I played my first game today against another player, and it was their first game as well. We had a situation come up today in our game. Using generic terrain models of a ruined town (burned and busted homes mostly, with some of the barricades thrown in for good measure) we were wondering about getting into buildings via windows. We could get in no problem by doorways, but what about windows? We figured you could shoot out them without issue....

If it's low enough a unit can step over it, probably treat it as difficult terrain, like hopping a fence or barricade.

Per da rules:

Quote

In particular, buildings will sometimes have parts that are impassable while the rest is open or difficult terrain—a mini may be able to move through a doorway or a large window as open terrain, but the building’s walls are impassable. When using a piece of terrain with mixed types, players should clearly define the terrain so that there is no ambiguity.