HVAC Ducts Reality Check: Are Ductwork Systems Dumb or Essential?
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- เผยแพร่เมื่อ 11 ม.ค. 2023
- Just wanted to spell out why central duct systems are a central part of ANY home design. Yes, ductless mini split heat pumps are awesome. Yes, radiant flooring is comfy. Yes, lots of people use decentralized HVAC strategies around the world and are happy with them (or at least they don't know what they're missing).
Duct systems can be used to filter and deliver healthy air to every room in the house- humidified/dehumidified, diluted with outdoor air, and pressure relieved for kitchen exhaust.
Learn more about designing ventilation and HVAC in general at: BuildingPerformanceWorkshop.com
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Our home located in the Hudson Valley in NY was built in 1987 with a joke of an HVAC system. The return consisted of two 4 x 10 inch vents for a 1900 sq ft house! The ductwork was fiberboard of some kind. Shortly after we bought the home the oil furnace heat exchanger was found to be cracked and couldn't be repaired. We replaced the furnace and they enlarged the return but only minimally and as we were new home owners had no idea there was still a problem. A few years later we got a heat pump and finally put in a properly sized return system. In the early Spring of 2021 the furnace started leaking heating oil which filled the house with an awful smell requiring us to open every window and door to vent it. Faced with repairing the furnace and replacing the 34 year old oil tank we decided to install Geothermal and avoided a mini split system because of all the hardware and maintenance. It required completely redoing the ductwork (a very big job) and upgrading the electric pane to 200 amp service (lucky this only required replacing the panel). After all is done we have a 5 ton Geothermal System, completely new, properly sized and insulated all metal ductwork and 200 amp electrical service. We are extremely happy with the decision and have also added solar and an electric car. The solar system is big enough to power everything and our last electric bill was -$415 reflecting what we had over paid to the electric company in 2022. Sorry to be so long winded!
That’s great to hear, Chris, keep up yhe great work for your family
you skipped the $50k-100k part that saves you $500/mo
@@justthink5854 Actually the system to date has saved us $7000!
Your dedication to your craft is admirable. It's obvious you have an analytical mind and it so benefits your viewers here. I am disturbed at how many people seem satisfied in having a living space with no fresh air for months at a time. We do get used to lousy air in the home. And that's a very dangerous adaptation.
your home is typically more ventilated than you think. especially if you have kids. open and close your doors and windows
@@claudecoleman8315 No it's not. That's why people say when they go out they like the 'FRESH AIR'. As in inside is stale air. Which is because the oxygen content has been depleted and there's too much CO2 from our exhaled breath. It's very simple.
Thank you for this very helpful video. We live in an area where most of the houses were built from 1890 to 1940 and it is often difficult to retrofit hvac. Heat pumps are very popular, but ours has old duct work from the '70s that I need to update (also asbestos). Dust is definitely a big problem and it was encouraging to see the merits of upgrading the old ductwork and filters rather than going with another solution.
Hope we helped save your duct plan then, Maarten- replacing is expensive, but worth it if you value these features
My 1950 bungalow had no insulation, aluminum single pane windows and only 1 wall furnace. Putting in multihead ductless for heat/Ac, a muilti branch duct system for an erv, and a separate/simpler ducted system for filtering and Dehum. And a make up air for range hood.
Air sealing and insulating the ceiling and floor. Replacing the old aluminum windows with fiberglass dual pane.
It’s definitely not the cheapest way to do it but i like each system being able to work independently as needed
Great content! Professional, clear and to the point! So glad to have found this video before deciding what to use for heating/cooling my attic as it turns into a living space!!
Speaking about ducted systems, I am in the process of redesigning my ducting system for my bedrooms-hvac, all attic installed-- reason is too much pressure in the bedrooms on one side if the house and tool low on the two bedrooms on the other side--the tow bedrooms with the high pressure are directly below the furnace and supply ducts are connected directly off the supply plenum, hence short run, the other side of the house (2 bedrooms) is supplied via a distribution plenum connected via a 30’ plus long 14” flexible duct--and its all made worse in that all ducting and distribution plenum is suspended above insulation so it becomes pretty hot-my plan was to have a new supply plenum distribution box fabricated and place that in the middle of the house, then run equal lengths of flex duct to each of the bedrooms from there--I spoke to a local contractor and he said plenum boxes were old technology and better way to do it would be using all wyes, is this how things are now done? Central California location, up to 105 degrees in summer and down to 30 degrees in winter and everything in between, thanks
What I've discovered is that the majority of TH-cam videos primarily emphasize the simplicity of installing ductless mini-split systems. In my view, such ductless systems are rarely necessary. Many individuals are unaware that they can purchase a ducted mini-split. Air ducts are exceptionally valuable in numerous scenarios, such as new construction or remodels, as they allow for even air distribution, unlike ductless mini-splits that only offer a single point of airflow.
I like the idea of having 3 ft of ductwork to clear rather than miles and miles of a central air system
We are about to install a similar system in our attic. Very helpful video - great job!
I'm sure you did plan on this video being funny, but the comment about transferring air from the bathroom to the office made me laugh way to hard. Your videos are very informative, I'm trying to figure out my HVAC system and building a tight home all by myself. So, your videos help so much to understand the technical stuff.
So many houses I've done, they'll rip out all the old electrical, all the old appliances, all the o!d plumbing - but either not change any 70's era ductwork, or expect the new stuff to be the same size, and perform better.
High velocity is the way for retros. Did high velocity Unico systems + radiant heating for 7 years, it delivers such a nice feeling home. It's the only way to deliver a home without major bulkheads on the main floor. Makes for the healthiest vaulted ceilings and greatrooms too.
my 1970's home has no ducts, but I wish it did. Would make things easier. I just have electric baseboards in a cold climate. I'm trying to find cost effective ways to upgrade hvac (add ventilation, dehumidification, and some cooling would be nice). Quote for whole home minisplits was so high, I might go for radiant floors instead and buy a couple air-filter appliances
i will be building several houses over the next few years, and they all have a set of things in common: 1. radiant floor heat. 2. an HRV. 3. a mini-split for minimal A/C. perfect combination and only a little duct work
Hopefully you get someone who knows what they’re doing for your ERV/HRV. I have an ERV and the contractor put in a simplified system. I’m going to be stripping out the insulation in the attic and in the area in the attic where we have the ERV I’m going to be removing the trusses and replacing them with rafters with the insulation between the rafters and putting in a dedicated system. I’ve spoken to a number of contractors and it appears the vast majority of them are clueless about a well designed system. As well as properly insulating a house. Radiant floor heating definitely is nice.
