DayZ field wiki · Survive
Indoor fire
A roof helps
Short answer
Some fireplaces work inside. Rain does not. A house fire is still a tell through the window.
Also: fireplace indoor
How it works
Barrels and indoor fireplaces exist. Not every room is a hearth. This is not a building list.
What to do
Use them. Don't live in them.
Don't
Don't burn the only house you wanted to sleep in as a bit.