It is hot. There is no escape.

June 19, 2007 4:03 PM

How can I vent hot air from my 3 open story condo? Is it a good idea?

So I have a home with two stories plus a loft, all of which are very open to each other. The second story where we sleep is very very tough to keep cool when oklahoma decides to get hot. I'm putting some tint on the windows that face west that are at the highest point in the house, but I'm curious about venting the hot air out.

I cannot go through the roof, but I could do a small hole or two in the wall at the very top of the loft (there's no attic). Is this a smart idea? What happens when it gets cold, does all the cold air have a place to come in now if the vent fan isn't on? What about bugs? I'm thinking something like http://www.amazon.com/Solar-Panel-Ventilator-Vent-House/dp/B000JT0O30/ but I could use some thoughts. Thanks!

posted by striker to home & garden (11 comments total)

Sounds like a good idea, but you need to find the right solution. Whole house fans used to be popular before AC. They can make a huge difference, but I don't think that solar ventilator is going to do the job. You want something that's wired to the house AC with louvers or similar to close it off when it's not in use. For winter you might want to make a special effort to close it off with an insulated tarp or hood.
posted by Good Brain at 4:13 PM on June 19, 2007

Um, open the windows on the top and bottom floors? Let nature do the work of ventilating. No need to cut holes where you already have them.

Also, see a professional about getting your a/c fixed. ;)
posted by wierdo at 4:30 PM on June 19, 2007

a/c works, just not big enough units I guess. Windows don't open on top floor. There are balcony doors on the second floor but it just seems to let heat in.
posted by striker at 4:36 PM on June 19, 2007

You say there's no attic, just a loft - is there any insulation between the roof and the living spaces? And are we talking window AC, or central? If you don't actually have the cold air coming in on the upper floors, it's going to be hard to get it up there. Physics is working against you. Only other suggestion I have without more details is ceiling fans, they can make a huge difference in keeping air circulating, but again, with convection, I'm not sure you're going to be able to pull cold air up 2 stories.
posted by pupdog at 4:59 PM on June 19, 2007

If you're letting hot air out, you'll presumably want cool air coming in to replace it. Do you have a window to a shaded space, or better still a garden, on the north side of your place?

If you're only going to make a small hole at the top of your loft, it will definitely need help from a fan, and you should certainly arrange some means (perhaps an external shutter with an internal control) to seal the hole up tight for winter. Put an insect screen on the upstream (inside) side of the fan and make sure it's easily removed for cleaning.

The bigger the hole, the slower and quieter you can run your fan. A double-hung window that you can open the top pane of would give you a useful amount of hot air exhaust without needing a fan. Put it on the eastern or northern side so it doesn't let in afternoon sun.

Simply fitting white blockout blinds inside your windows will keep out far more heat than tinting them (tints absorb rather than reflect radiation, absorption makes the glass hot, and the hot glass transfers heat directly to interior air).

To get an idea of just how much heat you can keep out with blockout blinds, work on the basis that every square metre of glazing that faces the sun directly is letting in about a kilowatt of radiated power.
posted by flabdablet at 5:03 PM on June 19, 2007

each of the main floors (level 1 and level 2) have a central air unit, the loft shares central air with the second level. Cold air is up there. I have fabric covered the windows in the past, it works well, but makes the space way too dark. I feel like if I could just move some of the high hot air out things would work great, but I have no experiences to know how much of an effect a small product would have, or if I need something larger, and more expensive.
posted by striker at 5:21 PM on June 19, 2007

Do some searching for "stack effect" and see if you can come up with some alternate solutions based on your home's configuration.

Also, do what you can to make sure the cold air stays cold for as long as possible. Open up those windows in the cool of the night and early morning and then try to trap it inside for as long as possible by closing up the windows and shading the south and western sides -- externally, if you can, with awnings or plantings for decks or lower levels. Trees and plants are your friends!

And, if you can, shade those western facing windows at the top level externally as much as possible -- you said "balcony," can you hang some kind of material just under the eaves to block? And maybe fill in the rails with a bamboo mat or something? By sunset, you're kind of screwed but having blinds on the inside that you can additionally close off at the latest hours of the day will help a little.
posted by amanda at 6:23 PM on June 19, 2007

If you've installed blockout blinds and the room is too dark, just open the blind a little bit. A 10%-open blind in full sun will let in plenty of light to see comfortably by, and it's still keeping 90% of that radiant energy from heating up your interior.

I like white interior blockout blinds better than external awnings for this job, even though the external awnings can keep a little more heat out, precisely because the interior blinds are so controllable.

If you install them so that the edges of the blind overlap the edges of the window frame and make something approaching a seal when the blind is closed, and put a pelmet over the top of them, the dead-air pocket between the blind and the window can also keep a remarkable amount of heat in on those cold winter nights.
posted by flabdablet at 11:39 PM on June 19, 2007

Probably makes sense to install a window that opens. Do some googling for passive cooling for technical advice. I've heard people talk about success with a swamp cooler. And fans really help because moving air feels cooler.
posted by theora55 at 4:50 AM on June 20, 2007

Big open spaces suck for energy efficiency because you will always have to heat or cool the entire space. They look impressive and all but they are functionally a PIA. Break up the space by either using partitions or curtains to isolate the bedroom space which will be easier to cool in the heat of summer. Get a portable AC unit for the bedroom and vent it into the main part of the loft.

The architects who designed that space should be shot...
posted by JJ86 at 6:21 AM on June 20, 2007

In my Condo I just open the window upstairs and put a fan pointing out. Open the window downstairs and in minutes you can really tell a difference.
posted by 4Lnqvv at 8:21 AM on June 20, 2007