Is a Roof Power Attic Fan a Waste of Money....or Even Worse?
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- เผยแพร่เมื่อ 17 ต.ค. 2024
- We see roofers and homeowners install power roof attic fans all the time, and we often find them to be incorrectly paired with make-up ventilation so that they either 1) do not cool the attic when they are running or 2) depressurize the attic when they are running (turn the attic into a vacuum) and pull the conditioned air from the home. In the latter case, it means that the home will be cooling the attic by using its air conditioner. And this is an atrocious waste of energy and the worst outcome of installing these fans!
Insulwise's contention is that more often than not, that power roof attic fans are not necessary, and that effectively installed passive ventilation systems work better.
If you live in the Pittsburgh, Pa area would like Insulwise to make your house cooler and more energy efficient (and the same for winter), call Insulwise at 412-260-6701 or stop by our website at www.insulwise.com.
I love the word “passive” so much when it comes to home heating and cooling.
Me too!
Dittos. I had a house with a power fan. I changed the ventilation and the convection flow did a better job of cooling the attic.
@@CR67 That's great, thanks for the comment and nice work!
Andy
I live in the south eastern US and these things are a must as is soffit venting and ridge venting. In many places here soffit venting and ridge venting are governed by building code. They also help your roofing shingles last a little longer as well. FLY NAVY!!!
Roof power fans can work well -- when they are sited correctly with respect to passive vents and there is enough make up air to prevent the fan from pulling air from inside the house.
Andy, the bashing of some (many, most?) roofers, many of whom do siding as well is warranted. Couple quick examples from neighbor, combo of house flipper and pros hired by new owner… soffit vents blocked by attic floor insulation; gable vent blocked by plywood sheathing; roof gutter level, NOT pitched toward downspout; and (opposite side) reconfigurated gutters to drain to lower roof and use it’s downspout ruining 1st floor ceiling. Neither roofer nor (inept) town inspector anticipated the problem they caused.
Re: power fans… some may miss your note in the comments that in right circumstance, done right mechanical fans are BETTER. Clearly, many got the wrong impression. BTW another pet peeve is over-sizing AC units by contractors… big units quickly cooling do not adequately remove humidity which is the prime source of discomfort. End rant 😀
Thanks for the comments and you are correct. This is a science, not a hobby for us, and we've seen mistakes cost our customers dearly over the years. With regard to AC size, we are HUGE fans of making the air and thermal barrier as as energy efficient as possible and then sizing the AC system accordingly (to run at steady state to remove humidity -- not flash cool the home -- like you said!)
Andy
You get what you pay for, just sayin.
@@kirkwilson5905 Well, what often happens is the homeowner just trusts the roofer to understand how to correctly set these up, and we find that often they don't, regardless of what they paid.
@@insulwiseenergycomfortsolu3293 Most don't consider soffit venting or anything else not actually in/on the roof to be roofing. And I have to agree with them... for the most part. So the quality roofer that includes the scope for correct venting is bypassed for the cheaper alternative. Mostly out of ignorance of the customer. At least this seems to be the norm.
@@kirkwilson6698 You're right, 100%. However, I'm not sure if you are versed in under shingle intake vents. They are a type of vent where a 1" wide cut is placed into the roof all around the perimeter, usually 1-2 ft up from the gutter. A piece is then inserted into it that allows air to flow into the bottom of the roof which is then shingled over. These are 100% installed by roofers and they are a fast, easy, smart add on that provides intake ventilation. Unfortunately most roofers still do not install them here, or for that matter even assess the existing roof / attic situation for proper ventilation prior to pitching the job. Here's how a smart roofer would sell it "mr homeowner if you want to dramatically reduce your attic / roof's risk of a mold problem while also reducing summertime attic temperatures, you can have us install this for XYZ. Or you can go cheap and pay for it down the road."
Andy
Beware of the ridge vents in areas subject to hurricanes! One family had the ridge vents and the wind was blowing water UP the slope of the roof where it entered the vent and flooded their house! There was no other damage to the house, only the water damage from that damn ridge vent!
That's a great point that most people aren't aware of. I've also found that a severe thunderstorm can lead to water intrusion if the wind is just right.
That is an excellent point you've raised as well as one that we don't have to deal with (so far) in the Northeast. I have seen wind driven rain cause issues with roof leaks, but it is a rare occurrence here. I'm not sure what the best solution would be in a region where those types of storms are common.
@@insulwiseenergycomfortsolu3293 It's obvious! You close up the ridge vents totally. Actual careful tests show the effectiveness of these puny vents to be ineffective. (no temperature difference between vent open and vent closed.)
I used to do maintenance on beach rental houses in North Carolina. An ocean front house will definitely get water blowing up the roof and into the vent on a regular basis, enough to stain the ceiling. Rain storms with 30-40 mph wind are common.
This is such a simple demonstration and explanation, well done! I’m about to be a new home owner and the attic has always seemed so intimidating. At the very least, this helps me better understand how attics can be cooled. Thank you!
Hey Alan, thanks for commenting! We try to keep things as simple as we can here, but it doesn't always work. In this situation I tried to explain that these fans are often not necessary, and sometimes even highly problematic. Usually the solution being sought can be achieved by air sealing the attic floor, insulating to R-49, and making sure the roof is ventilated properly with passive ventilation. Hope this helps!
We had just end cap vents, soffit vents, six inches of insulation and our attic would hit 120F+ during our 95F+ days in our Rocky Mountain high valley semi-arid climate; A/C would kick on at around noon at 80F setting. Added three turtles; didn't seem to do much. Blew in cellulose for a total of 18 to 20 inches of insulation, and that seemed to help. Added a three ton attic fan to roof in place of the center turtle, thermostatically controlled to kick on at 70F, and added a two closeable 4x12 inch vents in attic access panel and cracked opened a window in the basement to create a draw; 95F+ days and upstairs would be 78/79F and the A/C would kick on around 4pm. Interesting. Added a small humidifier (gallon every 18 hours) in the basement for a small swamp cooler effect, raising the humidity from interior 20% (lowest my gauge reads and weather station indicating 5% to 10% outside humidity in the afternoons) to 35% to 40% inside; more days where the outside temp was 95F+ and the A/C didn't kick on and the upstairs would stay 77/78F. Electric bills went from $120+ a month (July & Aug) down to $90/$105 range. Replaced 22 year old 10 SEER three ton with a 16 SEER three ton and current bills are $60 to $75 a month (June, July, Aug and Sept) with A/C setting of 78F. Taken 18+ years of experimenting and now on my second attic fan, yet I feel like the attic fan has worked well for me and my specific situation.
Last three days, 92F, 96F and 96F, with overnight lows in the upper 50 range with super low outside humidity and 35% interior humidity; no A/C kick on (78F setting) and basement started at 67F and rose to only 71F. Not bad.
Is your attic floor air sealed?
@@insulwiseenergycomfortsolu3293 I would not think so; soffit vents, turtles and end cap vents still in place. Nothing above the insulation or on the backside of the slanted roof; do not know what is under the insulation.
I wired a fan for our attic after a carpenter installed a fan near the roof peak, but I never considered where it got it's intake air from! There are just small vents at either end of the attic! We found that the fan didn't help keep the upstairs cool,so it wasn't used after that.
Thanks for pointing out something nobody considered as far as intake air was concerned!
Thanks for the comment! Yes, the location and size of the intake vents are crucial to the effectiveness of these fans. However for keeping the home cool, we are much bigger proponents of air sealing the attic floor and insulating the attic floor properly (or underside of the roof -- but only with closed cell spray foam).
As a roofer I can confirm most roofers don’t understand ventilation. They think more ridge vents, slant backs, turtle vents, etc solve every issue. I recently ran into one (thank god Allstate covered it) which was blistered so bad on the 2nd story roof that finding hail damage was almost impossible. It was a 14/12 pitch which meant 1 slope was shaded at most times of the day. The customer told me the AC would never turn off in the summer and wouldn’t cool. They upgraded their AC twice and still no luck. They had gable vents, ridge vents, turtle vents AND turbines. It was only venting the top 2 feet of roof. Below that 2’ line and down was purely blistered shingles, and they had soffit vents caked with latex paint. 4 different types of exhaust vents and virtually no intake.
