My house is 100 years old and has been remodeled a lot by previous owners (as evidenced by glass, nails, screws, etc buried in the yard). We're in Texas so, the central A/C is on a lot, but this isn't likely to be an HVAC issue. The smell only occurs on hot days, in my bedroom and closet, on the west side of the house. It smells like tar or burning motor oil. It's worst about 4pm. So, I'm thinking it's the insulation or tar paper heating up in the outside wall, but I'm open to other suggestions. Has anyone ever encountered this issue?

Details:

-The house is pier and beam on a slope (bedroom is only 2 feet off ground).

-Roof is metal

-Outer walls are asbestos shingles

-Smell is not noticeable in attic

-Floors are hardwood