NFRC Ratings and U-Factor: Specifying Window Energy Performance for US Projects

An NFRC rating is a whole-window energy performance figure — U-factor, Solar Heat Gain Coefficient (SHGC), Visible Transmittance (VT), Air Leakage and Condensation rating — determined under NFRC 100, 200, 400 and 500 for one specific frame, glazing and spacer combination, and printed on a label that a US code official will accept as evidence of compliance. Windows and doors from China can carry a genuine NFRC label if the factory is an NFRC licensee and the exact product line and glazing option is listed in the NFRC Certified Products Directory; a factory brochure that says “U-value 1.8 W/m²K” or a centre-of-glass number from the glass supplier is not an NFRC rating and will not pass a plan check. For a US commercial or multifamily project, the specification should therefore state the U-factor and SHGC required by the applicable energy code for the climate zone, and the procurement should verify that the Chinese factory’s NFRC listing covers the product actually being ordered. FBM Sourcing’s role here is as your sourcing partner, not a reseller.

What Does an NFRC Label Actually Report?

The National Fenestration Rating Council runs the only fenestration energy rating system that US energy codes reference by name. Its label carries up to five values, each from its own procedure:

• U-factor (NFRC 100): rate of heat transfer through the whole window — frame, glass edge, spacer and centre of glass together — in Btu/h·ft²·°F. Lower is better. To convert a metric U-value in W/m²·K, divide by 5.678: a window quoted at 1.8 W/m²·K is roughly 0.32 in US units.
• SHGC (NFRC 200): fraction of incident solar radiation admitted through the whole window, 0 to 1. Lower means less solar gain; hot climates want it low, heating climates may want it higher.
• VT (NFRC 200): fraction of visible light transmitted, 0 to 1. Daylighting credits and glare studies use it.
• Air Leakage (NFRC 400): in cfm/ft² at a 1.57 psf (75 Pa) pressure difference. Codes typically cap windows at 0.20 to 0.30 cfm/ft².
• Condensation rating (NFRC 500): a unitless index; higher resists condensation better. Optional on the label but often requested for cold-climate multifamily work.

The two facts about this system that matter most to a project buyer are that the ratings are whole-product and configuration-specific. A thermally broken aluminium casement with a double-glazed low-E argon unit and a warm-edge spacer might rate at 0.36; the same frame with a standard aluminium spacer and no argon might rate at 0.45; the glass supplier’s centre-of-glass figure for the low-E unit alone might be 0.25. Only the first two are NFRC ratings, and only the one that matches the ordered configuration is valid on your job.

Which U-Factor and SHGC Does a US Commercial Project Need?

The requirement comes from the energy code adopted in the project’s jurisdiction, applied to the ASHRAE climate zone of the site. Most US jurisdictions enforce a version of the International Energy Conservation Code (IECC) or ASHRAE 90.1; multifamily buildings of four storeys and above follow the commercial provisions. The prescriptive path values below are from IECC 2021 Table C402.4 and are the numbers a specifier will most often be asked to meet; older code cycles are less stringent, and states such as California (Title 24), Washington and New York run their own tables, so the local code must be checked before a specification is written.

Two things follow from that table. First, a project in Zone 4 or colder cannot be met by a standard thermally broken aluminium window with ordinary double glazing; it needs a deeper thermal break, a warm-edge spacer, argon fill and a low-E coating chosen for the zone, and in Zones 6–8 it will often need triple glazing or a uPVC or composite frame to reach 0.29–0.36 as a whole-window figure. Second, SHGC runs the other way — the hot southern zones cap it at 0.25, which drives the choice of low-E coating as much as U-factor does. Our comparison of casement, sliding and single-hung windows for commercial buildings covers why the operable type also moves the number.

What happens without an NFRC label?

