C402.4.3 Maximum U-factor and SHGC. The maximum U-factor and solar heat gain coefficient (SHGC) for fenestration shall be as specified in Table C402.4.
The window projection factor shall be determined in accordance with Equation 4-6.
PF = A/B
(Equation 4-6)
Where: | | |
PF | = | Projection factor (decimal). |
A | = | Distance measured horizontally from the furthest continuous extremity of any overhang, eave, or permanently attached shading device to the vertical surface of the glazing. |
B | = | Distance measured vertically from the bottom of the glazing to the underside of the overhang, eave, or permanently attached shading device. |
Where different windows or glass doors have different PF values, they shall each be evaluated separately.
C402.4.3.1 Reserved.
C402.4.3.2 Reserved.
C402.4.3.3 Dynamic glazing. Where dynamic glazing is intended to satisfy the SHGC and VT requirements of Table C402.4, the ratio of the higher to lower labeled SHGC shall be greater than or equal to 2.4, and the dynamic glazing shall be automatically controlled to modulate the amount of solar gain into the space in multiple steps. Dynamic glazing shall be considered separately from other fenestration, and area-weighted averaging with other fenestration that is not dynamic glazing shall not be permitted.
EXCEPTION: | Dynamic glazing is not required to comply with this section where both the lower and higher labeled SHGC already comply with the requirements of Table C402.4. |
C402.4.3.4 Area-weighted U-factor. An area-weighted average shall be permitted to satisfy the U-factor requirements for each fenestration product category listed in Table C402.4. Individual fenestration products from different fenestration product categories listed in Table C402.4 shall not be combined in calculating area-weighted average U-factor.