@@erictoulon5946 I have a Lennox HRV5/150 that I installed myself in this house, and i'm quite pleased with how it turned out. 4 supplies 3 returns, auto runs in low sunset-sunrise
@@BrianKrahmer I live in Hawaii so I'm wasn't that familiar with them other than knowing that I wanted one for my house that I just had built in Washington. I've been watching the technology evolve since majoring in industrial arts in the late 70's. The contractor did a really good job building the house but there were a few things I would have done differently had I known. All in all it was a great learning experience and the remodeling projects merely reinforce the learning curb. I've been in a few houses that had good ERV/HRV systems and that is what I am trying to achieve. Tight houses with poor circulation almost always trigger my allergies.
Thank you for this video. I am bouncing into the very same question during last 1-1.5 years and in some projects I am using ductless systems with 2-3-4 evaporators, or a combination of a regular ducted HVAC with a mini-split or two for bonus room/basement/attic… Thank you again for this video. If is very interesting to hear your ideas about the matter.
Wonderful to hear Ed, thanks for following
Great video! One thing I personally enjoy exposed ductwork because I know if it leaks it just leaks into the conditioned space so no big deal, also putting it in a plenum can make it less ugly to some (as long as the adjacent wall/ceiling is airtight). 👍
Haha nice
Good video. Just designed the house floor plan doing a manual J and manual D in parallel, so there is room for ductwork. Holistic approach following Healthy Heating guidelines
Good work man
We are building a new home and will have a mix of ductless and ducted. The ducted system will return air from all areas for filtration and deliver humidity to the main parts of the open living area, the bedrooms will be ductless. Great video!
Absolutely illuminating. I just had ducted mini splits installed from a top recommended contractor…. pretty good job, though I discovered the return air filter boxes are 20-40% below mfr Fujitsu recommendation- not hard to upsize them so I’ve done 2 of 3 so far with substantial benefit. I always find myself tweaking things after every type of contractor I’ve ever hired :). Also Definitely less household dust that our baseboard oil heat.
Wow Benjamin, I like your style
the standard is no more than 500 feet per minute average across any filter or coil.
you can always put duct work under the house or in dedicated chases that look like architectural features like we put in our house which is an ICE concrete house that has a grass roof that keeps the heat out here in central Texas.
Thanks for this, I have central air with a duct system. A roof top unit with no attic other than 2x8 rafters and soffits built to hide ducts. Makes for a very noisy system and I think I also loose a lot of energy in the ducks due to lack of proper insulation Was thinking o doing a few mini splits and some in wall fans to transfer air to other smaller rooms. Thanks for info on filtration, I forgot to account for that. I had idea to get a mini split for main space then use the central air only as needed for when bedrooms are occupied.
Wow perfect video. You hit every what if question in my head. I was literally going nuts trying to plan my remodel. I just knew it felt wierd pulling all the ducts out and leaving them out. My house would be DONE by now, If someone had made a video like this 5 years ago 😂
Glad to hear it
On suggestion: Avoid using Flex duct as much as possible. Yes it cheap & easy to install,but the plastic breaks down over time. At best Flex Duct has a lifespan of 20 years before the plastic starts to fail. I recommend PVC Pipe, Kool-Duct by Kingspan, or Metal Duct work. Using PVC pipe is the easiest to use since you can use PVC pipe fittings. You can use Sch 30 6" PVC for all of your branches. For the truck lines I recommend Kool-Duct as its R-6 and does transfer noise as much as metal duct.
Thx for the insight. Here in Germany (or the EU) ventilation systems are really unknown in homes. I do have a split ac and HRV and nobody here understands that. People still open the windows to get "fresh" air. My HRV filter tells me how fresh the air is. I am planning my next home with a ducted system for heat/cool/clean air/HRV...etc. Not using radiant floor heater, insulated house with air/air heatpump is sufficiant. But duct ACs have a very low COP. Will need professional help to design the duct system. So greetings from across the pond from a much colder climate zone.
Yeah, well good luck on actually getting a professional that will help design a system that will be what you need, not suck, and not be designed simply for the profit of the installer/designer. Oh and get them to put in writing their guarantee of performance, see how that works out especially in the US.
I've done thousands of real estate HVAC inspections that include duct evaluations, and always find the return area is to small. Not only does that hurt the system, when a high merv filter is used in these systems, it puts even more of a strain on the equipment. Sadly the high merv filters don't have a warning on them about the return sizing requirements. Return sizing when using high merv filters is the most overlooked part of a system.
Personally, I run a ducted system and a mini split. I also open the windows in my house on the nice days (69-74f outside) for natural fresh air cross breeze whole house air exchange. This is something most people never do these days.
A big problem I see, as a contractor, with energy efficient homes is that no one looked to see if all the energy efficient items work with each other. For example: An entire community was built with Rinnai water heaters, and water saving fixtures. After the 1st year was up for builder warranties, everyone was complaining that no hot water was available at the fixtures. Sure enough, all the water saving fixtures had low gmp devices on them that would not let the Rinnai fire up to heat the water.... LOL How does one tell the owners that got Tax Credits, that they either loose the Rinnai OR all the fixtures have to be replaced or modified with higher gpm devices??? LOL This is a problem that can get the owners in trouble with the tax credit program, and also that the final inspectors approving the tax credit don't understand or catch.
endless hot water means endless drips if using multi, they're expensive and you need 1 1/2" gas lines for them as they really need lost of gas when fired up.
