Air Conditioner Question
May 27, 2010 11:03 AM   Subscribe

My girlfriend and I live in an apartment on the 10th floor of our building. It gets very hot during the summer. However, we have an air conditioner in our bedroom. We're wondering how to keep our room as cool as possible.

Which of the following methods will give us the coolest temperature when we get home:

A: Keep the air conditioner turned on 24/7

B: Turn the air conditioner off when we're away, and then turn it on when we get home (so that the motor has a chance to rest)

C: Something else
posted by Proginoskes to Home & Garden (20 answers total) 1 user marked this as a favorite
I assume your AC does not have a thermostat?
posted by brainmouse at 11:06 AM on May 27, 2010

Keeping the air conditioner on 24/7 would keep the place the coolest. Though that will get expensive quickly.

I'm assuming the air conditioner vents to the outside.

This doesn't address wear and tear on the air conditioner how old is it? Older ones will wear outmore quickly than newer ones.
posted by dfriedman at 11:07 AM on May 27, 2010

A certainly beats B, and probably C. Expensive, though.
posted by jon1270 at 11:08 AM on May 27, 2010

I think B is the most cost effective / greenest.
posted by jockc at 11:08 AM on May 27, 2010

As cool as possible at the time of arriving home is A, at the cost of energy efficiency (and thus money). You shouldn't have to worry about B unless you have an exceedingly poorly engineered unit.

Both A and B should reach the same equilibrium temperature, although B will obviously take longer to get there.
posted by reptile at 11:08 AM on May 27, 2010

given that you're cooling just one room, and assuming that the insulation isn't 100% wonderful, and that you only use the bedroom at night, I would suggest that your best bet is to turn the air on in the bedroom a half hour before you go to bed, turn it off when you get up.
posted by HuronBob at 11:10 AM on May 27, 2010

Which side of the building does your bedroom face? Having light-blocking curtains or window film helps keep the room cool.
posted by HopperFan at 11:16 AM on May 27, 2010 [4 favorites]

Buy a timer, and set it to turn the AC on half an hour before you get home?
posted by schmod at 11:17 AM on May 27, 2010 [1 favorite]

We bought a heavy appliance timer. Since we had a cat we were concerned about we set it to turn on a couple of hours before we got home, essentially right before it got too hot. This was for the AC unit in the living room. For the bedroom we didn't turn on the unit till right before bedtime.

We also had a floor fan that was positioned so that it circulated air from the living room to other parts of the apartment.
posted by collocation at 11:24 AM on May 27, 2010

Leave the air conditioner on and keep your bedroom door closed.
posted by axismundi at 11:31 AM on May 27, 2010

Keep the door closed, turn on the a/c about an hour to two hours before you're going to be in the room, and I find having a small fan on somewhere else in the room (if you have a ceiling fan, that's perfect, but a little desk fan works pretty well too) to help circulate the air around the room is really helpful, as well. Kind of like the opposite effect of a convection oven.
posted by xingcat at 11:47 AM on May 27, 2010

I live on the 8th floor of a building and I've found that opening the door to the roof helps the building cool off faster. If your building has this option, go for it. If not, if you can find a way to get a cross breeze through your apartment - put box fans in the windows to drop the initial temperature and then resort to the A/C for sleeping.
posted by sciencegeek at 11:49 AM on May 27, 2010

Yes, keep the bedroom door closed and keep that room cool, give up on the others. One cool room is better than several warmish ones. Also, if your A/C unit can either recirc the air inside or ventilate with fresh air from outside, keep it in recirc mode for max effectiveness. (Seems obvious to me, but most people I mention that to with regard to their car A/C don't believe me for some reason.)
posted by ctmf at 11:50 AM on May 27, 2010

We also installed a ceiling fan last year and I'm definitely appreciating it now.
posted by sciencegeek at 11:51 AM on May 27, 2010

but most people I mention that to with regard to their car A/C don't believe me for some reason

Well -- and this is true whether for a car or an apartment -- for the first few minutes if the area you're trying to cool is actually hotter than the outside air, then having recirculate (or "MAX AC" as it is generally called in American cars) turned on will actually take longer and tax the AC harder than if you pulled in fresh air.

Once you get the area to be cooled down to the same temperature as the outside air, you should then switch to recirculating.

You run into this problem more with cars than with bigger spaces, but a house that's been closed up on a hot day with unshaded windows can easily be hotter than outside. Or in the evening as the ambient temperature drops quickly outside, the building insulation may trap heat.
posted by Kadin2048 at 11:56 AM on May 27, 2010

You might consider using one of one of these plug-in digital thermostats to control the AC so it only runs as necessary. I use one to control a space heater in the winter and a window AC during the summer. Very handy.
posted by jon1270 at 12:04 PM on May 27, 2010 [1 favorite]

You can make sort of a DIY mini air conditioner with a fan and a big bowl of ice cubes (or frozen containers of water). Set the container in front of the your fan and let the fan blow over the ice cubes. This should provide some cooling as well.
posted by Ostara at 12:39 PM on May 27, 2010

You should get light colored, heavy curtains and keep them closed during the day.
posted by shothotbot at 12:59 PM on May 27, 2010

I use this timer and set the A/C to start about an hour before I get home.
posted by WizKid at 1:02 PM on May 27, 2010

Stopping heat from getting in is the first step. If the room faces south or west, block out the windows.

Leaving it on all the time when you are only using it for 8 hours probably isn't cost effective. But it might not be comfort effective, either. If the room heats up to 90 during the day, all the stuff in the room gets up to 90 as well. All your stuff is now acting like a radiator, making you uncomfortable. If just turning it on before bed is not working, leave it run all day, but set the temperature at some kind of compromise. 85 or something. This keeps the humidity down, prevents the "stuff" from absorbing too much heat, and in the evening, knock it down to 80.

My AC unit has a economy setting, and what it does is turn on every X minutes, blows air for a minute, and if it has gotten past the set point, cools until it drops. (This saves energy because the fan isn't running ALL the time.)

This (for me), combined with a higher daytime setpoint, isn't as energy efficient as just turning it on when I'm home, but it IS much more comfortable, and cheaper than leaving it on all day. Because nothing sucks worse than laying in bed in a cold sweat because the bed is hot and the air is cold and clammy.
posted by gjc at 4:51 PM on May 27, 2010

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