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How Does a Window Qualify for an Energy Star® Rating?

Posted by January 31, 2022 Categories: Energy-Efficient Windows Home Renovation Tips Replacement Windows

Residential home with Stanek Windows

In this post, you will learn…

  • What qualifies a window as ENERGY STAR
  • Common product features of ENERGY STAR windows
  • How energy-efficient windows can save you money

If you’re looking for new windows, you’ve likely heard terms such as “ENERGY STAR rated” or “ENERGY STAR certified.” You may know that this indicates an energy-efficient window, but who decides this? And how energy efficient is it really? Learn all about how windows are deemed ENERGY STAR certified, common ENERGY STAR product features, and how energy-efficient windows can save you money.

Stanek Window custom window and energy star rating label

What is ENERGY STAR Certified?

So, what makes a product ENERGY STAR certified? ENERGY STAR windows must:

Stanek Window label with energy efficiency performance indicators

ENERGY STAR windows must meet several performance metrics. These metrics are set by the NFRC and are categorized into three main performance indicators:

  • U-Factor – measures the rate of non-solar heat transfer
  • Solar Heat Gain Coefficient – measures the solar energy admitted through a window whether transmitted directly or absorbed and then released as heat in a home
  • Air Leakage – measures the amount of air flowing through a window due to air pressure or temperature difference between the outside and inside of your home

For a window to qualify for ENERGY STAR, it must have NFRC-certified U-factor and solar heat gain coefficient ratings that meet or exceed the minimum requirement based on the applicable ENERGY STAR Climate Zone. See chart below for ENERGY STAR qualification criteria.

Energy efficiency requirements for windows chart

Energy efficiency requirements for skylights chart

Energy efficiency windows air leakage requirements chart

A window must also have air leakage ratings that meet or exceed the minimum requirement, as seen in the chart below.

Common ENERGY STAR Product Features

Although ENERGY STAR does not require specific technology, there are common product features among ENERGY STAR products that you will see while shopping for windows.


Manufacturers will use a combination of window technologies to meet the ENERGY STAR guidelines, including:

  • Quality framing materials
  • Multiple panes of glass
  • Low-E glass
  • Gas between the panes of glass
  • Warm edge spacers

Residential home with Stanek Windows and a piggy bank sitting on a stack of paper money

How Can ENERGY STAR Windows Save You Money?

When you install efficient windows, less energy is required to cool or heat your home, resulting in a lower energy bill. Standard households can save an average of $27 to $197 a year when replacing double-pane windows and a whopping $101 to $583 a year when replacing single-pane windows. Compared to non-certified products, ENERGY STAR products can cut energy bills by an average of 12% nationwide.

ENERGY STAR Certified Windows by Stanek

Choosing an ENERGY STAR window can be overwhelming with all the technical terminology and qualification criteria. Let the experts at Stanek Windows help you choose the perfect windows for your specific needs and design preference. We offer windows in many different styles, with all kinds of finishes.

Stanek ENERGY STAR compliant windows come in double-hung windows, sliding windows, awning & casement windows, bow & bay windows, and custom shaped windows. They also come in two glass options: Comfort-Gard Plus High-Performance Glass and Comfort-Gard Xtreme High-Performance Glass. Both options help to reduce energy usage and control window glare.

Schedule your free, in-home estimate, or give us a call at 1-800-230-8301 for more information. You can also visit our window buying resource centerfor helpful downloads.