Thanks for the tough lesson. I was definitely one of the ppl ready to delete ductwork from design especially when I came across a manufacturer that claims their system does radiant cooling. I was SO ready lol
HELL YEAH AARON! Hearts and minds buddy! Spread the news
OK. I went in between. I went with Mitsubishi also - I put a traditional 1 1/4 ton head in my conditioned garage, but on the living space, I went with pancake, above the ceiling air exchangers and ductwork...but each exchanger had 3 12x12 inch return filters going into a custom designed return plenum - and each had 4 supply ducts from a supply side plenum. I was able to have each do multiple rooms, but with very short runs on both supply and especially return.
Since these are low static units, you have to minimize bends in the ductwork and it's better to use metal near the ends and elbows rather than very mcy flex duct...just enough flex duct to keep things quiet. And man, are these things quiet.
Very good. We had a very similar problem recently on a custom design.
Keep up the good work Soleado
The most essential part of my HVAC system is ... not having a black asphalt roof. It's amazing what a difference metal, especially light colored metal makes.
👍🏽
Good teaching ! I'm sold on mini splits , in Phoenix there's 6 months of brutal heat. Something important is ext.doors, mine work often. As an incredible venting mechanism. In monsoon storms , system will work hard. I'd like to send you my plan for the next house . JIM
I’ll be here, Jim, thanks for watching
1 unit, 4 heads ... plus erv pulling air from baths and laundry.
but I completely agree about a need for iaq and great filtration. so I would recommend cassettes above the ceiling, of br's and office, and ducted casste above garage dumping to Great room. each cassette to transition to a Lennox Healthy Climate(minimum, prefer the Pure-Aire ... atleast for unit supplying Great Room) air cleaner.
as ERV pulls bad air from baths and laundry, replaced by conditioned air from BR's and Great Room. Incoming air from ERV to Great Room. house stays balanced and gets good IAQ. Filter media above BR's and office probably will need to be changed every 3 to 5 years, above Garage ... every 2 to 4 years. costs a little more, but done right.
Thank you this video will make my life easier when trying to explain to people the issues with going minisplit only and other issues as well. I can just have them watch this.... We will never see minisplits with adequate filtration because it will require a far more powerful blower in the unit which will increase noise and reduce efficiency.
The guys that put minisplits in their work shops basically have to build a large plenum/filter box to put in real filters to keep from plugging the unit and large filters to reduce the pressure drop. I plan to go to minisplits for my shop to replace the window unit after I'm done adding far more insulation to cut my AC needs from 5 tons to maybe 2. But I will have to do a filter system as well. Metal buildings are tough to cool even if they are already insulated due to the massive thermal bridging in their construction methods. So I'm building a building inside a building and it will be better insulated than the house...
Nice plan, Craftsman! Thanks
corbett-for a two zone system, ie committed to two heatpumps and two sources fo ventilation, what do you think about using a ventilated dehumidifier for bulk of make up air in summer/trunk season, and a standard ERV for most of the colder drier months ? ie size each so that each can handle non boost situations.
As humid/dehumid/filtration/fresh air is essential, it seems that ductwork is essential! The good news is that it can be optimized. When not distributing hot/cold air, the ductwork can be cheaper and simpler. But to know how to hit this goal requires engineering, not guesswork.
Modern housing should be equipped with an air exchange system to perfectly solve the problem you mentioned.
I appreciate your video's. I may not understand it all, but I'm learning. This isn't talked about much "out there". Wonder what you would think about a my 100 year old, 3-family house, in Connecticut. I'm looking around at my system thinking I need to change everything lol. The exterior wall weren't even insulated.
Having lived in homes with conventional ducting and now in a house where the AC has to be delivered by the small hoses, nothing else fits in the walls of this 1940's home. There is no doubt that the high pressure AC is noisier than ducted AC, however it runs a lot less so it sort of balances out. That said if I had a choice I would go with normal ducts but overall I am pretty happy with the high pressure small hose approach also. As far as filtering the air it is the same as ducted and uses the same filters and a central return.
but the higher velocity and higher static pressures do force more duct and dirt through the system
Would love to hear more pros/cons on radiant floor heating. Could you still install an ERV to refresh the air in the winter? Obviously it would still need a separate cooling system.
$$$$
I would also love to se some content on this.
Love this video! Thank you for creating. What are your thoughts on the Mitsubishi air handler for those of us with ducts? I was looking at retrofitting with minisplits and eliminating my ducts but for the reasons you detail the air handler caught my eye. Has humidifier, ERV. My local “diamond” Mitsubishi contractor really didn’t know anything about this. Hmmmm. I wonder if you or anyone on here has seen or used one of these. Thanks!
We have their 2-ton PV series multi-position air handler that’s been running nonstop for the past 2 years with zero problems. Hyperheat enabled in case of arctic weirdness (in Atlanta). Highly recommend.
I live in a largish house, and previous to installing some mini splits, it was heated via baseboard and radiant during the winter and expensively cooled via ducted central AC on hot days during the height of summer. There was no ducting in the bathrooms or laundry rooms. The ducts run through the unconditioned attic taking up a huge amount of space.
I can’t see how a ducting system that only ran intermittently 4 months a year helped air quality very much.
Maybe the fact I have daily vacuuming with the robots, but the air seems fine all year round without a huge amount of dust.
On the other hand, after putting in ceiling mounted mini splits in the bedrooms, everybody gets there own temperature all year round and it’s ⅓ the running cost of running the whole house ducted AC.
It isn’t picking up much dust, that is true.
Ys, there’s never just one way to achieve performance goals, but some products and technologies are marketed so aggressively that it helps to step back and remind ourselves of the whole system. I have tons of clients building from scratch and almost falling in psychological potholes embedded in experience in old homes.
I lived in a new house that had one minisplit in main area to circulate air. It was horrible. Being up north the ac part was not as important. Every room had a wall heater. Met code but was horrible.
I had caught a video a long while back where the guy talked about carefully positioning minisplits so it would push the air around the house. Downside was it involved keeping doors open for circulation to work.
