The U-factor ratings are determined in accordance with ANSI/NFRC 100 by either using a computer modeling simulation methodology or performing a physical hot box thermal test in those rare cases when a product cannot be simulated.

• There are two NFRC standards which cover the procedures to obtain U-Factor ratings. 
• ANSI/NFRC 100 covers the details of the simulation methodology, as well as the overall requirements for obtaining ratings.
• The NFRC 102 is a physical hot box thermal test, which is required by ANSI/NFRC 100 for validation of simulation results or when a product cannot be simulated per the ANSI/NFRC 100 modeling procedures.

The SHGC and VT ratings are determined in accordance with ANSI/NFRC 200 by either using a computer modeling simulation methodology or performing a physical test.

• There are four NFRC standards which cover the procedures to obtain SHGC and/or VT ratings.
  
  
  • ANSI/NFRC 200 covers the details of the simulation methodology as well as the overall requirements for obtaining ratings. For those products which cannot be simulated per the ANSI/NFRC 200 modeling procedures, three additional standards utilizing physical testing procedures have been developed for specific cases.
    
    
    • NFRC 201 is a physical test to determine the SHGC using a solar calorimeter and can be used for any products where simulation methods are not applicable
    • ANSI/NFRC 202 is a physical testing procedure to determine the VT of translucent products ANSI/NFRC 203 is a physical testing procedure to determine the VT of Tubular Daylighting Devices.

Currently NFRC recognizes condensation ratings utilizing both Condensation Resistance and Condensation Index methodologies. Both are determined by either using a computer modeling simulation methodology or performing a physical test.  Both are also calculated for frame, edge-of-glass, and center-of-glass, with the lowest rating used to represent the overall product.

• The original rating, specified in NFRC 500-2017, and being phased out in the coming years, is used to determine the Condensation Resistance rating.   The rating is calculated using an area-weighted summation of the temperature differential of the reference point temperature and dew point temperature from 3 different relative humidity levels (30%, 50%, & 70%).

• The newer rating, specified in ANSI/NFRC 500-2020, is used to determine the Condensation Index (CI).  The CI is calculated by taking a ratio of the difference from the profile's coldest temperature and the ambient exterior air temperature .

Language in IECC’s commercial and residential codes refer to providing U-factor, SHGC, and VT performance ratings in accordance with NFRC’s technical standards, ANSI/NFRC 100 and ANSI/NFRC 200 by an accredited and independent laboratory. In addition to requiring NFRC’s technical standards, IECC also requires the products to be labeled and certified by the manufacturer.

In accordance with IECC’s requirements, the label shall be of an organization concerned with product evaluation that maintains periodic inspection of the production of the labeled items and whose labeling indicates that the product meets identified standards that have been tested and found suitable for a specified purpose.

ASHRAE’s 90.1 references the following performance indices and labeling requirements for fenestration products.

All manufactured fenestration product’s U-factor, SHGC, and VT shall be determined in accordance with NFRC 100, 200, & 300 by a laboratory accredited by nationally recognized accreditation organization, such as NFRC. All manufactured and site-built fenestration and door products shall be labeled and certified, or a signed and dated certificate shall be provided, by the manufacturer, listing the U-factor, SHGC, VT, and AL ratings.

To meet ASHRAE 90.1 requirements, products are labeled with a symbol or other identifying mark attached by the manufacturer indicating compliance with a specified standard or performance in a specified manner.

As with all standards, compliance with ANSI/NFRC 100 requires following all requirements within ANSI/NFRC 100.

After generating a U-factor rating through simulation, the simulation must be validated through the physical testing of a baseline product. Without physically testing the baseline product and ensuring that the simulated values are within the requirements of ANSI/NFRC 100, the ratings are not in compliance with the standard.

Typically, the simulation results are reported separately from the validation test results. Therefore, two reports (one per ANSI/NFRC 100 and one per NFRC 102) are required to prove compliance with the standard. The presence of an official NFRC certification label on the product indicates full compliance to the rating procedures.

You may refer to ANSI/NFRC 100, Section 4.1, for specific compliance direction.  Significant steps are listed below:

• Per Section 4.1.1.B, U-factor rating calculations using the simulation methodology are performed per Sections 4.3.1 and 4.5.

• Per Section 4.1.1.C, a baseline product is determined per Section 4.2.6 and tested for validation purposes per Section 4.3.2.1 (NFRC 102 Test)

• Per Section 4.1.1.D, the simulation values are validated if the U-factor ratings from the simulation and test are deemed equivalent per Section 4.7.1.

• Any simulated ratings NOT validated by physical testing per the above are not compliant with ANSI/NFRC 100 and are neither recognized nor certified by NFRC .

NFRC is a nonprofit organization that administers a voluntary, uniform, fair, accurate, and credible rating, labeling, and certification system for the energy performance of many fenestration products.

NFRC’s product certification programs are based on technical and program documents using independent accredited or licensed entities. NFRC’s programs do not promote self-certification, which is evident by using 3^rd-party independent testing and independent certification agencies of a manufacturer’s product. The rating values are on the label meet the requirements of NFRC’s technical procedures as well as complying with annual product inspections.

The act of applying an NFRC Permanent and Temporary Label or the providing of an NFRC Label Certificate, are equivalent to certifying a product in accordance with NFRC’s programs and recognized by NFRC.