What could cause condensation inside my exterior walls?
I just started a bathroom remodeling project. When my contractor removed the tile off the walls in the shower and around the windows, the insulation was wet. Condensation seems to be the cause. The question is, how do I eliminate the condensation problem before re-tiling my bathroom? I got new siding three years ago and Tyvek was installed under my new vinyl siding. The Tyvek appears to be installed on top of the plywood without any additional insulation. My contractor feels that there should be additional insulation so the temperature changes of Chicago winters will be minimized on the wall. My siding installer said that is not necessary. As my contractor is working on removing existing tile, I am trying to decide what to do. The past two days, the wall and insulation dry out, but at night when the temperature drops, I can feel the wetness behind the interior insulation. I am at a loss as to what to do. Removing siding and Tyvek and installing insulation is a costly step and I am worried that the problem will not be corrected. Any suggestions?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Kim,
First of all, every standard wood-framed wall insulated with fiberglass batts is at risk for moisture accumulation in the sheathing during the winter. This type of wall always performs better when there is a layer of exterior rigid foam that is thick enough to keep the wall sheathing above the dew point during the winter.
Second, the moisture accumulation that you are observing may not be a problem. Undoubtedly, more moisture is accumulating in this location for the simple reason that you have opened the wall up. Opening up the wall allows warm, humid interior air to access the cold sheathing. Before the wall was opened up, the indoor air had only indirect (rather than direct) access to the cold sheathing.
Third, some moisture accumulation in this type of wall is normal in winter. Since it is usually invisible, homeowners usually don't notice it. As long as the sheathing can dry in the spring and summer -- it usually does -- this type of moisture accumulation may not be a problem.
Fourth, if you are worried about the performance of your wall, you can always throw away the fiberglass batts, allow the sheathing to dry, and install spray polyurethane foam in your bathroom walls.
Fifth, whatever you do, pay close attention to air sealing when reassembling your wall. As long as you do that, everything should be OK, regardless of what type of insulation you choose.
The bathroom is the highest moisture producing area in the home. Bathrooms are easily the worst rooms in a home for air sealing, tubs and showers adjoining outside walls being the worst offenders. The type of insulation will have little to do with future moisture accumulation as long as the wall is properly air sealed.
Thanks Martin and Doug! I appreciate your information. Replacing my siding from a company that was a storm chaser was my first mistake. I don't want to have a mold problem down the road from all the condensation. It will be interesting to see if there is condensation when we do the second bathroom in a few weeks. If adding extra insulation would have been offered, we would have done it from the start. We have learned a good lesson!