I currently heat our house solely with a quadra fire 5700. It does a great job but has a hard time with the -20° f nights lately. I have been thinking about hooking up an older energy mate boiler for next winter. It would go in the attached garage. I would put a coil in the lp furnace plenum and a side arm exchanger on the water heater. My thoughts are to provide better temps on colder days, heat our water, and warmer garage. I know the old boiler isn't very efficient but I already have it. Any suggestions or comments?