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Performance Standards: National Green Building Standard™

The National Green Building Standard provides recognition for sustainable and energy-saving building practices, including the use of energy-efficient windows, in all types of residential construction. This standard has been developed for by a consensus committee assembled by the National Association of Home Buildersexit disclaimer (NAHB) and the International Code Councilexit disclaimer (ICC).

Windows in the National Green Building Standard

The table below lists the mandatory and optional performance specifications for windows in the prescriptive path of the standard. Up to 13 points can be gained through the use of high-performance windows. For comparison, 30 points are needed in the energy-efficiency category for a home to qualify for the lowest (Bronze) recognition of the standard. The mandatory performance minimum must be fulfilled even if the performance path of the standard is chosen instead of the prescriptive path.

Climate Zones U-factor Windows & Exterior Doors SHGC Windows & Exterior Doors U-factor Skylights & TDDs SHGC Skylights & TDDs Points
1 0.40 0.25 0.60 0.28 1
2 0.40 0.25 0.60 0.28 1
3 0.30 0.25 0.53 0.28 2
4 0.30 0.40 0.53 0.35 3
5 0.27* Any 0.50 Any 3
6 0.27* Any 0.50 Any 4
7 0.27* Any 0.50 Any 4
8 0.27* Any 0.50 Any 4
*An equivalent energy performance is permitted based on fenestration meeting the requirements of Section B. Equivalent Energy Performance in ENERGY STAR Product Specification Residential Windows, Doors, and Skylights, Eligibility Criteria Version 6.0.
Climate Zones U-factor Windows & Exterior Doors SHGC Windows & Exterior Doors U-factor Skylights & TDDs SHGC Skylights & TDDs Points
1 0.38 0.25 0.55 0.28 2
2 0.38 0.25 0.53 0.28 3
3 0.30 0.25 0.50 0.28 4
4 0.28 0.40 0.50 0.35 4
5 0.25 Any 0.48 Any 4
6 0.25 Any 0.48 Any 5
7 0.25 Any 0.46 Any 5
8 0.25 Any 0.46 Any 4

Source: ICC 700-2015 National Green Building Standard

Window energy performance is also supported by credits for sun-tempered or passive solar design, which includes orientation-specific glazing selection, shading, and related design considerations.