Want to be more comfortable this summer? Moving air can remove heat from your home, and it also creates a wind chill effect that cools your body. Ventilation provides other benefits besides cooling: indoor pollutants tend to accumulate in homes with poor ventilation, and when homes are closed up for heating.

Heat Sources

Heat accumulates in homes from several sources and can make indoor temperatures higher than outdoors even in the hottest weather. Solar energy-which enters a home primarily through the roof and windows-is a major source of unwanted heat in most climates. Appliances, lights, and occupants generate heat as well.

To use ventilation for cooling, you should prevent heat from entering and accumulating in your home as much as possible. Some preventive measures include installing additional attic insulation, a reflective roof, awnings, and sun-blocking window treatments.

Operational changes-such as reducing the use of appliances, lighting, and hot water-will also reduce accumulated heat. When you've prevented as much heat accumulation as you can, develop a ventilating strategy.

Natural Ventilation

Natural ventilation relies on the wind and the "chimney effect" to keep a home cool. The chimney effect occurs when cool air enters a home on the first floor or basement, absorbs heat in the room, rises, and exits through upstairs windows. This creates a partial vacuum, which pulls more air in through lower-level windows.

The wind will naturally ventilate your home by entering or leaving windows, depending on their orientation to the wind. When wind blows against your home, air is forced into your windows. Heat accumulates in your home during the day, and the cool night air can flush it out.

Depending on the house design and wind direction, a windbreak-like a fence, hedge or row of trees that blocks the wind-can force air either into or away from nearby windows. Wind moving a long a wall creates a vacuum that pulls air out of the windows.

Natural Cross-Ventilation

You can create natural cross-ventilation by opening your windows and doors, and adjusting the size and location of the openings to ventilate different parts of the home. Inlets and outlets located directly opposite each other cool only those areas in between, in the direct path of the airflow. You'll cool more of your home if you force the air to take a longer path between the inlet and outlet. This increases air speed and improves the cooling effect. Air from cooler, shaded outdoor areas provides the best intake air.

Mechanical Ventilation

When you know how air moves naturally through your home, you can then optimize your mechanical ventilation. The quality and energy efficiency of these devices varies widely; shop carefully and always try to find ENERGY STAR® qualified fans. Mechanical ventilation devices include ceiling fans, table fans, floor fans, window and exhaust fans, whole-house fans, and evaporative coolers. These fans create a wind chill effect that will make you more comfortable in your home, even if it's also cooled by natural ventilation.

Managing Your Home's Ventilation

Remember the following if you plan to cool your home with ventilation:

• Learn how air flows naturally through your home.
• Take advantage of cool night air, and ventilate your home by natural or mechanical methods.
• Keep a clear path for airflow both inside and outside your windows.
• Close windows, doors, and window coverings in the morning before your home starts to heat up.
• Avoid producing heat in your home when it's hot outside.
• Wear cool clothing.

Here are some low-cost options for keeping the summer heat out of your home.

Add a Ceiling Fan
Average Price: $40 to $200

Fans don't cool the room, but they do make you feel cooler by circulating air. To save energy, turn off the fan when you leave the room.

• Fans work best when blades are 7 to 9 feet above the floor and 10 to 12 inches below the ceiling.
• Small- and medium-sized fans will provide efficient cooling in a 4- to 6-foot diameter area, while larger fans are effective up to 10 feet. Multiple fans work best in rooms longer than 18 feet.
• Look for the ENERGY STAR® qualified ceiling fans for the greatest energy savings. Ceiling fans that have earned the ENERGY STAR have high efficiency motors and improved, aerodynamic blade designs which allow them to push the equivalent or more air while using less electricity: as much as 20% more air movement than standard fan models. Add an Energy Star qualified light kit to the fan and see as much as 40% in energy savings.
• Ceiling fan models with a reverse fan flow control can also be taken advantage of during cold weather: operate the fan in slow speed, reverse direction, and this will create a gentle updraft which re-circulates the hot air trapped at the ceiling to provide even, comfortable heat throughout your room.

Add Window Fans
Average Price: $60 to $90

Window fans intensify any breeze or create a breeze when the air is still.

• Use reversible-type window fans so you can either pull air into the home of push air out, depending on which way the wind blows.
• Position fans in different windows to see which arrangement gives the best cooling effect.
• Heat accumulates in your home during the day, so use window fans at night to flush out the hot air.

Plant a Tree
Average Price: $30 to $100

Plant trees around the house that will provide cool summer shade. For maximum energy conservation, plant evergreens on the north side of your home as a windbreak and add deciduous trees that loose leaves in winter on the south. One well-placed tree can lower your annual cooling costs by 25 percent.

Sources: US Department of Energy, Office of Energy Efficiency and Renewable Energy. Energy Star Program.