficient. See my pinned comment for more details!
Clever to recognize coroplast as a useful material! Its thermal conductivity would suck compared to metal, but if the dwell time of the air inside then heat exchanger is long enough, that will compensate: Half the conductivity? Just double the dwell time. 1/4 => 4x, etc, etc.
It seems the duct fans are working fine for you, but a cheaper and potentially better solution could be a used squirrel-cage blower from an HVAC system, with the speed adjusted via either a cheap A/C speed controller (triad plus noise filter) or by putting a small motor on it, running it via a timing-belt setup (the kind of timing belts used for 3D printers. Squirrel cage blowers are great when dealing with back-pressure from filters or the stack itself.
Amen! Great points. I did indeed make the core larger to increase dwell time.
I had never heard of squirrel cage blowers, and that sounds like a fascinating idea. I guess they’re a high static pressure blower?
@@HealthyHomeGuide Exactly. They use them in HVAC systems to overcome the static pressure from the filter and all the ducting, registers, etc.I don't know the details of relative efficiency, etc, but you'll find them any time there's higher static pressure. (The rotor/impeller is an open-ended drum with angled slots around its periphery. The name comes from looking like something a squirrel (or hamster?) would use to exercise in :-)
The blower from a home HVAC system would be grossly overpowered for your application (and probably too big as well), but any time a furnace/air-handler is being changed out because an HVAC system is being completely redone for some reason, chances are the blower will still be good; I don't know if I've ever seen one wear out and have to be replaced; at least not in any houses I've lived in or owned.
You'll find smaller ones inside air conditioners and dehumidifiers that might be more size-appropriate for your use, but it might be a wrestle to get one out of a junked unit because they're not built for easy replacement.
@@DaveEtchells This is absolutely fascinating. I think I’ve seen the type of blower you’re referring to. I’ll put this on my list of investigational projects. Gotta see if I can find a smaller one - I suspect that one of these blowers might groan if I used an A/C speed controller to try to dial it down. I tried using an A/C speed controller on a very powerful duct fan and it wasn’t pretty haha. Lots of electrical moaning.
@@HealthyHomeGuide Yeah, I’d need to check, but now that you mention it, I think you can only speed-control universal motors, not induction ones :-/
The Panasonic NanoeX does an excellent job of reducing VOCs, if you can get your hands on one.
I’ll check it out, thanks for the suggestion.
It would be pretty easy to make that design with slight alterations self-standing on the floor and to act as a window shelf.
Very true!
That's an interesting design. I've actually seen a very similar design (using coroplast) from an HVAC company that fleeced me thousands of dollars some years ago for an HVAC design that included one of their custom ERVs. I got suspicious after seeing that they didn't have a test in HVI database, and after seeing the docs that they sent me, it literally showed 0% humidity recovery for their "ERV". Which made sense, since this type of design is non permeable and cannot recover humidity, making it an HRV only solution. Didn't have the time nor energy to try and get my money back.
Damn, that’s absolutely insane that that company had the audacity to sell an ERV with 0% humidity recovery. That’s laughable. It’s like selling a car that gets 0% gas mileage.
@@HealthyHomeGuide Yeah... the person in charge previously worked for ASHRAE in a fairly high ranking position too, which made me not as suspicious as I should have been initially, so it took too long to figure out that I'm being essentially scammed.
By the way, and I might have missed this in the video, you should consider using ECM 0-10v blowers as they're much more efficient, quieter, and easier to control using industry standard means. Makes balancing easier too.
@@parak4593 they worked for ASHRAE!? Unreal.
I did use fans with EC motors - do you think blowers would be better in this application?
@@HealthyHomeGuide Yeah the company is still in business too, continuing to sell what I think they call a "polymer fixed plate" core "ERVs". Oh well.
Yeah if you're already using EC inline fans that you can easily vary speeds on, then it's already all good.
