Understanding Energy Efficiency

Our Enviro-Star windows are state-of-the-art windows in the field of energy efficiency, which is why they’ve been awarded an Energy Star after being independently tested by the NFRC. That’s an important and impressive achievement that guarantees high quality and energy efficiency, but we realize not everyone is aware of the criteria behind this certificate or what exactly acronyms like NFRC stand for. That’s why we’re providing a little introduction into just how special these windows are.


The Energy Star

window1The Energy Star was created by the Environmental Protection Agency, together with the Department of Energy, in 1992. It is an international standard that marks energy efficiency in products ranging from kitchen appliances to entire houses. When it comes to windows, being awarded the Energy Star means you have to fill three requirements: the windows must have been manufactured by an Energy Star Partner, they must have been independently tested by the NRFC, and received a score from this testing that adheres to the strict energy efficiency guidelines as given by the U.S. Department of Energy. These requirements depend on the climate the window is intended for (for example Northern vs. Southern), and you can read more about those related to your climate at the Energy Star website.

National Fenestration Rating Council


The National Fenestration Rating Council (NFRC) is a non-profit organization dedicated to informing and educating about energy efficiency. Their certified ratings and independent tests are the basis of giving out the Energy Star award, so we’ve listed the information that is required from a window when it’s being tested by the NFRC:



U-factor is a measurement of the window’s ability to keep heat from escaping. The range of ratings is between 0.15 and 1.20, where the smaller the rating, the better the window in question is at keeping the heat from escaping. The rating required for an Energy Star award is 0.30, and all our energy-saving Enviro-Star windows are well below that, with the HeatSeal™ receiving a rating as low as 0.18.


Solar Heat Gain Coefficient (SHGC)

The SHGC is the measurement of how much heat generated by sunlight is blocked by the window. This is crucial in the summer months and within the southern climates, because a window that doesn’t block sunlight efficiently can easily make a big difference in the air conditioning costs of the house. The rating itself is between 0 and 1, where a lower number means increased energy blocking ability.


Visible Transmittance

Visible Transmittance is the measurement of how much light comes through the window. It’s particularly important in houses that, for various reasons, specifically require either more or less sunlight inside the house. Visible Transmittance is measured between 0 and 1, where the lower the number, the less sunlight passes through the window.


At this point, even after all that information, we’ve only scratched the surface of everything that goes into the making of energy-efficient windows and houses. As one of the leading installers of energy-efficient windows in South Jersey and elsewhere, we know all this tech talk can be a lot to take in. That’s why our expert staff is always willing to answer any questions you might have on how to maximize the energy-efficiency of your house with new windows.