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Old 12-06-2007, 09:43 AM   #1
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Q: Closed Cell Foam Thinckness


I was curious what the optimal thickness would be for my closed cell spray foam application. The contractor quoted me 2 inches in the walls and 2.5 inches in my vaulted ceiling. I asked about using more and he said it would be overkill. I would tend to believe him since he has money to loose by telling me this. But, I still would like to know if adding more foam, especially to the ceiling, would be worth while. I live near Atlantic City, NJ about 5 miles from the coast.
Also, he quoted me for 2.5 inches in my floor which resides over a vented crawl space. I am going to use radiant heat on the floor, so I am again wondering if adding more insulation under the floor would be worth while. Thanks for reading this.

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Old 12-06-2007, 04:09 PM   #2
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Q: Closed Cell Foam Thinckness


The amount sounds inadequate for all the applications. What weight foam was this. They come in various weights. More weight, better insulating factor. What about venting in the vaulted ceiling?
You need to supply more details, but just from the levels he's planning it sounds incorrect for the region you live. Call in a few other guys and do some research before hand. You should know what the recommendations are for your region before anyone opens their mouth. This way you know if the guy is blowing smoke. This is a fairly pricey job, put some effort in to get the best job for the money you can.
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Old 12-06-2007, 05:25 PM   #3
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Q: Closed Cell Foam Thinckness


there may even be a required level of insulation required by the building department in your area. I would contact them to be sure.

From what I remember, closed cell iso foam has an R-10/inch rating. That would give you r 25 in the ceiling, that sounds a bit shy. Also, why and how is the guy limiting the debth in the wall. It is typical to fully fill the cavity (3 1/2 in for a 2 X 4 wall)

I would put in as much as you can afford. Contrary to some folks belief, you cannot overinsulate. I have a friend with 12 in walls with blown in insul. He doesn;t have any gas in his house (all electric) and his elect bills avg. $90/month for ~1600 sq/ft in SW Michigan. That is to heat the house, heat water, cook, lighting, clothes washer and dryer.

The insulation saves him a lot of money.
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Old 12-06-2007, 05:52 PM   #4
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Q: Closed Cell Foam Thinckness


It really is quite perplexing to me why he would not want to put in as much insulation as he can sell me. After all, he should be in the business to put in as much insulation as possible. Only thing I can think of is that he is charging me too much for the amount he is using and he doesn't want to blow me out of the water by putting in too much. When I asked him why only 2 to 2.5", he said closed cell foam was so much more efficient that only 2 to 2.5" is necessary. Still, it seamed fishy to me. He quoted me $3500 to do 550 square foot with a 13' vaulted ceiling, one 14 foot wide vaulted gable and one 8 foot wide vaulted gable. Then he wanted $1500 additional to do the floor over my crawl space.

There isn't any venting required in my ceiling since I will be using closed cell foam.

Also, the foam has an aged R value of around 7
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Old 12-06-2007, 07:15 PM   #5
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Q: Closed Cell Foam Thinckness


strangeboy68 said: "There isn't any venting required in my ceiling since I will be using closed cell foam."

This is not true. If you meant that you didn't need a vapor barrier, then that's true. It's pretty obvious this is an unknown subject to you. This is not a position you want to be in.
You need to understand what people are doing to your house. The assumption they know what they are doing is the road to renovation doom. Some idiot contractor who installs a product incorrectly, can cause immense problems later on.
Educate yourself to the basics of the task at hand. It is time well spent.
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Old 12-06-2007, 08:19 PM   #6
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Q: Closed Cell Foam Thinckness


Actually Demilac has documentation and testing reports and I have done non vented attics, if you spray the underside of the deck and seal it completely it does not need vents, the attic becomes conditioned space. Closed cell is R-7 per inch, 2 1/2" won't do it. I had open cell installed and we were doing 8" on the underside of the deck.
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Old 12-06-2007, 08:52 PM   #7
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Q: Closed Cell Foam Thinckness


According to the company that we buy our supplies from, when using rigid foam, which is rated at 2 lb. per cubic foot, you get 96% of your insulating value in the first 2 inches. We try for 2.5 in. just to be sure of a 2 in. minimum. The .5 lb. foam, or open cell, is generally used when you want to fill a wall cavity completely. For more information I would suggest you visit sprayfoam.com.
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Old 12-06-2007, 09:01 PM   #8
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Q: Closed Cell Foam Thinckness


Quote:
Originally Posted by Chris Johnson View Post
Actually Demilac has documentation and testing reports and I have done non vented attics, if you spray the underside of the deck and seal it completely it does not need vents, the attic becomes conditioned space. Closed cell is R-7 per inch, 2 1/2" won't do it. I had open cell installed and we were doing 8" on the underside of the deck.
I understand the postition and agree BUT if there is any leakage in the roof itself, it will not be able to dry out as it will be sealed in so you will end up with rot.

I would rather have the ventilation. As well, unless the attic space is usable, it would be of no benefit to condition the attic space. It would be a waste of money.
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Old 12-06-2007, 09:46 PM   #9
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Q: Closed Cell Foam Thinckness


The advantage of it is when they are there insulating the walls they can do the attic at the same time as opposed to a seperate trip just for the attic (saves $$)

If you have a leak you will find and repair it before rot occurs whether it is an insulated deck or a insulated ceiling.
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Old 12-07-2007, 06:22 AM   #10
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Q: Closed Cell Foam Thinckness


I don't want to get into a discussion about venting here. All my research indicated that closed cell foam doesn't need venting. If you have research to the contrary, please don't hesitate to post it. Also, the roof has very large gables in it, making it impossible to vent the soffits since it hardly has any soffits. The only thing that could be done is a ridge vent, but that would be pointless without soffit vents.

As far as the thickness, I haven't been able to find any online info as to a recommended thickness to be used. There are tons of recommendations out there for traditional insulation, but not foam. All I find are the recommended R values. For the walls, they recommend R-21. In order to get that, I will need 3" of foam, not 2".
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Old 12-07-2007, 10:30 PM   #11
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Q: Closed Cell Foam Thinckness


It is necessary to have a standard such as R ratings to set minimum code requirements however, if given the option, I would consider other factors in my decision. Spray foam becomes part of the structure bonding the frame and shell into a one piece envelope while most other types of insulation are designed to stop air movement by filling a void. Whatever thickness you decide on be sure it is clear with your contractor whether you are speaking of average or minimum depth. In my limited experience it seems very difficult to spray rigid with less than an inch variation.

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