Amit Enventres wrote:
Building scientists get all wierd about vapor barriers. In zero energy homes you: yes, want a vapor barrier over everything. In fact, you want it so tight and thorough no air can get through. In traditional housing thought you absolutely do not want a vapor barrier because houses are meant to breathe and such a barrier will trap moisture in your walls causing mildew and mold.
Additional research on green housing evaluating the air barrier affect of multiple coats of paint of various types shows paint (already applied to just about all housing stock) is an air barrier. This seems to blow the whole barrier = mold thing out of the water. This old thinking seems to expect, perhaps no insulation (or limited) and perhaps less mold resistant building materials and perhaps more gaps allowing air to travel through, I'm thinking.
julian Gerona wrote:Let us say you are in a car in a very cold place. your heater is on. Inside is hotter than outside, where does the condensation occur? It is inside, right? the opposite is true here in our hot country. condensation occurs outside because we use air conditioning. Take one wall of your house, cold outside hot inside. Vapor will condense inside and soak your wall with water thus the wall loses its insulating property. Worst if there is enough water in the pores of the wall and it freezes your wall can crack. So yes vapor barrier is needed where there is a differential temperature and you need it on the hot side not the cold side.