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Staying cool with less AC

Q: I don't like the hot weather, but I am going to make an effort to air-condition less this summer to reduce my electric bills. What can I do to try to stay comfortable without running the air conditioner as much?

A: It is not difficult to live comfortably with much less summer air-conditioning. Up until just a couple of generations ago, residential air-conditioning didn't even exist and we survived. When I was a child, we had just one window fan and one floor fan for a family of four.

There are four methods to improve comfort without air-conditioning.

These are bringing in cooler outdoor air when possible, increasing air velocity indoors, minimizing the indoor humidity level and blocking heat transmission into the house.

Installing a whole-house fan accomplishes two of these goals. At night, it typically brings in cooler air and exhausts heat. A whole-house fan can also create a pleasant breeze throughout your house. Running one uses only a small fraction as much electricity as a central air conditioner.

Install a solar chimney to harness the sun to create a breeze throughout your house using no electricity. A solar chimney is a tall chimney made with standard lumber. Two sides of it are covered with clear acrylic sheets and the inside is painted flat black.

An opening at the base of the solar chimney is ducted through your house wall. When the sun shines through the acrylic onto the black interior, it gets hot and heats the air inside the chimney. Since hot air rises, it comes out the top and draws air in the bottom from inside your house to create a breeze indoors.

Increasing the velocity of the indoor air can make a room feel 5 to 10 degrees cooler than still air. This is the theory behind using ceiling paddle fans. They use very little electricity and can create quite a comforting effect even though they actually make the room air slightly warmer.

If you plan to rely on natural ventilation through windows, hopefully you have casement windows. When the sash projects out from the house, it tends to catch and direct the natural breezes into your house more than vertical or horizontal slider windows.

If you do have sliders, open the windows on the downwind side of your house fully. Open the windows somewhat less on the windward side. This creates a faster air flow in through these partly opened windows, making you more comfortable if you sit near them.

Run your kitchen and bathroom vent fans whenever you are cooking or bathing to remove the moisture. Make sure the clothes dryer vent duct is not leaky, allowing hot, humid air to stay indoors.

Block heat from entering your windows and glass doors with awnings and window film. Install reflective foil under the attic rafters to block radiant heat from a hot roof. Make sure you have adequate attic ventilation and that insulation is not blocking soffit vents.

R-value vs. U-value

Q: I have been looking at new garage doors and I want to get an energy-efficient one. I cannot see how to compare various ones because some quote R-value and others quote U-value. What is the difference?

A: U-value is the inverse of R-value. An R-value of 5 is equivalent to a U-value of 0.2. R-value is more commonly used by manufacturers to state the insulation of doors, but either value can be used.

Also compare the energy efficiency of the glass if the door has many windows. Even the best window glass will be less efficient than no windows at all, but you may save electricity with windows by not having to turn on lights.

Send inquiries to James Dulley, St. Petersburg Times, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit www.dulley.com.

Staying cool with less AC 08/07/09 [Last modified: Friday, August 7, 2009 5:30am]

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