Spray Foam a Basement Ceiling


Old 08-15-13, 01:34 PM
Thread Starter
Join Date: Aug 2013
Location: USA
Posts: 2
Spray Foam a Basement Ceiling

Hello all,

So I'm working on a project where an old, large farmhouse is in desperate need for an energy upgrade. I ran a blower door test, and the reading was about 14,500 CFMs, and it could only be depressurized to about -20pa, so the building was essentially a massive sieve with the heat just pouring out.

There are many issues with the home, but like anything, resources are limited, so our idea was to hit the basement first, primarily because the basement has zero insulation, whereas the attic and walls at least have some, albeit shoddy at best.

My thought was to spray foam, using closed cell foam, the entire basement ceiling and the rim joists. The basement has 2 attached crawl spaces which are sitting on dirt, making the rooms above them absolutely freezing. One of the rooms has a water pipe, which I'm planning on wrapping in heat tape to prevent pipe freezing. There is some moisture in the basement, but no standing water. I'd like to avoid fiberglass for a multitude of reasons, including the fact that if there is indeed moisture, that stuff will get destroyed. I feel that adding about 2.5 inches of spray foam is the best bet, and the material is fire rated, so shouldn't be a concern near the boiler/DHWT.

That said, am I missing anything here that could be a concern? There is some ventilation in the basement, and everything is stone, so it doesn't appear that mold would be a large worry. The homeowner has the money and wants to go this route, but before doing it, I want to make sure that we stay in line with the "do no harm" side of things.

Thanks in advance, it is much appreciated.

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Old 08-16-13, 06:24 AM
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Join Date: Oct 2004
Location: WI/MN
Posts: 18,651
Welcome to the forums.

Spray foaming a ceiling is, IMO, a decision based on whether the room under the insulation is conditioned - if it is, I would not insulate the ceiling.

If this room is not heated/cooled, then I like your spray foam idea.

The foam on the rim joists is a good idea either way.
Old 08-19-13, 08:09 AM
Thread Starter
Join Date: Aug 2013
Location: USA
Posts: 2
Hi Mitch,

Thanks, the room is simply a crawlspace/stone basement, so it's not conditioned, outside of the ambient heat coming off the heat plant.

My thought is that the spray foam would not only help make the first floor warmer, but it'd also help mitigate the moisture that is present in the basement, preventing it from wicking up.

Thanks for your help,


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