Spray foam question
I have a home built in the 1950’s, currently uninsulated in a vented crawlspace. I am thinking about adding in open-cell spray foam between the floor joists,however the hardwood flooring above does not have a subfloor. Instead, roofing felt was placed under the hardwood floor. This felt sits on top of the floor joist. It sags down a bit, maybe a half inch away from the flooring above it in some places. My question, if I spray foam (or insulate in any way), do I need to remove this roofing felt so the insulation can have direct contact with the flooring?
On the topic of open-cell…the humidity levels in my crawlspace are under control, which is why I consider it over closed-cell.
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As long as the old roofing felt is holding together ok you can probably leave it in place. If the old roofing felt is coming apart, that could be a problem. As long as your floor joists are somewhere around the usual spacing, the spray foam will be able to support itself AFTER it cures. The issue you could potentially have is that DURING application, the roofing felt is going to have to support the spray foam briefly during the curing process. This doesn’t take very long, but if that roofing felt is coming apart you might have some chunks fall out during application resulting in some holes in your foam.
Bill
You might consider going with an unvented crawlspace.
https://www.greenbuildingadvisor.com/article/building-an-unvented-crawl-space
Bill,
The framing is standard, 16 inches on center. For the most part the felt is intact. There are some rips here and there. Should I use some tape to repair any tears?
Steve,
Cost and labor is the main reason why I'm staying vented. Something is better than nothing! And I've done a lot of work to eliminate moisture issues by installing a sump pump, 8 mill barrier, and replacing all ductwork, adding wrap insulation, and wrapping up the plumbing.
For cost and labor reasons, going with an unvented crawl space is often the better alternative. The walls have less surface area than the floors, and they require less R-value. You can also use materials that are less expensive than spray foam. And finally, with the walls insulated, you still have access to the plumbing and wiring that would otherwise be buried in spray foam.
If I had done that much preliminary work, I would consider buying a DIY closed cell kit or a pallet of reclaimed foam and sealing the perimeter.
Correct me if I am wrong, but I have been under the impression that to encapsulate the crawl space, I would need to have a thicker vapor barrier, like 20 mil, taped up the foundation walls and piers. With that barrier you can then apply spray foam or rigid board. My barrier just sits at the bottom of the walls, untaped, only 8 mil.
Also, my access to the crawl space is from the outside, and there really is no door or well. It's a a small entrance with a block of wood that I pull in and out. I would think that I would have to create a door or well to achieve encapsulation.
These are some of the labor things I'd rather not deal with.
Let's start with some of the basics.
What IECC /DOE climate zone are you located in?
Are you air-conditioning the house in summer?
Climate zone 4 mixed-humid, close to the border of zone 5
I have a similar, but different situation. I have an uninsulated field stone walled basement. French drains, sump, and heat-pump water heater control the humidity. I am planning on open cell foam for the rim joists and between the floor joists, to both insulate and air seal the floor. Older house, also no sub-flooring so I really need the air sealing the most. I have no need to insulate the entire basement, as it will never be living space.
2x10 joists, I'm thinking of 3-5" foam. Is there any reason not to use the open cell foam?