Energy Efficiency

Energy-Efficient Windows – A Smart Investment

According to the U.S. Department of Energy, leaky and inefficient windows, skylights and doors account for up to 25 percent of the average household's energy bills. Some sources estimate as high as 40 percent. A lot depends on where you live... cold climates lose energy in the form of heat & hot climates lose energy in the form of cooling.

The colder or hotter the climate, the greater are your heating or cooling costs as well as expanded potential for saving money on energy costs. Nearly everyone can benefit by replacing leaky, inefficient windows with modern energy-efficient windows. Depending on your location, you can cut energy costs by as much as 15 percent. Replacing all of any home's windows can be a big investment, but the upside is that doing so often pays for itself in just a few years. Details on how listed below:

Improved Curb Appeal & Increased Resale Value

The recent Cost vs. Value Report (a combined effort by Remodeling Magazine and REALTOR® Magazine), indicated that homeowners can expect to recoup about 93 percent of their investment on vinyl or wood window replacements.

  • Reduces heating and/or cooling costs saving you money every year
  • Increases the comfort of your home
  • Can qualify you for rebates and tax incentives - Federal Energy Tax Credit which provides up to $1,500 for any efficiency improvements made to your home. (Save your sales order or NFRC label from the window and check for rebates and tax incentives in your area.)

To learn more about the many benefits of energy-efficient windows, visit the Efficient Windows Collaborative. The window selection tool on this site helps determine an approximate change in annual energy use given your home type, window type and geographic region.


ENERGY STAR® is a joint program of the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Energy (DOE). Its mission is to help us all save money and protect the environment through energy-efficient products and practices. EPA and DOE set strict energy-efficiency guidelines for ENERGY STAR qualified products. In 2007 alone, ENERGY STAR helped Americans save more than $16 billion on their utility bills. For more information on ENERGY STAR qualified products, visit

To become ENERGY STAR qualified, windows, doors and skylights must be independently tested and certified by the National Fenestration Rating Council and labeled according to ENERGY STAR climate zones. Manufacturers like Milgard® (an ENERGY STAR partner) tailor the components of their windows to work most efficiently where you live.

Take Advantage of the new 2009 Federal Tax Credits - President Obama revised the tax credit with the American Reinvestment and Recovery Act of 2009, signed into law on February 17. These revisions supersede the previous tax credit issued for 2009. Windows, doors, and skylights must now have a U-factor and Solar Heat Gain Coefficient (SHGC) less than or equal to 0.30, regardless of climate zone.

Other Tax Credits, Rebates and Offers – Many states and other governmental bodies, utilities and organizations offer rebates, tax credits and other special offers when you buy ENERGY STAR qualified products. Use the Special Offer/Rebate Finder on this page to see what's available in your area.

ENERGY STAR is a registered trademark of the U.S. government.

What to Look For - Components of an Energy-Efficient Window

What's an energy-efficient window? Most will have at a minimum:

  • Double-pane insulated glass
  • Heat-resistant (Low-E) glass coating
  • Airtight frames
  • ENERGY STAR® rating

Three Dimensions of Energy Efficient Window Design-An energy-efficient window is a synergy of its components. At Milgard®, we call this the "three dimensions of energy efficient window design." Here's what you should look for in each of the three dimensions: glass, spacer and frame.

Frame - One of the important considerations you need to make is frame material. Two of the more energy efficient frame materials are vinyl and fiberglass. They do a particularly good job of reducing heat transfer and contributing to insulation value. Your ultimate decision on which of these to use may be based on aesthetics and cost. In making your selection, be sure to look for vinyl or fiberglass frames that have been specifically engineered for performance. For instance, both can be designed with chambers within the frame that enhance strength, noise reduction and insulation value.

Glass - Dual-pane designs use an air- or gas-filled space between two panes of glass. This insulates much better than a single pane. Special Low-E coating on the glass blocks infrared light to keep heat inside in the winter and outside in the summer. It also filters damaging ultraviolet light (UV) to help protect interior furnishings from fading.

Spacer - A spacer keeps a window's dual glass panes the correct distance apart for optimal airflow between panes. Too much or too little airflow can affect the insulating glass efficiency. The design and material of the spacer also can make a big difference in the ability to handle expansion and contraction and thus reducing condensation.