Circulation is difficult in that scenario, yes
I'm thinking about tearing out my old furnace and ductwork (which runs in the crawlspace and has terrible insulation) and installing floor mounted electric radiators throughout the house. This would give me better temperature control room by room. AC is not a major concern due to the climate. I also need new windows so I was planning on a few units with makeup air slots in the frames and a timer for my bathroom exhaust fan. After new insulation I'll be ~R40 underfloor, ~R21 in my exterior walls and ~R60 in my attic so the house will be pretty tight. Hopefully the bathroom exhaust + window makeup air slots will sufficient to prevent mold growth. Chime in you have thoughts!
it is estimated that over 90% of homes has undersized ductwork , and most has a leak of some fashion. a leak on return side sucks air into the home a leak on the supply blows air out. as that air leaves, it must be replaced ... and it takes the path of least resistance, whether it is a hole cut for electrical or plumbing, a recessed light, a chimney, or a bad window seal.
there is a newer product that offers great benefits that could replace your ducts ... made by Kingspan, called KoolDuct. antimicrobial, fire and water resistant, lightweight, insulated, strong. just an option since you recognize your ducts being in poor condition. now would be the right time to make them right, have them properly sized. and when done you can have them pressure tested and sealed with aeroseal to ensure that you do not have any air intrusion or extrusion.
to do a good job with floor heat as you described your thoughts would really require new flooring. to do so from underneath ... you lose efficiency. might be cheaper to replace your ducts. but it is your home and you are the one that has to live with your choices ... I do not mean to sound negative about floor heating. just offering options.
It's amazing how humans survived without mechanical air conditioning before WWII.
My brother just put their bedrooms into their basement. The duct work caused low ceiling issues so they went without. They do have forced air upstairs. It will be interesting if they have moisture problems in a couple years.
I made the suggestion of cutting some holes in the floor connecting the basement air with the upstairs air.
Keep us updated buddy
You are a great teacher and you know your stuff.
My house in Los Alamos NM does not have ductwork or AC. It’s miserable for 2 to 3 months out of the year. We have very high ceilings and the master bedroom is a loft upstairs with outdoor deck. I have no idea what to do.
I hate window AC’s and am leery of those portable units.
What do you suggest? Are you open for consultation?
My daughters bedroom has a window unit. That leaves the family room, living room, kitchen, bedroom #2, and the upstairs loft unaccounted for.
Thanks,
Paul
Hi Paul- there’s a neighbor of yours you should talk to. He’s one of our longtime Patreon members, and he’s gone deep into this stuff! I’m taking a 3-month hiatus, but email me by tomorrow and I’ll put you in touch.
@@HomePerformanceOk. Where do I find your email address?
Thanks,
Paul
I agree with what you are saying, except the view that the house air will be dirty if it's not vacuumed by the furnace. The largest source of new dirt is the outdoor air coming in through the ERV. Put a high-end filter there, and it's good enough.
Oooh, I have to disagree with you there Josh, WE are probably the biggest source of new dirt. Most dust is actually skin flakes. Gross.
@@HomePerformance That's an oversimplification that has been dis-proven. Here's a Veritasium video about that: th-cam.com/video/jn5M48MVWyg/w-d-xo.html TLDW; about 20% of all dust is skin flakes.
Ok, so your plan for the 20% is what if not filtration?
@@HomePerformance the ERV will kick that dusty air outside. Just hepa filter the incoming air and its all good.
I have a hard time believing that will work, but test data could prove me wrong
Maybe I missed it, but if you have radiant heated floors + ERV or HRV, why would you not want the radiant heat to do all the heating?
What would happen if you used the attics in a house as supply side plenum and ducted the ERV and humidifier into return?
Actually you can add heat easily to a Zhender hrv/ERV system and I'm going to try to add cooling to mine. It's my understanding that humidity will not vary much if at all throughout a house so a stand alone dehumidifier should work. Not totally sure on that but don't think I'll need it so good luck to those that do.
Hi Corbett,
I have watched several of your videos and I find them especially helpful! I’m a little confused about this one; I’m hoping you can elaborate. I am currently general contracting my parents’ high performance home with them in NH. We are planning to use ductless mini splits and a whole house ERV as well as make up air kit, perhaps an Air Scape per your recommendation. I am wondering if, however, you are indicating in this video that all these systems can be combined into one single, ducted system which functions as an ERV, heating and cooling via heat pump, and also dehumidification. Does such a system exist, and if so who makes it?
Thank you
Greg in NH
You’d need each of those separate machines, but you plug them into one central duct system.
Is there a specific manufacturer I should look for that offers this type of compatibility?
Hey I've got a question on manual J. I'm building a new home addition, it's 1500sq ft of shop with 1k Sq ft living space above. Separated from homes envelope.
R21 insulation in all walls, r5 foam on the exterior. 9ft ceilings. 1st floor is slab on grade with insulated edges, r38 in the floor joists. It's got 4 18"x4' windows. Second floor also has r60 attic, it has a slider, a man door, and 3 4x5 windows. I've air sealed with foams and acoustic caulk everywhere I can see including soffit (left enough open for venting).
Area is eastern wa, design temp is 95 high 11 low. The calcs I get say I need 10k btu heating and 8 cooling. That seems wildly off base, and my original plan was a 24k mini on each floor (they are both wide open rooms). 18k minis are exceptionally cheaper so now I'm waffling between 18s or 24s.
Any advice??
Doing the math almost always shows you a much smaller than expected load. That’s because we were trained to think that every home needs a massive HVAC system, which is simply nonsense. Your load is feasible, but I’d need to see the details to completely agree.
FYI: if your load is 8k cooling and you install not one but two 24k units, you will be oversized by 600%. The inverters will ramp down to 16k minimum, no lower, so you’d be installing single speed 200% oversized equipment in reality.
Great video. I have an older house with terrible ductwork and will need to redo the entire HVAC system at some point. I really want to go ductless for the ease of install and attic space savings but I think you've convinced me otherwise.
