How to compare the energy saving properties of replacement windows

Look for the Energy Star^® Label

Energy Star® is a U.S. government program managed by the Dept of Energy. Over the past 10 years Energy Star® guidelines have helped double the efficiency of windows they endorse. To qualify for Energy Star® certification window brands must meet strict energy-efficiency standards. Gorell Windows and Doors, our manufacturing partner, is one of only two window companies to receive the national Energy Star® Sustained Excellence Award, and all Rite Window products carry the Energy Star® label.

Look for the U-Factor Insulation Rating

The U-Factor rating shows how well a window product prevents heat from escaping. The lower the U-Factor number the better its resistance to heat flow and the better its insulating properties. U-Factor ratings generally fall anywhere between 0.20 and 1.20. (lower the better)

As shown by the chart, the type of materials used in window construction can effect the U-Factor rating, and a significant improvement in U-Factor values is seen with windows using Low-E coated glass.

Since January of 2010, all Energy Star® qualified windows must have a U-Factor rating equal to or less than 0.30. This is the same rating needed for the window to qualify for a federal energy-saving tax credit.

Look for the NFRC Label

NFRC stands for the National Fenestration Rating Council; (The word fenestration has roots in the Latin word for window, fenestra. Fenestration defines any object that fills an opening in a building, such as windows, doors, skylights, etc.)

The National Fenestration Rating Council partners with the U.S. Dept of Energy to help consumers compare the energy-efficiency of window products. Manufacturers participating in their program are required to label every window with its thermal performance and U-Factor rating. Rite Window is a participant in the NFRC program.

The NFRC label to the right shows the two most important ratings in determining energy efficiency, the U-Factor, and the Solar Heat Gain Coefficient, (SHGC). Solar Heat Gain is a measure of the interior heat generated by sunlight through the window. For New England climates the SHGC is a trade-off. A higher SHGC rating means more heat from sunlight keeping the house warm in the winter, but also less efficient cooling in the summer.

Look for Low-E Coated Glass

Low-E is short for low-emissivity. It’s a very thin coat of material on the glass that reflects heat and ultraviolet radiation. Low-E coatings have been in use since 1979. Today’s Low-E coatings improve the energy-efficiency of clear glass by 30%. The huge benefit of Low-E versus the small additional cost makes installing new windows without Low-E unwise, therefore all our windows have a Low-E coating.

Look for Argon or Krypton Gas Fill

Window thermal performance is improved by adding argon or krypton gas between the panes. Argon and krypton gas minimizes the convection currents within the space, and the overall transfer of heat between the inside and outside is reduced. Rite Window uses an argon fill. The gas is nontoxic, nonreactive, clear, odorless, and improves the performance of our window by 20-to-30%.

Beware of Misleading Sales Practices

The U-Factor Rating Must Reflect the Whole Window
Be sure the U-Factors you’re comparing are “whole window” values. Energy Star requires heat transfer measurements be taken at 20 places on the window frame and glass, (as shown to the left). Some manufacturers report a “center-of-glass” value only, making their window appear more energy-efficient than it actually is. If the U-Factor seems suspiciously low, ask them to prove it’s a “whole window” rating.

R-Values are Not Recognized for Windows
R-Values are appropriate for wall insulation and roofing, but not for windows. Most consumers are aware that higher R-Values signify better insulating properties, but an R-Value can only be used to measure the window’s center-of-glass, not the entire window unit; therefore it is a rating method not accepted by the NFRC or the Energy Star® program.

Triple-Pane Windows are More Energy-Efficient

When you go outside, dressing “in layers” keeps you warmer. Adding a layer of glass to a window has the same effect. An additional layer of glass creates another air-pocket and a better insulated window. Our 5200TP triple-pane window has 3 layers of glass, most windows have two. The 5200TP's added glass layer lowers its U-Factor Insulation Rating to 0.25, one of the lowest in the industry. If you live in New England and have large fuel bills choosing a triple-pane window will pay a significant benefit. Another advantage of a triple-pane window is noise reduction; it helps to reduce outside noise inside your home.

Rite Window guarantees you will not find an Energy Star certified triple-pane window, with a 0.25 U-Factor, a lifetime warranty, installed for less than our price... Bottom line: The Rite Window 5200TP is one of the best window values in all of New England.

Rite Window offers our triple-pane window as an option. Some of our competitors only sell a triple-pane window, so it's the only option they push. These "triple-pane only" companies want homeowners to think a traditional two-pane window is hugely inferior, but in fact today's two-pane window is far more energy efficient than anything manufactured 15 years ago. For homeowners needing to stretch their budget a quality two-pane window is perfectly sufficient. Either way, Rite Window sells both the double and triple-pane and allows the customer to make the choice that best fits their needs.

A High Priced Window Doesn’t Guarantee Greater Energy-Efficiency

A brand name shirt might cost $100 at Macy's, yet the exact same shirt sells for $50 at Marshall's. A higher price doesn’t make the Macy’s shirt better, it only means Macy’s finds enough people in the market willing to pay the higher price. It’s a similar situation with window buying. Don’t assume a higher price buys far better quality or greater energy-efficiency. The best strategy is to compare the window’s U-Factor, the installation record of the company, the warranty, and determine which window brand gives you the most for the dollar.