Which Rating Applies? NFRC, Phius, PHI & CSA

Four names come up whenever high-performance windows are specified in North America: NFRC, Phius, the Passive House Institute (PHI) and CSA. They are often treated as interchangeable. They are not. Each answers a different question, is run by a different organization, gets its numbers in a different way, and is checked by different people. What applies also depends on what kind of building you are designing: a single-family house and a six-story dormitory fall under different code chapters, different inspection routines and, often, different Passive House pathways.

The short version: building codes ask for NFRC ratings in the United States, and for CSA or NFRC ratings in Canada, for every building type. Phius and PHI are voluntary building certifications that an owner or a funding program chooses. A Passive House certification does not, on its own, replace the rated window values a building department expects, except where the code says it does.

First, which kind of building is it?

Codes in both countries draw a line between small residential buildings and everything else. Where your project falls decides which energy code chapter applies, how windows are documented and how they are inspected.

States, provinces and some cities amend these thresholds, so confirm with the authority having jurisdiction. In both countries, a four-story apartment building, a hotel, a residence hall or a laboratory is normally treated as a commercial or Part 3 building, and that is the path most of our projects follow.

The four systems at a glance

How NFRC gets its numbers

A common belief is that NFRC ratings come from testing every window in a lab. In fact they come mostly from computer simulation, confirmed by a physical test:

• Simulation. An NFRC-accredited simulation lab models the frame sections and the glass in the Lawrence Berkeley National Laboratory programs THERM and WINDOW, following NFRC 100 for U-factor and NFRC 200 for SHGC and visible transmittance. Each product is rated at a fixed NFRC standard size, so different brands can be compared fairly.
• Validation test. A sample of the product line is built and tested in a calibrated hot box at an NFRC-accredited test lab. The measured U-factor must agree with the simulation within NFRC's tolerance. Once validated, the rest of the product line, every glass and spacer option, can be rated by simulation.
• Certification and inspection. An independent inspection agency reviews the results, authorizes the label, lists the product in the NFRC Certified Products Directory, and inspects the factory regularly to confirm that what ships matches what was rated.
• Material data. The simulation needs the thermal conductivity of every material in the frame. Common materials take values from NFRC's reference tables. A material that is not listed, such as a proprietary frame material, needs a measured conductivity from an accredited lab.

Residential vs. commercial. Factory-built windows for houses and low-rise residential carry an individual NFRC label on each unit. On commercial work, windows may be labeled the same way, or, for storefront, curtain wall and other site-assembled systems, rated through NFRC's Component Modeling Approach (CMA), which rates the frame, glass and spacer separately and combines them into a project-specific label certificate for the whole job.

How a commercial label certificate works

On larger commercial and multifamily projects, building departments often accept one NFRC CMA label certificate for the whole job instead of stickers on every unit. It is built from pre-approved components, by calculation, not by testing the project's windows:

• Frames. The manufacturer has each frame system simulated by an NFRC-accredited simulation lab, and a baseline sample physically tested in a hot box by an accredited test lab. An NFRC inspection agency compares the two and approves the frames, which are then listed in NFRC's online CMA Software Tool (CMAST). This step is done once per product line, not per project.
• Glass. The glass makers' measured optical data is approved through NFRC's spectral data program and listed in the International Glazing Database.
• Spacers. Simulated and reviewed against drawings and materials; no physical test.
• The project. The architect, engineer or supplier, acting as the Specifying Authority, sends the window schedule to an NFRC Approved Calculation Entity, which combines the approved frame, glass and spacer in CMAST, calculates U-factor, SHGC and visible transmittance for each product at its actual size, and issues the label certificate. The certificate is submitted with the energy compliance documents and checked by the plans examiner.

