Natural Cooling Strategies

Who needs air conditioning? These design strategies can help you keep your home cool without it.


| August/September 2011



House With Porch

Two elements of natural cooling are shady porches and deep window overhangs that block the sun in summer.


PHOTO: BARBARA BOURNE

Most people have limited tolerance for hot weather. As the thermostat rises, we quickly become uncomfortable, and if it becomes too hot inside our homes, it’s even dangerous. Our modern response to this problem is simple: “Turn up the air!” However, air conditioning consumes a lot of electricity, and most of it comes from polluting fossil fuels. Electricity is also a limited resource: On the hottest days of the year, some cities don’t have enough electricity to meet demand, leading to brownouts or rolling blackouts.

Fortunately, many old-fashioned design strategies can keep a house cool naturally, which conserves energy and saves money. Although home builders largely have stopped using these techniques over the past 100 years, there’s no reason we can’t rediscover them and use them in our homes. This article explains how to use a few basic natural cooling strategies, whether you’re building a new house or making improvements to an existing home.

Natural Ventilation

Before society embraced air conditioning, we all found simple ways to beat the heat. One was to sit on a shaded porch, sipping a cold drink. If the porch was positioned correctly, gentle breezes would blow past. Breezes help moisture evaporate from your skin — one of the body’s main methods for cooling off. In fact, many natural cooling techniques boil down to one basic principle: Keep the air moving. So how do you improve airflow within your home?

Ideally, when you’re building, you choose the site and orient your house to take advantage of naturally occurring wind patterns. You can also direct summer breezes into and through the house by carefully choosing the types and locations of windows and doors to funnel air through a building.

Many historic architectural styles, especially those used in hot climates, relied on tall windows on opposite sides of a room for cross ventilation. If you’re building a home or planning an addition, you can try this technique yourself. If you cannot place windows on opposite walls, try to place windows on adjacent walls, which still produces some airflow.

Another way to encourage natural ventilation is through a design technique called the stack effect. The general idea is to allow the warmer air in a home to rise up and out of the living space. To create the stack effect, you have to provide an opening toward the top of the space in conjunction with an opening toward the bottom, so that the hot indoor air will be naturally drawn up and out. The greater the height of the space and difference in temperature, the greater the natural draw. This essentially provides a naturally ventilating, unpowered fan system. You can take advantage of this effect by building a home with a ventilation tower. An option for retrofitting a home might include installing an operable skylight.

jay.lloyd.319
5/28/2013 1:19:23 PM

I agree with Baloobearmak, there is no way these designs can make life livable without an AC in the deep south, like where I live in Mississippi. It's just too hot for passive cooling to be the main cooling method. That being said, shade trees over windows, wind corridors, and these other methods are present in all the older house designs here, and I am glad to see some of these methods are making a resurgence to lower energy costs.


baloobearmak
5/24/2013 12:09:11 PM

Bah! Humbug!! Yeah right this design might lower Mississippi daytime inside temps from from 100+ to maybe 95+. This is not a design for the deep south. This "solar" slab can store the nightime 85+ temp to moderate the 100+ daytime temps(actually that 100+ is outdoors. No telling how hot this house would heat up to...cars in the sun can get up to 130+ degrees. Every one of these so called passive house designs are designed for somewhere other than the deep south.


gary reysa
8/21/2011 3:21:40 PM

Hi -- One of the studies on cooling says that for the homes they studied 47% of the heat gain was from solar radiation through windows, so the advice on shading windows is (I think) very good. Window shading on the outside is much more effective than inside blinds or the like. Shading with outside shades, trees, ... is (I think)more effective than overhangs because it blocks both the direct sunlight (like overhangs) and also the diffuse and ground reflected light -- the diffuse and ground reflected light are a surprising large part of the incident radiation on windows. Thanks -- Gary


k rhome
8/19/2011 11:03:31 AM

Why aren't earth tubes mentioned in this article? Aren't they a good option also?






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