Planning on ducting it by any chance? Exhaust from kitchen and bathrooms, fresh air supply to bedrooms and living and all that. Don't need to use large duct either, I think Zehnder for example uses only 3" ducts. Then you can do more neat stuff like set up boost modes for a limited amount of time when cooking and such, though you'd optimally want a recirculating hood there, but that's a separate subject hehe.
Chloroplast may work, and you appear to have built this one sufficently large to get fairly good efficency at the rate of air exchange.
But, know this. Plastic is inefficientl at moving heat across a given surface area. Your heat exchanger could get comparable efficency with a smaller design if the core were made of sheets of aluminum seperated by small three or four spacers each layer. Or you could achieve significantly higher efficency with an aluminum core built to to your existing core size.
i love this!! thanks soo much for sharing your creation and findings! soo helpful :)
You’re so welcome!
Thanks for this video! I think that you could make that box into a vertical version if you used plywood for the largest sides. It would not need to be more than 3/8" thick to support that core. Probably 3/16" would do. I bet masonite or "bath-board" (which has a nice finish on one side) would work very well. Adding some 1/2"x1/2" wood pieces in certain corners to further stiffen the housing would help as well. (even if using your current materials for the walls)
I think that you might get more efficient airflow if you used some internal ducting to reduce turbulence between the air inlets and the filters and the air outlets and the core. (The shape of the chambers the air passes through is probably causing a lot of turbulence) A piece of thin poster board could be formed into a cone that is the diameter of the inlet at one end. The other end could be creased into a square to fit the filter or core. (the circumference of the filter/core end should be equal to or slightly larger than the perimeter of the filter/core in order to fit) That would give you a custom duct for very little in the way of expense and effort. Another good material for this would be a used printing-press plate. They are usually aluminium and can be gotten at any place that prints posters etc on a lithographic press.
A layer of radiant-barrier material (like ArmaFoil from EnergyEfficientSolutions d0t c0m) over the block in the window and on the inside of the walls of the housing of the HRV would insulate the system and increase the efficiency a little more without adding much bulk or weight.
You could also make the core out of the lithographic plates I mentioned above. Just cut out a rectangle whose long side is longer than the short side by twice the distance you want between plates. Then fold the edges of each of the short sides down by the distance you want between plates; so the profile is like a very wide staple or 'u' shape.(if you cut them out and folded them right; they should be square now) Then you stack them alternating the sides that are closed by taping the folded edges to the unfolded edges on the next plate. You could use hvac foil tape for this to get maximum efficiency. This setup has three advantages over the current core design: The first is that aluminium transfers heat much more efficiently than plastic. The second is that the single layer walls would be more efficient. The third is that there would be better airflow through the core because of the undivided center of each layer. (A tip for cutting lithographic plates is to use an xacto knife and a straight edge. You do not need to cut all the way through. Just score it well and then bend it at the score lines and it will snap)
These are great ideas, thank you!
Very nice. Now I want to build an ERV
Glad you enjoyed it! To be clear, this is an HRV, not an ERV. I’m not sure how one would go about making a DIY ERV, but if you find out, do let me know!
This is exactly what I was looking for. Thanks.
Glad you found it useful!
I think the main thing stopping you from having better efficiency is the cross-flow. Your two airflows are perpendicular to each other, and you can get better heat transfer by having contraflow instead, where the airflows are in opposite directions. However, that makes construction slightly more tricky, and probably can't be done with the materials you are using, as the airflow needs to change direction in the middle of the core, and the core needs to be longer to have that contraflow section in the middle. I'm considering making a unit with (very cheap) aluminium foil, but I'm not 100% sure it is durable enough.
You’re absolutely right. I want to make a counterflow core eventually for that exact reason. Do you know how you’re going to mold the aluminum foil into channels and make it rigid enough to hold its shape?
It would be nice if there was a good filament that could 3D print a large 300 x 300 x 300 mm core. Maybe a filament that can easily be coated in copper later?
