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 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. 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 [and earthbags] 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 directly. 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.

Almost 100 videos at Earthbag Natural Houses YouTube channel.


Comments

Passive Cooling Strategies for Hot Climates — 11 Comments

  1. I’ve been looking and looking and cannot find instructions anywhere on proper thatching for palms. I want to know how good these roofs are against heavy rains (Belize) and winds. Also keep reading about the earthen roofs which supposedly keep houses cool. I get the concept but don’t understand the maintenance. Any thoughts or insights?

    • I’d hunt for locals who still build with thatch and hire them to help do the work.

      There are special tie downs used to minimize damage to thatch in high wind areas.

      Earthen roofs or living roofs are tricky, but will work in Belize and other tropical areas. You’ll have to decide if you want to do all the maintenance. It’s much like caring for a garden. Plan to be up on the roof regularly, especially until all the plants are thoroughly established. Use hardy plants because it’s more difficult to get things to grow up on a roof. For me, the cost of the heavy rubber bithuthene is almost a deal killer. Roots and rodents will eventually puncture cheap plastic, so the heavy rubber liner is pretty much required.

    • I worked with locals in Panama making true, old-school palm thatch roofs and there are many downfalls to this kind of roofing. First off is the bug issue. Any and every kind of cockroach, ant, scorpion and crawling creature will harbor in these damp, decomposing leaves. Second is the fact that these structures are temporary and need to be rebuilt about every 3-5 years depending on the storms that year. The fronds were simply attached with nails to a cross-beam. Lastly, there is hardly any structural integrity as a large tree branch or even a coconut from a neighboring tree may come crashing through if in a gale. So, if you want the look of thatch, then I know there is a faux thatch roof that can be installed, but surely they are made from a non-renewable resource. I would look to a green roof with cacti, succulents or other minimal-water plants. Make sure it has a good liner and it should last for decades.

  2. I enjoyed the nice and thorough video! The gap along the top was particularly interesting, i bet with some screening it can be adapted to other structures as well.

    • Not yet. The original plan was to screen the gap, but like many things we never got around to it. It hasn’t been a problem up until lately. Now a bird is coming in to gather nesting material. Great. Every so often there’s a mess of thatch on the floor.

  3. Owen,
    This has been one of the best presentations I have seen related to recommendations of keeping your Natural Home cool. Simple and effective!

    We also live in a “hotter climate” (Panama) and we fully agree to all the suggetions and recommendations you have provided in your video. We have experienced them to be realistic and proven as correct in our type of weather.

    You also recommend the Mango Tree. Many people may not know that besides one of the best shade providers the Mango Trees does not loose their leaves. So, you do not have a mess of collecting leaves throughout the year like so many other shade providing trees. And, you have the benefit of not only a beautiful shade, but also harvesting yummie Mangoes….

    Another species of tree we have found here in Panama with extraordinary charecteristics is Neem. You may want to look into this. This is an extraordinary tree not only providing many beneficial aspects known but we have also see some characteristics as natural “Mosquito Repellant” and as a “Cool Air Providing Tree”. It may not grow as high as a Mango Tree but for some reason it provides “coolness” to its surroundings which is not commonly known to many.

    Here is a weblink:
    http://en.wikipedia.org/wiki/Azadirachta_indica

    Well done!
    Walter

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