Can it be done for windows that have never been tested? Not for an NFRC rating. Whether the product is labeled unit by unit or through CMA, at least a baseline of the frame line must pass the NFRC hot-box validation test. Without NFRC ratings, a project in the U.S. generally has two options: use the code's default U-factor and SHGC, which are deliberately poor, or ask the building official to accept engineering calculations, such as THERM and WINDOW models prepared to NFRC 100 by a qualified engineer, under the code's provision for alternative methods. Acceptance is at the official's discretion and varies widely, so it should be raised at the start of design. Engineers and energy modelers do use unrated calculations every day for design studies, Passive House models and LEED, but for code compliance the certified rating is what is expected.

How Phius gets its numbers

Phius does not run its own hot-box tests. Its window certification program reviews simulations and publishes component and whole-window values that feed directly into Phius building models. A manufacturer can choose one of two paths, which Phius treats as equivalent:

• Blue Path (NFRC method). For products that already carry full NFRC certification. An NFRC-accredited simulation lab with a Phius-trained simulator converts the existing NFRC models to Phius conditions, and Phius reviews the files.
• Orange Path (European method). For products without NFRC certification, often imported windows. A Phius-trained simulator recalculates the window to European standards (EN 673 for glass, EN 410 for solar gain, ISO 10077-2 for frame and spacer), and Phius reviews it. No NFRC certification or physical thermal test is required.

Either way, Phius publishes the frame U-value, the spacer heat loss (psi), the center-of-glass U-value and SHGC, the whole-window U-value and SHGC at standard sizes, condensation resistance and air leakage (ASTM E283 or EN 1026). Phius calculates glass performance for each climate zone, because insulating glass performs differently at different temperatures, and awards a recommendation checkmark for each zone where the window meets the Phius target. The same window data serves single-family, multifamily and non-residential projects.

These are recommendations, not entry requirements. The project's own energy model decides what each building needs. Phius also sets a window comfort limit for every project regardless of size, a maximum U-value based on window height and the local design temperature, along with interior surface temperature limits that guard against condensation.

How the Passive House Institute gets its numbers

PHI certifies windows as Certified Passive House Components. The frame is simulated to EN ISO 10077-2, the glass is calculated to EN 673, and the spacer's edge heat loss is calculated for the glass and frame combination. PHI or its accredited partners check the calculations and issue the certificate. Results are reported at PHI's reference size of 1.23 × 1.48 m.

To be certified, a window must meet climate-zone criteria. In the cool, temperate zone, which covers much of the northern United States and southern Canada, the window must reach U_w ≤ 0.80 W/m²·K (about 0.14 Btu/h·ft²·°F) and a temperature factor f_Rsi ≥ 0.70 to prevent condensation and mold. Products are graded into efficiency classes, from phA+ at the top down to phC, according to how much heat the frame loses. PHI certificates also give installation heat-loss values (psi-install) for typical wall types, used directly in the PHPP energy model. PHI component certification applies equally to houses, apartment buildings and non-residential buildings.

How CSA gets its numbers

CSA A440.2, with its companion A440.3 user guide, is Canada's standard for window energy performance. It uses the same LBNL THERM and WINDOW tools and the same −18 °C / 21 °C conditions as NFRC, so the U-factors are close, but the standard sizes and some details differ. CSA adds two values NFRC does not:

• Energy Rating (ER). A single number that combines heat loss, useful solar gain and air leakage. It was designed for houses and low-rise residential buildings; ENERGY STAR Canada accepts either a U-factor or an ER. It is not used for Part 3 buildings.
• Temperature Index (I-value). An optional condensation rating, useful for any building type. See Condensation Resistance.

Products are certified by a certification body accredited by the Standards Council of Canada and carry its mark.

Where measured material data fits in

All four systems model the frame on a computer, and every model is only as good as the material data put into it. Our polyurethane fiberglass was tested by Intertek, one of the largest accredited testing and certification companies in North America, at a thermal conductivity of 0.114 W/m·K. A measured value from an accredited lab can stand in for generic reference values: NFRC procedures provide for measured material properties, PHI accepts them, and Phius can approve them. The result is a simulation that reflects the actual material instead of a conservative textbook figure for "fiberglass."