@@23lkjdfjsdlfj I like that idea. I wish I knew more about 3D printing. Someone has to do that.
Filtering the fresh air isn't a bad idea. I apply herbicides all day, but stop near evening because of the inversions carrying the product to unwanted places. I live near the field and wouldn't mind having something like this. Pretty big though.
Yup, temperature inversions are really disconcerting. If I were to build this device again, I’d do it with 2” thick filters instead of 4” thick filters, and I’d make the housing smaller.
Thank you for sharing this, truly. Definitely a thumbs up! Sharing knowledge and experience like this this is the internet at its best. Also nice to give credit to your sources at the end.
Question 1: High effective is 85% as compared to a commercial system? I could do my own research of course but in case somebody knows already ...
Question 2: Did you consider alternatives to spray adhesive for laminating the plastic heat exchanger stack? I am thinking it is an unnecessary source of VOC’s? Are there “healthier” adhesive options or am I being overly concerned?
Question 3: Would efficiency increase with a heat exchange filter material of greater thermal conductivity like copper or aluminum?
A am pretty sure moisture build up would be an issue if installed “properly” with outgoing air coming from high air moisture areas like bathroom, kitchen and laundry rooms however. But in any case really cool build!
What I need an HRV/ERV for is to lower the CO2 levels in our very air tight 1100sq/ft home with propane cook surface, 2 adults and 2, 80lb dogs. The CO2 levels quickly rise to over 2000 PPM without exhaust fan running and periodic use of the whole house fan with doors open. High CO2 levels cause headaches, drowsiness and other health problems. I bought a quality Ambient Weather indoor AQI monitor which tracks 2.5micron and 10micron particles as well as CO2 levels with reasonable accurance and was shocked at the dangerous CO2 levels we were living with.
Your thinking is spot on. In a tight house with that amount of occupants, CO2 levels can certainly rise to unhealthy levels. What is even more important for health than CO2 is VOC levels, which recent research has shown are up to 100x higher indoors than outdoors. That’s why it’s even more important to dilute your indoor air with outdoor air.
Thank you for this wonderful news! :-) Great inspiration! ... And I like your humor! ... lol
I see it as great news as well, thank you! Glad you’re on the wavelength.
Nicely done! Corbett mentioned this video in a video he uploaded today.
Glad you enjoyed it!
Such a great design! I may build something like it for my place. Wonderul.
Good luck!
A build video would be interesting. If you feel like building another one, I'd appreciate that.
Fantastic. Great useful information. Thank you. Cheers J
Cheers to you! Thanks 😊
8:52 Condensation needs much less air movement. You always deliver fresh energy, to evaporate the condensate. This is a great factor for efficiency at large temperature differences, but what can you do🤗
I can’t believe the efficiency from polypropylene. I”m pretty sure it has thermal conductivity 1/1000th that of aluminium.
this is so rad!
Hell yes! Glad you liked it.
Very cool. I’d love to see a full build video with parts and dimensions. I’m already wondering if I could fit this in the top of my entry closet. It’d require drilling holes in my exterior wall and the closet wall, but it’d solve the obstruction and looks issues here. Also curious to see the process of changing the filters. If you have to open the top for maintenance then this install location might not work (though I guess you could put it on the floor of the closet instead).
Thanks! I like the idea of putting it in a closet. To give you a rough idea, the housing is 36"x30"x14.25". I do indeed have to open the top cover to change the filters. It's fairly simple; I just secure them in place with a couple strips of tape. I put weather stripping around where the housing contacts the top cover and then secure the top cover down with clear, low VOC tape.
@@HealthyHomeGuide Great idea with the coroplast! Did you use the 4mm or 10mm?
@@Gnavitas thanks! I used 4mm.
Very cool to see the concept in action. If the plastic transfers heat so well, wouldn't you need another material to insulate the connection to the window?