If your house isn’t too big you can feasibly install new flex ducts in a plenum and punch through interior walls (in an airtight fashion, being mindful older interior walls have a close connection to the attic and crawl space)
Awesome Brent- so glad it was helpful
I wonder if ductless systems in older, leakier homes may be less problematic. Radiators, when they came out during the Spanish Flu, were designed to run hot enough to leave the windows open.
Having enjoyed the video, and having been given some new factors to consider, here's a question. When I build my monolithic dome home, how would you handle the air in such a structure? There may be multiple connected domes as well, and I know they must have a system to pull in fresh air, but the structure may be easily 100' across the width, and perhaps 70' deep. Thank you.
Short answer, Randall: Balanced ventilation, duct system connected to all rooms, high MERV filter, humidity control, pressure relief for any oneway exhaust fans.
Unsure why a (whole-house filtering) blower can't run while I'm running radiant floor heating...although I'm specifically referring to retrofit. New construction could warrant the investment of a heat-pump serving both heating and cooling.
It sure can, but you need properly sized transfer air duct and holes throughout the house. You definitely wouldn't be happy with that though, because you'd have a big hole in every bedroom wall, and you would no longer have room privacy or sound dampening.
I’m doing a new build with closed cell spray foam throughout and radiant floors. Do I need ductwork for the ERV?
If you aim for a healthy well controlled home yoy must have ducts of some kind.
I’m going with mini splits but ducting will still exist with the ERV system. I’ll be using 5 indoor units powered by 2 outdoor units. Though my house is really small at 1000 but I like the idea that each room could be it’s own temp
Your ERV will be running only maybe 100 cfm- not enough to circulate, humidity control, or pressure relieve 8000 cu ft of volume fyi.
So the auto solution is ducted hvac? @homeperformance
just keep in mind with small houses (yours is the same size as mine), even non-efficient ones like mine, getting small enough units can be a problem. also i don't recommend multi head heat pumps, especially if you can't size the heads well. it may be better to do a ducted system for the bedrooms.
Not the only solution, but centralizing the 5 Factors means less equipment with better fit, less complexity, simpler controls. It’s done in a decentralized way in Europe and Asia all the time, like Tweake comments from NZ.
@@HomePerformance , so one complete exchange every 80 minutes with an ERV isn't enough to circulate? But a closed system with no outside exchanger is? I get the humidity issue, ERV isnt a whole house dehumidifier, sure... Its filtration capabilities are also not good vs a massive filter. but not enough to circulate vs. one that doesn't do any outside air exchange? Got the confuse in my face
We have duct work all thru our home but we are about to add a top floor and finish the basement - any recommendations for how to heat and cool those areas ?
You might have enough HVAC power to heat/cool those spaces already. Have a Manual J load calc done and maybe swap out some of the ductwork.
Swap out the duct work for splits ? The basement will be 50% family use and 50% basement apartment; would that change anything?
Do the bathrooms need to be conditioned? I have a ducted system but didn't run ducts to the bathrooms. Don't need cooling in summer and in the winter an very small space heater with thermostat is more than enough.
Bathrooms are negative pressure zone, they’ll generally mooch off the rooms around them just fine as long as there’s not a bay window and a skylight in there.
We are building a 3200 square foot 2 story passive house with 12” thick outdoor walls, 12” of foam under the low carbon concrete slab, and amazing windows and doors on farmland near Vancouver BC Canada. We are struggling to find someone to give us a straight answer on what we need for an HRV and mini splits as a system. Thoughts?
On the surface, I've always disliked that mini-splits are such a large presence on the wall, and I don't like seeing them. But my more fundamental objection has always been filtration. The onboard filters are equivalent to what a window A/C has, and my allergies aren't agreeable. I love the idea of radiant heating, and cooling, but I can't imagine not having a ducted system too. I've seen a house with heating and cooling in the radiant floors, and I liked how it worked, but I noticed how stale the air felt not being stirred around and filtered by an HVAC system. I also need the humidity control, or the cooling will damage the floors with condensation... I forgot to ever ask the guy how they controlled the humidity, but between the temperature they set it to and Denver being fairly dry, they may be getting away without as much as I think would be necessary.
You can always separate filtration from heating and cooling.
Yes, with a central duct system
I am starting the design of a new house in Las Vegas and I was toying with the idea of doing mini splits for the whole home and I am happy I found your video so I do not do this. Thanks!! On the topic of ducts though what size depth of floor trusses would you say is optimal for ducting?
18 is usually fine, 24 is guaranteed no issue.
@@HomePerformance awesome thank you!! 🙏
What is the least energy efficient way to heat something, convection, conduction or radiation? The answer is convection, which is basically using forced air instead of being in direct contact or direct line of sight with the heat source. What is the most common type of heating used these days? Convection is most commonly used for heating, because we have developed these complex systems over the decades when being efficient was not the goal. The larger a centralized "air" system is, the less efficient it is. We do have a better understanding of how important it is to circulate air, and today's airtight home designs require it, so air handling is a necessity. Lumping in a centralized HVAC system with air handling takes advantage of the duct work needed for both, but that doesn't make it an efficient way to heat a home.
Why wouldn't you just put the furnace and water heater in the garage with a layout like this? Then you have a deeper primary bedroom closet and two lines to run to the wings of the house. I don't think most builders would put returns in bathrooms to lower the pressure, so you could just have a single return in the garage side of the great room. Putting the furnace next to the water heater may allow greater flexibility with your heat pump(s) and humidity control.
We have a 10 yr old Trane Heat pump with a backup Gas furnace (Midwest) and it gets cold in winters. We r building a new 2,000 sq ft house with no gas to property. Will be an air tight home. Is the newer Heat Pumps better at
Highly recommend an inverter. Goodman/Amana inverters can heat at 100% capacity down to 0 degrees. Some can do better. After that you’re use auxiliary heat like a heat kit during extreme temps. -hvac company owner.
@@daltonhadley Thanks for the detailed reply, I'm a new subscriber, will do a deep dive into your previous videos. Thx
Why not open the windows on good weather days and use AC only when its really hot/cold?
