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What R value do I need over slab in westchester county, NY

Hammer 🔨 | Posted in General Questions on

Hi trying to calculate the minimum amount of insulation I would need on my basement slab to prevent mold growth. I’m in Westchester County, NY. I’m using eps foam on top of slab with 5/8 interlocking carpet squares on top of eps. I’m using this model:

1. Does the 5/8 carpet squares have some insulation values that would be part of total r value for the floor?

2. Do I need a substrate between eps and carpet squares?

3. Can this become a mold sandwich?

Looking for minimum thickness, thanks for your help.

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  1. Charlie Sullivan | | #1

    1. Yes, the carpet squares have some R value, but that actually makes things worse--it keeps the interface between the carpet and the foam colder, and you are more likely to have condensation at that spot.

    2. Yes, you need a subfloor between the foam and the carpet. Otherwise, you will dent the foam each time your heel lands on it, or put a furniture leg down.

    3. It possibly will develop mold. The likelihood of a problem depends on the humidity and temperature in the basement. But you'd do better with a hard floor surface such as linoleum rather than carpet. As a general guess I'd say 1/2" of EPS under hard materials would keep you safe, or 1" under the carpet.

  2. Hammer 🔨 | | #2

    Hi Charlie thank you for answering some of my questions. Would this set up work better?

    1/2 eps over 6mm poly, floating marmoleum floor on top with area rugs? Marmoleum is more of a green product than vinyl, not sure if anyone has had experience using it or how it performs in basements or damp environments

    1. Charlie Sullivan | | #3

      I have in fact have Marmoleum in a basement bathroom: 6 mil poly, 2" of EPS, OSB subfloor, 1/4" plywood underlayment, Marmoleum. It's worked out great. That's in Zone 6. We had the headroom to do 2" of EPS, so we did, so that doesn't answer your question about what the minimum you need is. I think you'd be fine with 1/2 of EPS, but you do need a subfloor, something stiff enough not to flex when there's a point load on the floor.

      1. Hammer 🔨 | | #4

        Maybe I could use hardboard? My wife wants rugs, I think hardboard is denser than plywood or osb? It comes an 1/8 and 1/4. Maybe I could use 1/2 eps, hardwood, then put some kind of waterproof pad under a carpet to make it similar to foam mat. Basically make the carpet squares myself prob be cheaper and thinner. I think that would put me within a inch height of floor. Not sure if In my climate that would be enough protection against mold build up.

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