Once I did his roof he called the next day totally over the moon because his AC finally cooled the upstairs bedrooms and shut off.
where are you located I need an intelligent roofer in NNJ
Excellent work! We install intake vents on home ALL THE TIME for exactly the reason that you stated. It's a shame the poor homeowner kept attempting to correct a roofing mistake by upping their AC size..ugh!
Older houses, like mine, have an attic fan that pulls air through windows and blows it out through the attic vents. This cools the house and attic at the same time. When using the AC the attic gets hot because it's natural air flow doesn't keep up. I think I'll put a couple of wind turbines on the roof like our old house in Louisiana had. On that house I cut an 8 inch wide strip in the soffits all the way around and covered it with 1/4 inch hardware cloth. It breathed very well after that.
Turbine fans work great when combined with adequate intake vents. Our most effective measure at improved cooling ability is air sealing the attic floor and taking the insulation level to an R-49. It sounds like the previous fan that you used was a whole house fan, installed in the ceiling and not the roof? That would perform the way that you described.
@@insulwiseenergycomfortsolu3293 All the houses on our area had in the ceiling attic fans when I was young. Didn't have an AC until I was 15. An old second hand widow unit that was loud and made the whole house jump when it's compressor cut on. It did keep Dad's house under 85 degrees on those 100+ summer days. Drying out the 90%+ Louisiana humidity was enough to make 80 seem cool.
We have a whole house fan. We also have a ridge vent, gable vents, and soffit vents. When it is cool in the morning, we turn on the fan which cools off the house and the attic from the previous days heat build up. It works like a charm and delays the air conditioner from coming on until the afternoon.
You have a good system there. In dry climates that can work very well. In our climate though our heat comes with A LOT of humidity. When the whole house fans switch on they pull in humid outside air. You get the draft/ breeze effect, and you will cool the attic, but you're still stuck with the humidity.
We used to do that in NY, but in the Mid Atlantic coastal area, we get too much humidity - especially in early morning when its coolest. Very common to have over 90 percent humidity in the morning. Can lead to massive mold problems if the AC doesn't dry it out afterwards.
@@ratandmonkey2982 Yes, I can se where that would be a huge issue. I'm in California so the humidity is usually low.
Thanks for the video. He was almost right on everyting execpt for the last part of the video. One of the most important thing to keep in mind is that the attic tempreture hould be as close to the ouside tempeture as possibe. For two reasons. 1) To avoid condensation inside your attc due to the extreem different between outside tempreture and a unvented inside attic. 2) if you have snow on your roof, you want the attic to be as close to the outside tempreture as possilbe, otherwise a hot attic will melt your roof snow and the water will run down and refreze at the overhang or in the gutters, This will cause ice built up that can cuase a ice dam that can lead to a roof leak. You want snow melting to occur when it above freezing, that way it runs down the downspout or over your gutters.
Hi there and thanks for the comment. During the winter months you're absolutely right. Your attic temp should be the same as the outside. However during the summer months, if the attic floor has been air sealed, properly insulated to R-49 with cellulose, and vented properly (we prefer using passive ventilation measures), it won't matter how hot the attic gets --- the heat should not penetrate into the rooms below. This is has been the consistent result that we achieve with our customers using our attic upgrade measures.
Condensation / mold problems are not usually summertime problems. The attics get too hot and dry for wood to be consistently wet (at least from condensation). The roof power fans seem to be a cheaper way to cool the attic in the summer, which keeps the house cooler too if your attic is not properly air sealed and insulated. But the roof power fans, from what I have personally seen, do not offer much of an advantage during the winter here. The absolute biggest component of having a healthy, mold free attic during the winter months is 1) having a well air sealed attic floor 2) having bathroom fans vented to the outside 3) having enough balanced ventilation to allow for unplanned moisture to easily vent to the outside.
Andy
@@insulwiseenergycomfortsolu3293 Thanks Andy, Thanks for your reply, You are right It really does depend on the temps of yoru atti. My attic over 150 degress that was drying out my roof decking. My company calls this the double bake, Bake from the top and the bottom. With overheated attics you will dry out your roof deckign leading to delamination of the plywood due to the high heat. And as you said if its too cold you get mold. I traded my 150 degree attic and went with a white silcone roofing coating. I cut my ac bill cost in half as the attic tempretures drop 30-40 degress, but now I have mold growing on my roof decking bottom. I am still working on trying to figure out the right solution for the mold. The attic space in only 3 feet high and there is 2 1/2 feet of blown in insulation. This was in 2008. If I could do this all over I would use foam. Thanks for your replay, David
@@insulwiseenergycomfortsolu3293saying it doesn't matter how hot your attic gets as a general statement seems wrong, if your HVAC is in the attic, it matters how hot your attic is. Your flexible ductwork, no matter how good, does not have R-49, and nether does your HVAC.
@@davidhazen2394 Hi David, 150 for an attic is awful hot, and if you've only got that much clearance between your roof and your attic floor it will radiate more heat downward toward your living space than the roofs that are taller and provide more clearance. I haven't seen too many issues of plywood delaminating in our climate here in Pittsburgh, but that could more of a factor in other areas. When I've seen it occur here the roof being wet, usually from long exposure to condensation has been the bigger factor. If you can get enough intake ventilation somehow, that should help with the mold. Also, I'm not sure if the attic was air sealed or not, but that will also be a factor with mold, at least it is here.
Andy
@@insulwiseenergycomfortsolu3293 Thanks you for the hard work you do in helping me and so many others.
I love my power attic fan. Works great and is programable via my phone. Variable speed DC motor is quiet and efficient. And yes, duh, of course you need lots of soffit vents to provide fresh air into the attic.
When they're situated correctly they can be very effective. It sounds like whoever installed yours put some thought into it! Well done.
We have a 1970's bi-level with up graded R-38 installation,louvers, perforated soffits,power roof fan and ridge vent. We live in NJ. I had the fan thermostat set at 80 degrees. Well fan didn't last long I replaced the fan and set thermostat to the highest setting fan comes on aproxmate 130 degrees nice and cool no issues.
With a well insulated attic -- and it sounds like yours is -- the higher thermostat setting is better. When our customers have these fans that is what we set them to after air sealing and insulating their attics. As you have found you will get a lot more longevity out of that fan.
While living in the South the temperature in the Attic can get up to 150°. I have a two system house. The upstairs system is in the attic I have a vent on one side of the attic approximately 2 by 2 on the wall and on the other wall I also have a 82 * 2.0 with an attic fan attached to it. Since installing it I have reduced the temperature on my upstairs bedrooms by 8°. I noticed you live in Pittsburgh so this may not affect you as much but in the South attic fans are a necessity. If properly installed they can greatly reduce the heat of the upstairs rooms
Hi there, when properly installed and sited I too have seen them work well. Unfortunately most roofers don't bother to do this (from what I've seen) and install them just below a ridge vent, provide insufficient make up air, etc . You've sited yours perfectly to get a cross breeze, not sure if you have a ridge or soffit vents, but if you did they would likely short circuit that cross breeze, at least a bit anyway. If you don't have adequate make up air and you haven't air sealed your attic floor, attic fans will pull air conditioned air from your home in the process of cooling your attic. When we air seal the attic floor, ventilate the roof properly, and effectively insulate an attic floor, there is virtually no heat gain in the upper floor of the home after the work. This solution also pays massive dividends during our cold winters.
Andy
Similar here in NJ and most ANYWHERE in the country there’ll be days when a properly designed attic will benefit from power -assisted ventilation. I’ve recorded 140f and have gable-end fan (with soffit vents) set for 120f. Solar fans are an easy install but as rightfully explained here (in video), must be the right attic setup.
@@gr8dvd what you did right was install a t-stat. It will only run when necessary and shut off again on the overnight!
@@rupe53 Installed so long ago, I forgot many aren’t controlled by a thermostat, also guessed set at 120f but more like 105 or 110f.
Thanks for that explanation. We have a power roof fan but it quit working a few years ago and I left it that way.
Glad it helped
It always amazes me how many people, including roofers, don’t understand the need for intake air to enter the space for exhaust air to happen.
