Living room smells like attic

I just returned home from being away for a week. While I was gone I shut two bedroom doors. I left and it was 40 degrees, polar vortex happened and it dropped to record colds (negative 20?), and today it’s in the 40s again. I returned home to my living room smelling like attic. I have opened the bedrooms up and opened a window to move some air. I also have a wood piece of furniture that I bought to redo that is new in the room as well. I am washing that first.

In the past, if I have been away, I have thought there has been this oder before, so I dont think it’s the furniture. Would the 60 degree jump in temperature plus the shut up house cause this? I am not sure how to attack this to prevent it from happening again.