My wife and I use an electric mattress pad. We can comfortably sleep at 60 degrees and don’t need a half-dozen blankets to do so. Even at full-blast, the mattress pad only uses 300 watts, and outside of the 1/2 hr pre-heat cycle, we never run it that high; usually keep mine at “3” on the dial.
My bad… I forgot the smiley. :smack: I thought my brief explanation only proved that you’re right; we’re an intelligent audience. 
But unfortunately in this case the word limit has resulted in a huge percentage of people getting the wrong advice. If your second stage resistance kicks on when you set the temperature back up in the morning you will likely eat up all the savings in power had during the night and possibly more. The automatic thermostats avoid this problem by ramping the setting up slowly enough that secondary heat does not turn on, but doing it manually is not a good idea.
I’m the one who posed the question originally. Two reasons for using Fahrenheit: a) Because Straight Dope is an American column, so like the polite and deferential Canadian I am, I put the question in American units b) many Canadians of my generation were raised on Fahrenheit (the metric system was imposed by the [spit] Trudeau government in the early 70s) and still use it, as well as Celsius.
As for not being able to sleep in a cold room–we keep our bedroom at 55F at night. Flannel sheets, a blanket, a thick duvet…all covered up and snuggly…one sleeps like a stone…
Well the primary focus of the article is on programmable thermostats, not necessarily manual adjustment, and as you are aware most modern programmable thermostats have a “heat pump” setting on them to mitigate that. Perhaps you should send mail to Cecil and ask that he expand on his answer (I think the steam heat example in this thread is interesting too, although homes heated with actual steam are sort of rare).
I have a radiant-heated house with a “boiler”* and (traditional) radiators. To complicate things, it’s an electric boiler with a very tiny tank. And I live in Western Washington.
So, the end-result:
- The programmable thermostat made very little percentage difference in my heating bill, and didn’t work very well for my situation. (Since the system takes ~ 1 hour to warm up, and stays warm for ~ 2-3 hours… the thermostat has a ‘delay’ system, but its max setting is 15 minutes.)
- My heating bills are so damned high that it still paid for itself in less than a year.
- BUT I get much more substantial savings from just keeping one of those oil-filled space headers near where I am during the day, and keeping the thermostat off/low.
So if you do have radiant heat, and if it’s electric, space heaters are your friend.
- I’ll call it a boiler even though it maxes out at about 175-180 degrees, and the system isn’t really designed to have steam run through it anyway.
One topic not covered well in this discussion: the efficiency of the furnace.
Standard gas furnaces display efficiencies which can be quantified by an equation of the form:
E = Eb -aX -bX^2 -cX^3
where E = efficiency over some time span
Eb = equals efficiency during a lengthy time in which the furnace never shuts off ( for many designs, the efficiency posted on the nameplate)
a, b, c = constants
X = fraction of the time span in which the furnace is not operating.
The larger the fraction of time span in which the furnace is not operating, the worse the efficiency. Thus, the heat-up after a set back ends allows the furnace to run at higher efficiency while it warms the house.
Regards
Jason
Depends on how frigid she is to begin with.
It rarely gets above 65º in the house all winter, and usually is around 50º inside at night. I just like it cool, what can I say?
The kids’ mom is convinced of the valve theory. I tried telling her over and over the furnace only has one setting; hot. If you want it 90º in the house it’ll take longer to heat than if you want it to be 70º. I think she thought it worked like a gas stove burner or something.
