Our windows are built to resist the heat and cold, offering four-season comfort. Need proof? We meet or exceed the current standards for ENERGY STAR® Version 6.0 requirements in all 50 states and can exceed requirements for the Northern Zone, by up to 48% with select glass packages. Below are four common ratings that are provided for windows certified by the National Fenestration Rating Council (NFRC).

  • U-Factor – A measure of the rate of heat flow through a window. A lower U-Factor indicates a higher performing window that can help reduce heating and cooling costs.
  • Solar Heat Gain Coefficient (SHGC) – The amount of solar radiation allowed to pass through a window. The lower the number, the less solar heat gain and UV rays the window permits to enter.
  • Visible Light Transmittance (VT) – Ranging from 0 – 1, visible transmittance is a measure of how much light passes through the window. The higher the number the more light can pass through.
  • Condensation Rating (CR) – CR measures how well a window resists the formation of condensation on the inside surface. CR is expressed as a number between 1 – 100.The higher the number, the better a product is able to resist condensation.

Energy Efficient Glass Ratings

NFRC Ratings U-Factor SHGC VT CR
Energy Miser 2-IS .22 .24 .38 53
Energy Miser 2 .25 .24 .40 64
Energy Miser IS .26 .26 .50 41
Energy Miser .30 .27 .51 52
Clear (No LowE) .49 .59 .61 38

*Air Infiltration ratings are ≤ 0.3 US (≤ 1.5 Metric) or better for all Window Source Windows.

Energy Miser glass options keep you warmer in the winter and cooler in the summer.

All Energy Miser Options Are UV Resistant

Clear insulated glass can block some UV rays

Low-E insulated glass can block the vast majority of UV rays

Harmful UV rays can do more damage to your home than you might think. For example, if you don’t use the proper precautions on your windows, these rays can fade valuable items you have inside your home. Our UV resistant windows can act as a sunscreen for your house, blocking damaging ultraviolet rays without noticeably reducing the light coming inside. The Low-E coating options on our windows increase window performance and help to significantly reduce fading and sun damage to your furnishings, carpets and floor, so they stay colorful and beautiful.