Can a single AC keep my apartment cold

June 9, 2008 11:48 AM

Can a single AC keep my apartment cold?

I have a 1br apt. My living room is in the front, with a large picture window, south-east exposure. I have a galley kitchen with a half-height wall opening to the living room. The bedroom is in the back, with three 32"w windows. It gets the afternoon sun. A straight hallway connects the living room to the bedroom. Both LR and BR have ceiling fans.

The living room/kitchen area is where I spend nearly all my time, so I need it cool there. The picture window has two double-hung windows on either side, but they're only 19" wide and I can't put an AC in there. The casements aren't an option given the installation requirements.

I picked up a 10k btu portable unit from Costco yesterday, and it sort of works -- the living area is relatively comfortable. It works better with both fans running. But not after running the microwave for a few minutes. Which leaves me with the impression that it's wholly inadequate when I'm cooking.

So, my only other option is putting a proper window unit in the bedroom. The window I'd use faces out to the hallway, with roughly a straight shot out to the living room. But I want it to be *cold* in here. I want to walk in to relief after work. I want to cook and not use sweat as my secret ingredient. I want to watch TV or work at my computer without leaving soppy impressions where I sit.

Would a 12k BTU unit in the BR do that for me?

posted by jma to home & garden (15 comments total)

How big is your apartment? My understanding is that the usual formula is roughly 10K BTU / 500 square feet.

Can you use floor fans to circulate the cool air more efficiently?
posted by jenkinsEar at 11:56 AM on June 9, 2008

reference on the 10K BTU / 500 Sq feet: http://www.sizes.com/built/air_conditioners.htm
posted by jenkinsEar at 11:57 AM on June 9, 2008

Heh, I'm experiencing the same issue-ish.

Here's a good site for reference.

The one thing it doesn't really cover well is that if you have a large external exposure, or high ceilings (I've got 10' ceilings in my apartment), add 10%. I got an 8000 BTU/hr unit for 390 sq ft figuring that i could subtract 10% for being reasonably shaded, and having ceiling fans. I was wrong. That poor thing labored all weekend to keep that space at 76 - 78, with a moderately hot (i.e. 90) outside temp and high humidity. It'll be going back to Home Depot tonight for a 10,000 BTU/hr unit so it doesn't have to run ALL day.
posted by moitz at 12:10 PM on June 9, 2008

I checked the sizing stuff before I went out to buy something. I know the areas of the living room and bedroom to be about 400sq ft (combined). (over) Estimating the hallway at 15x3, and the kitchen at 6x8, total apt is around 500sq ft. 10k *should* be adequate, but apparently for portable units that's not enough. A 12k or 14k unit would be over $700, too.

My thinking on the 12k window unit is the extra power could help get the living room cold, even with it at the opposite side of the apartment.
posted by jma at 12:38 PM on June 9, 2008

Can you make any changes to your space to cut down on sun exposure and heat gain (like insulating/reflective blinds, or adding awnings outside)? Are there any internal sources of heat (such as unused appliances that are on 'standby' power) that you could eliminate?

You're trying to change a heat balance, so make sure you're looking at both sides of the equation.
posted by anthill at 12:45 PM on June 9, 2008

I assume you have done the obvious: cover all windows that get direct sun with a white or metallic blind, covering all of it, AND draw drapes across the window. We're talking "reflect as much of the light as you can OUT, and insulate." With that and some strategic fans, I would think one 10K or 12K unit can keep things fairly cool. I'm keeping my whole house cool that way. A window unit in the bedroom would be best because of the PM sun there. When placing fans, remember that you can't just blow cold air out of the bedroom, something has to come back in to replace it. So put a fan in the door, on the floor, blowing cold air out of the room. Warmer air rises and will flow back into the room at the top of the door.

It should be possible to find a unit for the 19" window, by the way. Mine is 18.5" wide.

And, a little microwaving should not knock out the effect of an AC, there's something amiss there. But, in any event, when it's hot, cook with less heat, eat salads, and like that.
posted by beagle at 12:51 PM on June 9, 2008

Ha ha ha, if my apartment (smaller, fewer windows) is any indication, it will probably be enough in 75 degree heat, but not 99 degree heat.

