Thanks for your input.
These are exterior walls so your probably right on both issues. Insulation and air quality.
This winter has been brutal with extreme cold and then warming up etc. That might have caused the issue.
I've had two properties this winter that had mold start up the wall in the main floor bedroom.
I've never had such a problem ever in the past and wondered if anyone knows why this would happen and how to stop it from re-occurring?
