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How to Read a Window Label

How Do You Know an Energy Efficient Window When You See One?

Finding an energy efficient window is not as simple as finding a well-known, or high-priced brand.

Even well know window brands may carry a range of windows of higher or lesser quality.

So how can you tell the difference? 

It all starts with learning how to read a window label.

NFRC Window Label – Your Guide to Energy Efficiency

Any window that markets itself as energy efficient should be certified and labeled by the NFRC.

NFRC-certified products are independently tested, certified, and labeled to help you make the best purchase decision for your needs.

A window label – much like a Nutrition Label – tells you what you are really getting for your purchase.

Although most of us are familiar with calories, protein, sodium and sugars, very few are familiar with the terms on the NFRC label.

Decoding the NFRC Window Label


  1. U-FactorInsulation – you need low
  2. SHGCBlocking Solar Heat – again low
  3. AL – Measures air drafts – Essentially: The amount of air allowed to leak into or out of your home – you want low
  4. VT – Natural light allowed through – higher numbers mean more natural light
  5. Condensation Resistance – water resistance – the higher the number the better. (Not required on an NFRC label)
platinum package window label
Gold Package Window Label
1. U-Factor

U-Factor tells you how well the window insulates by not allowing heat to escape. The lower the number the better. The minimum requirement for ENERGY STAR certification in Kansas City is 0.30 U-Factor. Depending on the style of window and the addition of grids the range can vary slightly. Window Depot KC’s triple pane windows range between 0.15 and .19 U-Factor. This rating and more, qualifies for 2020 ENERGY STAR Most Efficient

2. Solar Heat Gain (SHGC)

SHGC measures how well a product blocks the heat from the sun. The lower the number, the less you’ll spend on cooling. The minimum requirement for ENERGY STAR certification in Kansas City is 0.40 SHGC. Depending on the style, our windows SHGC range is 0.23-0.27.

3. Air Leakage (AL)

AL measures the rate at which air leaks around a window. The industry standard is 0.3 cfm/ft. Window Depot’s Windows have an Air Leakage rate of 0.05 cfm/ft surpassing the minimum requirement of 600%!

4. Visual Transmittance (VT)

VT measures the amount of healthy, natural light the window lets through.

A window with higher VT means it transmits more visible light. VT is expressed as a number between 0 and 1. The VT you need for a window depends on the daylighting requirements of your home and whether you need to reduce interior glare in a space.

Our windows provide a range of 0.37-0.50. This is in the range recommended for Kansas City.

5. Condensation Resistance (CR)

CR measures the resistance of a window to the formation of condensation on the inside surface. CR is expressed as a number between 1 and 100. It is based on interior surface temperatures at 30%, 50%, and 70% indoor relative humidity for a given outside air temperature of 0° Fahrenheit under 15 mph wind conditions.

The higher the Condensation Resistance number, the better the window resists condensation.

Our Triple Pane with Krypton Platinum Window has a Condensation Resistance of 73, a very high rating. This is shown in the NFRC website directory listing for this particular window. Our representatives will be happy to assist in finding the listing.

Condensation Resistance is not on every NFRC label – if it is not on the label – ask your window professional to show you from the NFRC website. 

Compare Replacement Windows in Kansas City

Put Your NFRC Label Reading Skills to Work:

– Weed out poor-quality windows

– Identify what window ratings are the best for the Kansas City climate

– Pay less for high quality windows as you compare apples to apples

 Now you are equipped with the knowledge you need to get the perfect windows for your home.

 Put us to the test!

We believe you’ll see that our affordable windows meet up with the standards of some of the most expensive windows out there! When you’re finished with your research, let us know! We’ll be happy to give you a custom estimate  for your home