Sealing and insulating a Whole House Fan
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- Опубліковано 8 вер 2024
- www.drenergysav... | 1-866-607-0191
Fifty years ago, before central air conditioners became the norm for cooling US homes, whole house fans were used for that purpose. Installed on the uppermost levels of the house, they were actually big exhausters, which would suck hot air from inside the house and into the vented attic, causing air from the outside to be sucked in through open windows and doors.
The reason why whole house fans became obsolete is that they don't allow homeowners to really control the temperature or comfort inside the house -- like they can do with air conditioners. If the outside air is too hot and muggy, that is the kind of air that will be brought into the home.
Nevertheless, many homes in the U.S. still have whole house fans installed -- and whole house fans represent a big gap in the building envelope, and can become a huge source of energy waste during the winter.
Because of a physics phenomenon known as the "stack effect," a lot of warm air -- the air that you pay to heat in the winter -- is escaping through that fan, into the vented attic, even when the fan is turned off.
When homeowners no longer use the whole house fan, Dr. Energy Saver usually recommends removing it entirely and patching the hole left in the ceiling with drywall.
Some homeowners, however, still like to use whole house fans to cool the house when the weather outside is nice and comfortable. So what can be done in these cases?
In episode 68 of the On the Job video series, Larry Janesky, shows us how Dr. Energy Saver deals with cases like this. The challenge is to allow the homeowner to use the whole house fan when he so chooses, but also keeping it from becoming a source of energy waste when the heating or air conditioning system is being used.
This particular attic received a lot of upgrades in order to become energy efficient, including an insulated storage deck, can light covers, Rockwool insulation and sealing around the chimney, duct sealing, a cat walk and insulation dams to contain several inches of blown cellulose, as well as professional air sealing.
The whole house fan in this case received a cover made of SilverGlo foam insulation board and completely air sealed. An airtight lid -- which can be removed by the homeowner when he turns the fan on -- keeps the unit fully functional, while preventing energy waste when the fan is not being used.
Whole house fans are only one of the many energy wasting details Dr. Energy Saver technicians find and fix every day, in homes across the U.S. -- and we would love to help you too!
Visit our website or call us to locate a Dr. Energy Saver dealer in your area that can make your home more comfortable and energy efficient.
*Well-made, delivered quickly, and easy to install with **Fastly.Cool** . I may be imagining it, but it seems quieter than the 14 year-old unit that I pulled out. Of course it was noisy at the end due to failed bearings, so hard to compare.*
I made one of those covers with 2" foam board. As far as your lid, you should patent a lid that raises on vertical poles on each corner that allows it to raise when the fan is on and lower when it's off. Send me a check when it's on the market. Thanks :)
I did the same thing about 10 years ago with a better idea to insulate the top. I built a wooden box much like you did with your foam. then built a double door top split in the middle and used hinges to open it up in the spring. I had the whole wooden box spray foamed with closed cell foam. After the foam dried, I took a knife and cut the foam so I could push the double doors open from down below. When spring comes, I open the louvers, and with a stick I push open the bi-fold doors while I stand on a short ladder in the hallway. The bi-fold doors flop open only to a certain point, and I built stops so they don't flop all the way. In the winter, I grab the stick again, and with a hook on the end pull the louvers one by one until they close. I also use 3M window plastic, and with the double sided sticky tape afix it to the metal frame, then reapply the plastic to make it air tight. I save the same pre-cut plastic and use it the following year. I also am considering using one inch foam board cut to fit the metal louver frame, and glue flat magnets on each corner of the foam board so the foam board can act as an insulator against any warm air escaping, and any cold attic air entering the hallway. That may be overkill, but it's cheap enough to execute that as well. Hope this helps others.
Seems like that cover could be hinged and the fan would just blow it open when you turn it on and it would seal again when you shut it off.
Yea you can make this with 2” foam board, some weather stripping, and two hinges. Fan turns on, lid lifts up. Fan turns off, lid falls down. Much easier than going up into your attic several times in the spring and fall when temperatures fluctuate.
