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Energy Efficiency

Understanding Energy Star Ratings

2 min read

Energy Efficient Product Ratings Explained

You know energy-efficient windows can reduce energy costs, but how much savings can you expect? The National Fenestration Rating Council (NFRC), an independent non-profit organization that establishes objective window, door, and skylight energy performance ratings, estimates that homes in the Chicago area can achieve an average annual savings of up to 22% when replacing clear single-pane windows or 9% when replacing clear double pane windows with energy-efficient windows.

NFRC is the organization that tests and certifies the energy performance of all ENERGY STAR-qualified windows, doors, and skylights. ENERGY STAR enables consumers to easily identify NFRC-certified products with superior energy performance.

What is Energy Efficiency?

The NFRC label can be found on all ENERGY STAR-certified windows, doors, and skylights and provides performance ratings in five categories:


U-factor measures how well a product can keep heat from escaping from the inside of a room. The lower the number, the better a product is at keeping heat in.

Range: 0.20–1.20

Look for: Low numbers (0.30 and lower in our area)

Solar Heat Gain Coefficient

Solar heat gain coefficient (or SHGC) measures how well a product can resist unwanted heat gain, which is especially important during the summer cooling season. The lower the number, the less you’ll spend on cooling.

Range: 0–1

Look for: Low numbers (0.42 and lower in our area)

Visible Transmittance

Visible transmittance measures how well a product is designed to effectively light your home with daylight, potentially saving you money on artificial lighting. The higher the number, the more natural light is let in.

Range: 0–1

Look for: High numbers

Air Leakage

Air leakage measures how much air will enter a room through a product. The lower the number, the fewer drafts you’ll experience.

Range: ≤ 0.3

Look for: Low numbers

Condensation Resistance

Condensation resistance measures how well the window resists water build-up. Condensation Resistance is scored on a scale from 0 to 100. The higher the condensation resistance factor, the less build-up the window allows. The condensation rating is optional for manufacturers to include, so you may or may not see it on the label.

Find Energy Efficient Exterior Products with Window World of Joliet

If you want new windows to result in lower energy costs this year, look for the ENERGY STAR logo and the NFRC label, which indicate products that have been tested and certified to save energy. Get your free estimate today and learn how you can cut costs on high energy bills with exterior home products from Window World of Joliet.