Publication date: 06/25/2010

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Be realistic about your air conditioner's abilities

Air conditioning is one of the greatest inventions of the 20th century and is a necessity these days. But even a home with central air can feel muggy and uncomfortable.

Now you hear weather forecasters talk about the heat index. That's a combination of temperature, relative humidity and dew point that determines your comfort level outdoors. The same is true for inside your home.

Air conditioners are designed to primarily dehumidify, then reduce the temperature of the indoor air. When a system is not correctly sized, it may not fully "condition," doing only half the job. For example, when an air conditioner's condenser is oversized, it may cool the air too quickly and then shut itself off before reducing the humidity.

When the humidity inside your home is too high, the thermostat may say it's 72 degrees, but it will feel much warmer. Keep the humidity level in your home below 50 percent in the summer months to maximize your comfort.

Use a hygrometer to check the humidity level in your home. When areas such as the basement are too humid, they can affect your entire house. Look at an Energy Star-rated, ultra-low-temperature dehumidifier. Some quality brands are DeLonghi, www.delonghiusa.com, and Whirlpool, www.whirlpool.com. If your bathroom gets really humid when you take a shower, try a DewStop exhaust fan switch, www.dewstop.com, designed to automatically control condensation.

"I see a lot of people turn their air off when they go to work and turn it on when they come home because they want to save energy," said Gary Marowske, president of Flame Heating, Cooling and Electrical, (888) 234-2340, www.flamefurnace.com. "But that means your air has to work even harder to cool your house, so it is better to set it and leave it on all day so it can condition the air properly."

Gary also recommends getting a blower door test now to see any air leaks in your home. The idea is to seal in the cool, dry, conditioned air and prevent the warm, moist, outdoor air from entering.

Of course, having the proper attic insulation, with soffit and ridge vents, is also important to keep your attic cool and maximize the effectiveness of your air conditioning. You could also add some attic vent fans to lower your attic's temperature.

If you have areas of your home that just don't get cool, or you live in a house without central air and want to cool just a room or two, you have three options: a window air conditioner, a portable one or a ductless mini-split air conditioner.

While window and portable air conditioners are inexpensive and can adequately cool either a large bedroom or small apartment, they are very noisy. The advantages of some portable units are that you can have it cool in summer and then switch to a heater in fall and winter. They also can be stored easily.

However, unlike many window air conditioners, portable units are not Energy-Star compliant and can be expensive to run.

Ductless mini-split air conditioners have a fan unit mounted on an inside wall that is connected with small refrigerant lines to an external condenser unit outside. While these systems are fairly expensive, you can cool more than just one room and can have individual thermostats to keep each at a constant temperature. Some major manufacturers include Carrier, www.carrier.com; Mitsubishi, www.mitsubishielectric.com; and Sanyo, http://us.sanyo.com/hvac.

No matter what type of air conditioner you have, another way to improve comfort is to use ceiling fans. For under $100 at most home centers, you can find the right size and style fan for every room in the house.

But remember to use ceiling fans only when someone is actually in the room. It's the circulation of the air over the skin that makes you feel cooler. Also make sure the switch is either down or to the right, with the blades turning counter-clockwise pushing air toward you.

Even if you are at the head of the home improvement class for air conditioning, central air is designed to make your home 15 degrees cooler than the outside air temperature, and window units aren't designed to cool an entire house. So be realistic about your expectations.

It's not the heat. It really is the humidity. You can feel it, and believe it.

Note: This article was accurate at the date of publication. However, information contained in it may have changed. If you plan to use the information contained herein for any purpose, verification of its continued accuracy is your responsibility.

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