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Interior view of a bedroom with two black Marvin Replacement Casement windows.

What are ENERGY STAR Windows?

The ENERGY STAR® sticker has become synonymous with energy savings. Replacing old windows with ENERGY STAR certified windows can lower household energy bills. It can lower bills an average of 12%, according to ENERGY STAR.* It’s easy to see why people want to add ENERGY STAR windows to their home. But what makes windows ENERGY STAR certified and energy efficient?

What Makes Windows ENERGY STAR certified?

ENERGY STAR certified windows must meet a set of criteria to earn the familiar blue sticker. The criteria includes:

  • Manufactured by an ENERGY STAR partner

  • Independently tested, certified, and verified by the National Fenestration Rating Council (NFRC)

  • NFRC ratings meet U.S. Environmental Protection Agency energy efficiency guidelines

The NFRC uses U-Factor, Solar Heat Gain Coefficient (SHGC), Air Leakage, Visible Transmittance, and Condensation Resistance ratings to test windows. It does not set minimum performance standards or mandate performance levels. ENERGY STAR qualification uses U-Factor and SHGC ratings.

Ratings Vary by Climate Zone

ENERGY STAR uses four climate zones: Northern, North Central, South Central, and Southern. It has established U-Factor ratings and SHGC figures for each climate zone. Those ratings help people find windows that make the most sense for their climate.

What Makes Windows Energy Efficient?

ENERGY STAR defines energy efficient windows as those with quality frame materials. They also have multiple panes, low-E glass, a gas fill, and warm-edge spacers.

Quality frame materials: ENERGY STAR defines quality frame materials as durable and low-maintenance. The material also reduces heat transfer and help insulate better. Our Ultrex® fiberglass frames reduce heat transfer 5,000x better than rolled-form aluminum frames.

Multiple panes: ENERGY STAR-certified windows have at least two panes of glass with an air or gas-filled space between the panes. Marvin Replacement windows feature two panes of glass with an argon gas fill for energy efficiency.

Low-E glass: Low emissivity (Low-E) glass has special transparent metallic coatings. The coatings reflect heat out of a home in summer. The coatings also help keep heat inside during winter. Low-E glass also reduces the amount of UV light into a room. UV rays can lead to color fading of furniture and other items.

Gas fills: Double pane windows contain an inert gas fill, like krypton or argon. Those gasses can provide better insulation than air. Marvin Replacement windows use an argon gas fill.

Spacers: Double pane windows have spacers to hold the glass panes the correct distance apart. Spacers can help insulate pane edges and reduce heat transfer. Marvin Replacement windows come standard as double pane windows with spacers.

Where Can You Find ENERGY STAR Windows?

Most window manufacturers create windows that meet ENERGY STAR certification. ENERGY STAR also has a helpful ENERGY STAR window finder tool. Marvin Replacement design consultants can help you select ENERGY STAR-certified windows for your climate.

ENERGY STAR Window Benefits

Installing ENERGY STAR window benefits include the energy savings you can enjoy. You can also reduce your carbon footprint. You can save between $101 and $583 a year on average when replacing single-pane windows with ENERGY STAR-certified windows. Replacing double-pane, clear glass windows with ENERGY STAR windows can save you between $27 and $197 a year.*



ENERGY STAR is a program by the U.S. Environmental Protection Agency. It helps people find energy efficient products. The blue ENERGY STAR logo indicates a product has met certification standards. It can help reduce energy use.

What are the benefits of ENERGY STAR certified windows and doors?

ENERGY STAR-certified windows and doors benefits include heating and cooling savings when you replace single pane or double pane clear glass windows. According to ENERGY STAR, savings range from $280 to $366 a year. Replacing double pane clear glass windows with ENERGY STAR-certified windows can net annual savings between $87 and $134, according to ENERGY STAR.

The interior side of the window glass can stay warmer during colder months to help retain indoor heat with ENERGY STAR-certified windows. ENERGY STAR-certified windows can also reduce heat gain in the summer. ENERGY STAR-certified windows can also defend against color fading by reducing the impact of UV rays.

Why does ENERGY STAR matter?

ENERGY STAR matters because the program attempts to reduce home energy usage. Lower energy usage can result in utility savings. ENERGY STAR-certified products have greater energy efficiency than those that aren’t. The program has helped save more than $500 billion in energy costs since 1992, according to ENERGY STAR.

*Savings reflect installing ENERGY STAR certified products compared to non-certified when replacing single pane windows based on the average savings among homes in modeled cities. Actual savings will vary by product type, location, method of installation, individual home characteristics, local climate and conditions, utility rates and other factors. 

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