Instructables
Picture of Whole House Fan
mansard.jpg
In the middle of summer, the second floor of our home gets unbearably hot and humid. Due to the shape of our home's roof (Mansard) it cannot be adequately insulated. I've already installed an Air Conditioning unit that is over sized for the square footage of our home to no avail.

I started looking into Whole House Fans (hereafter WHFs) and as another option, but upon further research found that they needed to vented into an attic space, or outside the home. Because of our Mansard roof, and the floor plan of the second floor neither of these options was possible. We did, however, have a narrow door into the attic of the garage at the end of the hall. This was enough to set my plan in motion.

I did some research on WHFs and found information online regarding sizing the fan to the square footage of your house, pricing, *CFM (Cubic Feet per Minute), etc. I found that I needed "X" amount of CFM for my home and did some online shopping for WHFs.

STICKER SHOCK....WHFs are expensive. While digging around online I stumbled across Drum Fans. These fans are typically used for moving air around workshops, so they're pretty capable of producing gale force winds. I also found that, on average, the drum fans have a higher CFM rating than any WHF with the same blade diameter, and they were 1/3 to 1/4 the price. So I started shopping around for a suitable Drum Fan that I could convert into a WHF. I spec'd one online that moved 2,000 CFM more than a suitably sized WHF, but being "Mr Instant Gratification" I looked for one locally and luckily stumbled across local hardware store that was out of stock, but had a floor model that they'd be willing to sell for less - so I was now at 1/5 the price of a WHF.... BONUS!!!
 
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trbotnen3 years ago
Are you worried about backdrafting? If you are forcing air out of the house through a fan, it could cause carbon monoxide from your furnace to be sucked backed indoors. Other than that, this is a great 'ible.
CementTruck (author)  trbotnen3 years ago
That's a good question. I'm no expert so I couldn't tell you for sure, but my furnace has an electric version of a "pilot light", so there isn't a flame burning all year long, and since this fan is only used in the summer the furnace isn't used at the same time, so I'm assuming I'm safe. I should probably be worried about Radon being sucked throughout the house though.

Another thought too would be the fact that whole house fans even exist, and are sold daily.

I'll have to do some research and get back to you on this. This was just my gut instinct.

Thanks for commenting.

We use a whole house fan.

We have a wood stove and when we run the fan in the summer we can smell the chimney even though we do not use the wood stove in the summer, since our fan is pushing a lot of air.

Just make sure you open your windows that will reduce air coming in from unwanted places. Even if you would suck some radon gas into the house, the volume of fresh air would be so much that it would lower the concentration to almost non-existent.

CementTruck (author)  shortw3 months ago

Thanks for the input @shortw. I thought as much, but as I mentioned "I am no expert" and will be the first to admit it. I'm glad you chimed in.

Do you have any background in this area, or are we cut from the same DIY cloth?

You also may want to look at this, since it will mention what kind of fan to use.

http://www.instructables.com/id/Whole-house-fan-blows-away-our-AC-bill/#step0

I consider myself an DIY, even though I had a lot of involvement with OSHA laws and regulation and exposing to fumes, but that was 20 years ago. I was one of those guys ( research and development )that came up with an chemical (paint related) and translate it into a material safety data sheet that was send with the product.

I have to explain a bit more.

I am limited how many windows I am able to open right now, because the way I have everything set up at this moment, which started as an experiment.

As current, I can only open 2 windows and that is why I have back drafts with my powerful fan. But I do not have to use the fan in the winter when I use the wood stove. And since I use a wood stove, I installed an carbon monoxide detector from lowes hardware which would work also if you have an gas appliance and expect exhaust gas to enter the dwelling.

All the other windows are covered with bubble wrap, which insulate the windows against heat and cold all year long plus I get the benefits of sunlight.

In the attic I added an additional R-30 insulation and this the 1st year where I can cool my 70 year old 1200sqft house down to 72 F with one 5,000 BTU AC here in the south. I use the whole house fan if the outside temps and humidity are lower.

My attic has a louver on each side of the house. I have a low powered fan on one of those louvers that is turned on automaticly if the temperature raised above 100 F this keeps the attic cooler and with it the living space, I done this before I added the R30 insulation.

We have an crawl space that is covered with plastic and that has many louvers, so build up on radon gas would be very limited or not existing at all.

They have companies that would specialize on this and if I am not mistaken Lowes hardware is selling testers for that too. With all the fresh air coming into the windows I am not worried about it,

Years back I used a ceiling fan speed controller to control the flow of a furnace fan. if you do so, pay a lot of attention on the amperage the motor has and what the controller can handle. Use only 75% of the capacity...in other words ...if the motor uses 5 amps per name tag...get a controller that can handle 7.5 amps. With the newer electronics that may or may not work.

