weatherbarr single hung new construction window

Energy Performance and Testing

Why Vinyl?

All parts are made from virgin Unplasticized PVC (uPVC) to ensure the components stand up to the test of the elements. uPVC is thoroughly maintenance free. It requires no painting or finishing. Wood can require significant maintenance over the life of the window.

We take care in our designs to ensure that the windows will perform to our strict guidelines and keep your home comfortable in the worst weather. uPVC is a warm material and does not readily conduct hot or cold. Aluminum is an excellent conductor, which can lead to increased heat/cold transfer and potentially condensation.

The multi-chambered design adds significant insulation value the added pockets of “dead” air. All vinyl waste is recaptured and recycled to ensure that there is minimal impact on our environment.


Since over 80% of your window is glass, we’ve developed Smart Glass to allow you to choose the glass that best fits your budget and performance requirements. You need glass that is smart enough to block what you don’t want and allow what you do want into your home. Smart Glass does that. It blocks the sun’s heat without resorting to room darkening tinted glass. It also provides excellent insulation value in the wintertime, reducing heat loss through the window and reflecting the heat you’re producing back into your home. The heat you’re paying for is kept inside.

3 Components of SMART GLASS

  1. Advanced Low-E Glass

    • Energy Smart (ES) Low-E glass is hard at work in the winter and summer to keep your home comfortable and save energy.
    • Solar Smart (SS) Low-E glass provides the same wintertime insulation benefits with an extra measure of solar protection in the summer.
  2. Warm Edge Spacers
    • Intercept Spacer - extremely durable U-Channel spacer is cushioned by hot melt butyl seal creating a warm edge minimizing heat transfer.
    • SuperSpacer - Insulating silicone foam spacer provides the warmest edge temperature in the industry, up to 16 degrees warmer than other spacers.
  3. Gas that pays you back
    • Argon gas is an odorless, non-toxic gas that is denser than atmospheric air. By displacing the air in insulated units with Argon, insulation value is improved by as much as 10%, and can also reduce convection.

Download a PDF of the complete list of NFRC ratings for the Cornerstone Series here.

Learn more about EnergyStar or see our complete list of WeatherBarr product performance ratings