A blog by Mel Riser about LifeBoat Permaculture and Solar Villages

Friday, July 23, 2010

Cooling Towers and Solar Fans

Space cooling and heating can account for up to 45 percent of your total home energy use every year, but there are numerous strategies you can employ to reduce cooling costs. For instance, a ceiling fan used in conjunction with air conditioning lets you raise the thermostat by as much as 4 degrees while maintaining the same comfort level in a room. The U.S. Department of Energy estimates that each degree below 78 degrees on your thermostat will increase your air conditioning bill by 8 percent. You also can use natural ventilation to capture and create breezes, or to help you take advantage of nighttime drops in temperature.
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Other money-saving ideas include minimizing heat gain, weather sealing, insulating, window shading and glazing, roof lightening and landscaping (see “Best Bets for Passive Cooling”). Because natural ventilation is one of the most cost-effective ways to cool your home, we’ll examine it here in greater detail.

Natural Ventilation

Natural ventilation makes the most of air motion to cool you and your home. This is the primary passive cooling strategy in all climate zones, but the nuances of its application vary by region. Understanding seasonal wind patterns will help you adjust your window openings, outdoor spaces and windbreaks to increase your comfort without relying on nonrenewable fuels.

Take some time to think about the breezes and winds around your home:

• At what time of day and year are the winds strongest?
• From which direction does your prevailing wind come (the one that blows most of the time, when there are no storms)?
• From what direction do storms come?
• Is there a noticeable breeze or wind most of the year? Does it vary much from season to season?
• Do your local breezes shift daily?
• Is local air movement influenced by geographic features or landscape elements?

There are several ways to learn about local wind direction and intensity, such as observing for yourself (at different times of the day and year), accessing weather data and asking local farmers or other people who work outdoors what they observe.

You also can hang a windsock in your yard. A friend who lives near the ocean has done this; she and her family enjoy being aware of changes in the wind’s direction and force, making them feel more like part of their natural surroundings: “Our prevailing wind comes from the northwest, so most of the time the windsock points to the southeast. But sometimes it suddenly turns and points north, and then we know there’s a storm coming in.” A weather vane on your home or garage can provide the same information.

Becoming familiar with local weather patterns can help you decide on a natural cooling strategy. In hot humid climates, for example, maximum airflow combined with shading is the dominant strategy. In hot arid climates, ventilation is welcome in the hot seasons, and night cooling of thermal mass is particularly useful due to lower nighttime temperatures. In cold climates with cool summers, there may be little need for enhanced natural ventilation. Many temperate and mixed climates will require a variety of tricks as the seasons move from one extreme to another. As you read on, think about your own climate zone and your experiences living there; focus on the approaches that feel most relevant to your situation, and see how you might improve the existing relationship between your home and the breezes.


This is very similar to the setup I created at my house.


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