Our heater has not been working efficiently lately, and when we had it checked out, the HVAC guy mentioned we might be keeping our furnace set too low to avoid frozen pipes. He wasn't sure what we should keep it set at, though, as he's never lived in a cold climate before. My question is, how low can a furnace be set without worrying about freezing pipes? Running water is not an option as we're on a very strict water budget and it's extremely expensive to go over budget. Our house is pretty well insulated, although I have no idea to what R value. We do have a finished basement with a bathroom that seems to get down into the upper 40s or low 50s when the space heater isn't being run.