How were homes insulated before 1900? I know this is a broad question, but I'm guessing, e.g., an Italianate with a brick outside wall simply wasn't insulated. A mason told me they were typically three bricks deep, and then lathe, then plaster, done. But then weren't there non-solid outside walls? I once visited New Harmony, Indiana, and I seem to remember something about mud and straw being used in a wall. I've also heard of coarse wool being used. Anyone know what hollow walls might have had for insulation before modern materials? Another angle would be to ask what natural materials could be used in hollow walls -- whether or not they were used in the past?