(Hey, any other New Yorkers notice that it's HOT?)
posted by sondrialiac at 12:53 PM on June 9, 2008

It sounds like problems with the microwave may be due more to electricity consumption than added heat (it's sort of hard to tell from the question), in which case getting a secondary or more powerful A/C might just make you blow a fuse.
posted by phoenixy at 12:53 PM on June 9, 2008

Ive always thought the calculations for sq footage per BTU were always pretty generous especially if you are used to a strong central cooling system. Id spring for a 15k BTU unit.

I imagine a second 10 or 12k unit should be okay but you may end up with a super cold bedroom and a warm apartment. Id put a 12k or 15k unit in the living room and the smaller one in the bedroom. id also invest in drapes, blinds, etc.
posted by damn dirty ape at 12:55 PM on June 9, 2008

10K and drapes should do you.
I've felt as you do RE: cooking, except with doing dishes.
Working around heat sources in weather like this (NYC) is begging for discomfort.
Get a fan to blow directly on you while cooking. It's going to be a losing battle.

I've got two 12K for my apt., which has 10' ceilings. one for my bedroom (350SF) and one for the common area of apt (400 SF). My bedroom is COLD and the main room is nice and cool. There's a lot of big windows on both sides of the space, so there's always direct light heating it up.
posted by Busithoth at 1:19 PM on June 9, 2008

anthill:
I have a computer server running 24x7. It definitely adds to the heat in here, but I can't turn it off.

beagle:
I'm keeping the blinds closed on all the windows. I thought about UV reflecting films for the windows, but reflective blinds sound way easier. I'll look into that, thanks.
I saw that many units are 18.5" wide, but they all want a min window width between 22-25". At it's widest, my window is 20". I'm figuring that extra width is for the a/c framing, required so the thing doesn't fall out and smash my car. I'm going to give this a try tonight with a custom frame though. My carpenter friend offered to help with it.

sodrialiac:
I'm in NY (the Bronx). So yeah, roasting right about now.

phoenixy:
I have separate 20a circuits for the a/c's. The microwave is alone on it's circuit. I know the heat added from the microwave itself is minimal, but the area immediately around it does warm noticeably after opening the door. Usually this dissipates quickly; it shouldn't stick around long enough to make me uncomfortable.
posted by jma at 1:28 PM on June 9, 2008

If the actual opening you've got is at least 18.5 wide by 13 high, you can fit all kinds of units. You just remove the flimsy sliding frame thing that comes with it, and improvise something in the minimal opening that's left. Just stuffing in foam rubber, for example, works great.
posted by beagle at 2:38 PM on June 9, 2008

Note that if your ceilings are high, the fans are blowing the warmer air back down - you might as well let it stack up by the ceiling and let the AC's output pool down by the floor where you are.

I'm in NYC too and I cool 950ft² (with 14ft ceilings) very well with one 18500 BTU Friedrich which was recommended and installed by Air-Wave which is near you on Jerome Ave. They've can answer all your questions and have always been honest and ethical with me and the many NYers to whom I've recommended them.
posted by nicwolff at 3:43 PM on June 9, 2008

I've found that portable units are way less effective than their equivalent-BTU window units. I had a great portable unit for my bedroom in my old apartment, but it had some heat radiating from the exhaust tube, and it doesn't do much to eliminate humidity, which can make it feel hotter. I think a 12 or 15k BTU unit in your bedroom will probably suffice. Turn off the ceiling fans and use floor fans to circulate the air. You could put a box fan at the end of the hallway to help get the cool air that's shooting out of the bedroom get to the front room.
posted by bedhead at 6:10 PM on June 9, 2008

Where is the exhaust (hot side) blowing? Where is it getting its intake air? What I'm going for is that it might be removing heat from your space, but if it's creating negative pressure and pulling in hot air (especially if your window seal isn't good for the exhaust tube) you are ending up with a sort of circular flow of heat- you are just processing and reprocessing the same heat, never making any progress at actually removing it from your environment.

Is your building brick? Because the afternoon heat on a brick wall will SERIOUSLY affect your btu/sq ft calculations.

Even still, 10k btu should make at least the front half of your house chilly. I have an 11k wall unit and it cools a 750 sq ft apartment quite well- too well, often, because it cools too quickly to remove all the humidity. Is your unit generating a lot of water? Is the water pan filling up and cutting the machine off?
posted by gjc at 7:28 AM on June 10, 2008