Six months after interior walls were painted water marks are showing up in various places what is that? No roof leaks and it is on interior walls inside house not just the outside interior walls.
Could be a few reasons:
- open attic above and wall cavities open into that attic allowing cold air penetration and condensation buildup
- humidifier setting too high causing condensation on walls
- very humid crawlspace (if you have crawlspace) and moisture migrating through the floor or floor vents
- flooded air ducts under the slab (if you have a slab)
Maybe none of the above but it’s difficult to answer without knowing the layout of your house and several other conditions that might be affecting what you describing… such as you location / climate, heating system, etc.