Vinyl Window Energy Efficiency

Energy EfficiencyEvery manufacturer brags about having the best window, and the sales and marketing experts can create a compelling story. The National Fenestration Rating Council takes the guesswork out of comparing windows by providing industry standards for the most common measures of vinyl window energy efficiency performance.


Energy Efficiency in Windows: What Is Measured?

The windows you are replacing probably have single pane or dual pane clear glass. Let’s look at what performance standards we measure to determine energy efficiency and how your old windows (didn’t) perform.

Energy Efficiency

Visible Light Transmittance (VLT) If we didn’t want light to come through, we would have built a wall, right? The higher the percent, the more light is passing through the glass.

       Single pane – 67%                 Dual Pane Clear – 63%

Energy EfficiencyU-Factor measures how well a product prevents heat from escaping.The rate of heat loss is indicated in terms of the U-Factor (or U-Value) of a window assembly. The lower the U-Value, the greater the window’s resistance to heat flow and the better its insulating value.

       Single pane – .83         Dual Pane Clear – .46

Energy EfficiencySolar Heat Gain Coefficient (SHGC) Solar radiation, whether directly transmitted or absorbed and re-radiated, can make a room too hot. The lower a window’s solar heat gain coefficient, the less solar heat it transmits.

        Single pane – .67         Dual Pane Clear – .62

Energy EfficiencyUV Block Invisible, yet harmful, ultraviolet (UV) rays found in every day sunlight can damage paint finishes and cause furniture, carpet and window treatments to fade. The higher the percent, the more harmful UV rays being blocked.

       Single pane – 29%         Dual Pane Clear – 39%

Energy EfficiencyAir Leakage (AL) is indicated by an air leakage rating expressed as the equivalent cubic feet of air passing through a square foot of window area (cfm/sq ft). Heat loss and gain occur by infiltration through cracks in the window assembly. The lower the AL, the less air will pass through cracks in the window assembly.

                                         Values vary with window construction

Energy EfficiencyCondensation Resistance (CR) measures the ability of a product to resist the formation of condensation on the interior surface of that product. While this rating cannot predict condensation, it can provide a credible method of comparing the potential of various products for condensation formation. CR is expressed as a number between 0 and 100. The higher the CR rating, the better that product is at resisting condensation formation.

                                        Values vary with window construction

Contact Lonestar Siding and Windows

Choosing replacement windows for your home is not an easy task. However, we know that even after reviewing energy efficiency information about our vinyl window options you will probably still have questions. Please give us a call at 804-266-1717, send us a message on Facebook, or contact us online so our experts can help you make the right decision for your new windows in Richmond, VA.

  • The Lonestar Approach

    At Lonestar Siding and Windows, We take pride in not only the job we do, but how we do it. We don't believe in high pressure sales tactics, or unbalanced payment structures. It's the reason why almost every customer becomes a repeat customer. Head over to the Lonestar Approach page to learn more about what makes us more than just another siding contractor!

    Learn why the Lonestar Approach makes us the best choice!