C402.1.5 Component Performance Alternative
Building envelope values and fenestration areas determined in accordance with Equation 4-2 shall be an alternative to compliance with the U-, F- and C-factors in Tables C402.1.4 and C402.4 and the maximum allowable fenestration areas in Section C402.4.1. Fenestration shall meet the applicable SHGC requirements of Section C402.4.3.
A = Sum of the (UA Dif) values for each distinct assembly type of the building thermal envelope, other than slabs on grade and below-grade walls.
UA Dif = UA Proposed - UA Table.
UA Proposed = Proposed U-value x Area.
B = Sum of the (FL Dif) values for each distinct slab-on-grade perimeter condition of the building thermal envelope.
FL Dif = FL Proposed - FL Table.
FL Proposed = Proposed F-value x Perimeter length.
FL Table = (F-factor specified in Table C402.1.4) x Perimeter length.
CA Dif = CA Proposed - CA Table.
CA Proposed = Proposed C-value x Area.
CA Table = (Maximum allowable C-factor specified in Table C402.1.4) x Area.
Where the proposed vertical glazing area is less than or equal to the maximum vertical glazing area allowed by Section C402.4.1, the value of D (Excess Vertical Glazing Value) shall be zero. Otherwise:
D = (DA x UV) - (DA x U Wall), but not less than zero.
DA = (Proposed Vertical Glazing Area) -(Vertical Glazing Area allowed by Section C402.4.1).
UA Wall = Sum of the (UA Proposed) values for each opaque assembly of the exterior wall.
U Wall = Area-weighted average U-value of all above-grade wall assemblies.
UAV = Sum of the (UA Proposed) values for each vertical glazing assembly.
UV = UAV/total vertical glazing area.
Where the proposed skylight area is less than or equal to the skylight area allowed by Section C402.4.1, the value of E (Excess Skylight Value) shall be zero. Otherwise:
E = (EA x US) - (EA x U Roof), but not less than zero.
EA = (Proposed Skylight Area) - (Allowable Skylight Area as specified in Section C402.4.1).
U Roof = Area-weighted average U-value of all roof assemblies.
UAS = Sum of the (UA Proposed) values for each skylight assembly.
US = UAS/total skylight area.