Q. In one of our rooms we continue to have that musty smell…

For the past few months, particularly in rainy season, there has been a strong musty smell, which seems to be coming from the windows. There is no visible mold. We’ve used Concrobium in a fogger for both rooms, which suppressed things quite well. That was two years ago. The smell is coming back with a vengeance this year. I’ve sprayed Concrobium on the windows and window trim, and it helped for a bit. We believe the mold is probably inside the window frames and may have even migrated to within the walls. It’s certainly not bats or mice or bees, as some have speculated.

What are your thoughts on this?

A. I am going to guess that you are correct and have a mold problem inside the walls. Just because you don’t see a leak does not mean you don’t have one. It can be around the windows or within a flashing detail above them. Over the years we have found many leaks that go undetected for years until we open things up for a remodel.

Sometimes you will need to open up the walls to replace or treat the wood or drywall. You would be surprised at how resilient wood can be; often it doesn’t have to be replaced — just dried out and treated. The treatment is key to ensuring the smells are eliminated before closing up the walls.