How To Cool a Room With No Air Conditioning!

Heat and sleep really do not mix. It’s not just a preference — it’s biology. The process of falling asleep comes with a natural lowering of body temperature, which stays about one degree lower until morning. Hot nights can really disturb the quality and length of our sleep.

All over the world, hot weather is becoming more and more of an issue, and for those of us without good air conditioning, it can really impact sleep. In Los Angeles, because it’s a desert climate, the air outside cools down when the sun goes down, but the inside of the house is still very warm.

I used to do what most people do to cool a room: position the fan so it blows cool air INTO the rooms. Makes sense, right?

Not the case at all! Trying to push cool air into a room is a slow and ineffective method. My dad — a scientist who also happens to have no air conditioning in his home, but always has a cool house for sleeping (even mid-August)–introduced me to this idea. When we’re home in the north east over the summer, I’m always amazed how the top level of his house can be comfortable and breezy — even in a room with no fan. The secret to his cool house (and now, mine), is blowing air out of the room. When you do this properly, you create a vacuum of air in the room and this will draw cool outside air in another open window. It takes some planning and positioning, but if you can get this system working in your bedroom, your sleep will thank you.

Here’s how it works. There are 2 windows involved: 

Place a fan in one window facing out, so the air in the room is being blown out the window. You’ll want to make this fit as well as possible, so there’s no space open in the window–the fan should cover the open window space.

In my kids’ room, they have a window that opens up, which is ideal. I put the box fan in front of it (I usually put more books than shown above, or a box under it to get it up higher to the base of the window) and closed the window just to the height of the top of the fan. If you have another window configuration, you can take a piece of poster board and place it on top of the fan, so it blocks whatever open space is left. The key is getting it so the fan fits neatly into the window without leftover space. 

Next, open another window in the room. If there aren’t two windows in the room you’re trying to cool, you’ll want to place a fan blowing out of a nearby window, and open the window in the room you’re cooling.

Now, this is pivotal: Close off the space. You have to create a vacuum, so that the warm air blown out of one window has to be replaced by cool air from outside (physics!).  In our room, that means simply closing the door, because both windows are in the room. If I left the bedroom door open, it would dilute the effect. You can also put the fan in one window, open another, and shut all the remaining windows in the house, including closing hallway doors or stair doors if that’s your house set up. Whatever makes a seal so that the air is forced to come in the open window.

When I got this set up in our house for the first time, it must have been 80 degrees in the kids’ room. I closed the bedroom door and went to stand by the open window in my newly-created air circulation system, and I couldn’t believe the gust of cool air streaming in.  After about 6:00 p.m. when the air temperature drops outside and I get the fan going properly, it’s as effective or even more so than an air conditioner. Give it a try! And also make sure to keep the curtains closed during the day in the bedroom, because the sun really heats up the room. — Heather