In order to take advantage of mountain views, a designer would like to include large glazing areas in a new home. Energy and Atmosphere Credit…

LEED for Homes treats large areas of glazing as a potential energy penalty. Energy & Atmosphere credit “Windows” (both 2008 and v4 Homes & Multifamily Low-Rise guides) states that if the window-to-exterior-wall-area ratio (WWR) is greater than 24 %, the project must meet more stringent whole-unit U-factor and SHGC requirements (Table EA-Windows-1) to earn the credit. Below that threshold, standard ENERGY STAR window specifications are acceptable. The 24 % value is therefore the trigger for the tightened performance, and it is expressed only relative to the exterior-wall area, not the conditioned-floor area.

A. 15 % WWR is below LEED’s high-glazing threshold; normal ENERGY STAR performance suffices.

B. LEED does not determine this credit with a window-to-floor-area ratio.

D. The 24 % threshold is applied to exterior-wall area, not floor area; this metric is not used in the credit.

1. USGBC. LEED for Homes Reference Guide (2008 Edition, rev. 2010), Energy & Atmosphere Credit – Windows, p. 118, “Projects with WWR > 24 % shall meet the enhanced U-factor/SHGC values in Table EA-W-1.”

2. USGBC. LEED v4 Homes & Multifamily Low-Rise Reference Guide (2013), EA Credit: Windows, Section “Increased Glazing Areas,” p. 318, “If window area > 24 % of gross above-grade wall area, use the more stringent U-factor and SHGC shown in Table 2.”

3. DOE / Lawrence Berkeley National Laboratory course note “High-Performance Residential Fenestration” (University of California extension, 2019), §3.2, citing LEED Homes requirement of 24 % WWR threshold for enhanced glazing performance.