How to calculate effective SHGC of a window?
For fenestration with a permanent external projection, including but not limited to overhangs, side fins, box frame, verandah, balcony, and fixed canopies that provide permanent shading to the fenestration, the equivalent SHGC for the proposed shaded fenestration may be determined as less than or equal to the SHGC requirements of Table 4-10 in ECBC 2017.
How to calculate effective SHGC?
Equivalent SHGC shall be calculated by following the steps listed below:
Projection factor (PF) for the external permanent projection, shall be calculated as per the applicable shading type listed in chapter 8 in ECBC 2017. The range of projection factor for using the SEF is 0.25≤𝑃𝐹≥1.0. Other shading devices shall be modeled through the Whole Building Performance Method in chapter 9 of ECBC 2017.
A shaded vertical fenestration on a non-cardinal direction, shall be categorized either under a particular cardinal direction or a primary inter-cardinal direction if its orientation is within the range of ±22.5 degrees of the cardinal or primary inter-cardinal direction.
The maximum allowable SHGC is calculated by multiplying the prescriptive SHGC requirement from Table 4-10 with the SEF.
𝑺𝑬𝑭 = (𝐶3×𝑃𝐹3)+(𝐶2 ×𝑃𝐹2)+(𝐶1× 𝑃𝐹)+𝐶0
C3, C2, C1 and C0 are the coefficient of shading equivalent factor (SEF)
Coefficients of Shading Equivalent Factors for Latitudes greater less than 15 ºN