Temperature setbacks - how much?

[precaud]

It's now getting cold enough that the central heat is kicking on in the morning and on days without sun, which always raises the question every year about where to set it. If one is heating primarily with wood but using a central heater to "hold up the bottom" when one is away, what's the best place to set it? Obviously, if it's set too low then it's impossible to bring it back up into a comfortable zone in a reasonable amount of time. So I'm wondering what others have arrived at. I'm currently using 63 degrees.

 

[wingnut]

61 to 64 degrees sounds reasonable to me!

 

[begreen]

What ever floats your boat . I have a friend that only has a furnace and sets it to 64. Too cool for me, but he likes it cool.

 

[elkimmeg]

Acccording to studies I have reviewed by the EPA On forced hot air systems the high low setback can have a gap of 8 degrees But they were talking about situation for night time setbacks not when wood stove heat enter the equasion. For FHW 5 degrees. Beyond the set back points mentioned it too fuel much is used to restore the temps wiping out any potential savings.
But again this study did not include the using you central system with a wood stove.

On a side note, if you are in a cold climate using FHW, one has to be concerned about pipes freezing. It is good to have some circulation

 

[precaud]

Elk, do I remember correctly that sometime in the past you were advocating for efficiency reasons a fairly small setback, say 5 degrees?

 

[Mike Wilson]

In the main zone, (3 zone heating), I keep things at 66 during the day, with a setback of 58 at night, an 8 degree split. With the stove, the house rarely gets below 64, and if it does, its just in the very morning before I add a few more splits. The last 2 years I was a purist, and let the stove bring the house back up to temperature, however this year I think I will let the boiler bring it up to 66 or 68, and then hand it over to the stove. The stove takes too long in the morning! In our bedroom/bathroom, the setback is from 70 to 64... the wife is from Newport Beach, California, and doesn't like the cold.



-- Mike

 

[DavidV]

since we redid the hvac completely this year..replaced and moved heatpump to front of the house because the wife said it was too loud during the summer when she was sitting outside with the kids... replaced the gas furnace and have a programmable thermostat now, I set the night temp at 62. set it to bring the house back up to 67 at 5 am....then it drops back to 62 at 8 am.....comes back to 67 in the afternoon for when the family gets home from school. Once they get home I expect them to stoke up the stove. So basicly.....
I get up in the morning. if the stove held the house above 62 the furnace doesn't come on till 5 am....I get up at 6 and stoke up the stove. I take off for work and if house stays at 62 the furnace is off till afternoon(and from what I understand it has been staying off so far during the day)...........
Hot water usage is insane with 3 kids.

 

[Mike Wilson]

This is from the Iowa State Energy Center (link) ... and basically dispels the myths about setbacks. Read on:

-- Mike

According to the U.S. Department of Energy, turning down the thermostat 8 degrees F for eight hours a day will save 8-10 percent on home heating costs. An easy way to take advantage of these savings is to lower the thermostat temperature while away from home or sleeping.

Any thermostat, even a digital electronic model, is essentially an on/off switch for the heating system. When it senses the room temperature has dropped, it signals the furnace to provide heat until the temperature rises to the selected temperature.

Some older thermostats may be inefficient, allowing temperature variations of up to 5 degrees F. Inefficient thermostats cause the furnace to cycle on/off frequently, wasting a great deal of energy. If it's time for a replacement, consider installing an automatic "setback" or programmable thermostat. While you might forget to turn down the heat before you leave for work in the morning, a programmable thermostat won't.

Programmable thermostats help save energy because they store and repeat multiple daily temperature settings, which you can manually override without affecting the rest of the daily or weekly program. Many models can even store six or more temperature settings a day. New programmable thermostats are also usually highly accurate—within .5 degrees F of the actual setting.

On a winter night, for example, when the house doesn't need to be heated to 72 degrees F, simply setting back the thermostat can save money. It is simple to program the thermostat to 65 degrees F from 11 p.m. to 5 a.m., and then bring it back to 72 degrees F so it is nice and warm to wake up to. In a well insulated home the temperature change may go unnoticed.

Myths about Setbacks
A common misconception associated with programmable thermostats is that a furnace works harder than normal to warm the home back to a comfortable temperature after the thermostat has been set back, resulting in little or no savings. Years of research and numerous studies have shown that the fuel required to reheat a home is roughly equal to the fuel saved as the home drops to the lower temperature. This will result in fuel savings between the times the temperature stabilizes at the lower level and the next time heat is needed. The longer the house remains at the lower temperature, the more energy saved.

Another misconception is that the higher the thermostat is raised, the more heat the furnace will put out or the faster the house will warm up. Furnaces put out the same amount of heat no matter how high the thermostat is set. The difference is the length of time it must stay on to reach the set temperature. In the winter, a significant amount of money can be saved by setting back the thermostat for as little as four hours per day. The savings can be attributed to a building's heat loss in the winter, which depends greatly on the difference between the inside and outside temperatures. By turning the thermostat back 15 degrees F for eight hours; it is possible to save 5-15 percent a year on the heating bill.

 

[johnsopi]

My oil furnace is set at 68,but it rarely drops that low at night.

 

[jjbaer]

If you're gone for extended stays (several days), set it back as far as you feel comfortable (don't let pipes freeze though....) because the heat required to raise it back to 72F is small compared to what you saved

 

[Mike Wilson]

If you're gone for extended stays (several days), set it back as far as you feel comfortable (don't let pipes freeze though....) because the heat required to raise it back to 72F is small compared to what you saved

Agreed but not lower than 55, or your sheetrock joints will start to crack.

-- Mike

 

[jjbaer]

If you're gone for extended stays (several days), set it back as far as you feel comfortable (don't let pipes freeze though....) because the heat required to raise it back to 72F is small compared to what you saved

Agreed but not lower than 55, or your sheetrock joints will start to crack.

-- Mike

Mike,

didn't know that.........thanks!

 

[kevinmoelk]

Never heard about the sheetrock problem. But I just finished jacking up my house this fall and repairing sills, etc... so nearly all of joints need to be redone.

When I'm gone I set the temperature to 50 degrees and when I'm home I set it at 60 degrees. I do like it cold, but mainly I feel it's easier to put on a sweater and hat then pay the oil guy more money. At night the setting is 55 degrees and I just bundle up under several blankets.

My savings for doing this vs. keeping the heat at 65 all the time saves me about $400 a year in oil. Can't wait to get the wood stove working as I suspect I'll be somewhere in the $600-800 dollar savings range.

-Kevin