The NFRC label is the energy performance label issued under the National Fenestration Rating Council's certification program for windows, doors and skylights sold in the United States. It gives a fixed set of figures that let a buyer compare one product against another, across manufacturers. This page is for a homeowner who has a label in front of them, on a new window or in a product listing, and wants to know what each figure means and whether a sun-struck room needs a different window or only shading.

The figure most people read first is U-factor. For a room that overheats in afternoon sun, it is the wrong figure to start with. U-factor measures heat loss and matters most in cold climates. The figure that measures sun coming through the glass is the Solar Heat Gain Coefficient (SHGC).

One figure on the label changed this autumn. From October 1, 2026, new NFRC-certified product lines carry a Condensation Index (CI) in place of the older Condensation Resistance (CR) rating. Labels printed between that date and September 30, 2027 may show either one, but never both.

What each figure on the label measures

The label can carry five ratings. Three are mandatory. Two are optional. The positions below are those given by the Efficient Windows Collaborative's window ratings page.

U-factor (mandatory, top left) : The rate of heat loss through the window. Values typically run from 0.10 to 2.00. A lower value means better insulation. U-factor is not the same as R-value. For an R-value, used for walls and roofs, higher is better. For a U-factor, lower is better.

Solar Heat Gain Coefficient, SHGC (mandatory, top right) : The share of the sun's heat that passes through the window. Values run from 0.00 to 1.00. A lower value means less solar heat gain. A low SHGC helps in hot climates and on windows that face strong afternoon sun.

Visible Transmittance, VT (mandatory, left side, middle or bottom row) : The share of visible daylight that passes through. Values run from 0.00 to 1.00. A higher value lets in more daylight.

Air Leakage (optional, right side, middle or bottom row) : How much air passes through the assembly. It is generally reported as less than or greater than 0.3. A rating above 0.3 can disqualify a product from ENERGY STAR certification.

Condensation rating (optional, bottom row, left side) : Either the legacy Condensation Resistance (CR) or the new Condensation Index (CI). Both use a scale of 1 to 100. On both, a higher number means better resistance to moisture forming on the inside surfaces. The rating matters most in cold climates.

The NFRC label page states that the condensation rating is optional. A manufacturer may leave it off. Its absence says nothing about how the window performs.

0.10 to 2.00
U-factor range
Lower is better. Efficient Windows Collaborative.
0.00 to 1.00
SHGC range
Lower means less solar heat gain. Efficient Windows Collaborative.
0.00 to 1.00
VT range
Higher means more daylight. Efficient Windows Collaborative.
1 to 100
CI and CR scale
Higher is better on both. NFRC and Efficient Windows Collaborative.

How the Condensation Index is calculated

CI is a computer-simulated rating produced under the ANSI/NFRC 500 standard. It is not a laboratory measurement of condensation. According to NFRC's Condensation Index page, the method is based on the Temperature Index approach in the Canadian standard CSA A440.

The simulation finds the coldest inside surface temperature in three zones of the product:

  • the frame (CIf)
  • the edge of the glazing (CIe)
  • the center of the glass (CIc)

Each zone gets a score. The product's CI is the lowest of the three. The weakest zone governs the rating.

The simulation uses fixed conditions: 0°F (-18°C) outside and 70°F (21°C) inside. These match the conditions NFRC has used for its other simulated ratings, such as U-factor.

The method traces to a 2018 paper by Hakim Elmahdy, "A Universal Approach to Laboratory Assessment of the Condensation Potential of Windows", as reported by Window & Door magazine in July 2021.

Point of difference Condensation Resistance (CR) Condensation Index (CI)
Scale (NFRC; Efficient Windows Collaborative) 1 to 100, higher is better 1 to 100, higher is better
What it is based on (NFRC CI page; Window & Door, 2021) A product-to-product comparison rating, developed more than 20 years before 2021 The coldest inside surface temperature across frame, edge of glass and center of glass; lowest zone governs
Can it predict condensation at a given house? (Window & Door, 2021) No. It ignores indoor humidity, indoor dew point and local winter design temperature Yes, as a minimum CI needed for a US or Canadian location, from Table 7-1 of the NFRC 501-2020 User Guide
New product lines from Oct 1, 2026 (Program Bulletin 2025-12) Not accepted The only accepted condensation rating
Temporary label, Oct 1, 2026 to Sept 30, 2027 (Program Bulletin 2025-12) Allowed, but not alongside CI Allowed, but not alongside CR
Temporary label from Oct 1, 2027 (Program Bulletin 2025-12) Removed from new labels The only condensation rating allowed

The sources give no conversion between a CR value and a CI value. The two numbers come from different methods. A CI of a given number and a CR of the same number should not be read as equal performance.

Reading a label, figure by figure

The steps below take a label from top to bottom and end with the question the label is usually read to answer: does the room need a different window, or does it need shading. Reading a label costs nothing. The only material needed is the label itself or the product's listing.

