Easy way to protect your stuff is build a pit house. Dig a hole in the ground about a wall & a half - 2 walls deep, ramp up to the front of make stairs, and slap a roof over each side, connected to the ground, use supports if it is bigger, hearth/fireplace in the centre on the floor. Roof covers the whole thing.

If the building is larger & ceiling is high up enough, you won't even need to vent it at the top, it will just pool up & stay at the top. Tried & tested.