A dimmer switch for lights will burn up if you use it with an motor, so do not use a dimmer switch to control the motor.

If you have any more questions let me know.

bajablue1 year ago
I grew up in California. My dad installed a powerful roof fan on our house for the hot summer months. Now I still love sleeping with white noise no matter what the temperature is!
CementTruck (author) 2 years ago
I'm not sure what your local climate is like JTomM129. Evaporative coolers work really well in hot dry climates, like Arizona, and New Mexico, but don't do much good in humid regions. They can also start the growth of dangerous molds in carpet and gypsum boards. If you live in a dry climate then this sounds like a great solution for your particular issue. Kudos on the carbon footprint reduction.
JTomM1292 years ago
Hiya CementTruck!

I just did a sweep of Amazon and found several drum fans slightly smaller (14 to 18 inch diameters) with 3 speeds for under $75 USD. Maybe slightly less fan at a lower speed will sound less like the Spitfires revving up to meet the Luftwaffe over the Chanel but still be enough to cool the place down . . . Just a thought. Also, I was thinking of building a "inside the room vented to the window" (anti covenant restrictions) evaporation cooler at one end of the home with smaller fan(s) blowing inward and a larger "exit fan" (like you WHF) at the other to channel the cooler air throughout my condo. I have a "Shotgun style" Condo (windows and sliding doors at either end of the long floor-plan with the over all effect of a long box with opening on each end) and figured if I could cut 10 to 15 degrees F off the outside temp. by channeling cool air though the tube I could leave my 25 year old inefficient AC unit off and still be more cost efficient and green(er). It turns out a few floor fans work well enough for me for this summer so I've let that idea slide for now, but may try it next year to reduce my carbon foot print.
Exposure1013 years ago
Very nice man! Thats why instructables is awesome!
I agree, great idea,

I will be doing something very similar. and I have a 1 & 1/2 Story addittion to our house that is a self contained home. The roof is tin, and I guess is not too well insulated, I was planning to put a cavity using drywall over some insluation and using small computer fans (12v) and some PV solar panels to run the fans whenever there is light, any thoughts?
CementTruck (author)  OTP13 years ago
@colincox1,

Thanks for the shout out.

I don't know how many computer fans you'll be using, however, PC fans don't move that much air, and so you'd need a lot of them. There are solar roof vent fans that move a little more air (CFM) . The drum fan I installed, however massive, makes the indoor temperature more tolerable, but not as much as I had hoped, or expected.

Depending on where you live, how much sun you get throughout the day, your budget, and a few other factors, the first thing I would suggest is insulating under the tin roof. This will probably be the best bang for your buck at cooler indoor temps. You would need a gap between the underside of the roof and insulation for airflow, as well as a way for that airflow to be refreshed continuously.
Cement truck,

Hey BIG thx, I had thought abot air flow CFM, but now you have made me think more I was thinking to have quiet a few, but as you said, need to understand the CFM better. The roof is insulated some, I do not want to take all what I have of a ceiling down to find out, I was just going to re insulate with batten cavitity with insulation. But the solar roof vent fan sounds good, your points about air flow with insulation is a good remindered for us all as it is often forgotten. PS based in mid OHIO, not the hottest of places, but hot enough for action! :-)

as for the drum fan, I am definitely, due to you , going to do that. just really like the idea of learing out large volumes of heat quickly, then suplement with specific a/c when you want to, than as you said, putting some ac on all day.

thx again.
Rgds Colin
kidproquo3 years ago
This turned out very well. An even cheaper alternative is to use an attic exhaust fan (Amazon has them for about $50). Probably would not move as much air as your setup but for those without quite so dire needs, it should work!
CementTruck (author)  kidproquo3 years ago
Thanks kidproquo.

I already had an attic fan. You're right, it didn't move enough volume, so I had to improvise with this monster.
bowdenja3 years ago
When I was kid we didn't have A/C , we use an atic fan, this while living in Florida.

Man that thing sure made the curtains stand straight out. Seems like that was the best sleep I ever got.

Good instructable and idea!
CementTruck (author)  bowdenja3 years ago
Florida without A/C? Whew!

I used to live in Eglin AFB/Ft. Walton Beach a couple of lifetimes ago, and as far north as that was it was still pretty warm. I miss it though. I also lived in a tropical country for 16 years without A/C and it didn't seem to bother me then. Ocean breezes make a BIG difference. Thjs mid-west heat and humidity sans breezes are a whole 'nother issue though.

Thanks for commenting.

CementTruck (author) 3 years ago
Thanks Sunshiine! Please vote if you get the chance (Epilog).
sunshiine3 years ago
I could use this idea! Nice ible! thanks for sharing!