I noticed some radiators have been removed in this re-hab project I'm taking on, and in terms of what heating is actually essential in the short haul, I could shut down some more. Is there a general rule to the numbers of radiators needed to remain 'on' in a steam system? The original ten radiators has become eight, and I would look to have five or less remaining on. Input BTU is 115,000 for a small (1000 - 1200 sq ft) two-story that sits atop a garage. Garage still has one radiator connected (used to have two) and one was disconnected from a top-floor room (no plumbing in the top floor) at the head of the stairs. I would like to use heat tape on exposed copper pipes near the garage ceiling (followed by insulating and enclosing them, to keep cold garage air away) so I can do without having to heat up the garage.