Talked with one hvac about using the sealed attic as the return duct. Filter on the machine.
I like the idea.. but I don't like the idea of sucking house fumes and dust into what was a semi clean attic. Over time it would accumulate.
I’m actually designing this exact setup into a client’s home right now
@@HomePerformance
Are you going to have filters installed between the living area and the attic?
What about noise transfer between rooms? The open holes on adjacent rooms would allow for noise transfer vs having duct work to kill off some.
Perhaps a short section of duct aimed in different directions?
Inspectors here would throw a fit using the attic as a return.
I'm building a 1200spft home in mid state NY. I am going to be using only electricity to power everything. Have been trying to decide between ducted and ductless heat pump system. After listening to this, I'm thinking that my decision to go with a ductless system that uses ceiling cassettes may be a bad choice. It's not too late for me to change my mind. If I were to go with a ducted system, would the ERV be connected to that? I'm also having a difficult time deciding on an ERV system. I get the feeling that the contractors in the area don't have a lot of experience with energy efficient homes. The last time I was involved in building a house was with my late husband (a tradesman) in 1992. Things were very different back then. Now I'm going to have 9" deep walls between the 2x6 studs, exterior comfort board, rain screen, siding.... Any advice?
Highly recommend you get on a consultation with me for an hour, Tina, small homes like yours have special challenges:
buildingperformanceworkshop.com/video-consulting
If not, at least check out my online course on Home Performance for Tiny Spaces:
buildingperformanceworkshop.com/tinyspaces
@@HomePerformance Thank you for the quick response. We are close to being done with framing. My daughter is running the show as I live 4 hours away. I will probably have her do the consultation, but I am also interested in the Tiny Spaces course. Is it appropriate for a 1200 sq ft home- which to me is not really a "tiny" home? Thanks
Question. Why is home heating ductwork so bulky and volumetric? What is the physics behind it? Does warm air need all that space to move from one end of a home to another?
Each ton of A/C moves 30 pounds of air, so yes, if you have a long or complicated route it gets bigger as a rule. Why designing your duct runs into the plans at the beginning is so important to keep them simple.
Another question. Why does the system use the AC compressor in the winter when the house gets too warm when there is plenty of very cold air outside? Seems like it could just pull in some of that cold outside air.
That's called an airside economizer, and it's done all the time on the commercial side. AirScape makes the only residential economizer that I know of.
@@ZergZfTw Cool!
A bit off topic… but what became of reversible duct systems that included registers both on the floor and near the ceiling to capture hot and cold air optimally?
Interesting q, Ty- I’d say if you have a good airtight insulated enclosure, you won’t have as much bleeding of heat, and if you keep the air mixing then you won’t have any hot or cold regions in any room.
In a 960 sqft house could you centrally locate a minisplit and then use a ducted ERV to mix the conditioned air throughout the space? Supplies in bedrooms and exhausts in bath and kitchen?
Hey Gerk- this is actually quite a common misunderstanding: an ERV does not circulate air (generally), it takes air from the home and throws it away outside while bringing air in and recovering some lost heat/humidity quality.
@@HomePerformance I phrased it wrong. I understand it's a heat exchanger and not an air exchanger. I meant circulate the heat or lack there of in cooling seasons. Circulate the the conditioning itself minus the actual air. I hope that's clear. Thanks for the response.
Ok, but just to be clear it won’t circulate heat well either- you’ll be running a deficit at all times on temp snd humidity because the core is only ~50% effective in total.
Do you really need HVAC in your small bathroom or closet/laundry? I have duct vents in those rooms but I shut them all and didn't notice any temperature differences from the main rooms.
If there's no exterior exposure, then there's no load- that's a common mistake
I'm considering building a house that will have uneven heating and cooling requirements, so mini splits seem like a natural fit. I was thinking of an HRV system alone, and make-up air would be required. I'd like to avoid using natural gas for heat. The house is compact with two 900 sq ft floors on top of each other with a 900 sq ft basement. The climate is cold dry winters (-29F) to dry summers (+95F).
I hadn't considered using central ducting for air filtration. I was hoping an HRV system running 24/7 would be enough to keep the air fresh? Though come to think of it, adding humidification throughout the house would be nice.
ERV/HRV is in most cases NOT enough to keep the house clean on its own.
@@HomePerformance How does a central ventilation system look/work without an attached furnace or air conditioner? That could make an interesting video.
Sorry about the typos in my comment.
That’s a good q, I’ve added it to the list. Vid forthcoming.
could you do ductless minis with a ERV system? would that be sufficient?
Check out today's video and the next one, will explain a few of the issues there.
So are you saying the Zehnder whole house unit in combination with mini splits won’t move air enough?
In most cases it won't clean, dry, and circulate the air enough for a truly healthy breathing space, no.
@@HomePerformance Thanks for the reply! So why does it seem like we see this Zehnder + mini splits setup in so many passive or net zero projects?
GREAT QUESTION. I wonder this myself- have not heard from people living there after a year though. They also like to say they put a recirc fan over the cooktop and an ERV exhaust in the kitchen, which I find quite vomity.
@@HomePerformance i have seen that setup here in passive houses. i got some flak for mentioning it.
Taking one for the team!
Can you design a Mr Cool ducted system for the ICF house I am building in NC?
Mr. Cool ducted system?
I recently went through this decision myself. I have a 2 story up and down duplex. Each unit was heated using electric baseboards. I looked at ductless options (as we had a ductless AC unit in the upper unit already) and i looked at high velocity tiny furnaces 15kbtu-30kbtu units). In the end i opted for 2 seperate firnaces 40k btu each in size, one in each unit with their own seperate ductwork.
