Volume 39, Issue 7,
The Next Move
A Look at NFRC’s Move Toward
Component Modeling for Site-Built Products
by Jim Benney
For the last seven years, the National Fenestration Rating Council (NFRC) has rated non-residential products the old-fashioned way. We created a system modeled closely after the one in use for residential products, with a few important modifications to take into account the different way site-built products in commercial applications are specified, built and installed. All in all, this site-built program had worked pretty well. It brought a whole new
class of products under the NFRC umbrella and provided architects, specifiers, glazing contractors and builders with fair, accurate and credible energy-performance ratings for field-glazed curtainwall and storefront systems. Responsible parties have certified hundreds of non-residential products and generated numerous label certificates.
Still, the program had limits. For one, it wasn’t much help to specifiers and architects as they selected fenestration systems for their projects. It also wasn’t particularly flexible or adaptable when dealing with the complexities of non-residential punched openings and site-built glazing systems.
A New Methodology
In 2001, a group of NFRC members representing non-residential product stakeholders decided to start from scratch. In an attempt to think “outside of the box,” they set aside the site-built program and began outlining a new system for rating non-residential products. Three years of hard work paid off this past March when the NFRC board of directors approved a new technical procedure for rating the energy performance of non-residential products. The procedure will be held until NFRC adopts certification protocols. At the heart of the new system is what we call the component modeling procedure.
Under the existing site-built program, non-residential products are tested, rated and certified at fixed sizes that often have little to do with the actual size of the product being installed. NFRC uses this technique because it recognizes two basic needs:
• To establish a basis for fair comparisons, product to product. As size and aspect ratio change, product ratings will change; therefore standardized sizes are needed to make comparisons meaningful; and
• To provide uniform specimens for validation testing (as required in NFRC’s standards and programs).
Standard sizes also provided the International Energy Conservation Code (and other energy codes) with a realistic basis for setting minimum performance requirements.
The component modeling procedure literally breaks up this requirement for a standard size. Component manufacturers test and rate their products then feed the resulting data into libraries established and maintained by NFRC. Glazing manufacturers feed center-of-glass ratings into the glazing library, spacer manufacturers feed spacer ratings into the spacer library, frame manufacturers provide validated performance ratings for various frame and extrusion types into a frame library and so on. Instead of only providing ratings for one size product, the new system provides (theoretically) an infinite number of permutations when rating an entire system.
Although certification procedures are not yet approved, we expect the new system to work in the following manner:
• Glazing, frame and spacer manufacturers hire NFRC-accredited laboratories to simulate ratings for their individual products (and validate the simulated results with physical testing, just as in the residential system) and feed those ratings into libraries within the NFRC database;
• Independent agencies verify the simulation and submitted data then issue each product a certification authorization
report that lists a unique certified number within the
• Architects, glazing contractors, builders or any other user can log on to the NFRC website, where a web-based tool will guide them through the process of building a site-built
system using component ratings;
• When complete, the user will sign a license agreement, which among other things, designates him or her as the responsible party when it comes to liability resulting from the ratings;
• Once the license is signed (and assuming all required dues have been paid), the responsible party can download and/or print a label certificate for filing in the proper
If a project includes multiple site-built systems, the user will go back and start from the beginning.
Benefits for Architects, Code Compliance
Architects are, arguably, the biggest beneficiaries of the new system, because it frees them from fixed-size constraints. They will be able to know how fenestration size and configuration affect energy performance. Potentially, they could try out different combinations using software designed to simulate performance ratings based on data from the component libraries and note the impact on energy ratings. Finally, in theory, they could design and specify systems right on their computers, ultimately printing label certificates for that system.
Those involved in code compliance will benefit as well. The ratings generated as part of the component modeling procedures allow for fixed-size comparisons and for component performance indices that can be use to calculate not just whole product performance but whole building performance. Label certificates posted onsite typically will note the NFRC standard size rating for the product, allowing for prescriptive compliance, as well as actual envelope performance, allowing for accurate energy calculations needed for other compliance paths.
It’s important to note that this new system for rating non-residential products preserves NFRC’s commitment to whole product performance certification. Manufacturers will rate individual components and may use those ratings in any way they see fit. But any label certificate generated will provide NFRC-certified ratings only for the entire system.
A Glimpse of Things to Come
As the team of non-residential stakeholders within NFRC moved closer to completion of the site-built technical procedure, the simplicity, adaptability and flexibility of the component modeling procedure captured the attention of the entire organization. There’s really no reason why the same component libraries can’t be used to rate actual residential products, too. If the system proves to be successful, a switch to component modeling on the residential side of the organization may be inevitable.
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