Whole house fans work well when the night air is usually cool. Where I live the cool air flows down from the mountains every night, despite the extremely hot summer days. Venting all night with the windows open gives good sleep and cools the house down enough so that no air conditioning is needed for most of the next day. Also plant trees where they will provide shade for the house in the hottest summer days, but that solution takes more time....
I wish he had turned the fan on for people who have never seen one in action. I know some anti-hvac folks will defend it, but its quite awful. Like he said, it sucks in humidity, allergens, and DIRT from the outside. It only “cools” if the outside temperature is cooler than the inside, which means its best to run it at night. But its significantly louder than any vacuum I’ve ever owned. Idk how anyone could sleep with it on, my pets cower in fear under the furniture. The few times I ran it, I noticed the streaks of dirt/soil that had been pulled in, outlining the windows, in the bevels of our panel doors. Besides the obvious efficiency-loss, these things are likely to ruin the interior of the home.
Wow. I wasn't sure if those even existed anymore. But I have a family relative that has a whole house fan that is actually larger than the one in the video. It is original to the house and is almost 60 years old. He replaced the motor and belts, when the motor stalled. I'll upload a video of it if you'd like to see. It's the largest one I've ever seen.
We just installed one last year (2018). They're standard stock items at our local home improvement stores (Michigan)
Great idea as long as the box fits and there isn't differant sizes
You can't get a patent for this, there are YT vids of people doing this going way back (prior art). Why is the box 2 feet high when the fan only protrudes 6 inches?
Two feet high so that its not a trip hazard if you have that cellulose peanut-type insulation all over the attic ?
Great idea- I would buy one.
TKS. JUST. BOUGHT. A. HOUSE. WITH. THIS. FAN. WHICH. WORKS. GREAT. EARLY. MORNINGS. SO. WATCHING. THIS. SO THANKS. !!!
Great solution! Thank you for the explanation. I'm going to call you.
I don't see anybody going up there to take that on and off.
What is the R Value of your 4 inch foam board? Not sure why the box is so tall. Like the idea of the pumpkin cut but a regular full size lid would do the same thing.
whats your thoughts on adding a filter to it that way not so much dust gets into the attic??
Would you as a contractor use a white roofing coating for energy savings and roof protection? I am looking at doing our roof in a white coating similar to Henry's Solarflex.
Great videos as always. I live in Central Florida and I have used your videos for help around our house.
i cant find your video on foam insulation into existing brick walls.
also I have seen foam insulation used to fill the "cavity" directly behind the brick and the tar paper on the sheeting? is this a good idea? house was built in 1973. has no weep holes and when it rains really hard from the north I get water leaking inside under sill plate. house is all paver brick. all 4 sides and 2 stories in back
Thanks for the great video, I am ready to call and set an appointment.
Best thing would be to remove it and put new drywall over it.
You’re a little off on the cfms lol...probably more like 4500 if it’s a 24 inch which it looks to be. More if it’s 30+
patent a foam box. Lol.
Whole house fan, attic air sealing and duct sealing.
Almost every house needs one of those three items.
I’ll bet that fan is probably from the 1970s judging by the harvest gold color scheme
Never mount theses fans on the wall
R-value?
This video is complete nonsense. The fan is mounted on top of the 2x4 joists. You can easily remove the cover from inside the house, unplug the fan, and insert 2” foam board under the cover (that’s just screwed up there and very light), then seal all the leak points and still have plenty of room left over to either put the cover back or completely cover the hole. Results as good or better than in the video and no nonsensical box that costs you exponentially more money but provides zero additional utility than my method. In my house, the metal blades on the cover would exceed 100 degrees in summer while the house was 78. Now they’re the same temperature as the rest of the ceiling. Not only would air leak through that cover because of the poor seal, it would actually heat the room. I just finished this project and the difference is startling. This is the most obvious area to address in a house with one of these fans. I bet mine has cost me hundreds of dollars in the last year.