I came to this conclusion for the same reasons you mention here. Air cleaning, central conditioning, fresh air dumps into return plenum and blends with homes return air and ditributes to each room, and cost! A quality ductless with 3 indoor heads can run near 15k canadian, and in extreme cold weather id still need backup heating...no thanks
Question.. I'm currently remodeling a house ( complete from basement to second floor ) built in 2010, ICF construction. The homeowner decided to have me remove all ductwork and is installing a split system heat pump for the entire house. ( 14 head units total ). I did mention my concerns with getting decent air filtration, dehum. / humidifiing, and getting fresh air/ removing stale air. So my question is, what should the homeowner look out for that could go " wrong " without having those mentioned benefits of a ducted system ? And would separate stand alone units like, air purifiers, dehum. / humidifiers help ? I realize this may be a complicated answer... I really appreciate your videos on TH-cam !!!
Buddy it sounds like you seriously need to go watch any air purification or filtration videos on this channel. Moisture, mould, germs, air quality, dry air causing cracking in flooring and wooden furniture, people straight up getting sick all the time... What a list.
In extremes, window seals getting broken and drying out as well. Not sure where you are, but in Canada the house would fail any inspection without at least an ERV or HRV for bringing in fresh air.
@@levidobbin5654 I appreciate the info. So the whole concept of having no ductwork in a house and just using mini splits was very new to me, and I think ( unfortunately ) the HVAC company hired to do the job, just went along with what the customer wanted and did not mention any pros or cons... There were some alarm bells going off in my head for sure...Again, thanks for the info !
@@levidobbin5654 We are in Western New York btw
@@derekdenning6342 Of course, we all have to look out for each other. Look into ERV or HRV systems - maybe from a different HVAC contractor, because they should've spoken up when they saw something this essential missing. ERVs or HRVs will probably do you the best with minimal ductwork...I say minimal because there still needs be a system. Western New York can be close to the same as Southern Ontario, where I am. Call an HVAC designer, bring the plans, see what they think you need for a ventilation plan. Go Bills.
In the south an insulated attics puts all the ducts in the air conditioned space seems very nice.
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downunder its a little different as homes don't have HVAC, so no ductwork. ductless mini splits are getting very common here. also ventilation systems. however once you start putting several ductless mini splits in, plus running ducts for the ventilation, its starts becoming cheaper to run full ducted HVAC. then its really easy to have hrv/erv and built in dehumidification.
Evolutionary HVAC
As a HVAC mechanic for 40 years I can tell you duct is filthy. Radiant floors, ductless ac, and a HRV provide a perfect environment. Hydronic heat is easily zonable giving every room its own thermostat. Ductless again, every room enjoys its own temperature setting. We have converted several homes from ducted a/c to ductless, not only did the customers cut their electric bill in half but the dehumidification mode on ductless allow for much better dehumidification. Crossover fans are not necessary as everything in the home falls into equilibrium. Never had a complaint that the bathroom was too hot. Why do we have so many kids today with breathing problems, much more so than European countries. Could it be the US is 98% ducted garbage and Europe is 99% hydronic...I would bet on it.
DO we have have have more breathing problems among kids here vs Europe? Reference?
I agree we may have more breathing problems than in the past, and probably more than some countries, but without data I’d bet we’re very similar to Europe. Leading immunology theories lean towards increase in allergies and autoimmune disorders being a result of us living in TOO clean an environment, where our bodies haven’t had enough exposure to learn to discern really bad pathogens from less harmful stuff like peanuts.
@@mrayoung Then by all means build your house with fiberglass duct, Ill stay with my radiant floor heat.
Anthony you are ahead of the time ! Good to see some who see reason to build better. Jim
How do radiant floors cool your house? And how do you fix it if it breaks? Rip up your whole floor? Doesn't sound very smart to me.
@@sa3270 I absolutely agree in every way!! I couldn’t have said it better.
Thoughts on stand alone HEPA boxes for each room? Combined with a timer and or motion detector they could deal with the filtration and circulation, and leave the heating and cooling for a separate system.
Hepa will not clean air from CO2
@@andreycham4797 Of course not, that's the job of the ERV.
FASCINATINGLY, there are now filters that can scrub CO2. Crazy, right?
Yes, that's a decentralized system, I'll describe it soon.
@@HomePerformance Submarines and spaceships have had CO2 scrubbing filters since they were invented, there are even CO2 scrubbing SCUBA systems used by the Navy seals and the like.
This may sound a little out there, but what do you think about a system with a central return, filter, and blower, but with micro heating and cooling coils distributed at the end of each duct run; maybe integrated into each supply grill? That way you could have continuous circulation and filtration but independent control of heating or cooling in each room. I know of a few commercial systems that operate similarly, I believe they are called induction units.
I just built us a custom home North of Atlanta (I think that’s where you are too?). We did a hybrid system based on the shape/design of our house. We did “traditional” ducted high efficiency variable speed trane systems for the 1st and 2nd floor. Our garage hangs off the back of the house in an L shape with finished space above (approximately 600 SF). We did a 1ton daikin ductless mini split in the finished space over the garage. Did a Fantech ERV. an Aprilaire E100 on the 2nd floor, and a Santa FE 70 in the unfinished basement for separate dehumidification. Fantech 830 CFM Hood vent (with the silencer per your recommendation, thank you) with makeup air pulling in from our screened porch. Our ERV also has the fresh air intake on our screened porch too. Spray foamed the roof deck for a conditioned attic. Zip system and air sealed envelope with 2x6 R19 batts in the walls. Got a 2.0 ACH50 on my blower door with a bunch of missing door weatherstripping (BD guy showed up earlier than I expected and the painters had just left the prior evening. I wasn’t finished re-installing all the weatherstripping they removed).
Good work Brad!
Problem in the US is most homes rely on the V to deliver the H and the AC. I've spent enough time in other parts of the world to know this isn't always the best. You elude to it but don't really make the point - you don't need to move the same volume of air to each living space to Ventilate it, if you don't have to rely on the same system to heat or cool it.
I think you meant allude (to refer to something, often vaguely). Elude is to avoid, like a solution to a difficult problem does to the one failing to solve it.
That being said, I agree. There are some valid concerns here, but those are concerns that can be addressed in better ways than "let's avoid this new problem and just stick with the problems we got used to".
