comfortable = comfortable?

January 15, 2008 12:12 PM

Why are we comfortable with the thermostat set at 70 (Fahrenheit) in winter for heater, but we would be cold if it was set that low for the air conditioner in summer? Also, in winter here in SW Fla., on days it's warmer outside than what the thermostat is set on, my husband turns the heat off and opens the house, and then the temperature inside drops. Same thing in summer - if it's cooler outside he turns the air off, opens up, and the temperature inside goes high. He says the heat/air won't come on when it's nicer outside. I say that's the thermostat's job - to keep the inside temperature steady regardless of what's happening outside. Who's right?
posted by viva viola to home & garden (12 comments total)

Your thermostat measures the temperature where it is and only where it is. Basically, in the winter, if the measured temperature at the thermostat is lower than the setting of the thermostat, your heating device comes on. In the summer, it works exactly the same, but the temperature must be higher than the measured temperature for the AC to come on.

In the summer, your house might be warmer than it is outside because the house absorbs heat from the sun and tends to trap warm air inside. I can't see how it would get colder in your house when it is warmer outside in the winter though, unless you are measuring the outside temperature in the sun, instead of in the shade.
posted by ssg at 12:43 PM on January 15, 2008

You're probably not wearing shorts indoors during the winter.
posted by MillMan at 12:51 PM on January 15, 2008 [1 favorite has favorites]

Overall I think this is a matter of perception. For example, when the winter begins to turn to spring and it's 50 degrees outside, I might go out and start doing some yard work with short sleeves on. Because it's so nice and "WARM" out! But if I were to set the thermostat at 50 in the house, I would be effing freezing. Also, on those "warm" 50 degree days, if I leave the doors to the house open, it gets effing freezing in there (though in reality it only goes a few degrees cooler than it was previously).

I could go over your examples point by point, but I think it all comes down to the same thing, and that's your perception of the temperature, based on what environment you're in and how you expect to feel in it.
posted by iguanapolitico at 12:51 PM on January 15, 2008

On days it's warmer outside than what the thermostat is set on, my husband turns the heat off and opens the house, and then the temperature inside drops.

What ssg said. If you're letting warmer air from outside into the house, the temperature can't possibly drop. One of your temperature readings is faulty.


Why are we comfortable with the thermostat set at 70 (Fahrenheit) in winter for heater, but we would be cold if it was set that low for the air conditioner in summer?

Because in the winter, you're typically wearing sweaters, long pants, etc, so you're better insulated and are comfortable in a cooler environment.


He says the heat/air won't come on when it's nicer outside. I say that's the thermostat's job - to keep the inside temperature steady regardless of what's happening outside. Who's right?

I don't understand what you're asking here. If your husband is saying that your thermostat is connected to the outside temperature, he's likely mistaken. However, it does make sense to save electricity by opening the windows on nice days, thereby allowing warmer (or cooler) air in.
posted by chrisamiller at 12:54 PM on January 15, 2008

I live in SW Fla too and I know it's an old saw, but it's not the heat -- it's the humidity. 70 or so in December or January is going to feel a bit cooler just by virtue of the fact that it's the dry season (drought season more like, at the moment) and there is nonexistent moisture in the air. July or August 70 degrees is probably going to feel like 75 or even 80 inside your house, stagnant and gross.

My parents have a schmancy thing on their thermostat which is a humidistat, that actually corrects the temperature for this (or something ... I donno, but it's always nice and dry and cool in their house regardless of time of year, even if they leave the sliding doors open). Consider getting one. Any Lowe's or Home Depot is sure to have one in the $100 or under range.

Also, where in SW FL if you don't mind me asking? There are so very few of us Mefites in this vast wasteland.
posted by contessa at 12:59 PM on January 15, 2008

One other thing at play is that when the system kicks on, in the winter it's blowing hot air and in the summer it's blowing cold air. So, as an example, in the winter half the time the air is being increasingly warmed. Your body is sensitive to this relatively rapid increase in temparature, so you require a lower absolute temperature. In the summer, the exact opposite occurs. Your body is sensitive to the cooling happening while the AC is on, so you need a higher absolute temperature to compensate.

Disclaimer: This is all just supposition from personal experience.
posted by pardonyou? at 1:01 PM on January 15, 2008

Some of this effect is likely caused by differences in temperature within your house. The thermostat obviously only measures temperature right at the device, but there are all sorts of variables that could cause the temperature to be different in other parts of the house. Drafts from cracks around windows and doors can bring in cold air and lower the nearby temperature. Conversely, lack of air flow or mixing can cause local heat build up in the room or part of the room you're in. Windows can provide poor insulation and often the nearby area has a noticeable temperature difference. The more thermostats you have in a house the more constant temperature you'll get. I'm living in a four bedroom house with a single thermostat so this something that bothers me a lot.
posted by Durin's Bane at 1:07 PM on January 15, 2008

Oh yeah, contessa touched on a point I forgot -- the humidity in the air does play in quite a bit. In the dry winter you'll find that turning on a humidifier actually helps make the air feel warmer. That in itself doesn't solve your problem, but the point is that it's all just due to head games that the weather likes to play with us.

To directly answer you last question about whether to let the thermostat have the final say over the temp in the house or whether to use outside air: that's just personal preference. And it can be a bit of math, too, if you want to be efficient about it. Sometimes you would have to make your heater or air conditioner work extremely hard to get the temp to where you want it to be. For example, sometimes in the summer you can have a supremely hot, 100 degree day, and then the next day you have some kind of cold snap, say to 65 ... if your A/C was chugging along on the hot day to barely keep the house at 77, on the next day you might want to just open the windows to let the 65 degree air stream in, to prepare for the next hot day.
posted by iguanapolitico at 1:21 PM on January 15, 2008

In the winter, you're probably wearing a sweater in a 20 degree house. In the summer, you're probably wearing a t-shirt in a 20 degree house.

I.e. in winter you're appropriately dressed for the temperature. In summer you're not.
posted by Kololo at 2:38 PM on January 15, 2008

Oh, and re: the thing with your husband - you're right. Tell him to dress in layers.
posted by Kololo at 2:39 PM on January 15, 2008

The part of the question dealing with why it feels different at 70 degrees is mostly due to humidity. Your ac is a dehumidifier, that is why it has a condensate drain line. 70 degrees at 65% humidity will feel much warmer than 70 at 45% humidity.
posted by HonestAbe at 3:09 PM on January 15, 2008

I live in SW Fla too and I know it's an old saw, but it's not the heat -- it's the humidity. 70 or so in December or January is going to feel a bit cooler just by virtue of the fact that it's the dry season (drought season more like, at the moment) and there is nonexistent moisture in the air. July or August 70 degrees is probably going to feel like 75 or even 80 inside your house, stagnant and gross.

This is the opposite of what the OP said. She said she's comfortably warm inside at 70 in the winter but would be cold at 70 in the summer.
posted by Dec One at 3:29 PM on January 15, 2008