Great question! I am using weather-sealing tape to ensure that cold air doesn’t blow through small cracks at the edges of the window insert. As for the plastic insert itself, coroplast has a 4 mm layer of air in between its two plastic layers. The air acts as an insulator.
Also, the plastic isn’t actually that fantastic at heat transfer compared to something like aluminum. The coroplast insert doesn’t seem to get that cold.
Cool, consider to separate the outside in and out to ensure you don't mix the out air with the in one!
Definitely. I ended up adding some duct attachments that channel the air in different directions
I Would like to see how adding thermal paste in-between the panels would perform...nice video
Hi, what a great job - well done! I may have to put one in my home. Would you do a design drawings for my house size layout if you could?
PS: for heat recovery and fans, I decicded to go with commercial solution which was in just about 600€, so I added only control, dampers for circulation mode and AC unit for cooling and heating😂
Congratulations and thanks for sharing. May i suggest you change your filter with 3M by example. Filter buy are not good filter. go see the Consumer Reports tests. A lot of merv 13 filters are actually not real good. 3M, Nordic Pure and Air Handler are good choices, to name a few
Agreed. I use 3M filters now. In my latest DIY build (an air purifier), I used 3M filtrete.
Very cool. 🤔 I like the idea of a charcoal filter, but I'm clueless where you would put it in the system. I'm building my retirement home in Arizona (a cute little hacienda style cottager) and I want to incorporate as many DIY solutions, and revive as much ancient technology as possible. Thick adobe walls will go a long way towards providing the thermal mass I'll need in the desert to moderate temperature swings. I think instead of the plastic body you could use ducting sheetmetal or the smooth fibreglass boards used in commercial kitchens, hospitals, etc. Both materials would give the same smoothness, but would be a lot more robust. Mine is NOT going to be proudly displayed in the living room! Sorry, although I'm now retired, you can take the girl out of the interior design business but... I plan to properly tuck it away in a conditioned attic space and cleverly vent the clean, temperature-moderated air throughout the house in inconspicuous or decorative ways. Can't wait to binge-watch some of your other videos.
Thanks Linda! I ended up using two 2” thick activated carbon filters that look similar to the filters I showed in this video, they’re just black. There are two available spots against the core where they can rest, in the same manner as the MERV-13 filters shown in this video.
I deeply appreciate your philosophy when it comes reviving ancient technology. I’ve been learning about Terra Preta recently - very cool ancient tech.
I used coroplast for the body because it’s very easy to cut, lightweight, non-toxic (polypropylene is BPA-free and does not off-gas at all), durable, moisture-resistant, recyclable (polypropylene is a thermoplastic that can be recycled), and CHEAP. I wanted to build it all from one cheap material, but I appreciate your point about the robustness.
Your interior design-friendly plan sounds amazing. If you end up doing that, I’d be happy to make a video featuring you on this channel if you’d like. Good luck!
@@HealthyHomeGuide 🥰 That you're a gardener. My favorite terra preta video is by David the Good th-cam.com/video/DnTaWiO5Eso/w-d-xo.htmlsi=xiT9K3iHJjA2ySeZ. I'll save you the suspense: it worked great, but David moved to new land and it petered out in a year. My theory: the deposit he created was only 3' deep. The deposits in the Amazon are frequently 60' deep, and were renewed annually for centuries. I think David's on to something, but I also think that it needs renewal every year for many years to become self sustaining. Enjoy!
commercial units I've seen have the schematics placing carbon sheets between pre filter and merv filter.
@@mikemotorbike4283 Yeah. That makes sense. But it's only a "sheet"? Huh. I didn't know that, I thought it was like the air filter, about 2 inches thick and approximately the same size as the Merv filter, just black. Interesting. Thanks for the info!
Yeah, you earned my subscription. Looking forward to more of your content.
I love to hear it! I’m coming out with some cool stuff soon.
Seriously though, well done you.