The ductwork in our house is amazingly terrible. For our first floor bedrooms, the ducts go: from the 1st floor garage, up to the 2nd floor attic, across the house, down a cavity in the wall back to the 1st floor, and out to the bedrooms.
unico is a modular system. there is hydronic module available. i would differ with you on the point of no opportunity for humidification. it can be fabricated for the system
It is hard to comment on this with no sizes up... But couldn't you have tucked a 5 head mini split near the office bedroom that would feed all main rooms? Then just put in cheap electric panels under the flooring in the bathroom for heat that if your house is sealed well will not really ever get used.. Then in the garage or laundry room, maybe a crawl space or attic put a ERV/HRV system an just run the 250cfm 2.5inch heads to the areas in need/ all the non bathrooms to keep the negative pressure you need or at least make sure it is less cfms to the rooms then the fans can take?
I've never lived in a home with ducts. Steam radiators mostly. I'm dog sitting for a friend. Her house has ducts. I'm not a fan. I understand wanting to filter indoor created pollutants, but I'm used to living with the windows open unless it's too cold or too hot outside.
In this video it is mentioned a 2 ton system for a 5,000 sq ft house. I can't find anything more on this topic so far searching through the channel. I have a 1250 sq ft condo with a 3 ton system built in '92 and HVAC guys trying to sell us on installing wider ducting. Seems to me if I had an efficient 1.5 ton system then there would be no need for wider ducting - assuming there truely is even such a need as is.
Search ‘Manual J’ or ‘Load calc’
My house always had a moldy smell and it was coming from the duct work. i was always sneezing and or coughing on a regular basis. I had constant problems with my whole house HVAC and finally it stopped working. I replaced my HVAC with Mini-splits and have never been happier. My air quality has been great no more moldy smelling air. And my electric bill is about 100 dollars cheaper each month. I can control the temperature of each room individually. Duct Systems are dumb to answer your question and a big waste of energy. In the future if I think I need some kind of whole house air cleaner I will buy a ductless system.
For folks who are not using a heat pump or condenser-type dryer, has anyone created a makeup air system for a standard electric dryer in the laundry room? I suppose this would be the equivalent of a range kitchen exhaust hood problem.
Very difficult challenge, much lower CFM than a kitchen exhaust. Video forthcoming.
How about ductless HRV 's in each room with radiant heat floors?
Video forthcoming. I wouldn’t advise it.
@Home Performance okay, thanks for the reply, looking forward to the video.
Watch Matt Risinger or someone else steal this video! Great video
Essentially dumb. I have radiant heat, a couple of mini splits and an HRV. It works pretty well in Montana but I wish I also had a whole house fan to bring in cool air during summer evenings.
A lot of Europe is ductless and I prefer it at least for smaller units or spaces. Like anything under 1800sqft or so would be dumb to do ducted both new and retro build - it takes up a lot of space, noisy, expensive labor, and chances are the HVAC contractor will design/size it wrong. Completely different when talking about 3k sqft or bigger building with multiple floors. In such cases you probably have the budget for a nice system, and contractor that has some engineers for a good/proper design.
Spot on!
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It would seem to me that heating cooling the home is primary and air movement and filtration is a close 2nd. They really are two seperate theories and we try to accomplish them both with one overall system that is really lip stick on a pig. Every house poses a specific method and if the house is not designed around the hvac/lungs then corners must be cut to offer some potential solution.
I say design the hvac then plan the structure and floor plan around that. Lungs first and bones 2nd when you have the choice. We are the God creators of our own environment in which we sleep, breath, eat and live. Plus we also shit in the very same enclosure, which factors into it all.
Ductless mini spit plus HRV for filtration. Done
Just to say, 3 times it was said showing something on screen and nothing appeared on screen with it. Also outro music volume is way louder than everything else.
Completely unprofessional and hack as charged.
@@HomePerformance I don't mean anything so extreme, just feedback and I was looking for the links
Like it or not there is no perfect solution
Now I’m more confused. It has felt like in the past you advocated separate duct systems ideally for all these systems, if not at least between ventilation and conditioning. This video seems to push a single duct systems to rule them all. Even if sized for all fans going, I’m not sure I could believe that the static pressure could not be out of the zone for some of the fans. I still see manufacturers and experts argue where systems can be joined (supply or return) and with what kind of controls and dampers and such.
Yes, I built a totally separate ductwork for my conditioning and ERV, Todd, but wouldn’t do it again. The cons outweigh the pros. And there’s no such thing as ductwork that’s too big, so you’d just upsize them to contain it all and then use ceiling fans for room mixing.
I would like to hear more on the conns. Perhaps a postmortem on your system a year later. I’m in the retrofit business- all the houses I work on are old, so often massive ducts are not a reality. Then again, lots of little ducts are not always great either as every time I open a wall it’s usually a WTF were they doing moment.
I think you're missing a few points. The first is that without zoning a single HVAC system has hot and cold spots throughout the house because there is always one room at the end of the line that gets the scraps of heat and cooled air. Then you have the basement which is too cold in winter because you're heating the upper floors or bloody freezing in summer because all the cool air pools down there. Then you have the fact that you are constantly conditioning the air everywhere in the house even though people may only be occupying those spaces for less than half the day. Personally, I am all for having two, three, or even four minisplits throughout the house. They can be programmed to turn on before the space is to occupied amd off when not, like at night.
Performance tuned homes with attention given to airtightness and insulation do not, in fact, work the way you describe. It’s a challenge to understand it if you haven’t spent time testing homes like this.
@@HomePerformance mine does. I think open concept from basement to upper floor throws all tuning and testing out the window. I know I could add automatic dampers to the supply ducts to help but when you're dealing with one open space over three floors it is a major challenge. We had a 168page report on hvac submitted to the city and it still doesn't work properly. I'm going with a wood burning fireplace and zones controlled by individual units next time. Centralizing with one furnace is also risky as they tend to break down on the coldest day of the year. Id like to have an alternative source of heat for when that inevitably happens.
Holy cow, that’s not supposed to happen, there must be a lot of things off with either the design or the install.