Here here! We this ALL the time. I've also worked in attics on many scorching summer days that had set ups like this (power fan located a short distance from a ridge vent) and the cooling effect was virtually ZERO. The fans run ALL DAY but only re-circulate the air in a small feedback loop. It's a total waste of money in situations like this.
Andy
I have also seen insulation covering the sofit vents on many occasions, and this prevents the ridge vents from working properly.
You're correct, we see insulation blocking soffit vents all the time and have to remove it and install baffles correctly
I have a simple roof. I put a gable fan on one end and a big vent on the other. It does a great job. My cable fan has a digital controller inside that is adjustable and shows attic temperature. Best thing I ever installed.
I have seen that set up work very well, especially when there is not a ridge vent. With your set up, when the fan turns on it will draw air from across the entire attic space, from one end of the attic to the other. Nicely done.
I knew some of this but you were very clear on the video. thanks
Glad it was helpful, thank you for posting a comment!
Timely. I don’t have an exhaust fan in my attic, but the large space is ridge and gable vented. This week outdoor temperatures where I live reached 112 and the attic was 122… (88 indoors without AC). Over night the morning outdoor temperature was 74 and my attic temperature was 84… (78 indoors by blowing out warm air in morning). So the attic is 10 degrees warmer than outdoor air, and my indoor temp rises 10 degrees without using AC. The insulation keeps the ceilings cool to the touch, I feel no radiating downward heat inside the home. It doesn’t seem that I would benefit from placing a fan in the attic to blow out the warm air in the mornings. What is your opinion on this? Central Valley CA, dry heat, humidity avg 40
We are huge fans of "old school" gable vents here, especially when they are large and aligned east / west. I would not install a power fan in your case. If the attic gets hot -- but the insulation is effectively keeping the heat from radiating / conducting down into your home -- then who cares if the attic is hot? That level of heat is not going to damage anything up there. I would seriously consider having your attic floor air sealed though, that would be a better use of resources than a power fan in my opinion.
Thanks! Andy
@@insulwiseenergycomfortsolu3293 thanks!
I just bought an old house in Florida and the attic gets blistering hot in the summertime. The attic was sealed with no soffit vents, no ridge vent, and gable ends closed off. I insulated the attic floor with fiberglass insulation and I recently opened up the gable vents and added ridge vents when the roof was re shingled. Standing on a ladder I can still feel the heat radiating through the ceiling. It seemed to help a little, but wondering what else can I do to increase airflow and keep the temperatures down? Thanks!
If you have ridge and gable vents those are both considered exhaust vents (but east / west aligned gable vents can be highly effective). Without intake vents in the form of soffit vents or undershingle intake vents, it's likely that your attic isn't allowing much heat to escape it. Attic insulation can help A LOT. We insulate with blown cellulose to R-49 (about 15") and air seal the attic floor first. When this is done there will be virtually no heat transfer from the attic to the home. If you cannot insulate more, I'd definitely recommend finding a way to add passive intake vents. You could also add a roof power fan or solar roof power fan --- BUT, if the fan doesn't have enough make up air and / or is not drawing air from across the attic, the effect will likely be limited or worse you could draw air conditioned air from your home. In your situation I'd look into adding intake vents lower down on your roof, possibly with slant back vents (they're designed for exhaust, but will also work as intake vents) and possibly installing a solar power fan in the middle of your roof (in between the ridge and intake vents). That would produce the best effect for you. Good luck with your project!
When the roofers installed the ridge vent in my new home they put landscape fabric over the opening below the ridge vent. They said it was to “keep bugs out” .I questioned that this would inhibit airflow and wasn’t a good idea . They said it was common practice and would be fine . What are your thoughts about this?
We see this done from time to time and it depends on the type of ridge vent that was installed. Some of the fabrics allow plenty of air flow, but some of them (like home wrap or ice and water shield ugh) will be highly restrictive. You could always test it with an incense stick or something else that will produce a visible draft. On a warm day you should be able to see the smoke go right out if it is drawing air.
Heat is not as much of a problem for our house near the coast in Oregon, but pollen and detritus from a heavily wooded property (Fir, Redwood, Pine and Cypress trees) free floats in the air here. House is constantly dusty inside and I'm wondering if some type of attic/ceiling system could help. (probably not but thought I'd ask) I've got an air filter running 24/7 in our main living area and it definitely helps but replacing filters constantly gets expensive. Great video, thanks for the info.!
I'd recommend having a blower door guided air sealing team go to work on your home. I'd get the air leaks sealed in the attic floor, basement rim joists, around windows and doors, etc. We see plenty of houses that are absolute sieves...outside air is cycling through them at much higher rates than you'd want. When this happens it degrades comfort, energy efficiency, and also will introduce all kinds of outside air pollutants. I've included a link for how to air seal an attic that has already been insulated. Hope this helps!
th-cam.com/video/PUSONSE7srE/w-d-xo.html&pp=ygUVaW5zdWx3aXNlIGFpciBzZWFsaW5n
How can a ridge vent work under heavy snow? Vent buried, limited soffit vents in my house.
That's a good question. In heavy snow a ridge vent would likely be impaired. In Pittsburgh we don't get a lot of heavy snows anymore, but if my memory is right even when we did have them, the ridge was usually the first thing to blow off / clear. I think just due to it's exposure to wind. But that's certainly a fair question.
Is it your opinion that a gable vent should be blocked off when a ridge vent is installed? The theory I’ve read is too much air will come thru the gable vent and not the soffit vent.
That theory is right, the gable vents will partially circumvent the draw coming up from the soffit / intake vents. However --- we never seal gable vents when we work on homes. I would MUCH rather use the positive pressure from wind pushing through large gable vents then rely on weak stack effect. I have actually solved serious moisture problems in attics by removing the blocking on gable vents. Especially when gable vents are aligned east/ west -- they can work tremendously.
Had the same issue, builder installed ridge vents, turbines and exhausts. Recently got rid of the ridge vents and exhausts, kept the turbines since work best on our hip roof, made a huge difference.
Sounds good, I've heard that turbines really move a lot of air. Do you have a source of intake ventilation for them?
@@insulwiseenergycomfortsolu3293 Yeah I have soffit vents. So far having only the turbines is working well. Humidity in attic dropped a bit and attic is now only 10-15F more than outside.
In the inland areas of Southern California I have found attics with a powered vent can have drywood termite infestations in the roof rafters. Attics without powered ventilation do not because the heat of summer kills the colonies.
Interesting, it's amazing the differences you can see in homes that exist in different climate conditions. I personally don't have any experience with that.
Thanks for the video! My roof is about 2500 sq ft, and it has 34 soffit vents, 4 gable vents, and a ridge vent above the living space. The garage has no ridge vent, and its the coolest part of the attic. It has a gable vent, soffits, and a roof turbine. Being that its the coolest part of the attic, I presumed the ridge vents are not working well. Its the honey comb style. I added a 3000 rpm smart gable fan on the opposite end of the home over the master bedroom. I am seeing improvement with attic temps by about 10 degrees with the gable fan. However, I dont want to interfere with the function of the ridge vents, even though I dont think they are working efficiently. My roofer also thinks they are not efficient and therefore no longer installs the style I have. Since I am questioning the effectiveness of our ridge vent, I am thinking about adding another smart gable fan on the other side of the home. What are your thoughts about this?
Power attic work fans can work well to cool an attic if they're sited effectively (not close to a ridge vent or some other opening that short circuits the air from being pulled across the attic). I would strongly encourage you to air seal your attic floor if you have the means to do so just so you know you're not pulling air conditioned air up from your home to cool your attic. Adding another fan could help you. Generally our approach is to seal and insulate the attic floor, install passive ventilation, and then just allow the attic to get hot. At this point there will be virtually zero heat conducting from the attic to the home below. The shingles and roof rafters, etc are fully capable of tolerating typical standard summer attic temps.
