Window Ratings Explained

May 13, 2024Glass Windows

Window Glass Replacement Ratings
In Bethany Beach, DE Explained

Breaking Down Window Ratings To Help
Help You Choose The Right Options

Window glass replacements in Bethany Beach, DE can grant you amazing energy efficiency to improve your home’s temperature and energy bill. This energy efficiency is proven with window ratings from qualified organizations and stickers to boot.

However, there are multiple ratings that can be quite confusing. The best way to understand them is to break them down so you can learn to read the labels easily; that’s exactly what GoGlass has done.

Who Assigns Window Ratings
On The Delmarva Peninsula?

The National Fenestration Rating Council (NFRC) assigns window ratings. They are a nonprofit organization that tests windows to see if they qualify for Energy Star labels. The NFRC developed the system to rate the performance of a window, and most ratings must come from them to be recognized as legitimate.

Because they are nonprofit, they are the only trustworthy entity that rates windows. That’s why they are recognized by every contractor and window company in the country. A for-profit rating system isn’t as easy to trust, which is why we banded together to accept the ratings of the NFRC.

Glass Replacement Window Ratings To Know

It’s important that window ratings are not empty numbers without proof to back them up. That’s why looking for specific ratings can help you find the best energy-efficient windows for your home.


  • The lower the number, the better it insulates.
  • Range of 0.20 to 1.20

The U-factor determines how much heat the window lets out. You can think of it as the insulating factor of the window. The U-factor is incredibly important in cool climates with harsh winters and less crucial in mild and hot climates.

The required U-factor for your windows depends on the climate. In southern climates, it’s fairly strict. In the Delmarva Peninsula, a U-factor equal to or below 0.27 qualifies for an Energy Star Rating.

Solar Heat Gain Coefficient (SHGC)

  • The lower the number, the better at keeping your home cool.
  • Range of 0 to 1.

Solar heat gain coefficient (SHGC) is a rating that measures the heat entering the home. In other words, it lets you know how much of the sun’s heat gets through the window. Because it still measures heat, northern areas like Delmarva don’t have a required SHGC like southern climates do.

Visible Transmittance (VT)

  • The lower the number, the less light.
  • Range of 0 to 1.

Visible transmittance (VT) has nothing to do with heat. It measures how much visible light gets through a window. Because it does not affect energy efficiency, there is no official Energy Star rating for it. It’s much more about preference. However, the more light that gets into your home, the less artificial light you use, which will lower your energy bill.

Air Leakage

  • The lower the number, the less leakage.
  • Range of 0.1 and 0.3

Air leakage isn’t about water leaks – it refers to how much air escapes through the window. So, in the summer, it shows how well your window keeps cool air in, and in the winter, it shows how well it keeps warm air out.

The rating is measured by showing how much air escapes per cubic foot per minute per square foot. Which is a complicated way of measuring how much air escapes. Because it takes all climates into account, there is a strict flat rate of less than or equal to 0.3 cfm/ft² required for Energy Star.

Condensation Resistance

  • The lower the number, the more condensation.
  • Range of 1 to 100.

Condensation resistance has the largest range and is also backward to other ratings, as the higher the number, the better. The rating is straightforward: the higher the number, the less condensation builds up. This is great for energy efficiency and gives your window its best chance at a long life. Condensation building up on a window may signal your window isn’t performing well.

GoGlass offers premium window glass replacements that we call Infinity Glass. These units come with all of the best energy ratings for Bethany Beach, DE. Call us today at 800-746-4527 for your free estimate.