How do I know what energy rating My windows are?

Window energy efficiency is an abstract notion for most people. It’s hard to know how energy efficient your window is. The good news is that you can understand this better by learning to read the energy efficiency label that exists on all new windows. After you read this piece, you’ll be able to get new windows that are incredibly energy-efficient, based on what the label says.

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Window Energy Efficiency Label Explained
Performance Ratings
How do I find out my windows rating?
How do I know if my windows are ENERGY STAR qualified?
Do windows have an energy rating?
What is a good energy rating on windows?

The National Fenestration Rating Council has created an energy efficiency label for windows, which serves as a single point of reference for both energy installment companies and homeowners to understand how energy efficient a window is.

Window Energy Efficiency Label Explained

To understand the label, we need to understand all the numbers and codes that exist on the label. Let’s see:

In the upper left corner is the NFRC certified stamp that says the window’s manufacturer was licensed by the National Fenestration Ratings Council (NFRC).
Under the label that says Energy Performance Ratings are two numbers: 1) To the left is the U-factor that measures how much the window keeps the heat from escaping a room. The range of the factor goes from 0.20 to 1.20, and the lower the number, the better the window is at keeping the heat inside. 2) To the right is the Solar Heat Gain Coefficient that measures how well the window resists heat gain. The range goes from 0 to 1, and the lower the number, the less money you’ll spend on cooling.
Under the lower label that says Additional Performance Ratings are also two numbers: 1) To the left is the Visible Transmittance number that measures how well the window is designed to let sunlight inside. The number ranges from 0 to 1, and the higher the number, the more light the window lets in the house. 2) To the right is the Air Leakage number that measures how much air enters the room through the window. It ranges from 0.1 to 0.3, and the lower the number, the less draft you’ll feel.

The rest of what you see on the label is information like the name of the product, the manufacturer, etc.

We at 1-800-HANSONS install only windows that are of the highest quality and of the highest energy efficiency as well. If you want to know more, feel free to contact us and inquire about our prices and our methods.

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The energy performance of all ENERGY STAR qualified windows, doors, and skylights must be independently tested, certified, and verified according to test procedures established by the National Fenestration Rating Council (NFRC).

NFRC is a third-party non-profit organization that sponsors certified rating and labeling to help consumers compare the performance of windows, doors, and skylights. NFRC does not distinguish between “good” and “bad” windows, set minimum performance standards, or mandate performance levels. This is where ENERGY STAR comes in. ENERGY STAR enables consumers to easily identify NFRC-certified products with superior energy performance.

Performance Ratings

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 the rate of heat transfer and tells you how well the window insulates. U-factor values generally range from 0.25 to 1.25 and are measured in Btu/h·ft²·°F. The lower the U-factor, the better the window insulates. (EPA requires that the U-Factor for ENERGY STAR labeled products is certified and listed on the product label.)
Solar Heat Gain Coefficient (SHGC) measures the fraction of solar energy transmitted and tells you how well the product blocks heat caused by sunlight. SHGC is measured on a scale of 0 to 1; values typically range from 0.25 to 0.80. The lower the SHGC, the less solar heat the window transmits. (EPA requires that the SHGC for ENERGY STAR labeled products is certified and listed on the product label.)
Air Leakage (AL) measures the rate at which air passes through joints in the window. AL is measured in cubic feet of air passing through one square foot of window area per minute. The lower the AL value, the less air leakage. Most industry standards and building codes require an AL of 0.3 cf·m/ft². (EPA requires that the AL for ENERGY STAR labeled products is certified.)
Visible Transmittance (VT) measures the amount of light the window lets through. VT is measured on a scale of 0 to 1; values generally range from 0.20 to 0.80. The higher the VT, the more light you see.
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.

For more information on NFRC performance ratings and label, visit NFRC’s Web site.

ENERGY STAR qualification is based on U-factor and SHGC ratings only.

How do I find out my windows rating?

U-Factor ratings for windows generally fall between 0.20 and 1.20. The lower the U-value, the greater a window's resistance to heat flow and the better its insulating value. (The window's insulating value is indicated by the R-value, which is the inverse of the U-value.)

How do I know if my windows are ENERGY STAR qualified?

In the North-Central Zone, the U-factor requirement is 0.30 or less and the SHGC must be 0.40 or less. The South-Central Zone allows U-factors of 0.30 or below and SHGC ratings of 0.25 or below. Windows qualified in the Southern Zone can have U-factors of 0.40 or less, but the SHGC must be 0.25 or below.

Do windows have an energy rating?

The National Fenestration Rating Council (NFRC) operates a voluntary program that tests, certifies, and labels windows, doors, and skylights based on their energy performance ratings. The NFRC label provides a reliable way to determine a window's energy properties and to compare products.