Your ridge vent is not working correctly because of the gable vents. Only need the soffit vents with ridge vent. Also check the amount of sq in of intake and exhaust. There's a calculator online to tell you how much you need. Finally the ridge vent might not be a good one. Check for external baffle style it also has internal baffle btw. My attic used to be insanely hot and is now never more than 20 degrees over ambient temperature year round. Power fans don't do anything for hot attics in winter and only work when the temperature rises. Why not keep the temperature from rising in the first place. Plus properly vented attics will cool down quicker in the evening. Good luck
@MikeM-bn2ij I thought so. I was thinking about sealing the gable vents, and then hoping there will be an intake and exhaust via the soffits and ridge vents. It's worth a try? I can do a before and after with a remote thermometer
@@rocketj7449 good chance your gable vents are too small, and the fan is not drawing properly. You need about 4 times more than the fan size for square inches at the gable / intakes. Example... 12" fan is roughly 113 sq in. X 4 = 452 sq in. Here's where people screw up... the louvers and screen on a gable vent cut the air flow by more than 50%. Basically, you need a PAIR of gable vents that are about 2x3 ft to get enough air.
@insulwiseenergycomfortsolu3293 what about spray foam on the underside of the roof deck? Spray Jones here on TH-cam says that it does not impact the shingle temperature as much as the choice of shingle color.
If you seal the conditioned space below, why not seal the attic and keep out a much heat from the structure as possible? Why allow a 'hot hat' on the building?
Our house was built in 1995. We originally had an attic fan added to our attic at the time of construction. We do have two gable vents on the side for intake (we're an end-unit townhouse). Now, after about 10 years of so, the attic fan motor blew and we never replaced it. Finally, in 2021, we had our asphalt shingle roof replaced. We had the roofing company hack saw off the exhaust vent, cover the hole with plywood, then they put in the new roof. It looks smooth, and you cannot tell there's an attic fan, unless you go up into the attic. Of course, we won't do an attic vent now, as we have solar roof panels installed over the back slop of our roof.
If your attic has been vented properly with passive ventilation methods, and your attic floor has been air sealed and insulated to at least an R-49 level, you'll be great.
Mine worked perfectly. Home was cooled considerably in minutes.
I have seen them work quite well when they've been configured properly (which where we live is often rare, unfortunately).
Woo....I lived in Tahus..Sorry Texas and we had a the attic fan. We had a different configuration which we would have the attic fan in the center of the house and we open windows from inside the house and the air from outside flew through the house and through the attic and out through the Attic what is your observation of this?
It sounds like you had a whole house fan. These are mounted in the ceiling of the home, not the roof itself and function the way that you describe. In dry climates they can work great (in humid climates they just pull hot humid air into the home..not the best feeling).
How well do the under-shingle or the other roof vents work for input ventilation? If there is snow cover over them, won't they suck snow in through them?
Great question. I first saw an undershingle vent in 2014. The openings inside the attic seemed extremely restricted (we later had mold issues in this attic which is not a good indicator of effectiveness). Since then I have seen many more undershingle intake vents that were obviously moving air and appeared obviously effective. I don't have much experience with how snow impacts them tbh, but nearly all of them have a mesh layer somewhere that I think would reduce the level of snow that could get sucked in. I think the roofing companies would have headed off that problem a while ago (one would hope!).
I put 64 bags of blown in insulation in my attic where 40 were recommended. I have a pea gravel roof where I cemented the pea gravel to four layers of 30 wt. tar paper. After a few years I removed all the loose gravel power washed the gravel and applied three layers of white elastomeric. I have reapplied the rubber every few years because it gets dull and dirty. Now my one of a kind roof is hermetically sealed , even hail cannot penetrate. My utility bills are low I mean really low.
If you have a working system that's efficient good on ya! It sounds original ; )
What should I lookout for or consider for a double wide mobile home with a new shingled roof that got a hot attic space?
I would hire a try to hire an insulation team that understands insulating mobile homes. If you can get that attic better insulated, as well as properly ventilated, your home will be much cooler.
Took our 120 volt powered attic vent out when our house was re-roofed last year. Added a little more ridge vent. Our power bill has been lower ever since. I doubt that kilowatt cost has gone down.
Interesting, and I'm not surprised. If there wasn't sufficient make up air in the attic for that fan, it could also have been pulling air conditioned air directly up from your home. Now that -- is bad for a power bill.
Wish I had seen this before I framed in my new roof! But at least now I can fix it!
Thanks, the main thing is making sure your intake air is 1) enough to adequately supply the fan size and 2) that it comes in from as far from the fan as possible (ideal from the soffits
Great video. I had one installed but quit working and I worked on the wires by unhook them and hook the back. It is fairly new and love for someone have an answer to the problem. Thanks for sharing
im an electrician ,unfortunately i have to go in hot attics all the time repaired/replaced hundreds of attic fans. most of the time the motor will go bad froze up (hard to turn) you can bypass the thermostat and hook power straight to the fan to test it. when i replace everything motor,fan blade and thermostat,the thermostat has a bypass on it for testing fan
Thanks for the info!
Great video, I have the same issue in my attic. Any chance you can recommend someone in Cleveland, OH area? Thank You!
Hi there, unfortunately I don't know roofers in Cleveland. Your best bet would be to learn as much as you can about roof ventilation, then call the highly rated ones on google and have them come out. You'll know when you've met the right guy.
I have always been told if your house had ridge vent and sofit vents, you should cover the gable vents, is that correct?
That is the correct theory. What I have found in practice on a number of occasions is that removing the covering (placed by roofers) over the gable vents allowed for a strong breeze to through the attic (very effective on homes with east / west alignments). My guess is this view will be contentious, but I've solved some nagging attic moisture problems by doing it.
This video didn't consider the gable ends of the attic. No need to cut any holes in the roof that can leak. Just use the gable ends for vents. And an exhaust fan on one end would be great for summer heat.
Holes in roofs don’t leak if they are installed correctly. Its a good idea to have some eyebrow vents high and low. Heat rises and needs to escape.
This was actually a hip roof (kind of like a pyramid) so a gable fan wouldn't work. You're right in understanding how that set up would work, but every roofer around us is programmed to close off all gable vents and slap on a ridge vent...and sometimes a power roof fan with it. The roofers seem to be getting better educated though. We do see more undershingle intake vents going in...gradually.
You are correct. We install vents all the time.
What kind of exhaust fan do you recommend for hot Florida!
Generally we'd recommened 1) Air seal the attic floor and get all bathroom vents vented to the outside 2) Confirm you have adequate intake and exhaust passive ventilation (or add if needed) 3) Insulate attic floor to R-49 with cellulose insulation 4) If you still have heat penetrating down into the living spaces, then install a fan as a last resort. We like solar fans because you don't have to worry about the wiring part
But did that fan and ridge vent installation meet the code minimum? There might be the problem.
I don't know that. However, I don't think the code people are that knowledgeable, seemingly, when it comes to this kind of thing. We see set ups like this so frequently that I don't think that code officials are routinely analyzing the placement of power roof fans and make up ventilation sources (passive intake and exhaust vents).
Andy, what do you do in older houses that may have blocking between the soffit area and the attic? Drill holes? I guess if the house needs a new roof anyway, under shingle vents are a good solution, though it seems you'd need a whole lot of those to equal the venting you could get from continuously vented soffits which would also be much more discreet. Love your channel!
Hi there and thank you! We usually don't attempt to vent solid soffits. I've done it a few times and its extremely laborious and time consuming. What we typically do is install a series of slant back vents, usually on the back of the home, to provide adequate intake ventilation. They work extremely well for us. Undershingle intake vents also work great for intake and we are huge fans of them when they can be installed. If you could have a roofer or siding contractor install a continuous soffit vent however by cutting through that wood, that would also be an excellent solution, and you wouldn't see the vents on the roof if you did that.
Andy
@@insulwiseenergycomfortsolu3293 What happens to the airflow into undershingle intake vents during snow events/ice damming?
I have an older house that I think is similar to the OP's description. It has holes drilled into the wood (2"?) with little metal vents with screens to keep the birds and larger bugs out. It provides some air coming in but their total area is not enough for the amount of vents near the ridge and they also covered some of the 'soffit' vents with insulation on the attic side.
Anyway I get pretty bad ice dams and have wondered if undershingle vents would work.
I have not found anyone around here who really knows what they're talking about along these lines. Wish you were in my area.