Where fenestration is not NFRC-labelled, the code directs the official to the default U-factor and SHGC tables (IECC Table C303.1.3 and its equivalents). Those defaults are deliberately conservative: a metal-framed double-glazed window without a certified rating is assigned a default U-factor in the region of 0.60 or higher, which fails the prescriptive path in every zone from 2 upward and forces the whole envelope into a trade-off or performance calculation. In practice an unlabelled window from China is not a slightly worse window on paper; it is a window that has to be re-justified by the energy consultant, and most projects will not accept that risk.

How Does a Chinese Factory Obtain a Valid NFRC Rating?

NFRC certification is a licensing and listing system, not a one-off test report, and its steps are the checklist a buyer should verify.

1. Licence: the manufacturer signs a licence agreement with NFRC and is assigned a manufacturer code. Chinese window and door factories can and do hold these licences.
2. Simulation: an NFRC-accredited simulation laboratory models the product line in LBNL WINDOW and THERM for each frame type, glazing option and spacer, producing the U-factor, SHGC and VT for the NFRC standard model size (for example 1.2 m × 1.5 m for a fixed unit and 0.6 m × 1.5 m for a casement).
3. Validation test: one baseline product from the line is physically tested at an NFRC-accredited test laboratory to confirm the simulation.
4. Certification Authorization Report (CAR): issued by an NFRC-licensed Inspection Agency, listing every certified product option and its ratings.
5. Plant inspection and labelling: the Inspection Agency audits the factory’s ability to build what was simulated; the factory then applies temporary NFRC labels to each unit and a permanent label inside the frame.
6. Directory listing: the ratings appear in the public NFRC Certified Products Directory (CPD) under the manufacturer’s name and CPD number, which is what a plan checker or energy consultant will look up.

For site-built and unitised curtain wall, NFRC uses the Component Modeling Approach (CMA), where approved frame, glass and spacer components are combined in NFRC’s CMAST software and a label certificate is issued for the project’s specific configuration. That route matters on high-rise multifamily and office work using Chinese curtain wall — see our comparison of curtain wall vs window wall for high-rise projects.

Five Checks to Run on a Chinese Factory’s NFRC Claim

Most disputes about “NFRC-rated” windows from China come down to a mismatch between what was certified and what was ordered. These five checks close that gap before the order is confirmed.

1. Find the listing yourself. Search the NFRC Certified Products Directory for the manufacturer name and CPD number. If the factory is not there, it does not hold a rating regardless of what its brochure shows. A licence held by an affiliated trading company under a different name is a warning sign; the licensee must be the entity that builds and labels the product.
2. Match the product line and option. The listing is by series (frame system), operator type, glazing option and spacer. Confirm the series you are specifying, the operator (fixed / casement / awning / horizontal slider / tilt-turn), the glass make-up (glass thickness, low-E product and surface number, gas fill, spacer type) and the frame colour and finish are all inside the certified options. A change of spacer or a swap of low-E product moves the number and can invalidate the label.
3. Check the standard size and the project size. Ratings are for the NFRC model size; a much larger or smaller unit has a different frame-to-glass ratio and therefore a different real U-factor. Codes accept the labelled figure, but the energy model may want size-adjusted values for large fixed lites.
4. Separate energy from structure. NFRC does not test wind load, water penetration or forced entry. Those sit under AAMA/WDMA/CSA 101/I.S.2/A440 (NAFS) performance grades and, in hurricane regions, ASTM E1886/E1996 or the Florida Building Code. A window can be excellent on the NFRC label and unrated structurally, or the reverse. Our note on factory test reports vs accredited lab testing explains which documents carry which weight.
5. Get the labelling arrangement in writing. Each unit needs the temporary NFRC label affixed at the factory before packing, and the permanent label applied in the frame. If units arrive unlabelled, the site inspector has nothing to accept, and re-labelling on site is not permitted.

What Whole-Window Values Are Realistic from Chinese Factories?

