- Igloos
- Caves
I should have noted that I assumed the hotlanders were cold-blooded due to their major struggles with the cold. This may not necessarily they're as cold-blooded as earth reptiles, but colder than earth's warm-blooded animals.
Of course, you'll need a fire of some sort, but if you can vent the smoke and can keep the opening protected, you can make it comfortably warm in a number of different settings even with medieval tech because we've been keeping ourselves warm in cold settings for millennia.