Cut Utility Bills by Blocking Summer Heat

Cut Utility Bills by Blocking Summer Heat

Keep your house cool in the summer by blocking unwanted heat. There are three major sources of unwanted heat in a home: waste heat generated by household appliances and light bulbs, radiant heat from sun and heat that comes in from walls and ceilings. Fortunately, there are many simple ways to keep unwanted outside heat from invading a home.

Waste Heat
Most home appliances such as dishwashers, stoves, refrigerators and lights give off a surprising amount of heat energy that raises the temperature inside of your home. For example, standard incandescent lights emit 90 percent of their energy in waste heat and only 10 percent in light. Delaying heat-producing tasks such as cooking, running the dishwasher and doing the laundry until the cooler evening hours will reduce the amount of strain on an air conditioner. Consider moving a freezer to the basement where it won't contribute its waste heat to the main living space.

Buying the most energy-efficient appliance models will help save money and reduce waste heat. Although the initial investment may be more than other inefficient models, energy-efficient appliances will save energy dollars in the long run. Check the EnergyGuidea at for a current listing of the most energy-efficient appliances and look for the Energy Star? label on appliances.

Heat Through Windows
Windows can be the largest source of unwanted heat in the summer, especially if the sun shines on unshaded east or west windows. The best way to combat unwanted heat through windows is to provide effective shading. Lowering blinds or closing curtains can keep a home from acquiring radiant heat as well as protecting furniture and rugs from fading caused by UV rays.

Sun screens, reflective films, and interior window treatments can reduce radiant heat by 60 to 95 percent. Sun screens made from fabric and installed on the exterior window can absorb 65 to 70 percent of the solar heat before it enters the house. Sun screens are usually the least expensive option for blocking solar heat. If the windows are old or inefficient, consider replacing them with more energy-efficient models with a low-e glazing. Windows with low-e glazing look perfectly normal but have a special coating that reduces unwanted heat gain by 50 to 75 percent. Window treatments that have reflective, metallic or bright white surfaces can effectively block solar heat. For example, an opaque roller shade with a white surface facing outward stops roughly 80 percent of solar heat. White Venetian blinds and white slim shades stop about 40 to 60 percent of radiant heat.

Trees and Landscaping
A majority of the heat infiltrating a home comes from sunlight, or radiant heat, hitting a roof and coming through the windows. Shading these areas of contact can stop those solar rays from entering a home and heating it up.
Trees and other plants that provide shade are the most effective means for blocking radiant heat and are long-term investments for reducing cooling costs. Temperatures directly under trees can be up to 25 degrees F cooler then air temperatures around nearby blacktop. The more shade you have, the more effectively you can use natural ventilation. Shade makes the ground around the house cooler and it prevents radiant heat from building up indoors. Proper landscaping can cut 15 to 50 percent from an unshaded home's summer air conditioning costs.

Deciduous trees are leafy during the warm months and bare in winter. They can block the summer sun, yet allow winter sunshine to come through their branches to warm a home. Trees should be planted on the southeast and west sides of a home for the maximum shading effect. Not only can trees reduce the monthly bills, they also add value to a property. Studies by real estate agents and professional foresters estimate that trees raise a home's resale value 7-20 percent.

Whenever the outdoor temperature is greater than the indoor temperature in the summer, the warmer outside air will invade a house through small cracks and gaps. The best way to reduce unwanted heat from entering through walls and ceilings is to insulate and tighten the house. A cost-effective way to save on both cooling and heating bills is to increase attic insulation to a full foot in depth. An energy auditor from a local utility company can help decide which insulation makes the most sense and how much each improvement will cost.

Finding Air Leaks Air leaks in your home can be costly problems, especially in humid climates like Iowa. Caulking, weatherstripping and insulation are some of the best tools for preventing unwanted heat and moisture from entering your home in the summer. They are also important in reducing heat loss in the winter months.

To find air leaks, have a blower door test done on your home. A blower door depressurizes a house, making it possible to measure the amount of air leakage and pinpoint air leaks that cannot be seen. The test allows you to actually feel where air loss is occurring.

Blower door tests can also identify health hazards created by back drafting. These tests are able to project whether your home has enough natural infiltration, the ability to draw in fresh air. Consult your local utility to see if they offer blower door tests or can recommend a qualified professional.

More Information and Additional Resources
Some of this information was adapted from the American Council on an Energy Efficient Economy's publication, Consumer Guide to Home Energy Savings, 7th Edition, the Energy Efficiency and Renewable Energy Network as well as Homemade Money by Richard Heede and staff of the Rocky Mountain Institute.

Additional information on home energy savings can be found in the Home Series: Home Cooling booklet available on the Iowa Energy Center's Web site, or by calling (515) 294-8819.

The Iowa Energy Center is a nonprofit organization dedicated to improving Iowa's energy efficiency and the use of renewable fuels.