Passive Cooling: Eco-Friendly Ways to Comfortable Summers; Introduction and What is Passive Cooling?

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One hot September day, shortly after I’d moved into my new energy-efficient home in the foothills of the Angeles Forest in Southern California, a white car pulled into my driveway and parked. Two women emerged, then walked to the front door. Dressed in business suits and carrying clip boards, I guessed that they were representatives of some branch of local or state government.

I greeted them at the door and quickly learned that they were from the county tax assessor’s office. They had arrived unannounced to look over my newly-built home to take measurements and to enumerate its various features so they could determine my property tax.

After stepping out of the 90+ degree summer heat into my naturally cooled home, one of the women glanced at the checklist on her clipboard and said, “You must have central air.

“No”, I said, “this house is naturally cooled”. She shot me a suspicious look, “Really” I said, “it’s super-insulated and earth-sheltered. Together, they keep it pretty cool in the summer. There’s no need for air conditioning”.

She gave me another look, this one a little more impatient. Her impatience, no doubt, stemmed from frequent conniving of members of the general public who want to dodge their duty to provide taxes needed to maintain our roads, pay for schools, and provide a host of other vital services, I don’t particularly like taxes, but I realize that if we’re going to have a decent education, snow-free roads, police protection, fire protection, and other vital services we’re got to pay for them. Undaunted, I repeated my earlier statement, then added, “Look around, there’s no air conditioner.”

With that, the ladies went about their business, measuring rooms and checking off various features of the home and secretly searching for ducts or vents that might deliver cool air to my home. Outside, I’m sure they scoured the landscape for some sign of a central air conditioner.

Cooling the various homes I’ve owned or rented over the years has been a challenge until I built my current house. This house, designed to be passively cooled, doesn’t have an air conditioner despite some pretty hot summer days.

You may face a summer cooling challenge, too, one that is only bound to get worse in the many parts of the world suffering from the ravages of global warming that is causing record-breaking heat waves with record- breaking frequency. Fortunately, you don’t have to build a new home to solve the puzzle. With time-tested techniques outlined in this section, you can single-handedly retrofit your home to greatly reduce — perhaps even eliminate — your need for mechanical cooling. All you need to do is to apply the principles and practices of the lost art of passive cooling.


Passive cooling is a key element of a larger strategy known as natural conditioning — providing heating, cooling, ventilation, and lighting naturally, without mechanical or electronic devices and without outside energy.

Like passive solar heating, passive cooling may require some backup from time to time. The goal, however, is to reduce our reliance on mechanical cooling and ventilation systems and the outside energy needed to run them, and to slash energy bills, In the process, we increase our level of independence, and dramatically reduce our impact on the environment, the life-support system of the planet and , lest we forget, the source of all our wealth.

How Does it Work?

Passive cooling taps into natural forces, such as cool breezes, shade, and cool nighttime air, and ordinary building components, such as insulation, overhangs, and energy-efficient windows, to cool homes or any other buildings. Many of the steps taken to heat a home passively also contribute to passive cooling. When building a new home, for instance, the simple act of orienting the building to the south increases wintertime passive solar gain while greatly reducing summertime heat gain. The net effect of this simple measure is that the house stays warm in the winter and cool in the summer, naturally. Other passive heating strategies like insulating homes well, installing energy efficient windows, and building with sufficient overhangs also contribute to year-round com fort, But there’s a lot more you can do to passively cool a new home, and there’s much you can do to an existing home to reduce its reliance on mechanical cooling and the costly, environmentally damaging energy supplies that power them.

Moreover, it doesn’t matter where you live, Passive cooling techniques work well in all climate zones from hot, humid regions like the midwestern and southeastern United States to hot, arid climates like the western and southwestern US, although humid climates pose greater challenges, as you shall soon see.

Why is Passive Cooling Important?

One of the main challenges of the coming decades will be finding substitutes for oil and natural gas sup plies that are rapidly declining. Fortunately, most homes in the United States are cooled by air conditioners powered by electricity derived from the combustion of coal. Nonetheless, some of the oil and natural gas we consume each year is used to generate electricity. Passive cooling will therefore help ease our demand on these fuels, allowing their diversion to other uses for which there are fewer alternatives (for example, natural gas can be used for cooking and making fertilizer; oil can be used for generating transportation fuel, plastics, and chemicals used to make medicines).

Passive cooling not only frees up natural gas and oil for other vital activities, it also reduces our reliance on coal-fired electricity, reducing environmental damage from the entire fuel cycle, from exploration and mining to the combustion of coal and the disposal of wastes from power plants. Increasing our reliance on passive cooling techniques will also reduce the growing strain on North America ’s already-taxed electrical supply sys tem. This, in turn, will help to reduce the potential for annoying, costly, and sometimes highly disruptive summer brownouts and blackouts.

Next: Passive Cooling: Tools of the Trade


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