Help with hot summer nights.

July 3, 2008 4:17 PM

Why is my bedroom consistently 10 degrees warmer than the rest of the house, and what can I do to cool it off?

Here's a rough diagram of my apartment's layout. There are 4 vents for the AC, and the one intake is in the ceiling of the living room. I have vertical blinds on my south-facing window that I keep closed all day, and an oscillating fan that blows into my room from near the door. Trees block the morning sun onto my window, but noon to sundown I get direct sunlight. The vent in my room blows cold, and is not blocked at all as far as I can tell. The problem persists throughout the night. What can I do?

posted by carsonb to home & garden (24 comments total)

Got a computer in there (and/or a big TV)? They can put a lot of heat.
posted by EndsOfInvention at 4:31 PM on July 3

Have you considered closing the other vents a bit to increase airflow into the bedroom?

Also, having the glass tinted will stop a lot of the heat getting through the glass, we had a west facing office which was like a sauna until we tinted the window. This may not be an option to you but it is worth considering.
posted by tomble at 4:32 PM on July 3

is it possible you're getting heat output from incandescent light bulbs? you may get some results from switching to fluorescent light bulbs- sounds like a minor change, but it made a big difference in my apartment.

also, be sure to keep all window coverings closed all day, even on non-south facing windows- and use light-coloured window coverings, as dark colours will absorb heat.
posted by twistofrhyme at 4:36 PM on July 3

We got some gauzy drapes which not only look pretty but make the whole room seem a little cooler.
posted by mdonley at 4:41 PM on July 3

EndsOfInvention: Yep, I sure do have a big crappy tower up on my desk. I use it during the day, but will try powering it off completely when I sleep at night.

tomble: Unfortunately, the vents are fixed. Tinting is a good suggestion...but probably not an option.

twistofrhyme: check, check, check. I love my fluorescents, and keep my eggshell blinds (as well as the ones on the living room window) closed.
posted by carsonb at 4:47 PM on July 3

It might be some issue endemic to the building, like there's less insulation in the bedroom wall than in the south living room wall. Does the tree block the sun from the living room for most of the day, especially in the afternoon? That would explain why your room is the hottest, but in general I think your problem is going to be "not enough insulation".

Otherwise, it might be things you're not mentioning, like there's a kitchen or water heater or your neighbors are growing pot on the other side of the shared wall, or something like that. I had a similar problem in my last apartment, though. My main wall faced slightly north of west, meaning I got blasted all afternoon throughout the summer--my place wouldn't be as cool as it was outdoors until the next morning.

You might think sunlight is sunlight as far as solar heat gain goes, but that's not necessarily the case. Outdoor temperature also plays a part and something called sol-air temperature plays a large part in determining cooling loads for buildings. Spaces that get afternoon sun will require more cooling than spaces that get morning sun, even if they each receive the exact same amount of direct exposure over the course of the day.
posted by LionIndex at 4:56 PM on July 3

Do you live in a city that cools off in the evening? If opening the window for an hour in the evening is an option, you could try buying a cheap, removable window fan like this
and use it to vent the warm air OUT for an hour or so.
Works for me.
posted by Toto_tot at 5:00 PM on July 3

The only other thing I could think to account for the difference between your room and the living room is that the living room has the return duct in it and is sucking all the cool air from the apartment into the room, but I don't know if that's a workable explanation or not--it's just a hunch. The conditioned air may have warmed up enough by the time it reaches the living room that that explanation wouldn't account for anything.
posted by LionIndex at 5:00 PM on July 3

Assuming, since you're hot, that you're in the northern hemisphere and it's summer and you have a south facing window most of the heat is probably coming from solar gain. Given that this is an apartment you are probably not able to plant the recommended deciduous trees along your south-facing wall. You should at least have shades that block the light during the sunny hours, which will help somewhat. A large amount of the heat, however, is being absorbed by the window and the entire wall, and the thermal mass of the wall is holding the heat and transferring it to your room. So it would be best if you could somehow block the sun before it hits the building. Trees that lose their leaves in winter and then let you take advantage of this property in the colder months. I don't know--an awning would probably help, but may also be difficult in an apartment. But at least have heavy shades or curtains to minimize the amount of burning hot sun coming in your room.
posted by ...tm... at 5:03 PM on July 3