Structural and weather testing is separate

Thermal ratings say nothing about wind load, air leakage or water penetration. Those are proven by physical testing under the North American Fenestration Standard (NAFS), with impact testing in hurricane regions. In the U.S., houses and townhouses are covered by the International Residential Code, while apartment buildings of every height, hotels and commercial buildings are covered by the International Building Code; both require NAFS ratings for windows within its scope. See Structural & Weather Ratings for the full picture, including design pressure, curtain wall and location-specific rules.

United States: houses and low-rise residential

Detached houses, townhouses, and apartment buildings and dormitories three stories or fewer.

• Energy code. The IECC residential provisions (or the energy chapter of the International Residential Code) require NFRC-rated U-factor and SHGC. A window without NFRC ratings must use the code's default values, which are deliberately poor.
• Who checks. The plans examiner reviews REScheck or the energy rating index report and the window schedule. The building inspector checks the temporary NFRC label left on each window until inspection. On houses and townhouses, a HERS rater often verifies windows too.
• ENERGY STAR. ENERGY STAR-labeled windows (Version 7) are a residential product program. ENERGY STAR Single-Family New Homes and many utility rebates rely on NFRC-certified values.
• Phius. Houses and townhouses certify under Phius CORE, and simple single-family homes can use the Phius CORE Prescriptive path, which is limited to single-family attached or detached homes. Phius requires single-family and townhouse projects to also earn ENERGY STAR, EPA Indoor airPLUS and DOE Efficient New Homes (formerly Zero Energy Ready Home) certification, all of which work from NFRC-rated values. These are voluntary federal programs; they become mandatory only because Phius makes them part of its certification.
• PHI. The certifier needs PHI component data or equivalent European calculations; the building department still needs NFRC values.

United States: multifamily, hotels, dormitories, labs and other commercial buildings

Apartment buildings and dormitories four stories or more, and all hotels, offices, laboratories, schools and other non-residential buildings.

• Energy code. The IECC commercial provisions or ASHRAE 90.1 require NFRC-rated U-factor, SHGC and visible transmittance. Windows may be individually labeled, or the project may use an NFRC label certificate under the Component Modeling Approach. Unrated products fall back to default values. Many projects comply through an energy model (the performance path), which still uses the rated window values.
• Who checks. The plans examiner reviews COMcheck or the energy model, and the window schedule. Rather than looking at stickers, commercial reviewers typically rely on submittals: NFRC label certificates or Certified Products Directory listings, shop drawings and test reports, reviewed by the architect of record and often a third-party energy reviewer or commissioning agent. Some jurisdictions require building envelope commissioning or field testing of air leakage and water penetration.
• ENERGY STAR. ENERGY STAR window labels do not apply to commercial buildings. Apartment buildings of any height can earn ENERGY STAR Multifamily New Construction, which certifies the building and uses the rated window values in its model or prescriptive path.
• Phius, multifamily. Apartment buildings, dormitories, residence halls, senior and supportive housing certify under Phius CORE and must also meet ENERGY STAR Multifamily New Construction and EPA Indoor airPLUS. Phius used to require these projects to also earn DOE Efficient New Homes Multifamily certification (formerly Zero Energy Ready Home). That was Phius's own rule, not a DOE mandate: DOE's program is voluntary, and Phius chose to make it a co-requisite. In 2026 Phius suspended that requirement indefinitely for multifamily, dormitory, residence hall, senior and supportive housing projects, while still requiring most of the DOE checklist items within its own review.
• Phius, non-residential. Offices, laboratories, schools and other non-residential buildings certify under Phius CORE COMM or Phius ZERO COMM. Hotels and mixed-use buildings should confirm with Phius which standard and which co-requisite programs apply.
• PHI. PHI certifies all building types through accredited certifiers using PHPP. NFRC values are still needed for the permit.
• On-site verification. A Phius Certified Verifier inspects multifamily and non-residential Phius projects; PHI certifiers review photo documentation and test results.

