We purchased this 1958 Ranch style home in Denver in July.

Problem is when it's REALLY cold out (single digits) we are hearing loud popping sounds from the main floor area. They are mostly concentrated in an area where where we installed a new oak wood floor to match the existing in the rest of the home. However, we have heard the pops in parts of the home that have original wood floor.

The basement is 1/2 finished and 1/2 crawl space. The popping floors also seems to come more from the section above the crawl area. The crawl space is NOT insulated but does have a vent for forced air so it's not too cold in there.

The attic is poorly insulated so maybe cold air is seeping down through the walls? I'm just out of ideas.

Any theories are appreciated.