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Old 12-01-10, 05:32 PM   #9
MN Renovator
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7 degree C outdoor temp is pretty warm(45f), I wasn't running my furnace then at all. It's a different story when it gets much colder though. It's 20f(-7c) outside right now and I lose a degree per hour from 60 degrees(f) going to down 50 degrees(f) with this temperature outside. Even moreso if I raise the temperature to 68f(20c). Just keeping the temperature at 50f in the house makes a gigantic difference versus 60f because of the ground sourced heat that comes up from my uninsulated basement(which is warmer than the upstairs and its heat rises).

Our dry bulb design temp for heating where I live is -20f(-29c) and I've seen it there or lower enough times to know that it makes a big difference. Doing some very crude and possibly very incorrect math(I'll be able to verify this year), I would lose 3 degrees(f) per hour(1.6c) average throughout January. Not sure what the average was for January last year but the worst days would have been plenty worse.
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