Much appreciated 😊
I'm looking into this myself as I'm struggling with keeping the cat litter smell at bay now that I have two cats, and great to see that this design with the plastic actually works well. I would have figured it would not have enough thermal conductivity. I might have to experiment with this and see if it will help. Right now I'm just opening the windows but that won't exactly be an option in the dead of winter!
Thanks for bringing this up! Ventilating is a great way to keep odors like cat litter at bay, but also comes with its risks if not done properly. If you haven’t seen my latest video yet, I think it’d actually be really relevant to your situation:
th-cam.com/video/80r9qwJPcTI/w-d-xo.html
The thermal capacity of air is so low compared to most solids that the conductivity is not too much of an issue. Conceptually, if you think of the HRV in a steady state of operation, there is a thermal gradient along each of the channels constantly re-enforced by the air passing through at almost the same temperature. The transfer of heat between the channel wall and the air is likely far more limited than the transfer of heat through the thin plastic wall. I built my own DIY HRV just using a BIG pair of concentric plastic pipes connected up to ducting. Primarily for ventilation, but why wouldn't you want some heat recovery? Capable of higher rates of ventilation as the airflow has little restriction, but better heat recovery at lower speed.
Drainage - I don't believe that you need a big slope to ensure that water will drain. You may need to balance the wetting of the surface with the size of the passages so that the droplet sizes (should they form) don't block the flow.
And just because the exchanger flow may pass the dew point, doesn't mean that there is energy exchange available to cover the latent heat part. You'll need to try it in a shower room (warm wet air) with exchange to a cold wet rainy exterior....
this is one of those (awesome!) things that works in specific climates. Another example is a swamp cooler. If i used this where i live my house interior would be covered in slime mold, too humid. Same with a swamp cooler. 😞
You’re absolutely right. I only used this HRV in the late fall, winter, and early spring when it’s not too humid. I took it down once the humidity came. The last thing I want is mold growth because I’m really sensitive to it.
You say that, but assuming your house is warmer than the outside then the HRV will still help reduce humidity inside.
Don't use carbon filters, they only absorb to equilibrium, then they re-emit when they get any warmer than that. The only way to make them work for a length of time requires periodic desorption cycles like a desiccant based dehumidifier.
That’s super interesting, thank you! I’d never considered this - I’ll have to do some research.
Excellent !! Thanks !!
You’re very welcome!
@@HealthyHomeGuide It s so simple and efficient !!!
Impressive and inspiring, thank you. For someone interested in trying this, why coroplast, other than it comes pre-corrugated for maximum surface area? Wouldn't metal plates work better at transferring heat? (but much more time-consuming to pleat by hand). Maybe the fins from old A/C and HVAC equipment can be repurposed for this. Amazing effort and spirit, blessings and apprecation.
I appreciate that, thank you for commenting! Good question. I used coroplast because it’s very easy to cut, lightweight, non-toxic (polypropylene is BPA-free and does not off-gas at all), durable, moisture-resistant, recyclable (polypropylene is a thermoplastic that can be recycled), and CHEAP. I wanted to build it all from one cheap material.
Coroplast transfers heat pretty well. Some commercial units built today actually use corrugated plastic for their cores!
I also don’t know how to cut metal, bond it properly, clean it right, and work with it safely in general (especially with old potentially rusty parts). For someone with expertise there, it could be cool!
Thanks again for your great question!
I have an existing HRV that is starting to show it's age (getting noisy) and replacing the fans would be something like 1200-1500€ so I am thinking about getting a new one. Doing some DIY work on it with third party fans is something I have been thinking about, but the original fans are custom built and I have been unable to find duct fans that I can properly control. The originals are radial fans and built specifically for the HRV...
Could you please post a list of materials used? I have no idea what kind of fans to get.
Thank you for asking! I’ve posted the tools and materials list at the bottom of the video description. The fan is on that list. Let me know if you have further questions.
