How Do I use the cool air in my basement to cool my house?

July 18, 2007 2:38 PM

How can i use the cool air in my basement to cool the upstairs rooms in the rest of the house? It's 66 degrees in the basement but a lot hotter upstairs. I don't have AC and the house has antiquated water-based radiators rather than air ducts. But it sure would be nice to move the cold to where the hot is. Ideas?
posted by storybored to home & garden (19 comments total)

Install a ceiling fan upstairs.
posted by GuyZero at 2:43 PM on July 18, 2007

if you have a window in the basement (screened), open the window, put a fan in an upstairs window (with the rest of your windows/doors closed) pointing OUT. Pushing the warm air out the upstairs window should draw the cooler air from the basement up...

This assumes, of course, that the house is fairly well sealed, otherwise, it probably won't help much.
posted by HuronBob at 2:43 PM on July 18, 2007

I think that the cool air in your basement is the result of the thermal mass of the concrete or stone foundation and the soil. The air is exposed to this cool rock for a long period and it cools. If you were to move the cool air upstairs and it took +/- 1 hour, it would probably take much longer to cool the new warmer replacement air.
You could probably circulate water through pipes under your basement and up into your house, but that would probably be very expensive.
posted by kuujjuarapik at 3:01 PM on July 18, 2007

Yeah, you will probably get best results with a ceiling fan upstairs, fans on the landings pulling the cool air up and a fan in an upstairs window blowing the hot air out (preferably in an area away from the stairs).

And by 'best results' I mean it might help a little. We have a similar situation and have found that in almost every case it's better to use the AC (we have central air, but prefer to not use it because of the costs), or to wait till it cools off at night and open up every window and pull in as much cool air as we can. We did experiment with putting AC in just one room that gets very hot. It was cheaper than running the central air for the whole upstairs and worked way better than trying to pull cool air from the basement.

Also: If possible, just spend time downstairs. It might not be finished (you don't say), but if you are just sitting around reading or watching TV, it's a lot easier to go where the cold is than to try to bring the cold to you.
posted by quin at 3:37 PM on July 18, 2007

Seconding what the others are saying: put one or more strong fans to exhaust hot air from the top floor. If you own the house, look into getting a whole-house fan which will move a huge amount of air to exhaust the house.

By the way, most people prefer "antiquated water-based radiators" to forced air heating.
posted by exogenous at 3:40 PM on July 18, 2007

The term for these fans, at least in the midwest, is 'attic fans'. They suck air from the rest of the house and blow it into the already-hot attic. Any open windows draw in a nice cool breeze, and or you leave the basement door open, you'll help circulate that air into your house.
posted by chrisamiller at 3:47 PM on July 18, 2007

The conventional way of doing this is with a two speed fan in a forced air furnace set on it's slow setting in no heat/cool mode. You can duplicate this effect with a salvaged squirrel cage fan out of a furnace and a little duct work. If you can cut a hole in the floor anywhere (maybe a closet?) you could just run the duct straight up. You can get all sorts of fancy cast floor grates to cover the hole. Other wise you'll have to buy enough pipe to run it along the ceiling in your stair case.

A small blower, sized say for a single wide trailer, and either some square ducting or a couple runs of round ducting and a plenum would be all you'd need.
posted by Mitheral at 3:47 PM on July 18, 2007

Before you use a solution involving opening a basement window, ask yourself: Do I mind having mold in the basement?

If you live in a humid climate, the wet air from outside will get in and allow mold to grow, in some cases (happened to me).

If you're basement isn't finished, you can tolerate mold, maybe. But if it's finished and drywalled, you probably can't.

Mold removal, if done by professionals, is hella expensive. Keep that in mind.
posted by Gordion Knott at 3:50 PM on July 18, 2007

+1 to attic based whole house fan. It'll suck air up through the house....

Open basement windows first, or at least close upstairs ones.

Also, use blinds on any east/west windows, and consider installing awnings. Thermal gain through windows can be massive.

Attic fans are also thermostat controlled, so set them for a temperature and they'll run themselves. Moisture shouldn't be an issue, as it generally isn't when the air is MOVING versus holding steady.
posted by TomMelee at 4:07 PM on July 18, 2007

A vent in the attic will allow warm air out. A fan in th eattic will accelerate getting the heat out.
posted by theora55 at 4:45 PM on July 18, 2007

Another thing to consider if you are circulating air up from your basement is the radon gas hazard. You can buy a kit that will measure for it.
posted by kuujjuarapik at 4:56 PM on July 18, 2007

For the love of all that's good, if you decide to retrofit duct work, don't put it on top of the walls. Rip the walls open. I have ducts on my walls and while they aren't hideous, he break the walls in ways that makes things like desks and shelves very, very difficult to place.

But a few fans is probably all you need. And/or a window A/C unit.
posted by GuyZero at 4:58 PM on July 18, 2007

Thanks for all the advice folks. I'll try the fan route. Moisture and mold don't seem to be issues where we're at. I was considering the installation of ducts but it might be overkill.
posted by storybored at 5:45 PM on July 18, 2007

The proper name for what you want is
"Attic Gable Fan".

There's no need to rip apart any walls or retrofit any ductwork, your gable end should already have a vent, you simply replace that with the fan.
posted by TomMelee at 6:18 PM on July 18, 2007

I think for a first move, fans is the way to go; put some big box fans in the upstairs windows blowing out, and then just crack the basement windows to let air in. If you have all the doorways open inside the house, hopefully this will result in air being pulled through the basement, cooled, and then sucked upstairs before being exhausted. Not sure how well it'll work, but it's worth a shot! Just be on the lookout for condensation on the basement walls.

The other option for retrofitting forced-air (and A/C) into a house that was built without ductwork is to use high-pressure/small-diameter systems that use 2 or 3" PVC. I don't know too much about the amount of energy they consume, but they basically just shove a lot of air through very narrow pipes, which you worm throughout your walls, theoretically without having to rip down drywall or plaster. Might be worth looking into, since it might pay for itself when you sell your home (I think A/C systems are usually worthwhile in terms of ROI, if you're in a hot or temperate region).
posted by Kadin2048 at 6:28 PM on July 18, 2007

By the way, most people prefer "antiquated water-based radiators" to forced air heating.

Really? I haven't met too many. Any source for that?
posted by Chrysostom at 7:14 PM on July 18, 2007

Chrysostom-
The reason is that, generally, radiant systems require less energy to get the same "feeling" of warmth. This comes as a combination of the way we perceive heat and the way radiant systems disburse it.

Generally speaking, a well-working radiant system does a better job of heating the floor to chest region, where a forced air system heats the ceiling space in a room. This means you feel WARMER in a COLDER room.

Also, because water has such a high thermal density, a recirculating water/glycol system generally doesn't use nearly the gas/electricity of their forced-air counterparts.

However, aged radiant systems are rarely efficient at all. Clogged radiators, radiators w/ air in them, rusted expansion tanks, and low efficiency boilers make them hell, not to mention that the old style was to place the heaters directly beneath windows.

The new kid on the block (relatively) are radiant floors---same principle as the wall radiators, but the lines are run under the floor. Great heat, low cost.
posted by TomMelee at 7:58 PM on July 18, 2007

Yeah, that's really what I was getting at. I've had experience with old-style radiators, and found them uniformly awful. The underfloor setup seems like it would be pretty good.
posted by Chrysostom at 5:46 AM on July 19, 2007

new kid on the block (relatively) are radiant floors---same principle as the wall radiators, but the lines are run under the floor

New? How very retro: hypocaust.
posted by meehawl at 9:20 AM on July 19, 2007