NFRC vs. ENERGY STAR®: What’s the Difference?

When you shop for energy-efficient products like windows, doors, or skylights, you will keep seeing the same two labels: NFRC and ENERGY STAR. Both matter for energy efficiency, but they play different roles in how homeowners and other consumers compare certified products and choose what is best for a home.

What Is the NFRC?

The National Fenestration Rating Council (NFRC) is a nonprofit organization that tests and rates the energy performance of windows, doors, and skylights.

Instead of approving or rejecting products, NFRC ratings provide objective numbers so you can compare windows doors and skylights side by side. The program is built around standardized tests that every manufacturer must pass before claiming a window insulates to a certain level or carries a specific rating. The goal is to assist consumers, builders, and experts with clear, comparable data.

The NFRC label reports several critical measurements:

• U-factor: Measures how well the window insulates and limits heat loss from the house. Lower values mean better insulation.
• Solar heat gain coefficient (SHGC): Measures how much solar heat and sunlight enter your home, expressed as a fraction between 0 and 1. Lower values mean less solar heat in hot regions.
• Visible transmittance (VT): Measures how much natural light and visible light is transmitted through the glass. Higher VT means more visible light and brighter rooms.
• Air leakage (AL): Indicates how much air passes through cracks or seals. Lower values reduce drafts and help keep the living space comfortable.
• Condensation resistance (CR): Shows how well a window resists moisture buildup. Higher values are beneficial, especially in colder climates.

In other words, the NFRC label and its consistent labeling do not tell you whether a window is “good” or “bad”. Instead, NFRC ratings give you the data you need to take your specific climate zone, project type, and design goals into account.

What Is ENERGY STAR?

ENERGY STAR is a certification program run by the U.S. Environmental Protection Agency (EPA) and the Department of Energy (DOE).

Unlike NFRC, ENERGY STAR doesn’t test windows — it sets the performance benchmarks that qualify products as energy-efficient.

To earn the ENERGY STAR label, a product must first be tested and rated by the NFRC, then meet or exceed specific criteria for:

• U-Factor
• Solar heat gain coefficient (SHGC)

These criteria vary by climate zone, because a window that performs well in Minnesota might not suit Florida.

The United States is divided into four ENERGY STAR climate zones:

1. Northern: Prioritizes insulation and low U-Factors for cold weather.
2. North-Central: Balances heat retention and solar control.
3. South-Central: Emphasizes SHGC to block solar heat.
4. Southern: Focuses on cooling efficiency and solar reflection.

So, ENERGY STAR picks the winners — based on the NFRC’s data.

How to Read an NFRC Label

Every certified window, door, or skylight in the U.S. must carry an NFRC label — usually found on the glass or frame. Here’s how to interpret it:

1. U-factor (0.20–0.50): The lower, the better the insulation.
2. SHGC (0.20–0.60): The lower, the better for hot climates.
3. VT (0.40–0.70): A higher value means more daylight.
4. AL (≤0.3 recommended): The lower, the fewer drafts.

If the window also shows the ENERGY STAR logo next to the NFRC label, that means it meets NFRC-tested criteria for your climate zones and is recognized as a certified product for energy efficiency.

Choosing the Right Windows for Your Climate

Whether you are building new or replacing old windows, using NFRC ratings and ENERGY STAR certification together is the simplest way to match performance to your climate and long-term goals.

• Cold climates: Look for low U-Factor and higher SHGC to capture free solar warmth and keep the house comfortable.
• Hot climates: Choose low U-Factor and low SHGC to block unwanted heat gain and allow less solar heat into living spaces.
• Mixed climates: Aim for a balanced combination, with low U-Factor, moderate SHGC, and high VT so you get natural light, comfort, and more visible light without sacrificing efficiency.

NFRC and ENERGY STAR in Modern Window Technology

High-quality vinyl, fiberglass, and aluminum-clad systems can all achieve strong NFRC and ENERGY STAR ratings when paired with the right glass and frame technologies, for example:

• Low-E coatings to control heat transfer
• Argon gas fills between panes
• Multi-chambered profiles for superior insulation

GEALAN’s European-engineered vinyl systems use these same principles to deliver exceptional energy performance and airtight seals, supporting both NFRC-rated results and ENERGY STAR-certified outcomes when fabricated by local partners.