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Roof mounted whole house fan

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Joined: Oct 25 2004

I've been toying with the idea of putting a roof mounted whole house fan in to cool down the house during the two months a year when it gets sweltering. Since I have no attic, the fan would be venting the air directly through the living space via some vents near the ceiling to pump the hot air out. Does anyone have any experience with this kind of application and/or any comments as to what to expect?

Joined: Aug 12 2004

If you are going to be putting in a new roof in the next few years, consider going to foam. That alone will drop your interior temps by 10 degs or more.

The noise form a whole house fan would be another consideration.

Here's what I've done and my house is about 15 deg cooler than it was before.

Foam roof. Went with DuraFoam and was one of the first. There are a few things to consider for proper installation. Think Dura-Foam was still in their learning curve and now notice that their "new" installations took care of them.

The garage should have a turbine fan/vent. These are the round, wind drive. No electric motor. Get the ones with two bearing, they last longer. Put this in ****BEFORE**** any new roof.

I put in a 4 foot x 4 foot sky light. It's operable, meanign it opens. When it's hot, we crack it during the day and fully open it during the nite. I've also put in a 3rd layer and used polycarbinate (Lexan), so this one is a triple layer (better insulation).

The original garage doors have been kept for the looks, but have insulated them. HomeDepot sells 1 inch thick styrofoam in sheets. Cut them to fit inbetween the door panels (inside). Then cover the whole thing with 1/8" thick paneling (door panel I found at HomeDepot) on the inside. Gives the interior a finished look and the doors no longer "glow" with heat after they've been baking all day with direct sun. Also keeps the garage decently warm during the winter. I didn't do this, but is an after thought. Foam in a can would have been the icing on the cake around the various edges/corners/etc where I couldnt/didn't cut the styrofoam well enough. Use screws to hold the door paneling on. Door paneling was very reasonable, but don't remember the exact price...just remembered very reasonable.

The above and then keeping all of the windows and doors closed during the hot day, keeps the cool air in and the hot air out.

Joined: Mar 31 2003

Well, we certainly attribute a good deal of our house's comfort to our foam roof. But we also have the orginal evaporatiive cooler "swamp cooler" that has a fan-only function. It sits on top of the house and when it's cooler outside, or if we just want to freshen up the house with outside air, we run it for a while in fan-only mode and it works extremeley well. Is this perhaps what you're asking about?

Joined: Oct 25 2004

hi mondomo,
i've been toying with something similar, to replace my overhead stove nutone 270 cfm useless kitchen fan with a 1200 cfm attic exhaust fan. here are my 2 cents: a) it would mean cutting a larger hole (making sure i don't cut through any wires); b) somehow make the ceiling asthestically pleasing to cover the fan blades (maybe some sort of clipon window screen), c) but, then it would have to hold the grease so now i'm going to need an aluminum cooking grill (do they make them 16"x16"?); and d) what about the motor noise? i think the noise would be minimal with the motor mounted outside (unlike the nutone fan which is mounted inside) but then should i worry about the vibration?
your thoughts are greatly appreciated.

Joined: Jan 4 2004

I have addressed this specific topic in great detail about 4-5 months ago in this chat forum; I have installed whole house fans in many homes; I've never installed one in an Eichler, but I have a few ideas to make it work, being that we have done many similiar roof modified/supported exhaust systems. Remember that if you do this type of installation and you have an older modified bitumen or tar & gravel roof, It will be difficult to find a roofing contractor that will warranty a repair to a penetration this large. Additionally, you will need to bring a 120V power source to the unit above the roof membrane, and fish a wire down the wall to the switch.
When properly installed, whole house fans are an effecient and effective means of cooling a house about 10 degrees; they are extremely uncommon in Eichler homes (I've never seen one installed and I have been working on Eichlers for over 20 years), because of the lack of attic and roof systems make it a bit cost prohibitive to install. Also, a sheet metal box will have to be constructed to allow access to the unit from the roof, and a special roof cap will need to be made to prevent water from entering, while not restricting air flow. Good Luck


Joined: Oct 25 2004

I suppose I should have been a bit clearer. I recently tore my chimney out, leaving a 7x3 foot hole in my roof. I've utilized the space that my old San Francisco studio sized fireplace took up to put in a new gas fired sealed fireplace unit and install a closet and expand the kitchen a bit. The new construction will go all the way to the ceiling where I've put new T&G pine roofing in to fill the 7x3 hole. The roof mounted whole house fan has all the "guts" on the roof, as opposed to the traditional attic installed house fan. Therefore mounting, installing, wiring, and putting vents in at the top of my fireplace/closet construction will be a piece of cake. Theoretically I think this will work well to cool the house in the evenings when I get home to a firey house, but I didn't know if anyone had tried this approach in a home with Eichler type ceilings or homes with a 10 degree roof pitch and had any problems/observations. As for a foam roof, its on the list, but I'm waiting for my $622 inheritance when my folks kick to help defray the $15,000 cost.

Joined: Mar 2 2004

It's GREAT to hear that you don't plan on blowing your inheritance...(Like on hats or something). Your plan sounds good to me. I've seen fans on skylight boxes, which is convenient if someone later decides they need a skylight more than a fan. A swamp cooler is a great suggestion, but can't go here, since the intake would be too close to your fireplace exhaust. Install a skylight box tall enough that the top edge of the wood box will be a minimum of 4" above the future finished roof surface. (Use a 2x10 or 2x12 for the box). If your fan can sit on top of the skylight box, and must be level, just add to the top of the box to level it.

Joined: Nov 24 2004

We live in a "flat top" Eichler in Sunnyvale that gets real hot in the summer. About 8 years ago my husband designed a whole house fan (at least that's what I call it) which we put in a central location in our home -- it works wonderful once the outside temperature is cooler than the inside temperature. I'd be happy to show it to you (as I am not good at describing it). Unfortunately, I'm not sure if my husband could find his plans for it (as he had the sheetmetal fan housing built by the company doing our remodel at that time). Please email me if you are interested. (We have a tar and gravel roof; we had to cut a hole in the roof for the fan, and get electrical to its location and to the wall below it for the controls, but we were remodeling so that was part of the remodel.)

Joined: Oct 25 2004

Happy to say that I am just finishing up the installation. The roof mounted fan sits on top of the roof and is open to a insulated "cubby hole" accessible through a trap door at the top of my hall closet. The cubby hole has vents that are close to the ceiling, and they only open when the pressure from the fan pulls them open. This way the house doesn't lose any heated air during the winter months when my wife has the heat cranked up. I'm looking forward to summer so I can test it out. On another note, I also had a Velux powered skylight installed for more cooling and more light. I was able to use the wiring that went though the roof to my old stove vent that I removed to power the skylight. Chris McGovern of McGovern Skylights in Petaluma is a certified Velux installer and did an excellent job.

Joined: Jul 23 2009

Has anyone put in a whole-house fan more recently than those in this conversation thread?  I am contemplating putting one in and trying to get a sense of what it would entail, recommendations on who could do it, etc.  We have an exhaust fan in the ceiling above our stove with an approximately 18" x 24" grate.  I've never looked inside the grate to see what sort of mechanism is inside, but whatever it is, it has recently stopped working.

Sarah Bagwell

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