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Thread: Attic Vents

  1. #1
    Join Date
    Jun 2007
    Posts
    9

    Question Attic Vents

    I have a 2 story brick home, Last summer I had foam insulation sprayed in my attic. The problem I have is that my second story still gets very hot during the summer. I have Gable fan and vent on oposite side and 2 small vents cut into roof near ridge. What else can I do to cool the upstairs?

  2. #2
    Join Date
    Aug 2009
    Posts
    1

    Default Attic Vents

    I am going through the same thing as you and as of yet am still undecided.

    First a couple things. To use Soythane you need a very large air compressor to apply. There is also debate on whether it is proper to spray insulation directly on the roof deck, some will claim it is perfectly acceptable while others will voice concerns over no airspace for venting either causing the shingles to overheat or the roof deck to have moisture problems and rot away. Some shingle manufacturers will not warranty their products unless they are installed on a vented roof deck while others do not care in the least.

    Insulating the attic as you say will help with heat loss during the winter as will insulating the attic floor. If you do spray the roof deck with insulation be sure to seal off the eaves and any ridge vents you might have. Also be on the lookout for moisture accumulation and be prepared to run a dehumidifier if need be.

    Insulating Unvented Attics With Spray Foam1.pdfInsulating Unvented Attics With Spray Foam.pdf444.8 KB Downloaded 18 times

  3. #3
    Join Date
    Aug 2009
    Posts
    62

    Default Re: Attic Vents

    You can install a radiative barrier on the underside of the roof. It is for all intents and purposes fancy aluminum foil that you attach to the deck and it prevents (well, reduces) radiative heat from warming up the attic.

    If it helps you any in my 2 story + basement townhouse if the main level is at 76F in the summer the basement is at about 71F and the top floor is at about 80F and this is with about R32-38 total insulation in central MD (I added R13 fiberglass over the blown in stuff about a year ago). The extra insulation helped a tiny bit, but maybe only by a degree during the daytime. Heat naturally rises, so your upstairs is always going to be hotter unless you run a whole house fan (like in say a central AC unit) full time to keep the air circulating around.

    Blinds/curtains with a white/light colored outter face being closed during the day helps as well by keeping the solar heat gain down.

  4. #4
    Join Date
    Mar 2009
    Posts
    1,387

    Default Re: Attic Vents

    Howdy consider installing a gable vent fan with a thermostat- most come with one. it will exhaust the heat from the attic and you do not need to make any roof openings that you would if installing a roof mounted fan.
    Is there any soffit, eve, vents to allow cooler air into the attic?

  5. #5
    Join Date
    Jun 2007
    Posts
    9

    Default Re: Attic Vents

    No Soffits or soffit vents. I Gable vent on one side and Gable Fan on the other, 2 small vents through the roof. Since the room further away from the Gable fan is the hottest, I thought about removing one of the roof vents and replaceing it with another fan to help exhaust the hot air faster, But I am not sure if that would creat more problem and if I am sucking too much air out of the attic

  6. #6
    Join Date
    Aug 2008
    Location
    Midwest
    Posts
    179

    Default Re: Attic Vents

    You do not say the temperature of the attic on the hottest days, or the size of the gable fan (diameter and amps, or cfm) or the size of the gable vent. I have a gable fan, and vents that equal 4 times the area of the fan. It keeps my attic about 115 degrees on the hottest days of the year. That is about the best I can do without using a lot of power. I have it set to come on at 95 degrees. Most people run theirs a lot hotter, but I have a lot of storage up there.

  7. #7
    Join Date
    Jul 2009
    Location
    Northeast
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    661

    Default Re: Attic Vents

    AS long as you have enough air coming in you'll be OK with what your taking out, I agree with Timothy Miller and the soffit vents, I put them in my house and they made a world of diff. cause your pulling cooler air in and they're cheap enough.

  8. #8
    Join Date
    Sep 2009
    Posts
    2

    Default Re: Attic Vents

    What was your purpose of spraying foam on your roof deck if you wern't going to close it off to outside air being vented into your attic? I take your ceiling is well insulated and you were slowing down the transfer into your attic space???I just finished a new construction for a customer and we foamed entire 4K sqft house, but completly sealed off all exterior walls and decking (except range vent). We used a dehumidifier and air replacer to cut down on the "problems" that a sealed house will have. The attic is about 7deg difference b/t conditioned space. The first cycle on the units took a while to bring the house down to 68 for the test but they maintain the desired temp w/o constantly cycleing on every couple minutes.
    I agree on the soffit vent!!!!! This would have been your cheapest way to start. You would be surprised how much air transfers through your house when you have ample cooler air for the gable/roof vents to pull through your house even when the units arn't powered.

  9. #9
    Join Date
    Aug 2008
    Location
    Midwest
    Posts
    179

    Default Re: Attic Vents

    Quote Originally Posted by aubtiger77 View Post
    What was your purpose of spraying foam on your roof deck if you wern't going to close it off to outside air being vented into your attic? I take your ceiling is well insulated and you were slowing down the transfer into your attic space???........
    I just now realized he sprayed the roof deck with foam,I was thinking they somehow sprayed the attic floor. I would agree that he needs to seal off the ventilation as the attic would be cooler without ventilation. That is how my friend's house is set up. It is of no purpose to have hot outside air above the roof and below it also, if the roof is supposed to be the insulating barrier. Am I missing something here?
    "Lead by Example"

  10. #10
    Join Date
    Jun 2007
    Posts
    9

    Default Re: Attic Vents

    The foam insulation was sprayed on the attic floor. The ceiling of the living spaces. I was told that would put a cap on the house so the heat in the winter would go no higher than that and the heat from the attic would not migrate down.

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