How do I make it the least environmentally damaging I can? We have plenty of insulation and double glazing. We don't want steam heat just to keep it reasonably livable. I've been told that in old houses it's best to leave the CH on very low all the time, than to switch it on for a few hours at a higher temp as then it has to heat up a load of cold air. Does anyone know if this is just a miff or has it some truth.