Old windows are almost as bad as having holes in your walls. Single-paned glass windows (still in 62 percent of homes) account for as much as 30 percent of your heating bill. In comparison, today's high-performance windows can cut those bills in half. Most of these savings come from using two panes of glass, separated by a nonconductive inert gas, and low-emissivity (low-E) coatings, which allow visible light through, but Nock infrared radiation (heat). Low-E coatings can reflect solar radiation away from, or back into a home depending on the climate. With all the scientific jargon and confusing acronyms, finding the right windows may seem harder than installation. That's where the National Fenestration Rating Council (NFRC) comes in. This nonprofit organization tests windows and then rates them with a standardized system. The results are stuck on participating manufacturer's windows. The NFRC tests four criteria, solar heat gain coefficient, visible transmittance, air leakage and U-factor, which measures how well a window prevents heat from escaping. U-values are the inverse of R-values, so the lower the number, the better. If you're still confused, look for the Energy Star label. Developed by the U.S. Department of Energy, this label identifies the most efficient windows for specific climates. Star-bearing windows are 15 to 40 percent more efficient than those that simply meet building codes. Replacing windows is a costly proposition; in most cases, it takes 15 to 20 years for the energy savings to pay back the installation cost. But adding storm windows is much less expensive, and can double the R-value of single-pane windows. Storm windows also help reduce drafts, condensation and frost formation. There are also many other improvements you can do to your existing windows to help them perform at their best. Cold weather solutions -- Start with basic repairs, such as applying putty to loose panes. If you're not planning to open the window during the winter months, seal the sash with removable rope caulk (see Page 74). [check] Plastic window sheeting creates an insulating dead-air space inside the window. This cuts down on the transfer of heat from inside to outside. With a few rolls of shrink-wrap plastic and a hair dryer, you can cut heat loss by 25 to 40 percent. In winter, you can find these window insulation kits at any hardware store. Saving Money with Compact Flourescent Lights check] Insulating shades use layers of insulating material, a radiant barrier and a moisture resistant layer to help prevent condensation. One manufacturer claims an R-value increase of R 1.3 to R 7.69, over a single-glazed window. A custom-made window shade can cost about $300, but you can make an insulated shade yourself using reflective materials available at most fabric stores for about $4 a yard. Warm weather solutions--According to Heede, a single 3-by-4 foot window can add as much as $24 a year to summer cooling costs. Here are some ways to save that cash. [check] White shades or miniblinds Call reduce solar heat gain by 50 percent. [check] Porches, overhangs and awnings are even more effective than blinds because they stop the sun without restricting the breeze. Install the awning so it extends about halfway down the window, blocking the sun during all but the early morning and late afternoon hours. [check] Low-E films -- Low-E plastic films can be installed on existing windows. They let in most visible light, but block out solar radiation. Be wary of less expensive "tinted" films--they can substantially reduce inside light. The films are not easily removable, so if you want to use sunlight in winter for heat gain, they may not be the right choice for you.

THE RIGHT LIGHTS

The average incandescent light bulb is a better heater than an illuminator--only 10 percent of the energy it consumes is convened into light energy; the rest is wasted as heat. Maybe that explains why lighting consumes nearly 25 percent of all the electricity generated in the United States. The solution is fast, easy and inexpensive: fluorescent lighting. According to EERC, replacing just 25 percent of your lights in high-use areas with fluorescents can slash your lighting bill by 50 percent. Don't let fluorescents' dim history scare you away. Early models did tend to hum and cast a cold, bluish light. But today more advanced ballasts (the mechanism that starts and regulates the light) and improved phosphers make fluorescents indistinguishable from incandescents. Look for compact fluorescent lights (CFLs). These bulbs have the same screw fittings as standard incandescents, so you can avoid having to install new fixtures. Compact fluorescents seem pricey at $25 per bulb, but as the chart at left shows, they last a very long time and will save you nearly $50 per bulb compared to incandescants, while providing the same amount of light.