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Spray foam questions

Stanger133 | Posted in General Questions on

Hello all, thanks for any help in advanced.
I built a house in East TN about 2 years ago, and I got sold on closed cell spay foam in my attic. My house has 2×6 walls with R19 in them and the floor is insulated. Right now the temp is around 85 in the afternoon and my A/C runs for about 9 min and then is off for about 3 min. My A/C ducts run through my floor, I have since found that having the A/C ducts in the floor does not benefit having foam insulation in the attic. I have also read that this could keep harmful gasses in your home. My question is, is there a way to properly vent your attic and blow insulation in there or would it be worth it since this seems to be an issue with my electric bill.

I have considered cutting a ridge vent in my roof, Putting cut in attic vents in my roof, or putting in gable vents to try to prevent moisture build up and blowing in insulation. I know that i would have wasted all the money on spray foam but my electric bill is about $80/month more then my neighbor that has about 1500 more sqft, and blown insulation in it. They have 3 less people living in their house but the A/C cycles should not be like that.
I would leave the majority of foam insulation on the roof and gables. I would just remove it in the places that I install vents.

Any advice or words of wisdom would be greatly appreciated.

My A/C has been checked and it is properly sized for my house and is functioning properly.

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  1. GBA Editor
    Martin Holladay | | #1

    First of all, can you tell us your name?

    You haven't really described a problem other than high electricity bills.

    Before we can help, we need to know the answers to the following questions:

    1. Are there any visible moisture problems in your unvented conditioned attic?

    2. What type of foundation do you have: crawlspace, basement, or piers?

    3. When you say that your AC ducts run through your floor, can you tell us whether there is any insulation on the exterior side of your ducts? If so, what type of insulation and what thickness?

    4. Do you observe any moisture problems in your floor assembly?

  2. Expert Member
    Peter Engle | | #2

    Please also describe your crawlspace. Is it vented to the outside? Is there insulation in the floors or on the walls? Is there a ground cover?

    Your air conditioner cycling does not seem right for those temperature conditions. When you say that it is properly sized, was it the installer who checked that? Did they run a real Manual J calculation, and what were the results? With a 9 minute on cycle, you're wasting about half of your electricity, since it takes about 5 minutes for most systems to start up and reach steady-state operation.

    How many zones of A/C do you have?

  3. Stanger133 | | #3

    My crawl space is insulated and the ground is covered with plastic. I have had a second individual, not the installer, come and look at the unit. I do not know how they came to the determination that the unit was properly sized, but they said that it is good. It has one zone. There is no visible moisture in the attic. I have a crawl space and some of the house is above the garage. The garage is insulated and has 5/8 drywall on the ceiling. The ducts are wrapped in insulation, I do not know the R value and I can not get to them as they are covered by drywall. My name is Derrick.

  4. GBA Editor
    Martin Holladay | | #4

    It sounds like there is nothing wrong with the spray foam in your attic, so you are jumping to conclusions if you think that the spray foam has anything to do with your high electricity bill.

    There are so many possible reasons why your electricity bill might be high that it's hard for anyone on this web site to diagnose your problem without a site visit.

  5. user-2310254 | | #5


    I think Martin is suggesting you should have an energy expert check out your home to isolate the problem. You can probably locate someone by going to the RESNET or BPI websites.

  6. Stanger133 | | #6

    You don't think that it could be the extra 1300 sqft that I am having to cool in the attic, and not having any A/C ducts up there? That was my best possible answer as I have done an energy consumption on all my major appliances and the A/C unit running for so long every day is the only thing I can come up with. My electric bill in the spring, with my A/C off, is substantially lower then the summer A/C bill. I know you all can not tell me the solution to my problem. But does anyone know if it is feasible to properly ventilate the attic with out removing all of the foam from the soffit area. Would it work to install ridge vent on the roof and install a few roof vents down low on the roof.

  7. Expert Member
    Peter Engle | | #7

    As the others have suggested, your descriptions do not suggest any problems with the insulation in the attic. having insulation in both the attic floor and roof is not generally a bad thing, and it certainly won't make your A/C run more than with a vented attic and insulated attic floor.

    There's a different reason that your electric bills are so high, and an energy expert should be able to help you figure it out.

    I realize that nobody is actually answering your question, so here goes: yes, it is entirely feasible to cut in a ridge vent, roof vents and/or gable vents without scraping all of the insulation off of the underside of the roof. Yes, that means that the insulation under the roof will have been a waste of money. And no, it probably won't improve your electric bills at all.

  8. GBA Editor
    Martin Holladay | | #8

    If your spray foam installer did a good job -- and there isn't any evidence they didn't -- then an unvented conditioned attic is a good thing to have. Enclosing your attic with spray foam insulation usually reduces air leakage from the interior of your house to the exterior, and that's a good thing.

    Trying to retrofit vents into your attic will almost certainly increase the air leakage from your house to the outdoors, increasing your energy bills. Don't do it.

  9. Stanger133 | | #9

    Thanks for everyone's input. I will have to get an expert in here to try to figure it out. Thanks again.

  10. Expert Member
    Dana Dorsett | | #10

    How thick is the closed cell foam in the attic? If it's only 2-3" (as is often the case with the "...that's all ya really need..." school foam installers) it needs more R value, and it would be apparent by the ceiling temperatures below.

    What sort of temperatures are you experiencing at the ceiling? (Buy a $50 pistol-grip infrared thermometer and start looking for hot spots in ceilings and walls.)

    Are there well defined and ample return air paths for every room with a supply register? If not there is a good chance that the big return duct known as "the great outdoors" is a significant fraction of the return path, a large parasitic load driving energy use higher.

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