Tips to keep house cool, make sure system is running efficiently

When the heat is on, your central air conditioning system needs to work at its best.

Here are some tips for getting the most out of your air conditioning in terms of both comfort and energy savings.

Quick fixes:

* Block the sunlight.

The sun's heat can increase the indoor temperature significantly, said Harvey Sachs, senior fellow with the nonprofit American Council for an Energy-Efficient Economy in Washington.

Close window coverings on the sunny sides of the house during the day, Sachs said. Longer term, you can consider measures such as adding awnings or planting trees to provide shade.

* Close the windows.

It's surprising how often people seek relief by opening windows while the air conditioning is running, said Mike Foraker, president of Jennings Heating and Cooling in Akron, Ohio. But all that does is let in hot, moist air.

Air conditioning works in part by removing moisture from the air. If you keep adding humid air to the house, the air conditioner has to struggle to dry it. Consequently, the indoor air can never reach a comfortable temperature and humidity level.

* Leave the unit on.

People sometimes turn the central air conditioning on only at night to save money. That's fine when the weather isn't too hot, but it's a bad idea when the temperature reaches 90 or so, Foraker said.

Turning off the air conditioning in extreme heat lets warmth and moisture build up in the house, he explained. The unit can't eliminate them quickly enough to make the house comfortable at night, and it uses a lot of electricity trying.

* Clear the condensing unit.

The outdoor condensing unit needs a supply of outside air to blow across the heated refrigerant, which is how hot air gets expelled from the house.

Make sure the condenser has enough space around it to permit a good air flow. Trim any plants that are growing close to the unit, and make sure no mulch, grass or debris is blocking the bottom openings.

Karl Bella, an energy auditor who runs Energy Pros of Ohio in Richfield, recommends a clearance of at least 8 inches all around. Sachs prefers as much as 3 to 4 feet, if possible.

* Check the air filter.

In almost every forced-air system, the furnace filter is also the air-conditioning filter. If it gets clogged, air flow is reduced.

Change or clean it as often as the manufacturer recommends, usually every one to three months.

* Set the fan on automatic.

Conventional wisdom used to dictate running the fan on an air conditioning system constantly to keep air moving throughout the house. Newer research suggests otherwise, Bella said.

Leaving the fan running increases what's called the stack effect, the tendency of a house to pull in outside air to replace air that rises and escapes through openings high in the building. The more hot outside air comes in, the harder the air conditioner has to work, he said.

In addition, Sachs noted that when the fan runs nonstop, the moving air picks up moisture from the saturated coils when the compressor isn't running. That defeats the unit's purpose of drying the air.

* Mind the registers.

Central air conditioning works best if air can flow through the house freely. If necessary, move furniture so it's not blocking supply registers or cold-air returns, Bella said.

Don't be tempted by magnetic covers designed to block air returns. It may seem logical that they'll keep the cooled air in a room, but instead they just keep the air from returning to the central unit.

Be careful about trying to save money by closing the supply registers in unoccupied rooms. Overdoing it unbalances the air flow throughout the house and results in cool and hot spots, the American Council for an Energy-Efficient Economy said.

* Leave the oven off.

Even when it's closed, an oven adds as much heat to the air as an air conditioner can take out in the same amount of time, Foraker said. Grill outdoors, order takeout, make a salad for dinner - just try not to cook indoors on the hottest days.

* Turn out the lights.

Incandescent light bulbs turn only 10 percent of the electricity they use into light, Foraker noted. The rest becomes heat. Turn off unneeded lights or switch to cooler compact fluorescent bulbs.

* Use ceiling fans.

A ceiling fan moves air over the skin, evaporating perspiration and making you feel cooler. Running one even when the air conditioning is on will increase your comfort, Foraker said.

The fans also help move air around the room, but only to a degree. It's not enough of a benefit to justify leaving a ceiling fan on in an unoccupied room, the Alliance to Save Energy said.

