# C402.1.5.2 SHGC Rate Calculations

Fenestration SHGC values for individual components and/or fenestration are permitted to exceed the SHGC values in Table C402.4 and/or the maximum allowable fenestration areas in Section C402.4.1 where the proposed total SHGC × A is less than the allowable total SHGC × A as determined by Equation 4-3.

Where:

Proposed Total SHGC × A |
= | SHGC × A-glaz-prop + SHGC × A sky-prop |

Allowable Total SHGC × A |
= | SHGC × A-glaz-allow + SHGC × A-sky-allow |

SHGC × A-glaz-prop |
= | Sum of (proposed SHGC × proposed area) for each distinct vertical fenestration type |

SHGC × A-sky-prop |
= | Sum of (proposed SHGC × proposed area) for each distinct skylight type |

SHGC × A-glaz-allow |
= | Sum of (code maximum vertical fenestration SHGC from Table C402.4, or Section C402.4.1.3 if applicable, × proposed area) for each distinct vertical fenestration type, not to exceed the code maximum area |

SHGC × A-sky-allow |
= | Sum of (code maximum skylight SHGC from Table C402.4 × proposed area) for each distinct skylight type, not to exceed the code maximum area |

If the proposed vertical fenestration area does not exceed the Vertical Fenestration Area allowed, the target area for each vertical fenestration type shall equal the proposed area. If the proposed vertical fenestration area exceeds the Vertical Fenestration Area allowed, the target area of each vertical fenestration element shall be reduced in the base envelope design by the same percentage and the net area of each above-grade wall type increased proportionately by the same percentage so that the total vertical fenestration area is exactly equal to the Vertical Fenestration Area allowed.

If the proposed skylight area does not exceed the Allowable Skylight Area from Section C402.4.1, the target area shall equal the proposed area. If the proposed skylight area exceeds the Allowable Skylight Area from Section C402.4.1, the area of each skylight element shall be reduced in the base envelope design by the same percentage and the net area of each roof type increased proportionately by the same percentage so that the total skylight area is exactly equal to the allowed percentage per Section C402.3.1 of the gross roof area.

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