I sent you a message saying: I have a lath and plaster house - as far as I know there is no vapor barrier. The house has rough stucco (chicken wire, etc.) on the outside. I'd like to remove the stucco, then put on sheets of blue rigid foam insulation and vinyl siding. I've already done that on one outside wall. I'm hesitant to do the other three walls in the same fashion because the inside wall of the wall that's already been done sometimes feels moist during the winter months. Do you think the blue insulation is not breathing and that condensation is forming inside the wall? Do you think I'll get rot inside the wall? Do you think I should use sheets of white (rather than blue rigid foam insulation to finish the house (i.e. does white breathe better than blue?) Is the R-factor with white as good as with blue? Ren, in your response to me you suggested that the blue insulation appears to be acting as a vapour barrier and is on the wrong side of the wall. You suggested using rigid glass fibre of the same thickness for the other walls, and you cautioned that the wall that already has the blue may rot out in the future. Ren, would you please respond to the following points: I've looked for rigid glass through a variety of stores in the Thunder Bay, Ontario area and I'm told it is no longer made. Do you know of a supplier who still carries it? Or do you know of another product that would serve the purpose just as well? And, is installing blue insulation on the outside of a wall that does not have vapour barrier incorrect practice, or do you think that maybe the blue insulation is not the problem at all? I've installed new windows and a mid-efficiency furnace in my little house. Could these strategies be causing the moisture on the inside surface of the wall? I notice there is condensation on the inside of my windows in the mornings, enough to wipe off with a sponge. The amount of condensation is somewhat decreased by having a large fan going during the night and cracking a window. Some suppliers I've spoken to suggest that blue insulation on the outside wall locks moisture in the wall; others suggest that putting blue on the outside is fine - that the new windows and furnace are the problem and I need a dehumidifier on the furnace. Thanks for "puttin' up" with all my questions! I'd appreciate any thoughts you have about strategies to rectify these challenges! Thanks a million! Your pen pal
Answer:
If your local outlets don't handle this material, your might have to go further afield for it but its out there. If the rigid foam insulation is 1.5" or more, it is its own VB so I would not install it because it can create condensation on the wall interiors. You should be able to do away with the window condensation completely with the fan and on rare occasions, you might have to open windows a bit. Whatever condensation is caused by new windows and a good furnace can be controlled without having to take into account the conventional way of doing insulation. A dehumidifier will not be your answer. Never hesitate to submit your questions! If I can be of help, I'm happy to deal with them and they are by no means an inconvenience to me.
