June 2010 Newsletter

While modern air conditioning provides houses with relief from the summer heat, centralized air conditioning is over-used in the United States. The following tips focus on ways to keep your home comfortable while simultaneously reducing air conditioning use. Keep in mind that Home Energy Audit identifies structural issues related to the thermal envelope of your building, and proper air sealing and insulation of a home's thermal envelope is more effective than any of the tips here:

"Green" Roofs: A "Green" roof isn't typically the color green. Rather, it is eco-friendly. The goal of a "Green" roof is to stop solar heat from being absorbed by your home. Reflective, light-colored surfaces don't absorb solar energy as readily as darker surfaces, which means homes with "Green" roofs require less air conditioning to hit a specific temperature. Thus, lighter-colored roofs and exterior paints can reduce a process known as solar heat gain. You can paint your roof, or wait until the next time you need to replace your roof. There are ENERGY STAR certified roof shingles such as the Certainteed X25 Star White (Brian installed this shingle at his home) that costs the same as any other shingle color.

Shading: Blocking solar radiation through the appropriate use of shading also can provide significant help in cooling down a house. Tree shade and awnings around windows can reduce heat gain by up to 75% according to the D.O.E. and is particularly effective on Southern and West-facing windows. You also want to add heavy curtains to those windows to prevent solar heat gain through your windows. Trees and foliage can also provide further help with cooling by creating microclimates. As green plants go through the process of photosynthesis they release oxygen and water vapor. Thus, trees not only block sunlight, but can actively cool an area by up to 10 degrees. (Trees also take carbon dioxide out of the air, reducing the amount of greenhouse gases).

Fans: Fans can also be used to help supplement central air conditioning. A simple room fan or ceiling fan can circulate air, making the room feel 5-7 degrees cooler, which lets you run your air conditioner warmer. Fans work by blowing a breeze on your skin. They don't actually change the temperature of the room. Thus, you should never run fans to cool a room while you are out of the room. A whole house fan can also help to draw in the cooler evening air while exhausting the hot and humid air. Fans are also much more energy efficient, using only a 10th of the power of a comparable air conditioner system. We generally do not recommend attic fans unless you are using your attic for storage of temperature-sensitive items. For most people, proper air sealing and insulation should isolate your attic from your living area, which means attic temperature does not affect your living spaces.

Reduce Heat Generation: Last, you should reduce the use of any heat-generating sources. For example, instead of cooking with your oven, use a microwave. If you use a stove top, turn on your kitchen fan when cooking to remove the excess hot air before it heats your home. When taking a hot shower, turn on the bathroom fan to exhaust the hot, humid vapors. As discussed below in detail, replacing your incandescent bulbs with compact fluorescent lights can also make a big difference. Not only do fluorescent lights use 75% less energy than incandescent bulbs, they also produce 90% less heat.

In 2005, 91 million US households consumed some 258 billion kilowatt hours to cool their homes, costing about $24 billion dollars and releasing 171 million tons of carbon. Taking these steps to cool off will not only save you money but reduce your carbon footprint.