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Posts Tagged ‘passive cooling’

Windcatchers have been employed for thousands of years to cool buildings in hot climates. The windcatcher is able to chill indoor spaces in the middle of the day in a desert to frigid temperatures.

Windcatchers have been employed for thousands of years to cool buildings in hot climates. The windcatcher is able to chill indoor spaces in the middle of the day in a desert to frigid temperatures.


The following list includes dozens of low tech, low cost ways to cool buildings in hot climates passively without electricity or machinery, i.e., passive cooling or natural cooling. This list is in addition to the 11 or so simple passive cooling techniques that I talked about in my video the other day. Altogether there are over 50 practical methods for cooling your home sustainably. Despite all these wonderful methods, most people – at least in North America – live in poorly insulated boxy houses with costly, wasteful air conditioners. This is one example of “ignorance is not bliss”.
– night cooling: open the windows at night to let in cooler, fresher air.
– roof vents for improved ventilation. This could include a ridge vent and cupola.
– gable vents on gable end walls
– adequately shaded clerestory windows
– smaller windows on the east and west to prevent overheating (if the walls aren’t shaded)
– louvers and vents
– well located doors
– 50-100% more or larger windows on the leeward side than the windward side to help hot air to escape
– earth berming with moist vegetation such as grass
– keeping vegetation moist around the house to help cool the breezes (the yard)
– planting trees to funnel air toward your house
– plant trees that don’t block breezes
– wing wall to direct cool breezes into the home
– building on stilts
– stack effect: multi-story designs can be very effective at encouraging natural convection
– open plan living areas that encourage air circulation
– narrow floorplans
– orientation to catch breezes more effectively
– location: breezy locations near lakes, etc.
– outdoor living areas
– porches/verandas that shade the walls
– shaded, high thermal mass walls such as earthbags, adobe, etc.
– windscoop/windcatcher (with possible addition of a water element)
– evaporative cool wall such as double terra-cotta brick walls (low fired brick) filled with moist sand
Venturi effect
– solar chimney: chimney designed to heat air and draw air from the house
– atrium or sunroom: can act like a solar chimney if properly designed
– basement: upper floors draw cool air upwards from the basement
– cool pantry and rootcellar
– well, open air cistern or underground water canal in the basement
– earth tubes in dry climates where mold is not a problem and digging is fairly easy
– roof insulation and reflective roof insulation
– fly roof (secondary roof over the main roof)
– green roof/living roof
– soffit vents and baffles between rafters to improve roof ventilation
– light roof color that reflects sunlight
– manmade water feature such as a lily pond on the windward side
– awnings (if you don’t have large roof overhangs)
– inner courtyard/open atrium
– pergolas and trellises to shade walls
– minimize sun reflection and re-radiation from surrounding environment: plants versus gravel or pavement
– blinds: close if sunlight is entering window
– avoid skylights unless openable and tinted
– smooth plaster reflects more light than textured plaster

Note: This is just a list of practical cooling strategies. There are plenty of ‘yeah, buts’ you should be aware of to prevent problems. There isn’t time or space here to cover everything. A fair amount of research is required to learn the details so you can optimize the passive cooling design for your home and building site.

Image source: Wiki – Windcatchers (good info on windcatchers)
Good reference with more details: Passive Cooling at House-Energy.com

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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 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.

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Ceramic tile floor

Ceramic tile floor


Soil-cement floor

Soil-cement floor


Stone floor

Stone floor


Recycled brick floor

Recycled brick floor


Earth coupled floors – high mass floors in contact with the soil below (slab on grade, tile, stone, CEB, earthen floors, salvaged brick) – are ideal for keeping homes cool in hot climates. They are not recommended for cold climates where underfloor insulation is best. Our earthbag roundhouse, which is in a hot climate, remains cool year-round due in part to the earth coupled floor. The indoor temperature is about 15 degrees F (8 degrees C) cooler inside than out, and the temperature remains nearly constant night and day. Plastic sheeting under the floor prevents wicking of moisture.

“Floors are often the primary link between the structure of a building and its foundations (the ground upon which it sits). Where floors are in direct contact with the ground, they can have a major influence on the internal climate by adding thermal inertia (capacitive insulation) which is assisted by thermal coupling with the mass of earth underneath the floor.

The coupling effect of the earth and building structure increases with depth. Walls and roofs can also be earth coupled if the structure is excavated below ground. Once a structure lies about 3.0 metres below ground, it has such great thermal inertia that it is no longer subject to day/night temperature swing, but only to slight effects from seasonal variation.”

Text source: TT Architecture
Image source: Ceramic-Floors.com
Image source: Rammed Earth Works
Image source: Inehome.com
Image source: Vintage Brick Salvage

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