Whole house fan - solution that does not require opening windows?

auroraborelisJune 4, 2012

Code requires us to install a whole house fan, which is a great idea as I expect when combined with a well insulated and well sealed house will drastically reduce both our heating and AC bills.

However, our builder was explaining about how you have to open the windows for the system to work. Does anyone know of a whole house fan solution that is automatic and doesn't require going around the house and opening/closing windows?

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kirkhall

Whole house fan to do what? If it just circulates air and has an air return, then, I wouldn't expect you to need to open windows. If it pulls air from the inside and dumps it outside, well then, a well-sealed house wouldn't work very well and you'd need to open windows to prevent a negative air pressure in the house (and subsequent air leakage from weakly sealed points.) I'd potentially post this on the HVAC forum also.

    Bookmark   June 4, 2012 at 4:52PM
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auroraborelis

The whole house fan circulates air from the outside to inside. I'm wondering if there is a way to set it up so it using the return air vents for the HVAC system so windows don't have to be opened.

Good idea to cross post it! Wasn't even thinking about that as I have been spending so much time here!

    Bookmark   June 4, 2012 at 4:54PM
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shifrbv

HRV does not require open windows, or simple 6" duct to outside with ventilation damper attached to tstat

    Bookmark   June 4, 2012 at 5:45PM
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auroraborelis

shifrbv, Just to clarify, do you mean that a simple 6" duct to the outside with a ventilation damper can be used instead of opening windows?

    Bookmark   June 4, 2012 at 5:53PM
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auroraborelis

Also, I may be missing something obvious, but what does HRV stand for?

    Bookmark   June 4, 2012 at 7:29PM
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auroraborelis

Ah, I figured it out HRV = Heat Recovery Ventilators.

That is different from what we need to install. A whole house fan which is required here pulls air from the outside to exchange it with the inside air, the air is filtered in the process, but there isn't a heat exchanger involved. Just a fan.

In our climate it is an excellent heating/cooling solution. During the summer it is 60 F at night, and 85++ during the day. Using the whole house fan in the evening you can cool down the house with the cool outside air very quickly (whereas you would otherwise need to turn the AC on). The reverse is also true, in the winter the daytime tempeture can be as high as 75 F while the evening temperatures are closer to 45. You can use the warm afternoon air to heat up your house, then close it all up before the sun goes down.

In any case, normally it is necessary to open the windows to allow the air to be exchanged (and thus avoiding creating negative air pressure). However I'm looking for a solution that is a bit more automatic. Ideally I was wondering if there is a way to use the air intake that is in each room for the HVAC for this purpose? Some sort of split system?

    Bookmark   June 4, 2012 at 7:41PM
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david_cary

You can have a fresh air intake with a damper. Sort of like the damper on an exhaust vent but in reverse.

Any damper is a leakage point, but in your climate that probably isn't a big problem. The better dampers leak less. You will need a large duct and a large damper.

What is the airflow you are looking for (or code is requiring)?

I'll second the HVAC forum suggestion.

    Bookmark   June 5, 2012 at 5:35AM
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auroraborelis

David_Cary - thanks again for the description.

I'm not sure what airflow is being required, we are still in pretty early planning stages, but we were got to talking about it when it was 80 F in the house and 65 F and still not cooling down in our house! :) (I realize an attic fan is also an essential part of the solution).

    Bookmark   June 5, 2012 at 9:59AM
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auroraborelis

For anyone interested in a more detailed answer to this question, David posted a great response on my cross post on the HVAC forum.

Here is a link that might be useful: Cross post on HVAC forum

    Bookmark   June 5, 2012 at 10:00AM
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tooskinneejs

i'm not aware of an automatic solution to your question, but I doubt it would work well anyway. the point of the whole house fan is to pull large volumes of fresh air into the house and out through the attic to cool the house. this won't be accomplished by simply recirculating the existing air through your house. it also won't work well at all by simply installing a small duct somewhere in your house. doing that will only cool the areas on the path of air flow between that duct and the fan - all the remaining rooms will stay hot.

opening a couple of windows really isn't that big of a deal. i've found that opening one on either end of the house (repeating on each floor) does the trick perfectly.

i used an airscape whole house fan (see link below), which has a 7 foot noise dampening duct between the fan and the opening in the ceiling. it is very quiet. the unit also has damper doors that automatically open and shut when the unit is powered on and off to keep a tight seal between the living area and the attic.

Here is a link that might be useful: Airscape

    Bookmark   June 5, 2012 at 10:16AM
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auroraborelis

Thanks for the explanation and link. Our reasons for wanting automation is 75% filtered air requirements (allergies) and 25% wanting to be able to start it automatically before we get home! :)

    Bookmark   June 5, 2012 at 2:21PM
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still_waters

It seems to me that you should be able to put your fan on a timer. Andersen windows has a motor that can open awning windows without touching them. Several windows can be controlled from the same base. You could put them in sync and arrive home to a cooler house. Also, with Smart Technology, you may be able to start both through your computer or iphone.

    Bookmark   June 5, 2012 at 9:47PM
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auroraborelis

Still_waters! Now there is a great idea!! :) Thanks! :)

I didn't know that such windows existed!

    Bookmark   June 5, 2012 at 9:55PM
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still_waters

Laura: I'm meeting with a window rep on Thursday. When I made the appointment with him I asked him about a transom window over the tub that could open from below without having to stand in the tub to open it. He told me about the motor. When I looked at the specs, I noticed that you can hook several into one system run by remote control. With today's technology, I don't see how you couldn't get what you want.

    Bookmark   June 5, 2012 at 11:07PM
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auroraborelis

Thanks!! :)

    Bookmark   June 5, 2012 at 11:20PM
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still_waters

Laura: I met with the Andersen rep. The motor/kit runs $375 list; additional kit for another window would be $151 list. They need to know when they manufacture the awning window that you will be using it with a motor. I'm in NC. FYI.

    Bookmark   June 7, 2012 at 6:02PM
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auroraborelis

Thanks so much for the pricing, that is actually less than I expected, so it may be a good solution.

    Bookmark   June 7, 2012 at 6:59PM
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david_cary

Wow that is pretty cheap. I am going to say at that price, you will get an on/off switch with no timer or external control. Sometimes adding that is not simple.

    Bookmark   June 8, 2012 at 7:36AM
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