  1. Find the label

    On a new window, the NFRC temporary label is fixed to the product. If the window is already installed and the label has gone, the manufacturer's product line may be listed in NFRC's Certified Products Directory (CPD). For older product lines, CR values stay in the CPD until that certification expires.

    It worked if you have a label or listing with at least U-factor, SHGC and VT.

  2. Read U-factor, top left

    Lower is better. Do not read it as an R-value. If the room's problem is cold, drafts or winter heating cost, this is the first figure to compare.

    It worked if you have a number between 0.10 and 2.00.

  3. Read SHGC, top right

    Lower means less of the sun's heat comes through the glass. If the room's problem is overheating in afternoon sun, this is the first figure to compare.

    It worked if you have a number between 0.00 and 1.00.

  4. Read VT

    Higher means more daylight. Note it before choosing any shading, because a low SHGC paired with a low VT means a darker room.

    It worked if you have a number between 0.00 and 1.00.

  5. Check Air Leakage, if shown

    It is optional. It is reported as less than or greater than 0.3. Above 0.3, the product can be disqualified from ENERGY STAR certification.

    It worked if you know whether the value is below or above 0.3, or you have confirmed the label does not carry it.

  6. Identify the condensation rating

    Look at the bottom row, left side. Check whether it is labeled Condensation Index (CI) or Condensation Resistance (CR). A label printed from October 1, 2026 to September 30, 2027 carries one or the other, never both. It may also carry neither, because the rating is optional.

    It worked if you know which rating you are reading.

  7. If the rating is CI, find the minimum for your house

    Use Table 7-1 in the NFRC 501-2020 User Guide. It needs two of three inputs: the winter design temperature for the location, the indoor relative humidity, or the indoor dew point temperature. The table gives the minimum CI needed to reduce the likelihood of condensation at that location. It covers US and Canadian locations.

    It worked if the window's CI is at or above the minimum the table gives.

  8. Decide what the room needs

    Sort the problem by figure. A high SHGC on a room that overheats in sun points to the sun as the problem. A high U-factor or a low condensation rating on a room that is cold or wet in winter points to the window itself. The next section works through one case.

Film, blinds or shutters, or new glass

The label rates the window as it was certified. It does not rate a film, blind or shutter added afterward. Shading acts on sunlight before it reaches the room or after it passes the glass. It does not change the frame, so it does not change the frame zone that can govern the CI.

This gives a plain way to sort a room:

  • If SHGC is the figure out of line and the complaint is summer heat, the problem is solar gain. Shading addresses solar gain.
  • If U-factor is the figure out of line and the complaint is winter cold, shading does not address the cause.
  • If the condensation rating is below the minimum from Table 7-1 and the complaint is moisture on the glass or frame in winter, shading does not address the cause.

The measured effect of exterior and interior shading on cooling, including film and cellular shades, is set out in what the Department of Energy measured on shading.

A west-facing bedroom (hypothetical figures)

Say a west-facing bedroom overheats on summer afternoons. Its window carries the label below. The figures are invented for illustration and sit inside the published ranges.

U-factor0.30
SHGC0.60
VT0.62
Air Leakageless than 0.3
Condensation Index58
ComplaintHot from mid-afternoon to evening, May to September
Winter complaintNone

The room's complaint is afternoon heat. The figure tied to afternoon heat is SHGC, and 0.60 lets in 60% of the sun's heat that strikes the glass. The U-factor and the absence of a winter complaint do not point to the window as a heat-loss problem. On these figures, the case is for shading the west window, not replacing it. Because VT is 0.62, any option that cuts SHGC should be checked for how much daylight it also removes.

Where readings go wrong

Reading U-factor like R-value. The window ratings page separates the two. Recognize it when a higher U-factor is being described as better insulation. Correct it by reversing the comparison: the lower U-factor insulates better.

Taking a missing condensation rating as a poor one. The rating is optional. Recognize it when a label shows only U-factor, SHGC and VT, with or without Air Leakage. Check the CPD listing instead of assuming.

Treating CR as a forecast. Window & Door magazine reports that CR allows product-to-product comparison but cannot say whether condensation will form at a given site, because it ignores indoor humidity, indoor dew point and local winter temperature. Recognize it when a CR value is offered as proof a window will stay dry. Correct it by using CI and Table 7-1, where CI is available.

Comparing a CI against a CR. A label from the transition period may show either. Two products on the same shelf may carry different ratings. Recognize it when one label says Condensation Index and the other says Condensation Resistance. Compare like with like, or look up both products in the CPD.

Reading CI as a lab test. CI is simulated under ANSI/NFRC 500 at 0°F (-18°C) outside and 70°F (21°C) inside. It is not a measurement of condensation on a real window in a real house.

