Potential Ventilation Issue?

[Steve Jenkins]

Hello Everyone,

I am posting here because I am out of ideas and I wanted to see if anyone has had a similar experience. I am fixing up a home from the late 1960s and have come across an interesting issue. When (and only when) the windows are open, a chemical-like almost rubber smell starts coming from some of the interior walls. The weather outside also plays a factor (the upper 70s seems to be the sweet spot) but I have identified the windows being the key factor.

Has anyone else had an issue where leaving the windows open creates some sort of air pressure differential that pulls a smell out of the walls? If so, what would be some good things to try or look for to remedy this issue?

I am open to all ideas and discussions. I appreciate your help!