Well done and nice and cheap. I well remember last century, pre internet, someone had constructed a very efficient HR unit out of pleated paper! Large pieces of paper, folded about every half inch or centimeter and laid cross ways like your core flute and connected just the same as yours. The paper being thin, had excellent heat transfer properties and low impedance to air flow. Question would be, how would it go in high humidity? Maybe spraying with a mixture of something non toxic but hydrophobic would be the answer. Plant wax?
I'd say your set up would suffer losses because if the poor heat transfer of the double layers of coreflute. I have seen single sided stuff around. That would improve efficiency. Maybe single sided corrugated cardboard would be the go?
Great video, could you please go into detail about how you made the Coroplast Square core? Thx for sharing your videos
You’re welcome! The videos I linked in the description are very helpful for demonstrating how to build a core. The one by Designed by Instinct is particularly useful.
Cool.
Thanks!
Now that your video is 6 months old have you inspected and cleaned the cleaned the HRV and particularly the core yet? One of the biggest hidden dangers of HRVs is that they require maintenance which could easily be skipped and result not just in decreased performance, but also mould growth in the core which would negate your efforts to improve air quality. You stated that your core is horizontal and hence is not able to be drained and that you didn't expect any difficulties due to your climate which may be a correct assumption, however the only way to know this is empirically. I would be very interested in the results of an inspection.
Thank you very much and all the best.
Good question. I inspected and cleaned it when I took it down at the end of the spring when the hot/humid weather came. The filters were very dirty and the core was clean. Still, I gave it a soap bath to kill any invisible mold spores/particulate.
The air is dry in northern Vermont in the winter, so condensation wasn’t an issue in the core, likely because coroplast doesn’t become as cold as, say, metal. There were times when the metal ducts developed condensation, but nothing major, and nothing that caused mold growth.
I didn’t use my HRV during warmer weather because I’m too afraid of mold growth. Instead, I used a MERV-16 fresh air intake that I built (I have a video on it). This winter, I’m probably going to install an ERV in my window. Stay tuned for an installation video.
@@HealthyHomeGuide Very interesting.
I am no HVAC engineer though I have some college HVAC knowledge, which leads me to think that the biggest contribution to high moisture in the core would actually come during the winter when moist warm indoor air would have the temperature reduced enough in the core for condensation to form (ie this air would reach its dew point).
I look forward to your future videos.
Thank you again! In the interest of full disclosure, I just posted a pinned comment in which I discuss some corrected efficiency tests that I did. My HRV turned out not to be 85% efficient. It’s actually 60% efficient. See the comment for more info!
Great work! I'd place in the attic or at least that is what I planned to do with mine. I assume you saw the Hackaday HRV and maybe also my comments there and his youtube videos.
I bought a few rolls, and even got some for free, of aluminum window screen. The thought was at some time 3D printing or maybe CNC in wood a tool and die to stamp like a linear ridge zig zag stamp so to increase the surface area of the alternating layers. I also found an old hair iron crip wave thing that is close, though small.
I plan to only space the one path of flow and use corrugate on the other path. The spaced path that would use two other maybe three strip of one width corrugate tubes would have the zig zag aluminum mesh. I left off wondering how to plastic weld both sides into the full sheet of corrugate. The other thought was just ironing into both side of the corrugate the aluminum screen. That might work suitable as well and just then placing the zig zag screen into contact.
I probably should work on again since I have now another size of corrugate material, 4mm, and not only the cutout 12x12 inch larger thickness 10mm corrugate.
What thickness corrugate did you use? Thanks for sharing. Great to see more of these designs being made successfully and cost effectively.
Thanks for the comment! I’d be curious to see how your design turns out. I used 4mm corrugated plastic.
@@HealthyHomeGuide I'll remember when I do and try to report back. I'm sure I'll post something on here as well. Your welcome and thank you! Very inspiring and yet creative.
Very nice! Hope you have other projects to show off as I just subscribed to your channel.
Nice design. Do you get a build up of water inside the unit?
