What Does That Energy Efficiency Label Mean, Exactly?

If you’re in the market for new windows, glass doors, or skylights, you’ve probably seen energy efficiency stickers on many of the products.

These labels tell you that a product is energy efficient, but what do they mean? Do you know how to “read” an energy efficiency label?

If not, this is your guide! Keep reading to learn how to use the most common energy efficiency labels to get the best window, door, or skylight for your home.


photo source: energystar.gov

The ENERGY STAR program labels products that have been independently certified to meet EPA standards for energy efficiency.

If a product has an ENERGY STAR label, it has met EPA qualifications for U-factor and solar heat gain coefficient performance.

ENERGY STAR has several versions of product labels. A product may have a label showing that it is ENERGY STAR Certified for the whole country, or it may have a label showing it is ENERGY STAR Certified in “Highlighted Regions.” (This label will picture the U.S. and have some areas colored in.) It’s important to pay attention to this part of the label: obviously, different parts of the country have different weather and climates, so not all windows will necessarily be efficient in all areas.

National Fenestration Rating Council (NFRC) Label

photo source: NFRC.org

The NFRC is an organization that independently tests, certifies, and rates windows, doors, and skylights.

Products that meet the NFRC’s standards are labeled with a sticker that shows ratings in several energy performance categories: U-factor, solar heat gain coefficient, visible transmittance, air leakage, and (optionally) condensation. These energy performance ratings are located on the label underneath the NFRC logo and the product name and number.

You can find the NFRC label on all ENERGY STAR products.

Energy Performance Ratings

Here is what each of the energy performance ratings used by ENERGY STAR and NFRC mean:

  • U-factor: This category measures how well a window prevents heat from escaping the inside. (This is especially important in winter, when you don’t want to pay to heat the outdoors!) The range is 0.20 to 1.20, and you want to look for low numbers. (The lower the number, the better the window is at holding in heat.)
  • Solar heat gain coefficient: This rating measures how well the window avoids gaining solar heat. (This is important in the summer, when you don’t want to feel the hot sun inside.) The range for this rating is 0 to 1. Like the U-factor rating, you want to look for a low number.
  • Visible transmittance: This is a measure of how much light the window lets in. (This rating is important if it’s important to you to allow as much natural light inside as possible.) The range is 0 to 1. Unlike the previous two ratings, you want to look for a high number (for maximum natural light).
  • Air leakage: As it sounds, this category measures how well the window protects against air leakage. The range is 0.1 to 0.3. You want to look for a low number: the lower the number, the less drafty the window will be.
  • Condensation: This is an optional category that may or may not appear on the NFRC label. It measures how well a window resists condensation. (This is important for avoiding wood rot and mold problems.) For this rating, the higher the number, the better the window is.

Choosing a Window

When it comes to choosing the best energy efficient window for your home, the Energy Star and NFRC labels serve different purposes.

The Energy Star label lets you know whether a window, door, or skylight is energy efficient or not in your region. This makes it an excellent starting point in your search.

The NFRC label helps you determine how energy efficient the product is in comparison with other products. As a result, this label is most helpful if you are deciding between multiple energy efficient windows.

If you want the most efficient windows possible for your home, the NFRC label will be more important to you. That’s because you’ll need to look closely at energy performance ratings. Windows that would be north-facing in your home, for example, should have a higher visible transmittance to let in more light. On the other hand, windows that would be south-facing in your home should have a lower solar heat gain coefficient so your home doesn’t overheat. Furthermore, windows in rooms that have important artwork and/or furnishings shouldn’t have a visible transmittance that’s too high, as sunlight causes fading. You’ll need to base your purchasing decisions on your home’s design and your specific energy efficiency concerns.

Contact Us Today

If you have more questions about energy efficient windows, the experts at Jack’s Glass are happy to answer them. We can help you determine which energy efficient windows are best for your home!

Our local, family-owned and -operated business has been helping Cincinnati and Northern Kentucky homeowners with their commercial glass, auto glass, glass shower and window needs for more than 70 years. Contact us today at our Elsmere, Covington, or Dry Ridge locations.