[GBlist] Wall permeability

[Kirsten Flynn <kir@declan.com>]

Title: Wall permeability

Dear listers,
I have been lurking and occasionally commenting on the more general topics for a while now.  My goal has been to learn from the impressive expertise on this list.  I had a question about a building issue that I have not seen addressed on this list.  

First, I will briefly introduce myself.  I am an Interior designer just starting my business and planning to do exclusively green work.  This is a second career for me, and it is time to follow my values, and do something that makes a difference, albeit small.  I am extremely interested in building construction and how to affect the energy use of the finished building.

I would very much like to know your thoughts on wall permeability to vapor.  I have been hearing that there is a movement in Europe, (called Baubiology?) which puts forward the idea that the building envelope should be permeable to gasses.  This idea seems to be popular with some of the IAQ folks, because out gassing does not remain inside the building to combine with other outgasses, and/or be redeposited on indoor surfaces.  However, here the conventional wisdom seems to be the tighter the better, (and I am not talking about the jeans on your carpenters.)  I can also see the logic of this, as it seems like it would be the most energy efficient.  I also am curious about the path of water vapor is such a house, and how one would be sure that the dew point did create enough moisture inside a wall that it might be damaged.

I realize that this is a shades-of -grey world, and there is probably merit in both points of view.  Perhaps they are not mutually exclusive, in some way I do not see.  I look forward to reading your responses.  Feel free to refer me to reference material, rather than answering my questions directly.  I realize they are rather broad.

Thank You
Kirsten.