Using the ENERGY STAR mark as the figures. The NFRC label page states that ENERGY STAR indicates general efficiency only. The NFRC label gives the separate figures needed for a direct comparison.

Expecting every window to have converted. Existing product lines certified under the older method keep their five-year certification cycle. They move to LEAFF and CI only at their normal recertification. A CR label on a product sold after October 1, 2026 is not by itself an error.

Dates, product types and places that change the answer

The CI change comes from NFRC's move to a new rating method called LEAFF (Linear Energy Analysis for Fenestration). LEAFF was formerly known as RCBC (Residential Component-Based Calculation). It builds performance trendlines from a product line's characteristics. In NFRC's words, quoted by Building Design+Construction in February 2020, it "uses product-line characteristics to determine trendlines that replace the need to run numerous simulations separately." CI was planned to launch with LEAFF. The schedule is set by NFRC Program Bulletin 2025-12 and confirmed on NFRC's LEAFF reference page.

The LEAFF and CI schedule

  1. November 24, 2025
    Program Bulletin 2025-12 issued

    Sets the mandatory dates for LEAFF and CI.

  2. January 1, 2026
    LEAFF mandatory for recertifications

    Existing product lines that come up for recertification must use LEAFF.

  3. May 29, 2026
    Site-built label certificates end

    Per Intertek (June 2026). This route applied to commercial site-built work, not to typical home windows.

  4. October 1, 2026
    LEAFF and CI mandatory for new product lines

    CI is the only condensation rating accepted on new product lines. The temporary label may show CI or CR, not both.

  5. September 30, 2027
    Transition window closes

    Last day a new temporary label may carry CR.

  6. October 1, 2027
    CI only on the temporary label

    CR is removed from new labels.

Existing product lines

A product line already in the CPD under the older method is not forced to convert. It keeps its five-year certification cycle. Its CR value stays in the CPD until that certification expires. A homeowner may therefore see CR on some products well after October 2027, in the directory if not on new temporary labels.

Residential and commercial products

Residential products are certified under NFRC 700, the Product Certification Program, and listed in the CPD. Intertek, an NFRC-accredited certification body, states in its June 2026 guidance that they are recertified every five years with retesting. Commercial products fall under NFRC 715 and are listed in a separate directory, the Commercial Trendline Approach Directory (CTAD). A home window is a residential product.

Climate

In a cold climate, U-factor and the condensation rating carry the most weight. In a hot climate, or on a window facing strong afternoon sun, SHGC carries the most weight. The right targets depend on climate zone and on which way the window faces. The sources used here do not publish target values by zone.

United States, Canada and the United Kingdom

The CI method is based on the Canadian CSA A440 Temperature Index. NFRC has worked with CSA Group to add the ANSI/NFRC 500 simulation method for CI to CSA A440.2/.3. Table 7-1 covers US and Canadian locations. The sources used for this guide describe the North American system only. They do not describe how windows are energy-labeled in the UK, so this guide gives no UK equivalent. A UK homeowner can still use the physics: SHGC, U-factor and VT measure the same things wherever the window is installed.

What the label is worth in money

The label itself is free to read. Its value is in what depends on it. According to the NFRC label page, NFRC ratings are used by:

  • building energy codes
  • federal and state tax credit programs
  • utility rebate and incentive programs
  • the ENERGY STAR program

A product that lacks the right rating, or that carries an Air Leakage value above 0.3, can fall outside a program that requires it. Check the program's own rules for the figures it needs before buying.

The sources used for this guide give no prices for re-glazing, replacement windows, window film, blinds or shutters. They give no dated cost for any of these. A cost comparison between shading a west window and replacing it cannot be made from these sources. The sorting in the section above tells a homeowner which kind of fix the figures point to. A price for that fix has to come from a quote.

Questions people ask about NFRC labels

It is a simulated rating from 1 to 100 of how well a window resists condensation on its inside surfaces. Higher is better. It is based on the coldest surface of the frame, the edge of the glass and the center of the glass, and the lowest of the three sets the rating. Since October 1, 2026, it is the only condensation rating accepted on new NFRC product lines.

Two reasons are allowed under NFRC Program Bulletin 2025-12. From October 1, 2026 to September 30, 2027, a temporary label may carry either CI or CR. Separately, existing product lines keep CR until their normal five-year recertification.

No. A lower U-factor means less heat loss. U-factor works the opposite way to R-value, where higher is better.

SHGC. It measures how much of the sun's heat passes through the window, on a scale of 0.00 to 1.00. A lower value lets in less heat and suits windows facing strong afternoon sun.

No. The label rates the window product as certified. Any shading added afterward is outside the rating.

It can give a minimum. Table 7-1 of the NFRC 501-2020 User Guide gives the minimum CI for a US or Canadian location from two of three inputs: winter design temperature, indoor relative humidity or indoor dew point. A window at or above that minimum is less likely to see condensation. The old CR rating could not be used this way.