The castles and mansions were relatively modern. Most people didn't have "good" home design, they had older, practical architecture. Their homes had thin walls, were drafty, and had no chimneys; there was a hole in the roof where the smoke from your fire would go, so your attic was filled with smoke (where you'd smoke meats for winter).

You're better served by looking to 19th century lower and middle class architecture. Right before air conditioning, but with relatively modern designs using modern building materials and practices ("insulation" (horsehair and newspaper), fireplaces/stoves, corridors with doors to separate cold rooms from hot ones, windows designed to allow cross-breezes, covered porches to provide shade in summer, etc). Right before air conditioning came in, we had pretty much gotten to the peak of design that used natural forms of temperature regulation. Some designs even created mini greenhouses of glass, with half the wall mounted with earth, for thermal regulation as well as solar heating. The only better passive methods invented since then is geothermal.

The peak of winter heat management were the pechka, Russian rocket stoves built into literal tons of masonry, for the most thermal mass possible. You'd heat it up once with a small amount of wood and it warms the house the whole day. They were so big you could sleep on top of it.