Where Passive House is written into code or funding.

• Massachusetts. Under the Stretch Code, Phius or PHI certification is a compliance path for any building type, and multifamily buildings over 12,000 ft² that do not pursue Passive House or HERS must meet demanding heating-demand (TEDI) limits. Under the Specialized Opt-in Code, adopted by about 60 cities and towns including Boston and Cambridge, multifamily buildings over 12,000 ft² must meet Passive House standards. Mass Save offers per-unit incentives for certified projects of five units or more.
• Washington State. Offers an alternative compliance path for certified projects under its residential energy code, which covers houses and low-rise residential.
• New York. NYSERDA programs have funded Passive House multifamily, and New York City has a large and growing stock of Passive House apartment buildings.
• Affordable housing. Pennsylvania introduced bonus points for Passive House in its Low-Income Housing Tax Credit allocation plan, and a number of other state housing agencies have followed with points or incentives, almost always for multifamily.
• Utilities. Programs such as Xcel Energy's Marshall Fire rebuild rebates in Colorado, for houses, and Energize Connecticut support certified projects.

For state-by-state and city-by-city detail, see Codes by State, Province & City.

Even where Passive House certification satisfies the energy code, plans examiners may still ask for rated window values. Ask the building department early how it will verify windows on a certified project.

Is ENERGY STAR ever required?

ENERGY STAR is a voluntary federal program. No building code requires it, and an ordinary market-rate apartment building, hotel or office never has to be ENERGY STAR certified. It becomes a requirement only when something else makes it one:

• Affordable housing finance. State housing finance agencies set green requirements in their Low-Income Housing Tax Credit allocation plans. North Carolina and Kansas, for example, require ENERGY STAR for new construction, and many other states require Enterprise Green Communities, whose criteria call for an energy certification such as ENERGY STAR, a DOE program or Passive House.
• Other certifications. Phius requires ENERGY STAR for its residential projects, and some green building programs use it as a prerequisite.
• Utility and city incentives. Many rebates and density or fee incentives are tied to ENERGY STAR or an equivalent.
• Federal programs. HUD's HOME and Housing Trust Fund programs require minimum energy codes, not ENERGY STAR, and a 2024 rule that would have raised codes for FHA and USDA lending was rescinded in 2026. The federal 45L tax credit, which paid developers per unit for ENERGY STAR and DOE-certified homes and apartments, ended for units acquired after June 30, 2026.

How a building gets certified. The developer signs a free partnership agreement with the EPA, then hires a certified rater early in design. For apartment buildings, ENERGY STAR Multifamily New Construction offers three paths: an energy rating index path, unit by unit; an ASHRAE path, modeled against ASHRAE 90.1; and a prescriptive path. The rater reviews the design, inspects and tests during construction, and a functional testing agent checks the HVAC systems. A Multifamily Review Organization or rating oversight body reviews the file and issues the certificates. The owner pays the rater, modeler and review fees; there is no EPA fee. Windows simply need NFRC-rated values that meet the chosen path.

ENERGY STAR for windows is a separate, product-level label for residential windows, earned by the manufacturer through NFRC certification. It does not apply to commercial buildings.

Canada: houses and small buildings (Part 9)

Up to three storeys and 600 m²: houses, townhouses, small apartment buildings and small commercial buildings.

• Energy code. The prescriptive energy path in Section 9.36 requires window U-values determined under either CSA A440.2/A440.3 or NFRC 100 and 200. Unlike U.S. codes, Canadian codes accept both systems. Under performance paths, such as the BC Energy Step Code, window values feed an energy model, and a British Columbia appeal decision confirmed that these paths do not require labeled values in the same way.
• Structural and weather. NAFS with CSA A440S1, with manufacturer marking and a performance label.
• Who checks. The municipal plans examiner and building inspector, and an energy advisor on Step Code and performance-path projects.
• ENERGY STAR Canada. Run by Natural Resources Canada for residential windows, qualifying by U-factor or Energy Rating through an accredited certification body. British Columbia also regulates the energy performance of windows sold for houses through its Energy Efficiency Standards Regulation.