I don’t use AC at all. I’d like to suck out the hot air from the house itself.
Hot air pools near the ceiling.
Does it make sense!
What’s the best way to do that?
If you live in a dry climate a whole house air can do a great job (not a roof fan). If your climate is humid like ours you will likely need AC to be comfortable.
@@insulwiseenergycomfortsolu3293
Dry climate, central/north California, near the coast.
Nice concise video, thanks!
I have a large solar powered fan I am getting installed and was thinking of foaming shut the ridge vent adjacent to the fan so it pulls air from farther away in my attic. I have a large gable vent at the furthest part of the attic so plenty of ventilation.
"plenty of air" through a gable vent would need to be 2-4 times the fan area in square inches. If you don't have that then you don't have plenty.
There calculations for that, one gable vent might not be enough to supply air fan needs.
Good thinking that would work better. You just need to make sure your gable vents are large enough to provide the required NFA (net free air) so that the fan does not depressurize the attic and pull from your home. You could also augment the gable vents with a few slant back vents placed lower down on the roof and far from the vent for additional intake.
Not sure I understand, if u have just a ridge vent and an attic fan to pull air thats hotter than outside air out of the space, then why would it be a fail?
I will have to do a test with attic thermometer to see if there is no reduction in attic temperature.
What my experience has been is that the air from the fan and ridge vent re-circulates in a relatively small area. And on a sunny day that air will be going over top of a roof that can be 150-170 degrees -- as opposed to coming in from soffit, undershingle intake, or even gable vents. The air in that one location could be cooler, but the air will not be getting drawn from across the attic --- which is what you want. We've worked in hot attics with these things running all day when they've been placed in close proximity to a passive vent (usually a ridge vent), and there's very little if any impact on temps in the rest of the attic (it was as annoying as it was enlightening!).
I'm on the fence about putting a 24" 4200 cfm exhaust fan on the side of the my house where there's a vent I do have soffit air intakes and ridge vent on top of the roof. I think that fan will help with the extreme heat in my attic
Is the heat in your attic conducting downward into your home and making it hotter? Is the heat damaging things you have stored in your attic? If neither is the case, I wouldn't. And in your case you'd need to install it in a place like the middle of your roof so that it pulled from both the soffit and ridge vent. If you installed it at one end it will pull only from the local vents and may not impact things much.
Not just houses, but all buildings need proper ventilation of the roof structure. Moisture rots wood. Having proper air flow to keep your structure dry is critical. I just finished building my post-frame barn out back with 24 inch overhangs on all sides, plus 100% vented soffit panels and a full-length ridge vent. The roof has OSB on top of the 2x6 purlins which are top edge flush-mount between the trusses using joist hangers. Passive ventilation will keep everything dry. The white steel roof will keep it all cool.
what do you mean by white steel? Is it a standard metal roof painted white?
You've got a smart system there down to the light roof color. Your type of system is what we like the most and recommend to our customers. Cheers!
About 28 years ago I installed a gable fan on one of my gable vents. This along with great soffit venting, my basic 3 tab shingles lasted 30 years and still looks good. My cheap OSB plywood roofing looks new too. Only replacing my roof to be proactive. All the roofers are telling me they only do ridge venting and now I have to block my gable vents. I bet my roof only lasts 20 years max with this inferior system.
That's too bad, if you have something that's working I hate to mess with it. However with full soffit vents and a ridge vent, you should -- should be just fine. That said, 30 years on a 3 tab shingle roof is outstanding!
For air to cool your roof space, it need to flow from somewhere cool like the soffit and exit near the ridge.
You are correct! Thanks for the comment.
Andy
Good overview. When I reroofed, they added shingle vents along the full lower roof line (as my soffits are too narrow for typical vents) and added a full ridge vent. Summer does cause the attic to get rather warm just from the normal full sun the roof receives. I'm wondering if augmenting the ridge vent with a solar powered fan (or two) would be of any benefit to pull some extra air through the shingle vents or if its a waste and the air would simply pull through the ridge.
That's the way the one at my parents was done last time it was roofed. It rarely gets into the 90s around here, so it probably wouldn't have even occurred to them to have an actual fan installed as previously there was no ventilation at all. It was a couple layers of asphalt roofing over the top of cedar shakes. I haven't noticed a difference when I've been over there. The box fan that I bought them years ago to get a good cross breeze going on the top floor of the house has made a much, much bigger impact.
The roof fan will pull from the nearest vents, so if you place it near the ridge I wouldn't expect much of an impact. If you placed it in the middle of your roof, equidistant from the exhaust and intake vents, that would pull air from a wider area and more than likely get you a better result.
I purchased a house in Mount Lebanon 30 years ago and installed one of those power attic fans on a thermostat. I had a walk up attic with a door on the second floor. Whenever that fan kicked on, I opened the door and it sucked all the hot air out of the entire house. It was better than central air.
If you don't mind the extra work there's ways to make a system like that work, for sure.
The international energy code requires 1sq.ft of soffit ventilation for every 100 square feet of attic space . If you use as many Power vents as are required to vent your attic space you will use as much or more electrical energy as you save . Not counting the cost of the power vents and the labor to install them and there average life span is about 5 years. You need turbine roof vents or ridge vents or stand alone vents. Ridge vents that don't have baffles can leak from wind blowing in rain or snow. You need attic ventilation in the winter to help stop moisture that lowers the effectiveness for your insulation. When insulation gets wet its like putting on a thick wet sweeter on a winter day.
We are big fans of effectively sized and placed passive ventilation for sure, for all of the reasons that you mentioned. Cheers!
Andy
@@insulwiseenergycomfortsolu3293 Thanks Andy you know your stuff.
My dad had a gable vent fan that cooled the attic a little. Contractors sided over the vent opening, installed perforated soffits, ridge vents and powered roof fan; absolutely no cooling effect in the attic. Dad's gable vent alone was the most effective of all these efforts. Cannot find a contractor who will install gable vent/fan.
We have seen this many times. That power fan is probably located too close to the ridge vent if I had to guess. At this point if you had a power gable vent installed it would likely have the same result because it would also pull from nearby ridge and soffit vents -- short circuiting air flow from coming across the attic. Either way the goal is to cool the house --- not the attic. To do it the right way you want to air seal the attic floor and have the attic effectively insulated. If you do this, you should have virtually zero heat transfer from the attic down into the home. Then you'll have the benefit of a far cooler home, and also a warmer home in the winter that uses significantly less energy year round to heat and cool itself.
Andy
@@insulwiseenergycomfortsolu3293 observation is correct; power roof vent was installed2+ feet below the ridge line. We have great insulation in the attic floor (house ceiling joists) with craft foil facing into the attic; NO heat transfer into house from attic; but attic becomes very hot; attic used as storage area, have melted some plastic items; may have to uninstall the power roof fan since ineffective, and place radiant reflective barrier in inside of attic rafters?
For those of us who have HVAC ducts in our attics and an AC that can't keep up with the heat, passive ridge venting is often not enough. I'm looking into radiant barrier and ridge vent fans (Ridge Blaster). Anyone have experience with this type of fan?
In this attic we spray foamed the solid metal ducts, air sealed the attic floor, and then blew the attic to R-49 with cellulose insulation. That process dramatically reduced the cooling load of the home, and is highly effective at reducing cooling loads in nearly all the homes that we work in. Is that something that you've considered?
Thank you for this video. Now I think I'm wasting my money with my powered attic fan. I live in Fort Worth, TX, in a 100-year-old, 1,500 sq ft bungalow with a simple gable-style roof with large gable vents at either end. I installed a powered attic fan near the ridge many years ago, thinking it would improve the removal of hot air from my attic in the summer. But I have exposed eaves, so I don't have soffit vents. So it is probably pulling conditioned air in through the many penetrations in the ceiling and walls of my home. Looks like I've got a big job ahead of me before the brutal heat wave gets here and roasts my house again this summer, starting with sealing things up well, of course. So, thanks again for this video!