LionIndex: Yes the living room window (which I forgot in the diagram) is shaded until late afternoon. I don't know about the insulation in this building, but the closet wall I share with the kitchen houses the water heater. Again, I couldn't tell you if those closet walls are insulated behind the sheetrock, but the unit itself is bare. I can look into fixing that, I guess. Any specific recommendations?

(Thank you all for your ideas so far!)
posted by carsonb at 5:09 PM on July 3

I'm sorry, I've made a bad assumption: I live in Los Angeles, California, United States, Northern Hemisphere, Occidental.
posted by carsonb at 5:12 PM on July 3

Yes the living room window (which I forgot in the diagram) is shaded until late afternoon

Well, not just the window; I mean the whole wall. As ..tm.. mentions, you're getting heat gain through the entire wall surface, not just the windows. You just get heat gain *faster* through windows, but you'll get it across the entire wall surface if the building is underinsulated, and the mass of your wall will continue heating the room even after the sun goes down. I was guessing that the tree shades the living room wall during the more gnarly parts of the day, so it doesn't get as much heat.
posted by LionIndex at 5:17 PM on July 3

You can try curtaining the entire south facing wall from ceiling to floor. Anything relatively solid in that wall is going to absorb and release heat over a long period, possibly all night. Insulating the wall would be the best thing to do, but hanging a curtain will help the warm air radiating off the wall out of your space. If it cools off at night, crack the window, then close it during the day.
posted by oneirodynia at 5:22 PM on July 3

Wild theory -- your kitchen backs up to the kitchen of the apartment next to you. That would make sense in order to share space for gas lines and so forth. Your neighbors use their oven a lot. You're on the same wall, and get some radiating heat from their oven.
posted by Cool Papa Bell at 5:23 PM on July 3

Is that oscilating fan on the floor pointing up? I have a similarly unbearably hot room and I find that the air on the floor is much colder than at face or bed-level (I have a soft mat under my desk and wear socks all the time since my feet are so cold from air at the bottom of the room). You could just have poor air flow and the cool air doesn't have a chance to mix.
posted by cowbellemoo at 5:48 PM on July 3

The biggest difference between your bedroom and the living room at night, is that you are in the bedroom. You are one of the biggest heat sources in your apartment.

The other big ones are the refrigerator, the air conditioner, and your roommate. (And your computer, if you're in the habit of leaving it on at night.)
posted by Class Goat at 6:03 PM on July 3

This is a common problem with a simple solution. But first, let me make an educated guess: you sleep with your bedroom door closed, don't you?

Here's what's going on: When an A/C unit blows cold air into a space, the air that's already there has to be displaced to some other place; otherwise, the incoming air just tries to blow up the room like a big rigid balloon. The "intake" you refer to in the ceiling of the living room is more accurately called the "return"; it's where the displaced air goes. When you close your bedroom door, the conditioned air trying to come in through the vents meets resistance from the air already in the room; since your door is closed it has nowhere to go. Therefore, the conditioned air takes the path of least resistance and flows into other rooms where it can more easily displace the ambient air. That's why these other rooms are cooler that yours.

By now, you've probably already figured out the solution: open your door. And by now, I've already figured out why you don't: privacy.

Try this: check the space at the bottom of your bedroom door. If your bedroom is carpeted and/or the space at the bottom of the door is small almost no air will be able to "escape" to the return. Simply take the door off and cut about an inch off the bottom. Try to imagine making an "escape route" equal in size to the vents attempting to pour cold air into the room.

A symptom you will sometime see in situations like this is that the carpet at the bottom of the door will be discolored and somewhat dirty. This is an indication that the carpet at that point is acting like a filter, trapping dust and impurities from the air as it is forced through the small opening at the bottom of the door.

