Here in Michigan, it's been bitterly cold for the last couple of days.
I have an automatic thermostat which I lower the house to 65 during the
day, and back up to 69-70 at 4:30 so it's warm by the time I get home
The problem is, it took FOREVER to get back to that temp last night.
When I first came home I thought my furnace wasn't working right (had
the ignitor replaced last week), but it was running... It just wasn't
I change the filter regularly, but I have a lot of windows in my
So the question is, is it worth it (energy wise) to lower the temp
during the day, when it takes so long to get back up to temp? I'm
thinking I'm buring as much gas to bring it back up than I might save
during the day.
If the time spent at the lower temperature is longer than the recovery time,
yes, you save.
The greater the temperature differential between inside and outside, the
faster the heat flows to the outside. Lowering the temperature 5 degrees
lessens the heat flow. Since there is a greater loss rate at say, 0 deg.
outside (70 degree differential) than 35 deg. (35 degree differential) it
will take longer to recover.
In some cases that might be true. In my case I leave my heat off
completely during the day and most of the night. My programmable timer
turns it on for about an hour in the morning so I can step out of the
shower into a warm room. When I get home from work it's in the 60's,
even when it's been 17 degress outside all day, even with no heat on.
And my house has no insulation in the walls and I have no
weatherstripping on my exterior doors (I'm refinishing those areas
right now). I live in the northeast US. I think the difference is that
either your furnace is undersized, your house is poorly insulated, or
you have a heat pump. Perhaps if you could give more details we might
be able to help you better.
With fossil fuel furnaces (as opposed to heat pumps with heat strips) you
save ANYTIME you set the thermostat back. The rate of heat loss is
proportional to the temperature differential. The cooler your house is the
slower it loses heat. As the house cools it loses less heat even if it never
reaches the setback temperature.
The ammount of heat your furnace produces is equal to the heat you lost.
When the house is colder, you are losing less heat. The temp difference
across the wall is less. And the heated air leaking out is lower temp.
Yes, it's a saving. The long reheat time might be more a pain than the
savings are worth.
Energy wise, the amount of heat you lose is directly proportional to the
temperature difference between the inside and outside of your house, so
setbacks do work. If it's taking too long to heat up your house, that is a
different issue. Either your furnace is too small or it needs fixing.
I think Edwin's response makes the most sense. Remember that heating a
house entails not just heating the air space, but the building materials
themselves (bricks, floor, drywall). If the temperature swings are too
extreme, there are diminishing, if not negative, returns.
Be cautious about turning your heat off completely as one suggested unless
your pipes are sure to remain reasonably warm.
"Be cautious about turning your heat off completely as one suggested
unless your pipes are sure to remain reasonably warm"
That was me who is doing that. Even with no heat and no insulation my
house never got below 50 degrees even on really cold nights. With
insulation it's obviously warmer. I have no idea why, just the way the
house was built, or something. No need to worry about broken water
"That was me who is doing that. Even with no heat and no insulation my
house never got below 50 degrees even on really cold nights."
I'd like to hear more about what kind of heat you have, what kind of
how big, where it's located, etc. It's hard to believe that in the
in winter, like now with it 17 outside as you indicated, you could get
the furnace on for only about an hour during the early AM, have the
in the 60's during the day and only go down to 50 overnight. Or that
in the AM could bring it from 50 back to 70 under those conditions.
I could see this in maybe a condo, where you have common shared walls
least a couple of sides, but can't see how it could work in a single
It would have to be awfully cold for heat to only be off for a portion
of the day to lead to actual freezing of pipes solid enough to cause
It is possible over a longer period such as vacation that pipes in an
exterior wall, for example, may not receive sufficient waste heat and
cause a problem even though the interior temperature is still well above
I've found that my furnace works the best if I don't move my thermostat
around. It's about 5 off the floor, which is perfect for me. I tried
lowering it to 2 feet, but that was inconveinient, and I found that
sometimes mice (or the little tiny people that live in the fireplace,
not sure which) would play with the thermostat, which was fun for
awhile - but quickly just got plain old annoying. So then I tried
raising it to 10 feet; but then I needed a ladder to get to it.
So, to answer your question - don't lower your thermostat. Your plumber
put it where it is for a reason.
You did not tell us what kind of energy you are using. If you have a
heatpump then it depends, you may or may not save or may pay more. Heat
pumps are less efficient when it is colder.
Gas and electric resistance don't really differ much in efficiency. So
you will always save if you are using them and they don't have a time of day
differential as electric sometimes does.
As your home cools less heat is lost so while you home cools it saves X
amount of energy and when it reaches the lower time it continues to save say
Y amount of energy. When you get home and turn it back up it will take X
amount to re-heat it, but you will not have to pay back that Y amount.
If you reduce the temperature difference by 10% you will save 10% of the
heating expense while your home is cooler.
I'm not sure I follow that one Joseph. Are you saying that because the
outside air is likely to be colder in the early evenings than it is
during the days the reduced efficiency of a heat pump at lower outside
temperatures will make each "raising" BTU cost more if you replace them
in the evening than if you put them back continuously throughout the
day? And maybe by enough more to turn the whole equation around and make
your electric bill higher if you let the house temperature drop down
during the day than if you don't?
Our home (Boston area) uses two heat pumps (two zones), and the
auxillary resistance heaters have been kicking on a lot lately. It was 4
degrees F this morning, quite a bit colder than we usually see this time
of year. Global warming? Bullshit!
At least one thermostat (a Honeywell costing approx. $80 at Menards, but
I don't recall the Model#) is claimed to "learn" how long it takes to
get the house to the required temperature at a particular time and
adjust its switch-on time accordingly. I had one in my possession for a
couple of days but had to take it back because it doesn't work with
On 01/18/05 08:47 am email@example.com tossed the following
ingredients into the ever-growing pot of cybersoup:
All HVAC dealers carry 2-stage Honeywell stats, or you can buy one on the
internet (and perhaps pay more...).
http://www.honeywell-thermostat.com/honeywell/th8320-thermostat.htm (its NOT
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