h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

If there wasn't glass, how would they have kept rain and snow out?

(Yes, I know these must be strange questions, but it's hard for us moderns to imagine a world without glass, let alone indoor plumbing and air conditioning.)

Easy: very few and tiny windows, as you see on the pictures. They may have been covered with thin animal hides, too. I can imagine (just a guess) that in cold weather they were just closed completely. It was simply rather dark in houses and not only during these times but for a long time. Even when glass became available later it was a luxury. EVen farm houses from just a few hundred years ago are still pretty dark inside. Much of the daily life took place outside anyway - if the weather permitted it.

Early American houses might use animal horn, or hides, or greased paper.

Ah, I haven't heard about horn being used.

The Romans sometimes used very thin sheets of marble.

We had lots of animal horn back then. They made eating utensils out of them, I've got a spoon. (Contemporary, made by an artisan who sells at reenactments.)