It's generally not cost-effective to replace old windows for energy saving purposes alone, because the high cost of new windows is rarely paid back by energy savings. The cost-effective time to buy high-performance windows is when you are building a new home, putting on an addition, or replacing damaged or nonfunctional windows. It is often possible to repair and improve old windows to make them perform almost as well as new ones but at a fraction of the cost.

If your windows feel cold or drafty, here are some steps that you can take:

• Replace cracked glazing
• Be sure that sashes close and latch properly
• Use a window weatherization kit, available at hardware stores, that includes weather-stripping and plastic covering
• Install storm windows

If you buy new windows, look for the ENERGY STAR ® label for northern climates. The ENERGY STAR label is an indicator of high efficiency. Also look for the National Fenestration Rating Council (NFRC) label. The NFRC label shows you how energy efficient a window is. Most notably, look for these ratings:

Efficiency Vermont offers incentives on certain energy efficiency improvements that are the most cost-effective when it comes to saving electricity. Since the savings from replacing windows and doors is usually small and very site specific, we don't offer rebates on these items.

If you're looking to save money by reducing heat loss around your home, look at reducing air leakage first. It's typically the greatest single source of heat loss in any house, and reducing it is one of the most cost-effective ways to lower your heating and cooling bill.

For other ways to save energy in your home, contact a certified Home Performance with ENERGY STAR contractor. These professionals can help you identify the best energy-saving opportunities, while also protecting health and safety and improving the comfort and durability of your home. You can find a list of certified contractors in your area at the Marketplace.

U-FACTOR

A low U-factor indicates that the window has a high insulating value. Look for a U-factor of .35 or less.

SOLAR HEAT GAIN COEFFICIENT (SHGC)

Windows that have a higher SHGC allow more heat from the sun into the house. Place these on the south side of the house to take advantage of low-angled sunlight during winter months. Use windows with a low SHGC rating on east and west facing windows to reduce heat entry in summer months. The high range of SHGC is .40 and above, while a low SHGC­rated window is .32 or below.

Also look for these features:

DOUBLE­GLAZING

Double-glazing can take the form of single-paned window plus storm window or a window with two or more layers of glass built in.

low­E

Some double-glazed windows have a transparent, low emissivity (low­E) coating on one or more layers of the glass that can reflect heat back into the room in winter and back outside in summer. To identify these windows, hold a light up to the glass: a bluish reflection can indicate the presence of a low­E coating. With new windows, look for the NFRC label, which should confirm that a window has a low­E coating.

GAS-FILLED

Some double-glazed windows have two panes of glass with argon or krypton gas sealed between them. This minimizes heat loss through the glass.

WARM EDGE SPACER