Windows represent one of the biggest sources of heat loss in a typical home—about 25%, according to the U.S. Department of Energy. Installing energy-efficient windows is a great way to save money on heating and cooling costs.

Simple ways to reduce your energy costs

• If you open your windows at night for cooling, close your windows during the day to minimize cooling losses.
• About 40 percent of unwanted heat comes through windows. If you have air conditioning, consider keeping your shades, blinds and curtains closed during the summer. Keeping blinds and curtains closed acts as a layer of insulation and helps keep the cool air in.

Replacing windows: How much can you save?

Many older buildings in northern Illinois have their original windows, consisting of wooden frames around a single pane of glass.

• The U.S. Department of Energy estimates that homeowners in northern Illinois who replace single-pane windows with ENERGY STAR^® windows can save over $300 a year.
• Even replacing older double-pane windows with their ENERGY STAR counterparts will reduce energy costs, on average, $65 per year.

When purchasing windows

• Look for windows with the ENERGY STAR label. ENERGY STAR certifies that the window is a top product in terms of energy efficiency.
• Windows should be installed by a trained professional following the manufacturer’s instructions.
• Verify that windows are properly installed. Leaky windows allow heated and air-conditioned air to escape and outside air to enter your home, increasing energy usage.

What you need to know about windows

New technologies have been developed to keep windows from acting as a source of heat loss during the winter and heat gain during the summer. They include:

• Framing: The window frame can be a major source of heat loss in a house with older metal frames. In our area of the country, it is necessary to have a window frame that can expand and contract with the weather. ENERGY STAR suggests that Chicago-area homes use wood, wood composites, vinyl or fiberglass frames to optimize energy efficiency.
• Multi-pane windows: Windows manufactured today have at least two panes of glass with space in between. Owners of homes with single-pane windows can see tremendous savings on their energy bills after an upgrade to multi-pane windows.
• Glass Coating: A ”Low-E” low-emissions thin film coating on windows can help reduce energy costs by selectively keeping heat out during the summer and heat in during the winter. For our area, ENERGY STAR recommends a moderate solar gain low-E coating with a Solar Heat Gain Coefficient of between 0.41 and 0.55.
• Gas Fills: Sometimes window energy performance can be enhanced by filling the space between the panes of glass with a gas, such as argon or krypton, that acts as an additional insulator. This type of window must be specified when ordering from a manufacturer.