Latest Green Building Standard Provides New Pathways to ComplianceMay 6th, 2020 by Drew Vass
The National Association of Homebuilders (NAHB) released its latest ICC-700 National Green Building Standard (NGBS), announcing that the 2020 edition is approved by the American National Standards Institute (ANSI) and available for public download and use. Introduced in 2008, the standard stems from a collaborative effort between NAHB and the International Code Council (ICC), providing architects, builders and developers with parameters for designing and constructing homes and remodeling projects to exceed code requirements in areas pertaining to sustainability via third-party certification. Four levels of certification, ranging from Bronze to Emerald, allow builders and homeowners to receive federal and/or state incentives.
In its fourth edition, the standard now offers an alternative to the existing points-based system, allowing for certification via a new, mandatory checklist of “green practices.” Meanwhile, a newly added chapter, titled “Certified Compliance Path for Single-Family Homes, Townhomes and Duplexes,” provides a compliance path that’s customized for single-family dwellings, officials say, while a “substantially revised” chapter on remodeling offers a choice of prescriptive or performance compliance paths for energy efficiency.
Fenestration is defined by the guide as products that are either vertical or skylights. Vertical fenestration includes windows (fixed or movable), opaque doors, glazed doors, glazed block and combination opaque/glazed doors composed of glass or other transparent or translucent glazing materials, which are installed at a slope of at least 60 degrees from horizontal.
Under the guidelines for new construction, in the category of resource efficiency, enhanced durability and reduced maintenance, exterior door assemblies earn a maximum of six points when covered and protected from the effects of precipitation and solar radiation. Protective measures include storm doors, porch or roof awnings, or roof overhangs. Alternatively, doors can be recessed for the same purposes.
Under minimum energy efficiency requirements, when tested in accordance with NFRC 400 or AAMA/WDMA/CSA 101/I.S.2/A440, air leakage associated with windows, skylights and sliding glass doors is limited to 0.3 cfm per square foot, while swinging doors are limited to no more than 0.5 cfm per square foot.
For a prescriptive path to certification, U-factor requirements for fenestration range from 0.50 to 0.30 for windows and exterior doors across eight climate zones, while solar heat gain coefficient (SHGC) ratings range from 0.40 to 0.25. Dynamic glazing is allowable for meeting SHGC requirements, so long as certain ratio requirements are met and glazing is automatically controlled via a stepped approach to modulating heat gain; the exception includes cases when the lower and higher labeled SHGC settings comply with the requirements established for static glazing.
Enhanced fenestration earns anywhere from one to five points toward accreditation by incorporating U-factors ranging from 0.40 to 0.25, depending on climate zone, and SHGC ratings of 0.40 to 0.25 across five zones (other zones only specify U-factor).
Under the category of Additional Practices, on-site inspection is required for installation, including flashing, caulk and other sealing requirements per manufacturers’ instructions.
Standards for remodeling projects carry the same or similar requirements for air leakage, SHGC, U-factor and protective overhangs.
“Green building and sustainable construction solutions help to maintain the health and safety benefits that building codes and standards provide for communities worldwide,” says ICC CEO Dominic Sims. “The updated NGBS ICC-700 provides designers, contractors, developers and policy makers with the tools and blueprint for green construction strategies and practices. These tools also aid occupant comfort and health, save money and preserve resources during the design, construction and operation of buildings.”
A copy of the full standards can be downloaded at www.nahb.org/ngbs.