Is a Roof Power Attic Fan a Waste of Money....or Even Worse?
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- Опубликовано: 14 апр 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. 
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As a Homeowner: another example of idiots working on a House and no one to monitor nor control the mistakes
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!
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
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
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
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
Great video
Thanks!
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.