Hello,
I have just built a basement with Thermomur 350. According to Jackon and E&D, you can mount drywall directly against the foam insulation on the inside, which I find unsettling. You are also not supposed to use a vapor barrier.
Thermomur 350 has 100mm of foam insulation on the outside, 150mm of concrete in the middle, and 100mm of foam insulation on the inside. As I see it, the concrete should maintain a temperature close to the average between indoor and outdoor temperatures.
Warm and humid indoor air should be able to get through the joints in the foam insulation, condense on the concrete, and then run back in, making the drywall or OSB damp, which over time could lead to mold.
Is there anyone here who knows about this and can explain where I might be reasoning incorrectly?
/Fredrik
I have just built a basement with Thermomur 350. According to Jackon and E&D, you can mount drywall directly against the foam insulation on the inside, which I find unsettling. You are also not supposed to use a vapor barrier.
Thermomur 350 has 100mm of foam insulation on the outside, 150mm of concrete in the middle, and 100mm of foam insulation on the inside. As I see it, the concrete should maintain a temperature close to the average between indoor and outdoor temperatures.
Warm and humid indoor air should be able to get through the joints in the foam insulation, condense on the concrete, and then run back in, making the drywall or OSB damp, which over time could lead to mold.
Is there anyone here who knows about this and can explain where I might be reasoning incorrectly?
/Fredrik
Concrete is a hygroscopic material that can absorb significant amounts of moisture. Condensation in concrete does not flow back. Consider all the older basement walls made of concrete block that were surely exposed to a lot of condensation. As long as the walls were not covered internally with a moisture-sensitive material, it was fine. The primary purpose of the vapor barrier is to prevent condensation in materials that cannot withstand it or whose function is impaired by it. This is not relevant in this type of construction.