Understand how compliant shading affects SHGC checks and why roof lights are assessed separately.
By the end of this lesson you should be able to identify when shading can be counted and when roof-light rules apply.
Where shading is used to satisfy fenestration requirements, it should be a durable external feature or device that can be measured and documented. Temporary curtains or occupant-controlled internal blinds should not be treated the same as fixed external shading.
Overhang-type shading is assessed by comparing projection with the height relationship described by the standard. The point is not only whether shade exists, but whether it is deep enough and wide enough for the relevant facade.
Roof lights bring solar gain through the roof plane and are not checked as ordinary vertical windows. Track roof-light area, U-value and SHGC separately from wall fenestration.
Only select a shading option when the design can be justified from drawings or dimensions. If not, treat it as unshaded until evidence is available.
A single storey has 52 m2 nett floor area and three glazed elements: 1.8 m2 at U 2.8 / SHGC 0.32, 5.0 m2 at U 2.2 / SHGC 0.25, and 1.1 m2 at U 3.0 / SHGC 0.35.
Enter each glazed element with its area, orientation, U-value and SHGC. Use the result cards to check glazing percentage and weighted performance.
The important decision is not only whether the numbers pass, but whether every value can be traced to drawings and supplier data.
Is the shading outside the glazing?
Choose one north-facing window and sketch its overhang.
Flag the missing evidence, use a conservative assumption where appropriate, and avoid claiming compliance until the information is confirmed.
Fencalc XA2021