I’m working on a 1907 remodel with single pane windows and open crawlspace to basement. The weather has been dipping into the 20’s this past week. I work there 3-4 days a week.
When I’m not there the temp inside the house drops to 42.
The house is fully insulated including the main floor over the basement and crawlspace.
I have the thermostat set a 60 right now. It takes awhile for the house to heat up 20 degrees. Do you think its more cost effective to turn it off each time or leave it on? Thanks for your thoughts
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It's more cost-effective to turn it off when not occupied, but far safer for plumbing, et al, to just set the thermostat to the lowest effective setting.
What would you say is the lowest effective setting. Isn't there a chance of mold spore growth in an unheated house?
Lowest "effective" setting is one that will still cause the furnace to come on -- usually around 45-50.Mold growth is related to humidity, and will actually be slowed by cooler temps, so long as the humidity is controlled. The less frequent operation of the furnace fan (allowing damp air to stagnate) is more apt to cause mold problems than is the cool temps.
(That assumes you don't have a heat pump.)
Unless it'a 90+ coindensing furnace, it can damage the furnace to operate in such cold temps because of the increased chances of coindensation and rust inside the system.
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Sojourners: Christians for Justice and Peace
Its an 80% and its in the basement, the coldest area of the house. So probably better to leave it on at a certain temp?
The 80 plus furnace installation instructions say they should not be used during the construction phase because the low temps typical during construction can lead to condensation within the flue and damage from that condensation draining back into the furnace.It seems to me that the "lowest" OK temp is going to depend on the installation, especially the amount of exposed flue in the colder air, as well as the temps of the combustion air. In a finished home, with an 80+ you want the flue gas temps to be between 300 and 400 degrees just above the furnace after 3 minutes or so.If I had a lot of exposed flue, I wouldn't want them to be much below 300 at the top of the flue after a couple of minutes.
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Sojourners: Christians for Justice and Peace
Thanks for the insights.
The temperature on the furnace flue is over my head.
So "on" is probably better.