Thanks! If you’re interested in knowing how this HRV performed, I made a video on it: th-cam.com/video/LiptsaKmq80/w-d-xo.htmlsi=V-saehGltDKRwl6c
@@HealthyHomeGuide thank you 😁
Well done.
Many thanks!
Can you repurpose UFH components to use in a ceiling for cooling, hooked up to a heat dump somewhere?
That’s an intriguing idea, thank you!
Hey. Nice video. I have a few questions if you don't mind fielding them. I also have a few tips. I use a similar Panasonic unit, but I made modifications to it (some similar to what you made).
1. It looked like you had a filter for your exhaust air (right before the air entered the heat exchanger core). Was that to prevent dust from getting into the core and clogging it up when the walls of the tubes got damp?
2. I either missed it or you didn't say. Did you lay the sheets of corrugated plastic at alternating right angles to each other as you stacked up that core? Cool idea.
For tips, you should DEFINTELY separate the intakes and exhaust vents as soon as you can - especially for the inside outlets. I'm sure you're immediately dumping a fair bit of your newly pumped in fresh air. As soon as you can spread those apart, do it. If you have a radon issue in your house, consider grabbing the air to exhaust from down in the lowest part of your house. If you have any occasional smoke (like from a fireplace), consider grabbing air to exhaust from up high where smoky air rises to. Overly humid bathroom would be a good place to collect waste air too. You get the idea. Consider dumping fresh air where you want things to dry out. Mine dumps over my kitchen sink where I do dishes. The dishes dry in no time. That wasn't planned ahead of time, but it's appreciated.
Those fans are awesome by the way. I use those for venting air all over the place. I use that exact 6" model for running hot air under my concrete floors to warm them like old Roman baths used to. Very reliable.
Great video. Thx for sharing!
Thanks for watching!
Yes, I filtered the exhaust airstream before the core to prevent particulate (mostly dust) from building up in the core. Factory made units generally do this too.
Yup, I laid sheets of coroplast at alternating right angles to form the core.
Agreed. After this video came out, I installed elbow duct attachments to the indoor supply and outdoor exhaust to the direct the air streams away from the intakes 🙂
Thanks for the tips! Using fans for indoor air circulation works for drying as well.
That’s good to know that you find those fans reliable! Thanks so much for your support.
Don't thank me for watching your videos, thank YOU for taking the time to make them. As a fellow TH-cam creator, I know we don't make much on most of our videos. Although with 66K views, that's got to be adding up to at least something, but still generally (for me anyhow) less than I'd make if I were doing a normal job at minimum wage. Making videos is def more fun though! @@HealthyHomeGuide
@@PraxisPrepper I actually just got monetized this week, so I won’t make anything on the $66k views I had racked up before monetization unfortunately. I’d love to make TH-cam my main career eventually because it’s so fun. I’m hopeful!
Best luck in that endeavor. I'm definitely no expert at it, but I can share a few bits of advice from someone who's been doing it for a bit.
1. In my last 3 months, my channel had 57k views and that resulted in $275. So that's a bit of a ballpark.
2. Not all videos seem to be treated the same when it comes to payments for ads. I've had many videos with pretty much the same views and numbers of ads per video get wildly different revenue amounts. So just be aware of that.
3. TH-cam is definitely serious about pulling down one's channel's ad impressions (which are what lead to views) if one does things that aren't popular at the time. I also run a channel that's all about different language learning for kids (alphabets, counting, simple math, colors, etc.) Some of the lessons that I've posted in the past have been in languages like English, Spanish, Italian, German, Russian, Chinese, etc. Those were all very cool with TH-cam until recently when I posted a video teaching the Russian alphabet and that day my channel got pretty much shut down (meaning going from consistent thousands of views per day to consistently just a few dozen views per day). I guess Russian anything (even the alphabet) is taboo now. I've experienced similar things during covid in regard to items such as back when the official public word was that it wasn't airborne and I openly spoke about how I thought it very likely was actually airborne (given that it was a type of coronavirus and those are commonly spread through the air). It's hard to predict (for me anyhow) but sticking to truthful things or reality isn't a shield for your channel. Where you do a lot of videos about health-related topics, just be aware that if you make a video about something that's totally 100% true, but that truth becomes controversial (like cold viruses being airborne), it can create a big issue in terms of growing your channel. Again, I can't offer any specific advice, but I share that reality with you so if it ever happens to you, you'll understand what's going on and won't think you're alone in your treatment.