Hey there, you're welcome for the video. I can't encourage people enough to air seal the penetrations in their attic floor. I have another video that details how we do that. Powered roof fans can work well for cooling an attic, but we've seen them cause problems as well when 1) they're not sited properly and 2) when they don't have enough make up air in the roof assembly and pull air conditioned air from the home when they operate
@@insulwiseenergycomfortsolu3293 Yes. I bought a Flir thermal camera and have been hunting down all the areas of cooling loss and heat gain. I think I'm going to have to vacuum all the old insulation out of my attic to really get to everything. There are so many old penetrations that are covered up by old insulation. It's hard to find them all. But I'm probably long overdue for vacuuming out that attic anyway.
A temporary solution while you get around to sealing the attic floor may be to install a gable mount fan on the opposite gable vent, but flipped around to be an intake. If it has the same CFM as the exhaust fan, you won't be depressurizing the attic and therefore won't be sucking conditioned air out of the living space. Be mindful that the open blades will be a hazard if others will be wandering into the attic. Might be a simple way to keep the attic very close to outside temp. Curious what Andy thinks of this.
You have two gables just install an intake fan on the other one. Easy peasy. I live in Dallas and fans work. My attic temps have never been more than 10F off of my inside home temps and my heat pump works way less. Definitely save on energy bills since I installed it years ago. Not to take anything away from this guy but he lives in PA. Way different temps and situations. He seems like a knowledgeable person but he doesn’t have experience with your situation. They dont get 115F for months straight like we do.
@@zimvader25 I never see attic fans that are designed or marketed as intake fans. All the ones I've seen are designed to be exhaust. Have you seen any? Or do you just flip the exhaust fan around as I suggested in prior comment?
You are blaming the roofer at 0:48 - no, it might be the siding guy that did that. And the insulator should have stapled in some vent troughs before the insulation went in.
Now, I don't know whereabouts this was shot, but there's inadequate insulation there, and the ducting should be insulated.
We had a solar fan in the roof from the previous owner - didn't work, so I upped the insulation and we had a mini-split installed for the upper room - normally we only get 25° max, but occasionally it hits a high of 32°C and a low of minus 5°C... the mini-split keeps the missus happy.
In this case we know it was the roofer, but you're right siding and many trades will perform this task. We actually were the the insulating company working here. We did not install soffit baffles because there were no soffit vents on this home. Part of the work scope was spray foaming the exposed duct lines to seal and insulate them, air sealing the attic floor with foam, and then blowing the attic to an R-49 level with cellulose insulation. But I'm glad that you're seeing good results with the repairs you've made to your home!
@@insulwiseenergycomfortsolu3293 Thanks for the update. You do an important job!
Add sofit vents and put a pipe that attaches to the bottom of the fan and hangs down into the attic space so it does not suck from the ridge vent. Convection buy itself does not always work you need a temp differential.
Interesting, I haven't seen a pipe used to draw air from lower in the attic, but that would probably work better than having the fan opening situated directly next to the ridge vent as it is here. Thanks for commenting!
Between the video and the comments on the video, I have a much better understanding of my roof and attic parts, and why its so hot up there.😂
Glad that you found it helpful!
how do you blame the roofers for no bird block vents or eve vents ??, Thats a load of B S unless they framed the house
BS video.
@@loboxx337correct- it is not up to the roofers- it is the job of the framers.
I just think someone being told to do something should understand it enough to say "there's no vents for this to suck from" instead of taking money and asking no questions.
Good Roofers can fix what the Framers did not do properly. I just had my Roof done and they added Openings in the Soffit (was Solid Plywood) and Perforated Soffit Covers and then added a Fan to work with them. My attic is now at least 15 degrees cooler (probably more) especially on 90 degree days. It used to be about 10 degrees hotter in the attic than outside, and that is no longer the case by at least 5 degrees.
👍 agreed
Good info.
Thank you!
My gable mounted fan is exhausting hot air from the attic. The make-up is coming from the soffit and the ridge vents. All my bathroom fans vent directly to the outside.
The bath fans vented to the outside is perfect. Your configuration could work, but I would expect for the bulk of the make up air to be coming from the soffit and ridge vents located nearest the gable fan. I would expect a measurable increase in attic temperature for every foot you moved away from the gable with the fan to the opposite gable without the fan. But perhaps not.
Great video!
Glad you enjoyed it!
I'm wondering if the power vent was installed prior to the ridge vent being cut in it a later time. In any case I agree with others that the fault likely does not lie with the roofer.
All other points made are dead on!
Good question, but the roof and power fan were both new. We see roofers do this all the time. They don't understand the theory (which is sometimes shown in a picture on the back of the box) for how these are supposed to work.
@@insulwiseenergycomfortsolu3293 You have to wonder how someone could not comprehend such an obvious concept!
My powered vent motor was seized. That means it was trying to spin?
We see bearing failures in these things all the time. They're usually durable, but they often run forever due to the temp or humidity settings they are set to. That's another reason that we don't like them. Even if they're properly situated on the roof and have adequate make up air -- as soon as or if they break down -- you will likely have a problem. You noticed this issue, but many homeowners are oblivious...out of sight out of mind kind of thing.
My house has the soffit vents plus 3 gable openings to pull in cooler air.
That could work excellently assuming the gable vents are large enough for the fan to get all of its make up air from them.
I just had a new roof installed on my house and I called the contractor and said that I would disconnect the wiring to the power vent and they could install a new hood on it because hail damaged it. He said great appreciate it. The next day I went back up and they boarded up the hole. 😡. Is this worth fighting over? Or did they do me a favor?
It depends. If you previously had enough passive exhaust vents and they were balanced between intake and exhaust, (and your attic floor is insulated to at least an R-49 and ideally also air sealed), you should be fine without it. But --- if that fan was functioning as your only source of exhaust ventilation (sometimes it's done this way), then you probably need it back.
a properly vented roof extends the life of the shingles......like to the warranty and maybe beyond, plus less ice damage.
Correct, properly vented roofs do A LOT of good.
You kind of answered the question. If you do not have ridge vents, and you do have rafter vents it will work great.. You skipped over your own question.
If by rafter vents you mean soffit vents, than yes -- a roof power vent can work very well to cool down an attic (assuming that you have enough soffit intake vents to provide adequate make up air for the fan. If you do not, the fan will depressurize the attic and pull the air from the house. This is the last outcome that you want, but unfortunately a common one).
if you have gable vents it defeats the purpose of ridge/soffit vents. Just the rules. The fan fixes that mess up
I'm aware of this "rule" with the vents, the idea being that gable vents short circuit some of the flow between ridge and soffit vents. I'm sure that is true. However, I have seen many cases where east/ west aligned gable vents do a phenomenal job of moving air through attics because they take advantage of natural air flows. I have even solved a few serious condensation issues by unblocking gable vents that had been blocked by roofers after they have installed ridge and soffit vents. The most notable being an obvious whoosh of cool outside air blowing through one of them as soon as I removed it. I no longer adhere to this rule. For me it's a case by case basis depending on the orientation of the home.
Yes, great video, thanks!
Glad you liked it!
Hey dude Roofers don’t install the gable vents or soffit vents. While they do install the power attic vents it’s already tacked in place and they have no choice but to install them.
Roofers can install a variety of roof vents, such as undershingle intake vents which are thank God becoming more common. If a roofer is knowledgeable about how these things work, they should never install them in scenarios like this. The homeowner is relying on the roofer to understand these situations. Often, sadly, the roofers don't (from what we see).
A manometer in the attic will indicate if the attic has too much vacuum. You should have a manometer and know how to use it. It's your job.
I had several square feet of soffit vents installed 20 years ago.
I wasn't there to prove that the attic was depressurized when the fan was operating, I was there to show an example of how not install a powered attic fan (right next to a ridge vent) and also highlight that these fans CAN depressurize attics when not enough make up air is present.
So it's faulty venting not a fan that's wasteful......
The passive vents work together as a system with the roof power fan. If not configured correctly, the fan becomes wasteful at best.
Would a gable fan work in this situation?
I am not an expert but can pretty confidently say "no" unless you were to pair it with some kind of make up air from the opposite gable
If you don't have ridge vents and you have a gable vent at the opposite end that will permit enough make up air than yes, that array could work well
They work great ridge vents suck.
