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Energy Performance Ratings: How to Read Energy Efficiency Labels

You may already know that windows, doors and skylights can be awarded energy performance ratings by the National Fenestration Rating Council (NFRC). These ratings are typically displayed on labels directly on the products.

But before you begin shopping for new energy-efficient products for your home, it is important to understand what these ratings actually mean. This knowledge will help you make an informed, worthwhile investment.

In simplest terms, the NFRC label allows you to compare different energy-efficient windows, doors and skylights by telling you each product’s energy performance in multiple categories. All NFRC-certified products are independently tested, certified and labeled.

Heat Gain and Loss

Windows, doors and skylights can allow heat to enter or leave your home in a number of ways. Energy-efficient products are tested and rated according to the following characteristics:

1. U-Factor

  • Measures: How well a product can keep heat from escaping from the inside of a room. NFRC U-factor ratings take into account the glass, framing and spacer materials of a product.
  • Range: 0.20–1.20
  • Look for: Low numbers; the lower the U-factor, the more energy-efficient the window, door or skylight.

2. Solar Heat Gain Coefficient

  • Measures: How well a product can resist unwanted heat gain from solar radiation.
  • Range: 0–1
  • Look for: Low numbers IF you live in a warm climate; the lower the number, the less you’ll spend on cooling during the summer. High numbers IF you live in a cold climate; the higher the number, the less you’ll spend on heating during the winter.

3. Air Leakage

  • Measures: How much outside air will enter a room through a window, door or skylight.
  • Range: 0.1-0.3
  • Look for: Low numbers; the lower the number, the tighter the seal on the product (and the less drafts you’ll experience).

Sunlight Transmittance

A window, door or skylight’s ability to transmit sunlight into a home can be measured and rated according to the following energy performance characteristic:

1. Visible Transmittance

  • Measures: How well a product is designed to effectively light your home with daylight.
  • Range: 0–1
  • Look for: High numbers; the higher the number, the more natural daylight that will be let in (and the less you may need to spend on artificial interior lighting).

2. Optional: Light-to-Solar Gain (LSG)

Another optional energy performance rating is light-to-solar gain (LSG), although this rating is  not always included on the label.

This is the ratio between the SHGC and VT, and provides a gauge of the relative efficiency of different glass or glazing types in transmitting daylight while blocking heat gains. The higher the number, the more light transmitted without adding excessive amounts of heat.

Now that you know how to read energy efficiency labels on windows, doors and skylights, you will be better prepared to make the right purchase decision for your home.

Better yet, why not have a door and window expert from Unique Home Solutions help you choose the best products for improving your home’s energy efficiency? Contact us today for more information and your free estimate!

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