Ask Chris

I am looking to have new energy efficient windows installed in my house, but am somewhat confused by the term ‘Energy Star rated’ and whether these windows will meet current tax credit requirements?

Unlike tax credits for energy-efficient windows and doors in prior years, this years “30/30” criteria is stricter than the government’s Energy Star rating program. Not all Energy Star labeled windows and doors will qualify for the new tax credit. Consumers should look for the manufacturer’s labels on the glass window product packaging. The labels should show that the qualifying replacement glass windows meet or exceed U-factor and Solar Heat Gain Coefficient (SHGC) ratings, also called the “30/30” criteria. In other words, the U-factor rating must be .30 or less and the SHGC must be .30 or less. The U-factor rating measures the passage of heat through the glass or how well a product prevents heat from escaping. The rate of heat loss is indicated in terms of the U-factor of a window assembly. U-factor ratings generally fall between 0.20 and 1.20. The lower the U-factor, the greater a window's resistance to heat flow and the better its insulating value.

The Solar Heat Gain Coefficient or SHGC rating measures the percentage of heat in the room gained from absorbed heat and direct sunlight. Windows with lower SHGC ratings reduce the solar heat gain in the house. The lower the SHGC, the less solar heat the window transmits. SHGC is measured on a scale of 0 to 1; values typically range from 0.25 to 0.80.

The most energy-efficient replacement windows on the market, triple-pane replacement windows with gas insulation (commonly called Insulated Glass Units or IG units), are eligible for the tax credits. Double-pane replacement windows with low-E coating or Argon gas insulation may or may not qualify. Customers should insist on checking for the Energy Star label as well as the U-factor and SHGC ratings on the replacement window manufacturer’s labels before allowing the windows to be installed

Energy-efficient replacement glass windows and doors that meet or exceed the “30/30” criteria now qualify for a federal income tax credit of 30 percent of the cost up to $1,500 per household. The tax credit is available in 2009 and 2010 according to the economic stimulus bill signed by President Barack Obama on Feb. 17.