Caveat --- they can work great when sited properly on the roof along with effective intake ventilation --- until their motors or bearings go.
A ridge vent & soffit vents are really all that is necessary. Let simple science work FOR you. 🙏❤😇
I had a new roof installed on my house last year, and had significant changes made compared to the old one...first, they created a ridge vent, and second, I went with light grey shingles as opposed to the dark blue ones before, (which basically became almost black over the years), but I had the attic fan re-installed. I have a big, easy-to-read outdoor thermometer in my attic and I have found the difference between the fan running and not running on hot days is about 8 to 10 degrees. Worth it?...I think so.
@@CarlGerhardt1is lookup attic foil. Put it up against the rafters and over the insulation on the attic floor
We agree!
I have worked in attics where these have been sited properly, and when the fan turned on experienced a 30+ degree drop in a matter of minutes. The further these are located from passive vents the better they work (to draw air from as far across the attic as possible). If you're happy with the performance however power to you.
I was a home inspector for 30 years. Was the open elbow pointing up into the attic from an interior exhaust fan? Certainly appeared like it. That's a big no no.
This attic was still a work in process and it would not have been left that way. But you're right, big no no for sure!
thank for info
You're welcome!
Great video
Thanks!
The *_only_* time a powered vent makes sense...
When I was growing up, my parents had a large powered vent fan installed in an upstairs central hallway. It had a timer on it and was used at bed time to draw cooler air in from open bedroom windows and pump it up into the attic displacing the accumulated hot air. It worked rather well. Now, keep in mind, this puts a rather large uninsulated penetration in the ceiling of the second floor living space. Think of it as an open bathtub drain for hot interior air to disappear through during the Winter months...
A typical gable attic fan will not move enough air regardless of eave venting to dissipate the heat wattage dumped on to the roof by the Summer sun.
So, what a homeowner should do is: 1) Air seal the highest story conditioned living living space with canned spray foam. 2) make sure there are plenty of eave vents, install quality and durable attic insulation baffles. 3) Insulate the attic to three or more feet of fluffy stuff.
Optional) Go with some type of radiant barrier properly installed with an air gap.
Thanks for commenting, you're spot on with the ceiling mounted whole house fan, except for that during hot days the thin aluminum louvers allow intense attic heat to radiate into the living space, and if you live in a humid climate -- the outside air getting sucked in will be unpleasant. I have seen roof mounted attic fans work to cool the attic, but the best solution is the one you mentioned --- air sealing and insulating the attic floor and making sure you have effective intake and exhaust passive ventilation.
Andy
@@insulwiseenergycomfortsolu3293 Yep!
I've never run the air conditioning in any of my homes unless requested to do so by visiting guests. FYI, I'm at 40°N latitude in the Midwest And, I'm not uncomfortable. It's all in the air handling.
And a whole house attic fan? Not necessary. A couple of $20 box fans placed in windows with blocking so the breeze is blowing out, allow bedroom windows to be open for the incoming make-up air.
Air sealing, eave vents, and lots of fluffy stuff!
Here's a video on my take on DIY attic eave insulation baffles:
th-cam.com/video/ZB346-ng_8Q/w-d-xo.html
Been using a pair of turbines for 3 decades..............not a watt yet.
Turbine fans can work great...hopefully you have good intake vents to feed them (otherwise you'll be feeding them with air from your home...which is likely being air conditioned during the summer).
consider some more insulation.
After this video we air sealed the attic floor, spray foamed the exposed duct lines, and insulated the attic to R-49. Good observation!
You're the 2nd guy I've seen who wants me to suspend my belief in the laws of physics when you said that, while having soffit vents and continuous ridge vents, the ridge vent becomes ineffective when also having a power vent. Do you want me to believe that hot air ceases to rise? Who writes your script? The objective is to vent out hot air. Who cares how it gets accomplished.
Hot air certainly rises, that is not what this was about. The point was that power roof fans are often installed too closely to passive vents for them to create the desired impact of cooling the attic. If your power fan is a short distance from either a ridge, gable, or soffit vent, then it's going to pull much of its air from that vent -- causing the air to circulate in somewhat of a loop. It very well may not affect temperature at all in the bulk of the attic area. This isn't theoretical. I have spent thousands of hours working in attics on hot summer days and have seen this effect repeatedly.
If you're going to install a fan in your roof, you want it to pull air from as far across the attic as possible, rather than in just a small localized area. If you're going to have a fan at the peak of the roof, then you probably want to either seal off or restrict your ridge vents so that it pulls almost exclusively from soffit or gable vents. That will maximize its effect. However, you are then reliant purely on that fan working in order for your attic ventilation to work. If it breaks or wears out (and they all do at some point), than you have a severely restricted exhaust ventilation which is not ideal (until you fix or replace the fan, and often people don't realize that's broken / not working). That's why we are much bigger fans, in the majority of cases, of passive ventilation combined with an air sealed and effectively insulated attic floor.
Andy
anyone with two brain cells to rub together can understand the importance of an attic fan. Think of your car on a hot day. When the windows are up does your car get hotter inside than outside. Obviously. So how do you cool it down? open the windows. Can you open your roof? Obviously not. So you blow out the heat with a fan and it sucks in new cooler air--still hot but not as hot
The first goal (generally) is to keep the house cool which we accomplish by air sealing and insulating the attic to an R-49 level with cellulose insulation. But if your goal is truly to cool your attic, then roof power fans can work well --- when they are sited properly with reference to passive roof vents for make up air --- and when there is enough NFA (net free air) being supplied by the passive vents to avoid the fan pulling air conditioned air up from the home.
@@insulwiseenergycomfortsolu3293 yeah, you can spend 20k trying to re-insulate your attic and save about $50 a month on your HVAC bill. Or you can just put in a $300 attic fan or even 2 for a total cost of $700 and accomplish 95% of what 20k gets you.
The best you're ever going to do is cool your attic down to the temperature of the outdoors. If it's 110 outside, your attic is going to be 110 sooner or later in the day.
And most if not all people don't understand building science! Even the people that write the codes! Remember building codes are the "minimum" building codes! Fiberglass and Cellulose should be outlawed! They just don't work! Convection (air leakage) can't be stopped by loose fill insulation! And HVAC (Heating, Ventilation, Air Conditioning) 99% of the time is installed incorrectly! In your video you have equipment "outside" of the thermal envelope! If you insulate the "shell" of the home everything you do in the future is "inside" the thermal envelope!
You're right, they are minimum codes, and I don't know how much building science code officials are often aware of. That said, we get consistent and excellent results by combining intensive attic air sealing measures with thick R-49 levels of cellulose insulation. It's certainly ALWAYS ideal to have the HVAC equipment located inside the conditioned space of the home, but sometimes you just don't get that. In this attic we spray foamed all of the exposed duct work which definitely helps.
@@insulwiseenergycomfortsolu3293 Cellulose doesn't air seal. Spray foam insulation is the only way to go.
I have ridge vents in Louisiana and they don’t seem to work worth a hoot. My attic is hotter than balls.
With roof ventilation you need to have both exhaust (ridge vent) and also intake (soffit, under shingle, or slant back vents placed down low on the roof). Also, how well is your attic insulated. In most cases the end goal is to keep the home cooler, not so much to keep the attic cooler.
good
Thanks
And the air that the attic fan pulls from you house has to be replaced some how so hot moist air is drawn in from outside increasing the load on your AC system.
whether you have a ridge or passive gable end vents or powered gable end fans, if you have proper soffit intakes gown low, you arent going to be drawing air from the living area.
its the absense of intakes that makes ridges not work and powered fans to suck ait from inside the house.
You are 100% correct. When roof power fans are not configured properly (and in Pittsburgh they rarely seem to be) they are a waste of electricity at best and at worst cause you to cool your home with your air conditioner -- while pulling in additional hot outside air which as you stated increases the cooling load of the home which is bad bad bad...
Radiant barrier is step one.
Maybe in the southwest, but I believe in the utility of them up here.
@1:50 As an expert, you lost credibility when you claimed the attic fan would draw air conditioned air out of the house. HuH?
