Prescriptive Requirements for Vertical Fenestrations as per ECBC 2017

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For all climatic zones, vertical fenestration compliance requirements for all three incremental energy efficiency levels, i.e. ECBC, ECBC+, and SuperECBC, shall comply with the following:

(a) Maximum allowable Window Wall Ratio (WWR) is 40% (applicable to buildings showing compliance using the Prescriptive Method, including Building Envelope Trade-off Method)

(b) Minimum allowable Visual Light Transmittance (VLT) is 0.27

(c) Assembly U-factor includes both frame and glass area weighted U-factors

(d) Assembly SHGC includes both frame and glass area weighted SHGC

How to calculate WWR?

Window to wall ratio is the ratio of total glazing area to the gross exterior wall area.
What is Visual Light transmittance (VLT) ?
Visible light transmission indicates the percentage of the visible portion of the solar spectrum that is transmitted through a given glass product.

Preliminary Requirements for Vertical Fenestration

Vertical fenestration shall comply with the maximum Solar Heat Gain Coefficient (SHGC) and U-factor requirements of given tables below. Vertical fenestration on non-cardinal direction, shall be categorized under a particular cardinal direction if its orientation is within ± 22.5° of that cardinal direction.

Following are the maximum u-value and SHGC for ECBC compliant, ECBC+ & Super ECBC compliant building:

Vertical Fenestration Assembly U-factor and SHGC Requirements for ECBC Buildings

Vertical Fenestration U-factor and SHGC Requirements for ECBC+ buildings and SuperECBC buildings