4. Last, I recently found out that TH-cam has a blacklist of videos that (for undisclosed reasons) they don't send ad impressions out for. I recently created a short video (the vertical TH-cam Short style) and it had a 100% CTR, an average viewing duration of 250%, and 100% likes. But after more than a month, TH-cam had only given it 22 ad impressions (several tens of thousands is more what I'm used to). I was on with a TH-cam tech for about an hour (using it as a case study) to try to understand why that video wasn't being shared at all. They refused to give specifics, but told me that TH-cam keeps a list of videos that are deemed "ineligible" for ad impressions. I still to this day have no idea why. It was just some silly short about an AI image Id created that looked weird in how it came out. Totes vanilla content.
Anyhow... welcome to the wild world of TH-cam creating!@@HealthyHomeGuide
@@PraxisPrepper Thank you for that. Hearing about the nuances of your experience is really helpful. I’ll be on the lookout for all those things.
My first observation is that since being monetized on October 16th, my views have gone down significantly. Like, a stark difference. Night and day. Before monetization, I was getting 1500 views per day consistently, and after monetization, I’m getting 500.
You would get better heat transfer if you only used a full sheet of coroplast every other layer. The intermediate layers would just use a strip of coroplast at the edge for a separator. Of course the downside is that it would unbalanced.
The biggest drawback is intake being right next to outtake, so probably not so efficient or fresh.
I disagree for two reasons:
Firstly, I measured CO2 levels with and without the HRV to ensure fresh air is being brought in, and it is. Data for that is in the video.
Secondly, one of the ducts extends further externally than the other. So one extends 2 feet outside and the other extends 1 foot, which helps them avoid exchanging air. It's difficult to see in the video because the longer outside duct curves downward. Internally, since I released this video, I actually put a curve in the supply outlet, so it blows in a different direction that the return (exhaust).
@@HealthyHomeGuide To be fair to Beny, it is difficult to tell the extensions of your intake/exhausts from the presentation. Given that, one addition that you should check is the distance of the intake to any other exhausts on that side of the house (and this includes windows-unless they are never to be opened again). Normally, 5' seems to be the magic number. Good job on the rest.
Great job! I've seen a similar design on "build it solar" website before, but good to actually see a working prototype.
One question: do you get condensation inside your core? Some HRV design includes a heating element to combat the condensation.
Thanks so much! I used this HRV only when it was dry outside in the late fall, winter, and early spring. So I didn’t run into condensation issues. I’m too paranoid about mold growth to use it in the more humid months. But I am working on a DIY ERV installation video for year-round ventilation. To be clear: I’m not making the ERV myself, I’m installing it myself.
I built the unit you saw on Build it Solar back in about 1988 or so. The painted plywood enclosure was around four feet square, as I recall, and about one foot deep. The core was a stack of coroplast sheets siliconed together. I had no way of measuring its performance at the time but it worked very well in our small cottage. All these years later, I'm thinking about doing it again for our off-grid home. Yes, it IS do-able for the do-it-yourselfer!
Very interesting, but we need a better way to warm air and cool air in the opposing seasons. Have you had any such thoughts for folks who want/need to have highly efficient homes as far as energy consumption and insulation goes?
As far as year-round ventilation goes, ERVs are the way to go. I’m actually working on a DIY ERV installation video. To be clear: I’m not making the ERV myself, I’m installing it myself.
@@HealthyHomeGuide hmmm, I'm thinking about options that would facilitate a highly flex