How can I cool my top floor?
July 8, 2011 9:09 AM   Subscribe

How can I cool the upper bedroom of my house?

I recently moved into a turn-of-the-century craftsman home on the East side of LA. It's three floors set against a hill. The bottom floor is a basement converted into a separate unit. The middle floor is most of our living space, and the top floor is a mid-sized bedroom that serves as my office.

The place has central air conditioning, but it's rarely necessary, except upstairs. Even when we turn it on, though, it gets cold downstairs and barely makes it to tolerable upstairs. Every window in the place is off-kilter and single pane, so I'm sure it must be really pumping out the AC to get there.

What can I do to get to a tolerable temperature upstairs? I've thought about a portable or window AC unit, but they're ugly, expensive and noisy. Is there some kind of fan system that would help? Putting those magnet things over the AC grates in other rooms?

Please help me. I'm from San Francisco - I've never even had central air conditioning in my life.
posted by YoungAmerican to Home & Garden (12 answers total) 6 users marked this as a favorite
ceiling fan?
posted by jerseygirl at 9:14 AM on July 8, 2011

If you haven't done this already, try closing or blocking the central air output vents on the lower floor(s).
posted by exogenous at 9:20 AM on July 8, 2011

When I was house shopping, I ran into this exact problem. We only wanted to look at 1 1/2 story houses. They all had central air. They all had really hot upper floors.

--They all had window or portable A/C units.
--They all had some registers closed on the lower floors.

After looking at thirteen houses with the same problem and the same solutions, I learned two things:
--There likely aren't any other solutions.
--Those solutions still weren't very good.

These were all older homes, too, so I don't know what else could be done short of a lot of demolition and starting over.

On preview: Ceiling fans do rather amazing things, as I know from personal experience. Also on preview: We were recommended a Mr. Slim type device for our add-on living room which never had its own HVAC installed into it (cheap DIY previous owners). It works, but it looks like a long and narrow window AC unit instead of a square one; super quiet, though.
posted by TinWhistle at 9:21 AM on July 8, 2011

How 'bout shutting every A/C vent in the house except for the one in the office? That would force all the cold air into the room that needs it most. And there should be enough leakage even through the closed vents to provide a little coolness to the rest of the house without overkill.
posted by The Deej at 9:21 AM on July 8, 2011

If air is still escaping through closed downstairs vents, the magnetic AC vent covers should do the trick. Instead of dumping the cold air out via the path of least resistance, it'll be forced to blow out of the upstairs vents. Rather than shelling out all the cash for the fancy covers, though, just go to the nearest Home Depot and buy a sheet of pink insulation foam (extruded polystyrene). You should be able to get a gigantic piece for around 8 bucks.

Cut out rectangles to fit exactly in the vents, unscrew the vents, pop in a piece of foam, and screw the vents back on. You won't be able to see it unless you're looking directly in the vent. Then when you run the AC, it'll shunt all the air to your office rather than waste it cooling the places that don't need to be cooled. If you still want to cool some of the downstairs, leave one vent open.
posted by phunniemee at 9:21 AM on July 8, 2011 [3 favorites]

First get heavy, light-blocking curtains in there, especially on any windows that get a lot of sun.

You can close some of the vents in the rest of the house but you don't want to block the majority of the vents (think of a big fan trying to exhaust through a small straw, not particularly efficient) and you're still going to end up with rooms that are colder than you want and a hot upstairs. The split-units, like the Mr Slim, are significantly more expensive than window units and they need installation. But they sure are a lot nicer than window-style.

The other thing to tackle is the attic, if you have one. Attics get really hot so you want insulation up there (or more insulation if it's under-insulated). Depending on the type of insulation and your handiness it's not a particularly hard job to do yourself (watch for nails and only step on the beams!) but shouldn't be particularly expensive to have done either.

If the walls aren't insulated you can get it blown in. Not cheap (more expensive than doing the attic typically).

Install double-glazed windows.

If you'll be there long term might want to plant shade blocking trees.

And honestly, a window unit is going to be your easiest, most cost effective, and most efficient solution if the rest of the house rarely or never needs AC and you're only looking to cool one room.
posted by 6550 at 12:10 PM on July 8, 2011

You might have seen my recent AskMe seeking help with a similar problem. Too many hot nights I have lain awake pondering this dilemma in sweaty delerium. My (not so) bright idea was to put a window fan in the upper pane of a double-hung window at the top of the house, blowing out, to help pull the cold air to the top of the house. It does make the room much more comfortable, but I'm sure it significantly reduces the efficiency of the A/C system overall. (Sometimes I'm too hot to care!)

The problem is that, for the A/C up top to work well, you need two things:
(1) a way to get the cold air all the way up to the top room, and
(2) a return duct, to circulate the hot air from the top of the house back down to the A/C.

So you need to (1) make cold air go up, AND (2) make hot air go down.

Problem #1 is pretty easy to solve, by closing A/C outlets in the lower rooms, and/or putting a small fan at the top A/C outlet, blowing out from the vent (I almost said "blowing up," but we hope not). Doing those things, even without addressing problem #2, will help some, but not as much as you would expect.

Problem #2 has no real solution short of major construction work to add a return duct to the system. The most helpful compromises seem to be either just using a fan (ceiling or other) to create an evenly too-warm breeze in the hot room, or using a window fan like I did if you can afford to sacrifice efficiency.

Or, another possibility if your floor plan allows it: figure out what is functioning as the return pathway for air from your top floor to the lower level--probably a staircase--and out a fan there, blowing down. I think a pretty big fan would be needed for this job.

If you come up with something that works, please post!
posted by Corvid at 12:35 PM on July 8, 2011

Response by poster: I should mention that this is a rental.
posted by YoungAmerican at 1:30 PM on July 8, 2011

Window AC units aren't necessarily that noisy or expensive, IME. It's a more efficient solution not to run a whole-house AC system, if you really only need to cool one room for part of the day (for sleeping). The noise is basically white-noise which is pretty easy to get accustomed to and tune out. They are clunky and it eats up your window, which is not so great.

If you are in a desert climate there are "swamp coolers" which are cheaper to run than AC units. I don't know if your part of LA is dry enough for this to work, and I can't speak to the noisiness.
posted by LobsterMitten at 8:11 PM on July 8, 2011

And the advice about window shades that really block sun in your sun-exposed windows is excellent; I was amazed at what a difference it made in our un-airconditioned house when we became vigilant about keeping the blinds closed, shades down, etc during the sunny part of the day.
posted by LobsterMitten at 8:13 PM on July 8, 2011

You might be able to do without the AC entirely and instead install a whole-house fan to suck that cool lower-level SF air upstairs… my next-door neighbor swears by his.
posted by mumkin at 12:15 AM on July 9, 2011

Sorry, on re-reading, that not-quite-so-cool lower-level LA air.

I should add that neighbor's strategy for house cooling involves a large whole house fan installed in the ceiling at the top of his stairs, running at a fairly slow-speed, which he mainly uses to cycle the air through his house a few times a day rather than continuously. I think he said he turns it on when he gets home from work, to flush out the heated air of the day, and then for a bit before going to bed, to bring in a batch of cooler night air to tide him over. So to your noise concerns, it's not in operation much. Granted, this is Portland, not LA, so our hot days have a bit less hot to them.
posted by mumkin at 12:45 AM on July 9, 2011

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