Passive Cooling Strategies

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Today I want to talk about passive cooling strategies for keeping your home cool in hot climates. This is a very hot climate and yet our earthbag roundhouse is about 15 degrees Fahrenheit cooler inside than out. So 15 degrees Fahrenheit, 8 degrees Celsius temperature difference with no mechanical cooling systems. No air conditioners, no fans, no anything. It's just passive strategies, natural strategies for keeping the home cool without the use of machinery or electricity. So we'll discuss about 11 different strategies that you can use. They're all very low cost and simple. The first one is the color of your wall -- your exterior wall. You want the walls to have a light color so they reflect the sunlight. One of the most important things is to have wide roof overhangs. This is about 4 feet, a little over one meter. So the sun almost never hits the wall. Because they're high mass walls, if the sun hit the walls frequently, that mass would heat up and eventually that heat would transfer inside. So we keep the sun off the walls as much as possible. Another important strategy is windows. We have casement windows that swing open and catch the prevailing breezes. So the breezes come from this way and these are like a scoop -- a wind scoop -- to pull the wind into the roundhouse. We also have windows on all sides of the house so the breeze is always blowing through. If you look up above the window, we have screened openings above the windows that keep insects out, but let hot air escape this way. And I don't know if you can see it, you might want to come closer. Above the bond beam is a gap of a few inches. In between the rafters there's a gap where hot air can escape. So the hot air is rising and it goes out the top. Also we use thatch roofing and some air passes through the thatch. We also have one of these screened openings above the door as a transom. Let's go inside and I'll show you the earth coupled floor. This is our earth coupled floor right here. What that means is the floor -- the high mass floor -- in this case concrete, but it could be tamped earth, stone, CEBs, brick, recycled brick, whatever. The floor is in direct contact with the earth underneath with a moisture barrier to prevent wicking of moisture. So the floor is absorbing the coolness of the earth. It's very cool, surprisingly cool even in this hot climate where you can start sweating in just a few minutes. So this is surprisingly cool. We also have earthen plaster on the inside. All that mass and this mass partition wall all absorb the coolness of the earth -- the coolness coming up from the earth. And the breezes help all the hot air escape. So the temperature inside stays the same night and day. You don't need an air conditioner or even a fan. It's surprisingly comfortable in here. Some other strategies, you want to look up and see the high ceiling. So there's plenty of space for hot air to rise and escape. There you can see the gap above the bond beam to improve ventilation. The last strategy I'm going to talk about is vegetation -- using plants to keep the building cool. Here we've used a mango tree on the hot southwest side of the house. That's the hottest direction. We have different plants here. So the sun, as you can see, almost never hits the house directiy. And also we have a very large tree above here that protects and shades the house through most of the day. Again, these are all simple, low cost strategies that anyone can do. Very low cost, very simple. You can save a lot of money on energy bills and also help the environment.