Speaking of filters, the filter for your system is located in the cold air return in the living room. Replace it often for maximum cooling efficiency.
posted by dinger at 6:27 PM on July 3 [1 favorite]

I have a similar problem. I paid eight grand for an entirely new AC system, which included some additional duct work to alleviate this problem, which I clearly explained to the company, which they felt they could definitely fix.

No change.

In researching the issue, it became clear that designing the cooling system for a house is not a trivial thing, to be done by random workmen who's only qualifications are that they know how to use drills and hammers. There are all kinds of pressure and volume issues that need to be taken into account by someone with a serious clue.

So should all the simple and obvious steps (eliminating heat sources, properly covering windows both inside and outside, frequently changing filters, etc) not work out, you might want to consider hiring an HVAC engineer.
posted by TheManChild2000 at 6:31 PM on July 3

It's quite possible you're not getting good circulation in your room due to the fact that your vent is right next to the door, and the door leads to the room with the AC intake. So perhaps most of your cool air comes out your vent and goes right out your door again, leaving a large "dead area" in your room where the air never really circulates. Even with a fan perhaps this dead air is just blowing in a big circle all the time & never really getting into the loop that includes the a/c's air flow.

If you're going to experiment with partially closing/redirecting some of the vents, they sell panels just the size of the vents, that stick to the vents via a magnetic backing. That may be a simple and non-permanent way to experiment with re-directing more cool air flow into your room. You can adjust this panel to cover 1/8, 1/4, 1/2, 3/4, or whatever of your vent.
posted by flug at 6:34 PM on July 3

-Do not sleep with bedroom door closed: this will create a high pressure area in your room that is akin to blocking your vent

-You can temporarily tint, or completely aluminum foil part, or all of, your windows: this does wonders. Other than outside appearances, there is nothing wrong with foiling over the chunks of the window surface that you do not actively use.

-Adjust the vents in the others rooms (or block them altogether with masking tape and posterboard): This is especially useful if you do it in the room with the thermostat.

-Get an "indoor/outdoor" thermometer: watch both temps and blow the hatches when it is cooler outside. Window/box fans are useful for accelerating this.

-Sleep under only a sheet: screw the rest of the blankets

-Cool shower before bed (it can have a slight effect on your core temperature)
posted by milqman at 7:06 PM on July 3

Following dinger's logic, try pointing the fan so it blows the warm air out of the room, encouraging more cool air to come out of the vent. You can also buy a small fan that sits on top of the vent and helps pull more of the cool air out.
posted by metahawk at 10:27 PM on July 3

If you're looking to tint windows, you might consider a removable window insert I've hung them in a couple of my own windows and they helped not to make those (very small) rooms feel like caves.

Plenty more smarter people know heaps more about heat conduction than do I so I'm not even going to waste anyone's time talking out my arse about that.
posted by mcbeth at 1:10 AM on July 4

That south-facing wall isn't helping any either. If you don't mind the darkness (or the inevitable alien invaders jokes), put some aluminum foil, shiny side out, on the south windows, or get shades with a reflective backing (more elegant, but also costly). You might also try a ceiling fan to help the air circulate in your room more efficiently. Also, sleep with your door open when possible.
posted by nax at 7:29 AM on July 4

Okay, after a few days fooling around with different arrangements, I think I've figured out what's happening. LionIndex is right; when my door is open the cold air from the vent is being sucked out the top of my door frame and into the living room before it has a chance to circulate in the bedroom. When the door is closed there isn't enough room underneath for good airflow, and the pressure keeps the air from flowing through the vent. I don't know if widening the space beneath the door would help much, because wouldn't that create a similar circumstance to when the door is open?

I'm not too happy with my current solution—closing the door at night and cracking the window open to draw air across the room—because I don't like air conditioning the entirety of Echo Park. Any ideas?
posted by carsonb at 10:58 AM on July 9