I have a block building in the region between Pa and NY, cold climate. It is uninsulated, slab above crawl space. I have furred out the walls, and rolled in pink poly. I plan on putting up T%G Pine over that, I am not sure if it is ok to apply a plastic vapor barrier over the pink poly or not. I have been told it will trap moisture, but everything I find tells me that can be a problem in an underground block setting, or in a warm climate, but not here in the mountains. The outside of the building is painted but the paint is pretty worn out, but I was planning on painting it.
When I read "slab above crawl space". the credibility of everything else goes south. Please explain, and also please explain what you mean by "rolled in pink poly".
In general, there should always be a vapor retarder on the winter warm side of any wall assembly. The question is, have you incorporated anything into the wall which would act as a full or partial second vapor retarder? I will leave those answers to the manufacturers of the various components you have incorporated into the wall.
Architect (NY) and Home Designer (PA)
Posts: 2859 | Location: Tobyhanna, PA | Registered: 24 October 2005
Bought this camp at a tax auction. It's a cement block building, with a concrete slab floor. The floor was cast on some sort of metal framing, suspended above the dirt ground beneath it. The slab is from 4 - 8 inches above the soil. The cement blocks that form the foundation are set on a concrete footer.
The concrete block are hollow, no insulation in their voids. I have used 2x4's to fir out the walls and I have installed pink Fiberglass insulation between the 2x4's (I meant pink fiberglass not poly sorry). The interior side of the cement blocks are bare, no paint on that surface. The pink fiberglass is stapled to the 2x4, but I wish to install some 6 mil plastic to ensure a good vapor seal.
I have been told that will cause mildew because it will trap moisture either on the inner surface of the cement block, or within the fiberglass. I don't see how that is possible in the winter if the vapor barrier is installed correctly, except for the moisture that may be wicked up from the foundation...
Your region requires at least R-19 faced fiberglass insulation for your newly framed walls...which means at least 2x6 framed walls with faced fiberglass in between your studded interior walls.
As long as your interior framed walls (under your drywall) are installed to at least an R-19 with a vapor retarder, you have no worries.
