Hi, thanks in advance for any help. We recently had a plumber install a high efficiency peerless purfire 110000 BTU boiler. Last night it got down to 4, and we were only able to maintain a temperature of 61 when we had it set to 65. We asked our plumber how he figured the size of the boiler and he said he measured the baseboards. Our house was built in the 50s and is probably not the most efficient, but we can't really afford new windows. Any suggestions?