* Minimize humidity.

Don't add more moisture to the air than necessary. Run exhaust fans when you shower, and run hot-water appliances such as dishwashers and clothes washers in the evening, the American Council for an Energy-Efficient Economy recommends.

* Check the duct dampers.

In a house with more than one floor, adjusting the balancing dampers helps send the cool air where you want it.

A damper is essentially a little door in the duct that directs more or less air to a particular part of the house. A lever on the outside of the duct controls the damper.

Look for the dampers in the supply ducts somewhere near the furnace.

In winter, you want to direct most of the heated air to the lower level, because warm air rises. In summer, you want to direct most of the cool air to the upper level.

You may have to experiment until you find the damper positions that makes your house most comfortable, Foraker said. You can also ask the technician to help the next time you have your furnace or air conditioner serviced.

Once you find those positions, mark them with a W for winter and an S for summer. You might even make a notation in your calender to change the dampers in spring and fall.

Bigger undertakings:

* Seal air leaks.

Cracks, holes and other openings in a house's exterior let cooled air out and hot, moist air in.

Minimize those leaks by sealing them with caulk or foam sealer. Pay particular attention to the upper areas of the house, where conditioned air is likely to escape, Bella said.

* Have the unit checked.

It's a good idea to get your air conditioner serviced regularly. Many manufacturers and contractors recommend annual checks, but have it done at least every three years, Sachs said.

Choose a good contractor. Sachs recommends choosing one that's a member of either the Air Conditioning Contractors of America (http://www.acca.org) or the Sheet Metal and Air Conditioning Contractors' National Association (http://www.smacna.org).

The technician should check the refrigerant level, Sachs said. If it's low, the system will run less efficiently.

* Seal and insulate ducts.

Conditioned air loses some of its coolness as it travels from your air conditioner to your rooms. Some of the loss comes from air leaking out seams and other openings in the ducts, and some of the loss occurs because the thin sheet metal conducts heat easily.

For do-it-yourselfers, Bella recommended sealing ducts with aluminum tape and insulating them with duct insulation wherever they're exposed. Don't use duct tape, because the adhesive dries out over time.

* Install a programmable thermostat.

It's easy to forget to change the setting when you leave the house or go to bed. A programmable thermostat does it automatically, cutting your cooling costs.

* Improve your insulation.

Insulation slows the movement of heat, so it helps keep cooled air inside a home's living areas in summer in the same way it keeps heated air inside in winter.

The attic is the easiest and most logical place to add insulation, although Bella recommended considering the exterior walls, too. Attic insulation is especially important if the upper level of your home is hot, Foraker said.

* Add an attic fan.

An attic fan boosts ventilation by kicking on when the temperature reaches a certain level and drawing the hot air out of the attic. It's different from a whole-house fan, a bigger unit that pulls air through the entire house and is used as an alternative to air conditioning.

Some attic fans are also triggered by the humidity level, which makes them beneficial in winter, too.

Most are powered by electricity, but solar-powered units are available, too, Foraker said.

* Install a light-colored roof.

If your roof needs replacing, Foraker recommends considering a light-colored roof to reflect some of the sun's heat. Darker-colored "cool roofs" are also available that use special coatings to reflect rays.

Don't worry about losing the heat-absorbing benefits of a dark roof in winter, Foraker said. The heat gain isn't great when the sun is less intense and the days are shorter and often cloudy.

* Upgrade your system.

If your heating and air conditioning system is approaching 15 years old, Sachs said it's wise to start planning to replace it rather than waiting for a failure.

Insist on an installation that meets the standards of the Air Conditioning Contractors of America, he said. Its standards include ensuring the unit is the right size for your home and improving ducts to minimize loss of conditioned air.

Proper sizing of an air conditioning unit is critical, Bella said. An oversized unit may cool the house quickly, he said, but it doesn't stay on long enough to sufficiently dry the air. You end of feeling clammy instead of comfortable.