Source: www.energy.gov

Windows provide natural light and a panoramic view of the outdoors, but they can also add to your energy bill by bringing in unwanted solar heat in summer and leaking out conditioned air all yearlong. This is especially true if you have older, single pane windows. While upgrading to new, energy-efficient windows will reduce your energy costs, an expensive window replacement project may not fit your budget. Fortunately, there are a number of simple, low-cost measures you can take to improve the efficiency of your existing windows.

 

1. Weatherize. Caulking and weatherstripping are two of the easiest and most cost-effective ways to reduce leaks and drafts due to small cracks and gaps around window frames. Use caulk to seal gaps around window frames. Install weatherstripping to tighten window panels, while leaving room for opening and closing.    

2. Use window treatments. Shades, blinds, and draperies save energy by reducing summer heat gain and winter heat loss.

• Shades are the simplest, and often the most effective, window treatment for saving energy. Mount shades close to the glass with the sides touching the wall to create a sealed space. Lower shades on sunlit windows in the summer. In the winter, raise shades on south-facing windows during the day and lower them at night.
• Interior blinds can reduce solar heat gain by up to 45 percent although they provide little protection against winter heat loss.
• Draperies may help to reduce heat loss and heat gain, depending on the color and weight of the fabric. Studies have shown that conventional, medium-colored draperies can reduce heat gain by 33 percent and heat loss by 10 percent.

3. Install storm windows. Storm windows save energy by reducing air leakage. They can be installed on the inside or outside of windows and are available in plastic or glass. Interior storm windows are more convenient; they're easier to install and maintain. Glass units offer better visibility and longer life. Plastic panes cost less and are easier to install and remove with the changing seasons.   

4. Install window film. Window films are available as a simple, do-it-yourself project for reducing winter heat loss. The film is typically sold in sheets that you can cut to fit each window. Attach the film to the window frame with double-sided tape and use a hair dryer to shrink the film, creating a tight seal. Low-emissivity (low-e) window film is made from a nearly invisible metallic coating that is more effective at reducing heat loss. However, Low-e film is more expensive and more difficult to install than standard film. 

If you do decide to replace your windows, select units that are ENERGY STAR certified. ENERGY STAR windows are 15 percent more energy efficient than standard models. The Efficient Windows Collaborative provides valuable information on window selection, performance, and available incentives.