Canada: larger buildings (Part 3)

Over three storeys or 600 m², which in practice includes most hotels, residence halls, laboratories, schools and healthcare buildings.

• Energy code. The NECB or a provincial equivalent, such as Ontario's SB-10 or the BC Energy Step Code steps for Part 3 buildings. Window performance comes from CSA or NFRC values, usually in an energy model prepared by the design team.
• Structural and weather. Specified by the architect or engineer of record and confirmed through submittals, testing and field review, rather than unit labels.
• Who checks. The building official, the registered professionals of record, and, where required, an energy modeler and building envelope consultant.

Passive House in Canada

Both standards are used for every building type. PHI's standard is supported by Passive House Canada, which provides training and works with policymakers. The BC Energy Step Code, which has separate steps for Part 9 and Part 3 buildings, recognizes Passive House at its top steps, and Vancouver has required Passive House or an equivalent zero-emission standard for city-owned buildings and city-funded affordable housing. Phius also certifies Canadian projects, has a Canadian chapter, Phius Alliance Canada, and publishes climate data for Canadian locations. Phius's co-requisite programs, such as ENERGY STAR and EPA Indoor airPLUS, are American programs, so Canadian teams should confirm current requirements with Phius at the start of a project. In both countries, the permit still needs code-recognized window values.

Who's who in Passive House

• Passive House Institute (PHI), Germany. Created the Passive House standard in the 1990s. Sets the standard, certifies buildings through accredited certifiers worldwide, certifies components such as windows, and publishes the PHPP energy modeling tool.
• Phius, United States. Founded in 2007 as the Passive House Institute US and independent of PHI since 2011. Phius writes its own climate-specific standards: Phius CORE and Phius ZERO for residential and multifamily, CORE COMM and ZERO COMM for non-residential buildings, and CORE Prescriptive for single-family homes. It certifies buildings, windows and doors; trains and credentials Certified Passive House Consultants (CPHC), raters and verifiers; and works on public policy. It is both a standards body and a product certifier.
• Passive House Network (PHN). A U.S. nonprofit, formerly the North American Passive House Network, aligned with PHI's international standard. It focuses on education, conferences, research and policy. It does not certify buildings or products.
• Regional groups. Organizations such as Passive House Massachusetts, New York Passive House, Passive House California and Passive House Canada offer local training and advocacy and help shape state and provincial policy.

Which rating does my project need?

Where GlasFëns stands

Our GR85 window is a Certified Passive House Component under PHI, certified for the cold and the cool, temperate climate zones in the top efficiency class, phA, with installation values for three wall types. Our polyurethane fiberglass has an Intertek-measured thermal conductivity of 0.114 W/m·K. NFRC and CSA certification of our F-Series is in progress; until each label is issued, we publish whole-window values calculated in LBNL THERM and WINDOW to NFRC 100 at NFRC standard sizes, marked Calculated. Our A-Series hurricane line carries Florida Product Approvals, and two systems also carry Miami-Dade NOAs.

Most of our work is multifamily, hospitality, education and laboratory buildings, where windows are documented through submittals and project-specific data rather than unit stickers. Tell us where your project is, what type of building it is, and which certification you are pursuing. We will provide the PHPP or WUFI Passive inputs, calculated values, shop drawings and documentation your certifier, architect and building department need. Contact us.

Summarized from published NFRC, Phius, PHI, CSA, ICC and NRC documents as of 2026. Codes, thresholds, adoption and program rules change and are amended locally; confirm current requirements with the authority having jurisdiction and the certifying organization.