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Community and Q&A

Whole House Fan style ventilation in attic-less SIP roof home

ColumbiaGorgeCharlie | Posted in Green Building Techniques on

I’m commissioning a new construction home in the Columbia River Gorge area that I would like to be comfortable without air conditioning. The home will be one story, made of faswall.

In this area we have a very wide diurnal temperature range. For example today the low is 49 and the high is 87. If that natural range can be evened out, it’s very comfortable most of the year without any artificial heat or air conditioning.

I was considering using a traditional attic with a whole house fan to help cool the house at bedtime. The problem is at 10 PM it is nice and cool out but the house might still be retaining a lot of heat from the day. When it’s bed time I want to be able to blast the cool evening air through the house to change the temperature.

My architect would like to consider a SIP roof (no attic of course) with vaulted ceiling, shed or skillian roof line. That rules out the whole house fan.

What I’m wondering is – is there a good alternative to the attic whole house fan that works in the SIP/vaulted ceiling?

For example with a shed/skillion roof one could imagine sticking a large vent fan through a wall on the high side of the building just under the eaves – can that be done? Are there whole house fans designed for wall application? Or other solutions?

Obviously the old “box fan in a window” method works, but doesn’t flow a ton of air and is rather a clunky plan for a new construction home.

– Charles

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  1. GBA Editor
    Martin Holladay | | #1

    See Comment #11 to my article on whole-house fans ("Fans in the Attic: Do They Help or Do They Hurt?").

    Many manufacturers sell whole-house fans designed for houses without attics. The best such fan is probably the Tamarack TC1000-H Solid Roof Home Ventilator, but other manufacturers make cheaper models -- for example, see this "A Trendy Home" web page.

    Is it a good idea to cut a hole in your SIP roof to install one of these fans? You decide.

  2. ColumbiaGorgeCharlie | | #2

    Thanks Martin. I definitely would not punch a hole in the SIP roof!

    But I see the TC1000 can be installed vertically in walls as well. That makes a lot of sense to me, at the high point of the skillion/shed roof vaulted ceiling, it will get the hottest air, and it's protected from rain by the eaves.

    I don't love having an R-10 hole in the wall, but I suppose I could mount some insulated shutters over it and just cover it up in the winter.

    I found this helpful video review of the TC 1000 with sample noise :

  3. AlanB4 | | #3

    I have looked for a removable fan i can install in a window (like a window AC) but have not found anything with high enough cfm. The few Vornado fans i bought were dismal performers, barely achieving 1/3 of their rated cfm on a garbage bag test so i have not found a low cost option yet. Perhaps retrofitting a 1000+ cfm range hood fan?

  4. user-3258290 | | #4

    (We're veering off course here): Alan, I've been happy with the Lasko 2155A window fan, but I'll admit I haven't measured the flow rate. I believe that fan is identical to the Air King 9155.

  5. AlanB4 | | #5

    I would not consider it veering off course, its another option that would avoid the need to punch a hole in the roof.
    That said i don't believe the 2470-3560 cfm claims, i had a blower door test done with a fan that moved closer to 1500cfm and it blew the pants off any fan i have used and it was larger then the Lasko/King. The rpm may be higher but if they do move that many cfm then they are the best answer and extremely cost effective...

  6. walta100 | | #6

    Take a look at this fan. It is made to mount on the exterior of the building if you had 2 36” fans one mounted over the other on the outside and a 48” exterior grade door on the inside. With the door closed you would have a good air seal and fair insulation. With the door open and the fans running you could move 20,000 CFM. It would be great if you could put the door at the end of the upstairs hallway.

    The fan in the link is 3 phase motor that is a good thing power them with variable frequency drive or VFR would allow you to control the speed / air flow.

    When I had an attic fan it was great when we had the right conditions.

    1 If the outdoor temp is not at least 10° cooler than indoors all the fan did was make noise and wind and did not change the indoor temp.
    2 If anyone is trying to sleep my fan made too much noise. I had turn down the speed / air flow to the point that the fan as ineffective.
    3 My fan was poorly sealed and insulated, I am sure lost more energy thru my fan than it ever saved in few hours per year, I had the right conditions to operate the fan.


  7. ColumbiaGorgeCharlie | | #7

    Unfortunately all the residential range fume hoods that I've seen that claim to blow 1000 CFM actually blow way way less, and make a ton of noise. Perhaps going commercial restaurant grade would work better.

    It seems that CFM and decibel levels of fans are not regulated, so manufacturers make wildly inaccurate claims.

    I've got a Powermatic fan for my wood shop that blows a ton of air, and uses a standard 12x24 panel filter. Something like that for the home would be awesome, other than the fact that it's huge and loud as heck.

  8. AlanB4 | | #8

    That is a very good point, even my current Vornado is very loud even though it does not move much. Until i started using it i didn't realize how much a headache loud omnipresent noise is
    And i agree that its not regulated, they claimed mine was taken into a wind tunnel and tested before being sent to me, so either they are lying or their cubic feet is about 1/3 of an actual cubic foot.

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