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Lowering the thermostat during the day
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 from work. 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 getting warm. I change the filter regularly, but I have a lot of windows in my house... 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. |
wrote in message 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. |
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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. -- Christopher A. Young Learn more about Jesus www.lds.org www.mormons.com wrote in message oups.com... 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 from work. 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 getting warm. I change the filter regularly, but I have a lot of windows in my house... 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. |
wrote 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. 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. |
wrote in message oups.com... 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 from work. 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 getting warm. I change the filter regularly, but I have a lot of windows in my house... 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. 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. |
Buck Turgidson wrote:
/snip/ 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. Please cite source for your statement regarding 'negative returns'. |
"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 pipes. |
Edwin Pawlowski wrote:
If the time spent at the lower temperature is longer than the recovery time, yes, you save. No. If a house spends 1 hour at 67 F and returning to 68 takes 2, you save. Nick |
"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 house, how big, where it's located, etc. It's hard to believe that in the northeast in winter, like now with it 17 outside as you indicated, you could get by with the furnace on for only about an hour during the early AM, have the house remain in the 60's during the day and only go down to 50 overnight. Or that an hour 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 on at least a couple of sides, but can't see how it could work in a single family house. |
Buck Turgidson wrote:
.... Be cautious about turning your heat off completely as one suggested unless your pipes are sure to remain reasonably warm. 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 damage... 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 freezing. |
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. |
Buck Turgidson wrote:
snip 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. No, there's ever increasing returns in terms of energy savings, but you may incurr sufficient PITA 'costs' to make those savings not seem worthwhile. John -- Remove the dead poet to e-mail, tho CC'd posts are unwelcome. Ask me about joining the NRA. |
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Percival P. Cassidy wrote:
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 2-stage furnaces. 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/...thermostat.htm http://www.honeywell-thermostat.com/...thermostat.htm (its NOT really pink) |
Looking at the specs. of these two, it looks as though only the first
(T8624) is "smart". The description of the TH8320 doesn't mention "Adaptive Intelligent Recovery." Perce On 01/18/05 03:56 pm Travis Jordan 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/...thermostat.htm http://www.honeywell-thermostat.com/...thermostat.htm (its NOT really pink) |
Percival P. Cassidy wrote:
Looking at the specs. of these two, it looks as though only the first (T8624) is "smart". The description of the TH8320 doesn't mention "Adaptive Intelligent Recovery." Just on oversight on the seller's web page, I would guess. http://customer.honeywell.com/Honeyw...ID=69-1701.pdf see page 30-31 |
Joseph Meehan wrote:
wrote: 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 from work. 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 getting warm. I change the filter regularly, but I have a lot of windows in my house... 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. 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. 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? Bull****! Jeff 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. -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) "As long as there are final exams, there will be prayer in public schools" |
OK, so it does have that feature. How well does this feature cope with
abrupt changes in weather? And does the option to connect an external sensor to the T8624 make it work better, or is that just a gimmick? We already have an outside remote temperature sensor with an indoor display. Perce On 01/18/05 04:31 pm Travis Jordan tossed the following ingredients into the ever-growing pot of cybersoup: Looking at the specs. of these two, it looks as though only the first (T8624) is "smart". The description of the TH8320 doesn't mention "Adaptive Intelligent Recovery." Just on oversight on the seller's web page, I would guess. http://customer.honeywell.com/Honeyw...ID=69-1701.pdf see page 30-31 |
Jeff Wisnia wrote:
Joseph Meehan wrote: wrote: 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 from work. 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 getting warm. I change the filter regularly, but I have a lot of windows in my house... 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. 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. 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? Yes. 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? Bull****! Jeff 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. -- Joseph Meehan 26 + 6 = 1 It's Irish Math |
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"Rob Gray" wrote in message I think it depends somewhat on what you home is constructed of. I live in a stone house built about 200 years ago in the old style (meaning the walls are entirely stone not a stone facade). The stone walls tend to hold the heat for a time. What I generally do is keep the house at the lowest setting on the thermostat during the week and just use a woodstove at night ;) Rob The stone walls can hold a lot of sensible heat, but they are also very poor insulators and move that heat out quickly. You don't give any indication of climate either. Your heating pattern will vary quite a bit if you are in South Carolina or in Ontario. |
Edwin Pawlowski wrote:
"Rob Gray" wrote in message I think it depends somewhat on what you home is constructed of. I live in a stone house built about 200 years ago in the old style (meaning the walls are entirely stone not a stone facade). The stone walls tend to hold the heat for a time. What I generally do is keep the house at the lowest setting on the thermostat during the week and just use a woodstove at night ;) Rob The stone walls can hold a lot of sensible heat, but they are also very poor insulators and move that heat out quickly. You don't give any indication of climate either. Your heating pattern will vary quite a bit if you are in South Carolina or in Ontario. Pennsylvania. It is 4 degrees farenheit outside right now but toasty here by the woodstove :) Rob |
Percival P. Cassidy wrote:
OK, so it does have that feature. How well does this feature cope with abrupt changes in weather? And does the option to connect an external sensor to the T8624 make it work better, or is that just a gimmick? We already have an outside remote temperature sensor with an indoor display. All Honeywell thermostats use the same logic for adaptive recovery. I've never had a problem with control during abrupt changes in weather. For example - the other day the overnight low temperature here went from about 65 to about 40, and the next morning the 'wake' setpoint was reached at 7:00 AM, right on schedule. Not sure how they do it, but it works. The external sensor on the T8624 is only used for temperature display. OTOH, the external sensor on the TH8320 can be used for extended control of heat pump systems such as locking out the heat strips above a certain outdoor temperature. http://hbctechlit.honeywell.com/tech...0s/69-1706.pdf |
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