Sorry, but you are incorrect. It is widely understood that power roof fans --- IF not supplied with adequate make up air in the form of passive roof vents --- will depressurize the attic (effectively turning the attic into a vacuum) and pull air upward from the home (through air leaks in the attic floor) and exhaust it through the fan. When this happens in a home that is using an air conditioner, that is air conditioned air that is getting sucked into the attic and blown out through the power fan. It is an idiotic, but common mistake that happens when these fans are installed (unless it is the homeowner's strange goal to cool their attic with their air conditioner...)
@@insulwiseenergycomfortsolu3293 I am right, as why would anyone use an air conditioner in a home that leaks air into the attic? You must be talking about sub-standard homes? Even my 80 year old house doesn't leak air into the attic. Electrical and plumbing orifices are sealed with caulking, and newer homes are supposed to be sealed with plastic air barriers? AND, every sub-standard home that does not have some type of soffit or end gable venting, plus roof venting should be remediated, BEFORE any attic fan is installed. Even BARNS have fans to either bring in fresh air or exhaust gasses, or huge venting.
whole house fan. Cools both the house and the attic.
where would it go and how would it work. Im interested
In dry climates they work great. In humid climates like ours the effect is less so because you end up sucking in all the humidity that's in the outside air.
@@Laguna2013 I googled "whole house fan" and found a lot of references. Mine is installed (by me) over the center hall next to the heater intake in the ceiling. It was a matter of placing ceiling joists in a box configuration that the fan sits on, then putting a hole in the ceiling there. A vent cover (supplied with the fan) goes on the bottom, then you run power to the fan, and I installed the fan switch (also provided with the fan) in the wall of the hall under the fan by drilling a hole in the top plate and running a wire down to the switch. I believe I got the fan from home depot. Its been there for more than 20 years.
It works by sucking air from the ceiling in the center hall and pushing it into the attic. There are three big vents in the attic that let the air out. The efficacy of the fan depends on the outside air temperature. I usually wait until the outside is 10f lower than the inside temp before running the fan. It can take a while to equalize the inside and outside temperature. I believe this is because the house itself has absorbed a lot of heat during the day. This is one reason the fan is so effective, the attic has a lot of heat stored in it during the day that needs to be gotten rid of.
We are in 100f+ temperatures of late, so it is getting a good workout.
As a Homeowner: another example of idiots working on a House and no one to monitor nor control the mistakes
Unfortunately yes
If your good at math it does not take much effort to figure out attic fans do not provide enough air flow for temperature management. The point behind attic ventilation is moisture control. To keep the humidity as low as possible. Then the next step is to ensure you have enough insulation of the proper type to keep your house cool. air sealing your deck is also very desirable.
I’m good at math. A 250 cfm fan will do a full air exchange in a 2000 cu ft attic once every 8 minutes. That’s 15 air exchanges every two hours. Go sit up in an attic for two hours on a hot summer day, and then tell me you don’t wish you had a fan.
@@FFL-vg9ro Even though an attic exhaust fan can incrementally lower the temperature of a very hot attic, using a fan does not stop the source-radiant heat. During the day, any cooler air brought in by the fan will be heated up immediately by the surrounding structure. Most fans cannot keep up, because Physics
An attic fan that is properly sited with properly sited and adequate intake air can make a big difference, I have experienced it personally. But most of them are not set up properly, they're just kind of "tossed on" like this one. But the overall goal is to keep the house cool, at least in my opinion, less so the attic. A properly air sealed attic floor that is then insulated to R-49 with blown cellulose with properly sized and sited passive ventilation will perform that job the vast majority of the time.
I havs a solar powered roof vent fan.
Good deal, hopefully it's arrayed right and doing a good job for you.
Hard to hear
I started using a microphone for videos right after we did this video. Good observation!
Finish carpenters install soffit vents roofers roof. Power roof vents work, I know, I had one.
You're mistaken on just about everything you said.
Sorry, but I'm not. Power roof fans not doing their job when ineffective make up ventilation is present is well understood in the building science community as well as among the better roofers.
I once read that the only way an attic fan would be effective at reducing heat is if it could move massive volumes of air -- along the lines of a small propeller-driven aircraft engine.
If that is true, then how in hell can a passive ridge vent move enough air to do anything at all. Your argument is illogical on its face.
@@FFL-vg9ro Not arguing anything, just sharing an anecdote. Happy to be proven otherwise. I did have 2 attic fans in my old house and they didn't seem to make much difference though.
@@FFL-vg9ro I have the same point as you brother... a powered fan is Working and exchanging air in ways a passive cant come close to approaching..with proper soffit intake all around the roof,. hot air, in a best case scenerio with a ridge, is just slowly oozing out those ridge baffles and thats assuming the ridge Doesnt have a gauze type filter pad blocking even that meager flow... I'd love to see the actual cfm and air exchange rate of a ridge vs two 16' powered gable end fans rated at 1900 cfm each.
I have seen one well positioned power fan drop the temperature in an attic from 120 degrees to about 80 in less than 10 minutes. The fan was positioned at the top of a hip roof, there was plenty of intake ventilation around the perimeter, and there was no other exhaust ventilation (vents up high) other than the power fan. So they CAN work excellently. However, the majority of the time that we encounter them they are positioned too close to passive vents (usually ridge vents) to have that effect. In these cases, like in the video, the fan runs and runs and has little effect on attic temperature.
Why do proponents of power roof fans never mention the fact they don't do anything for those in cold climates in winter. it's not good for a hot attic when the outside temperature is 30f and the attic is 70. Ice dams mold etc
If you have intake like from soffit vents, it would help. You want a cold attic so snow doesn't melt from the bottom only to refreeze, form ice dams, and back up under the shingles. In this setup, your insulation is between the attic and the living space.
I would think it would be good because it would exhaust the hot air out of the attic and pull cold air (less ice damning) dry air (less condensation) into the attic
You need that air flow in the winter, For dampness and condensation.. you always need fully vented soffits, gable vents, and roof vents 8 ft apart... Over ventilated, and the shingles will last much longer... Plywood last longer and may not de laminate...
gable end fans also have thermostats that can be set according to what ur trying to achieve...
For exactly this reason we are huge of proponents of 1) air sealing the attic floor 2) insulating the attic floor to R-49 with cellulose insulation 3) installing passive ventilation that is adequate and balanced for the size of the attic. If you do these three things correctly, you should have a comfortable and energy efficient house year round (assuming the rest of the home is properly insulated), and not have to worry about ice dams or attic mold. Annnndddd...you will not have issues with an attic fan that is potentially installed incorrectly for a variety of different reasons.
Yup, there can be no exhaust of hot air if there's no intake of cool air. I disagree on the insulation thing, the hot attic, if not properly ventilated, will still "heat soak" down into the house. My house in Cleveland had minimal venting and it was literally impossible to add more to the soffit, so the fan I installed helped, but not enough. It was hottest in the house in the evening AFTER the sun went down as the heat energy came down. You could feel it when you went from sitting down to standing up and your head got into the warmer layer INSIDE the top floor. I don't think even my new build house (2019) has enough vents. If I ever do a new roof, I'll have it done my way. My builder allowed no modifications like that to the approved plan.
This is an interesting comment. I can see how "heat sink" could happen, but I haven't seen that when attics have been insulated to R-49 with cellulose and also air sealed effectively. Our typical feedback from our homeowners is that after doing the work, the temperature difference between the first and second floors on hot days goes from 8-15 degrees to 1-3 degrees (you'd still expect it to be a little warmer at the upper story just because heat in the home naturally rises).
That said if a home had a dark shingled and or low sloping roof, and it wasn't insulated and air sealed effectively, I could see this definitely happening. Effective roof ventilation is definitely important though.
@@insulwiseenergycomfortsolu3293 "Heat SOAK". Insulation slows and limits the heat transfer, but does not eliminate it, so, if there is an attic full of really hot air, no matter how well insulated the top floor ceiling is, if the heat can't escape upward, it WILL come downward into the house, it just does so after a period of time. Which is why it was always hottest in my house in OH hours AFTER the hottest part of the day. Even newer houses aren't built with adequate ventilation IMO. My next house will be more of a full custom, bulit the way I want it, and will include some novel ventilation designs.