LEAFF is the Linear Energy Analysis for Fenestration. Back in 2011, at an NFRC meeting in Las Vegas, NFRC membership expressed an interest in developing a residential component-based calculation (RCBC) program similar to the component modeling approach (CMA) program that NFRC had developed for the commercial market. It has taken NFRC staff and member volunteers 10 years to develop, research, and approve the methodology for the program that is now rebranded from RCBC to LEAFF.

Recently, the NFRC Board of Directors has approved the continuation of the Linear Energy Analysis for Fenestration (LEAFF) pilot program, with a phased implementation plan and a mandatory adoption deadline of January 1, 2026.

During the Pilot Program, new certifications and re-certifications of existing product lines may use either the non-LEAFF or LEAFF methodologies. Regardless of the methodology chosen, these product lines are entitled to a full 5-year life cycle as prescribed in NFRC 700.

Mandatory Implementation Deadlines:

• Mandatory for Recertified Product Lines by 2026: Starting January 1, 2026, recertified product lines are required to use the LEAFF methodology.
• Mandatory for New Products Lines: As of October 1, 2026, new product lines seeking certification are required to use the LEAFF methodology.

The current methodology requires the modeling or simulating of many individual product options for one product line. For example, a product line with a hundred individual product options could require the modeling of 20 to 100 individual options. By contrast, the LEAFF methodology uses a regression line (trendline) approach based on the center-of-glass (COG) U-factor values.

To calculate the whole product U-factor rating for the 100 individual product options, the simulator will develop the trendlines for all the options, for example, this could be 3 trendlines. The simulator then simply places the COG value for a specific glazing option in the corresponding trendline formula. So, when you look at the product line example with 100 options, and you only have 3 trendlines when using the LEAFF method, the simulator is required to model just 9 options as compared to modeling 20 to 100 options using the current methodology.

We see two major benefits of the LEAFF methodology, the possible reduction in the number of options that will be simulated and a streamlined method that may allow manufacturers to get their new and innovative products to the market quicker.

To take advantage of the new simulation methods, manufacturers will need to request the LEAFF methodology when contacting their lab(s). Only NFRC 701 accredited labs are authorized to provide LEAFF product lines for PCP certification. The LEAFF Certified Simulator is a new tier of certified simulator that requires additional training and evaluation of competence above the standard NFRC Certified Simulator.

Product lines authorized for certification (listed in the CPD) and using non-LEAFF methodology at the time of full implementation of the LEAFF methodology, shall retain a five-year certification cycle. During the entire certification period, the product line may be updated as needed using the non-LEAFF methodology.

Alternatively, a non-LEAFF product line may be converted to the LEAFF methodology through the simple addendum process. This requires all individual product ratings within the product line to be converted.

The LEAFF generated ratings will be compared to the validation test used for the existing certification to determine validation. In this case, the converted product line will retain the remainder of the current five-year certification cycle and retain the current expiration date.

If the original validation test does not validate the LEAFF rating, a new validation test shall be performed, and the expiration date shall be determined per Section 5.6 of the NFRC 700.

As always, participants are permitted to recertify product lines anytime during the certification cycle and per the requirements in Section 5.6 of NFRC 700.

A product line shall not contain ratings determined by both simulation methodologies.

One year after the full implementation of the LEAFF methodology, only the Condensation Index (CI) rating can be included on the NFRC temporary label. The intent is to fully implement the LEAFF methodology on October 1, 2026. Certification participants with non-LEAFF product lines will be required to remove the voluntary Condensation Resistance rating from the NFRC temporary label. The Condensation Resistance values shall remain in the CPD until the certification expires.

During the one-year transition, either the LEAF CI or the non-LEAFF Condensation Resistance rating may be displayed on the NFRC temporary label, not both.

For more information on the LEAFF program and implementation, please contact Scott Hanlon, Director, Residential Programs.