I get it that depending on what data you look at, the thermostat problem can seem to be solved in a number of ways – most of which appear to be a wash in the long run. It’s a mystery why the government at this late date hasn’t thrown a few megabucks at some research facility to get to the bottom of all this – you’d think it would bring big dividends to a lot of people, especially the part about making the geeky setback thermostat understandable to us yokels (they should also redesign DVD player remotes while they’re at it). However, no one seems to be factoring in the ambient temperature of the home interior and the real cost of bringing every piece of furniture, drapery, rug, bedding, books, pots and pans, etc. etc. back up to a comfortable temperature. It’s one thing to heat just the AIR mass in the home to 70 degrees F., which will quickly register with the thermostat to shut off the heat function, thinking all is well and toasty at 70 degrees. However, all of the objects in the house are still at 65 degrees, say, and they quickly start drawing all that precious heat out of the air in an attempt to equalize the average temperatures. Within a few minutes, they’ve sucked a couple of degrees away from the interior air mass and will continue to do so until everything in the interior is balanced with the air temperature. Net result is now a lower overall temperature than the sacred 70 degrees, so the good ol’ thermostat wakes up and kicks on the heat again, and this second heating (and subsequent heatings) are what’s not being factored into the savings figures, methinks. This on and off seesaw will continue until all of the air AND the interior items are equalized to 70 degrees, when the thermostat can go back to snooze. So this can be a fairly drawn out adjustment period resulting in extra fuel costs, and at some point the chilly outside air temp starts to work it’s magic and begin to lower the combined temp of the interior air mass plus windows, walls, pipes, plants etc. so a new adjustment interval starts all over again. :smack:
Welcome to SDMB, Ralphem. Since not everyone may have seen the article you refer to, it’s always a good idea to link to it right away before the thread kickoff. Here ya go.
It’s also a good idea to organize your thoughts into paragraphs. Makes ‘em more likely to be read than just a mass o’ text.
So, are you agreeing or disagreeing with Cecil? Hard to tell.
I know the valve theory is wrong, but I wonder if it works for some people the same way it works for me in my car. Strictly speaking, 77°F is just perfect (during winter) in my car. But on a damned cold morning, I crank it to 90°F until I’m uncomfortably hot, then back down to my normal 77°F. It’s like, 77°F isn’t good enough because I’ve previously been so damned bloody cold.
Air gains and loses temperature quickly. Most solids do so much more slowly. (So do most liquids, which is why a body of water moderates temperatures next to a city. However, if you have bodies of water inside your house you probably have bigger problems than thermostats.)
What this says is that regulating air temperature is primary. The ambient temperatures of the objects in your house are so secondary that they can be ignored for any casual appraisal of thermostat controls. Probably for serious appraisals as well, because every other variable - like outside temperatures - will swamp the decimal point changes your furniture and pots involve.
I bought into a friend’s argument that keeping the house at constant temperature would save money one year and kept the house at an even 68 during the summer. My electric bill doubled.
I now only care about the the house temperature when I’m at home.
The house can be considered as a system as you say, but it doesn’t make any difference. Everything in the house transfers heat under the laws of thermodynamics. As the house shell loses heat, it becomes a lower temperature than the interior air and objects, which transfer heat to it via conduction, convection, or radiation. As the house cools to a temperature which is closer to ambient, it loses less heat. You still save energy by keeping the house as close to ambient as you can for as long as you can.
The government has studied it. All you have to do is visit the DoE and other government-related energy websites. There is some question over how much programmable thermostats save (for a variety of reasons, which Cecil did not have column space to list), there is no open question on whether or not setbacks work. Try doing the math yourself - set it up in a spreadsheet. This isn’t hard, this is undergraduate-level Mechanical Engineering. It may seem counterintuitive but it does work.
Whew! This was my very first post to The Straight Dope and I am floored by the rapid and learned responses that have been tacked on to it! My thanks to Musicat for helpful posting hints, and to the others for an education – you guys are waaaay beyond my level of knowledge and understanding on this item (and my doing a spreadsheet is not even a possibility, believe me). Open mouth, insert foot…
Not for us, apparently. Besides, the blanket only covers up to the neck!
Powers &8^]
Not to worry, Ralphem, that’s often the reaction of newcomers… at first. Hang around a little, get involved in discussions, look for threads about YOUR areas of expertise, you’ll fit in jes’ fine!
Tried setting my thermostat for 68 daytime, 60 night.
Never again.
Too chilly for me!
Just a suggestion. Try setting days at 67 for a week and nights at 66. Then lower it another degree for a couple more weeks.