Expert: Bruce E. Johnson - 3/27/2009

Question
I have an old brick building (3 or 4 bricks thick) and the inside walls are looking pretty sad.  I'd like to put up a stud wall (2x4), insulate (fibreglass), and drywall.  I've had some conflicting opinions about vapor barriers.  Do I need one against the brick to protect the 2x4's and insulation and then another behind the drywall to protect the insulation?  Or, as on person said, don't put one in either place, let it breathe.

Thanks!

Answer
Hi Chuck, I am not a big fan of interior vapor barriers because they tend to trap moisture on the inside face of the barrier and this moisture can then run down to the floor and eventually cause the edges of your walls to get damp and funky.  However you can get products that will stop moisture from penetrating the brick from the outside (which is where the first line of defense against moisture originates).  Penetrating silicone sealers are awesome for brick.  Dry-lok is a cementious type of product that can be applied to the inside walls for another form of vapor barrier.  If your brick wall is triple wythe then it probably has an air gap and a weep system built into it which also catches and removes moisture.  So getting back to your question, I wouldn't put a sheet type of vapor barrier around the inside of either wall face.  I would use a foil or paper backed insulation and put the paper toward the living space as specified by the manufacturer.  I hope this information helps, feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com