Buyers new to NFRC often specify a centre-of-glass number and are surprised when the whole-window figure is 0.10 to 0.15 higher. Working ranges for products in current export production, at NFRC model size, are:

• Thermally broken aluminium, double glazed low-E, argon, warm-edge spacer: whole-window U roughly 0.32–0.42 depending on thermal break depth (a 24–35 mm polyamide strut is common) and operator type; SHGC 0.20–0.40 by coating.
• Thermally broken aluminium, triple glazed: roughly 0.24–0.32.
• uPVC multi-chamber, double glazed low-E argon: roughly 0.26–0.32; triple glazed 0.17–0.24.
• Aluminium-clad timber or composite, double glazed: roughly 0.28–0.34.
• Non-thermally-broken aluminium (not appropriate for conditioned US buildings): 0.60 and above.

The glass unit is where most of the number is decided. Chinese IGU production for export commonly uses low-E coatings from Guardian, Saint-Gobain, AGC or CSG-type domestic producers, 12–16 mm argon-filled cavities and stainless or thermoplastic warm-edge spacers; specify the coating family and its emissivity, and require the IGU to carry its own certification (IGCC/IGMA in the US market) for seal durability. On glass safety and impact standards, see glass safety standards EN 12150 and ANSI Z97.1.

How Should the Specification Be Written for a China-Sourced Window Package?

A specification that will survive submittal review and site inspection states, per window type: the maximum U-factor and SHGC from the applicable code and zone; the requirement that ratings be NFRC-certified and labelled, with the CPD listing submitted at shop-drawing stage; the minimum VT where daylighting credits are being claimed; the maximum air leakage (typically 0.20 cfm/ft² under IECC 2021 for windows tested to NAFS or NFRC 400); the NAFS performance grade for structural and water performance; and the glazing make-up in full so the factory cannot substitute a spacer or coating that changes the label. Where the project is pursuing ENERGY STAR (a residential and low-rise programme, currently Version 7.0, with zone criteria such as U ≤0.22 in the Northern zone and U ≤0.32 with SHGC ≤0.23 in the Southern zone), the specification should say so, because the label is issued against the NFRC data and the product must be listed under that programme too.

The frame material and system are chosen against those numbers rather than before them. Our comparison of powder coating vs anodised aluminium on commercial projects and the shortlist of aluminium window and door manufacturers in China are the next reads once the target U-factor is fixed.

Whole-window ratings start with the glass build-up, compared in double glazing vs Low-E vs triple glazing.

How FBM Sourcing Handles NFRC on a Window Package

FBM Sourcing manages the entire China procurement package for overseas construction projects. On a US window and door package that starts with the code: we take the project’s climate zone and adopted code cycle, confirm the U-factor, SHGC and air-leakage limits per opening type with the design team, and shortlist only factories whose NFRC Certified Products Directory listing covers the series, operator types and glazing options the project needs. The CPD listing, the CAR and the glazing make-up are checked against the shop drawings before the order is confirmed, and the labelling arrangement is written into the purchase order.

All inspection is carried out by FBM Sourcing’s own team at the factory. Before shipment we check that the glazing make-up, spacer and coating on the production units match the certified option, that temporary NFRC labels are affixed to every unit and permanent labels are in place, and that packing will bring the units to site without label damage; photo and video records are delivered before shipment. All quotations, invoices and shipping documents are issued by FBM Sourcing — you deal with us, and we carry the responsibility. For products you have selected yourself, we charge a 5–8% commission (8% below USD 50,000, 5% above); for products we source for you, we quote a direct price. As a building material sourcing agent for the whole package, we also carry the fenestration decision through to doors, curtain wall, glazing hardware and the trades that meet them on site.

On Californian projects the NFRC numbers are only half the test — see what California Title 24 requires from lighting and glazing on China-sourced products for the prescriptive limits and the appliance registration that decides what can be installed.

Get a China Procurement Quote for Your Project

If you are specifying windows, doors or curtain wall for a US hotel, multifamily, office, school or retail project and need NFRC-labelled products sourced and inspected in China as part of the full package, send us the window schedule, the climate zone or project address, the code cycle your jurisdiction enforces, the destination port and the required-on-site dates. Our team will review the package and set out a quotation with the service fee stated clearly.

Use the quote button above or WhatsApp +86 135 6007 5057 to start the conversation.