Since the 1970s our Government has required car manufacturers to glue MPG stickers on every new car sold in the United States. They’re there to help us choose more fuel efficient vehicles that save us money on gas – or at least show a car buyer that one car will go further on a dollar of gas than another.

Since 1999 our government has also required windows to be clearly labeled with “fuel efficiency” data in order to qualify as an Energy Star product.

In order for any fenestration product to qualify for Energy Star, the product must be rated according to the procedures established by the National Fenestration Rating Council (NFRC). Since the IRS uses the Energy Star program for tax credits that may be available for doors and windows, it may be worthwhile to review the numbers on the NFRC label to determine if the fenestration you are buying qualifies for and eligible for tax credits. Be aware that Energy Star qualifications differ depending on where you live because the program takes into account that different regions spend more fuel on heating or cooling.

Door and window products carrying the NFRC Label have been independently tested and certified by the manufacturer. NFRC labeling is a voluntary program that allows you – the consumer – to accurately compare unbiased product ratings. The NFRC label shows homeowners the real energy efficiency of the window they choose to buy. Now window buyers can compare the energy efficiency of the different windows they are considering instead of just relying on a salesman’s claims.

Just like how the MPG sticker doesn’t recommend which car or truck to buy, the NFRC label doesn’t recommend which door or window to buy. They both simply tell how a product will perform so the consumer can decide for themselves what the best value is.

Like the MPG sticker on cars, the NFRC sticker should only be removed by the consumer to insure the window installed has exactly the same energy efficiency ratings as the window they were sold and contracted to be installed – not a less energy-efficient, less expensive, inferior product.

A breakdown of the NFRC label. Photo: NFRC
A breakdown of the NFRC label. Photo: NFRC

Reading the “NFRC” Sticker for Energy Efficiency

Although the test ratings on the label can be confusing, I recommend everyone who owns a home with doors and windows to take the time to learn about the energy efficiency of their new window before they buy, or they could be disappointed in how comfortable their home is and how much they are still spending on heating and cooling costs.

Here is an example of the NFRC label and the numbers you may see on the label found on their site:


A graphic provided by the NRFC to interpret the label's meaning.
A graphic provided by the NFRC to interpret the label’s meaning.


U-Factor measures the heat from INSIDE a room that can escape. The lower the number, the lower the potential for wasted heating expenses, since U-Factor is the inverse of R-Value,

Solar Heat Gain Coefficient (SHGC)

SHGC measures the amount of OUTDOOR heat that can enter a room due to passive solar heat gain. The lower the number, the lower the potential for wasting cooling expenses.

Visible Transmittance (VT)

VT Measures how much natural light can come into a room. A high number means more natural light and less electricity wasted for lighting a room.

Air Leakage (AL)

AL is an optional rating and, since manufacturers may choose not to include it on their labels, you won’t see a number rating a window for air leakage on most windows. The lower the number, the better a window is at keeping air out.

Design Pressure Rating (DP Rating)

Although DP is not found on the NFRC Label I include this rating here because it is a valuable tool for the consumer. DP Ratings measures a window’s overall ability to resist air infiltration, water penetration, forced entry and structural strength. It is a cumulative measurement combining all 4 categories; however the individual ratings are available. DP Ratings are also the result of independently performed tests, but they are administered and overseen by AAMA, the American Architectural Manufacturer’s Association. The DP Rating label has a metallic finish and is affixed to the frame of each window rated. The higher the number the better a window is able to protect against air drafts, water leaks, structural stress and break-in.



  1. Mark,
    This was an excellent write up and could actually serve as a nice summary to help consumers navigate through an NFRC Label during a window purchase. Don’t forget the CR rating, which is also optional, to compare the relative condensation resistance. CR ratings can tell the consumer how well a given window resists the formation of condensation on the surface of the inner pane during the cold winter months! The higher the CR rating, the better. Drier windows provide a clearer view and are also healthier for the homeowner since there is a lower propensity for mold formation.
    Anyway, this was a great blog Mark!

  2. JIm,
    Thank you for reading and commenting… Condensation Reduction is important to homeowners concerned about moisture inside their home. I should have included this information. During my overall conversation with clients during window and door presentations I “teach” a variety of subjects including:

    “Crash Test Ratings for Windows”
    “MPG for WIndows”

    I feel so strongly about the importance of educating the consumer I wrote this:
    “Can You Teach Doors & Windows”

    If you agree that educating the consumer is critical please share my blog-posts with colleagues in our industry…

    Thanks again for reading!

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