What Is Passive Cooling and What Can You Do to Make It Work for You?

Passive cooling is natural air conditioning. By reducing a home’s internal and external heat gains, with clever techniques like properly positioned shade trees, houses can be completely cooled without using a mechanical air conditioner.

| April 2016

  • Evergreens on the south side of homes block the low-angled winter sun and increase passive cooling effect.
    Photo courtesy Dan Chiras
  • Vine-draped arbors such as this provide many benefits and are a great passive cooling measure.
    Photo courtesy Dan Chiras
  • "The Homeowner’s Guide to Renewable Energy: Achieving Energy Independence Through Solar, Wind, Biomass and Hydropower" by Dan Chiras, completely revised and updated edition.
    Cover courtesy New Society Publishers

Well-illustrated, and highly accessible, The Homeowner’s Guide to Renewable Energy by Dan Chiras (New Society Publishers, 2011) is an essential resource for anyone wanting to enter the renewable energy field, whether their goal is a lower monthly utility bill or complete energy independence. In this excerpt from Chapter 7, you will learn how passive cooling works, how to reduce internal heat gain, and how to use natural shade trees to promote cooling.

You can purchase this book from the MOTHER EARTH NEWS store: The Homeowner’s Guide to Renewable Energy.

What Is Passive Cooling?

Passive cooling is a key element of a larger strategy known as natural conditioning — heating, cooling, ventilating and lighting a building naturally, that is, 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. In the process, we slash our energy bills, increase our energy 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, as well as ordinary building components, such as insulation, overhangs and energy-efficient windows. As noted in Chapter 4, 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 a building to true 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 sealing leaks in the building envelope, insulating well, installing energy-efficient windows and building with sufficient overhangs also enhance year-round comfort. 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 fuels that power it.

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 United States, although humid climates pose greater challenges, as you shall soon see.

8/16/2017 10:50:15 AM

Window placement / window types can also help here. Windows that block UV rays can block out heat in direct sun, as the sun moves over and past parts of the home. We recommend taking this into consideration often for customers! http://www.empirewindowcompany.com/

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