C402.4.1 Maximum area. The total building vertical fenestration area (not including opaque doors and opaque spandrel panels) shall not exceed 30 percent of the total building gross above-grade wall area. The skylight area shall not exceed 5 percent of the total building gross roof area (skylight-to-roof ratio).
For buildings with more than one space conditioning category, compliance with the maximum allowed window-to-wall ratio and skylight-to-roof ratio shall be demonstrated separately for each space conditioning category. Interior partition ceiling, wall, fenestration and floor areas that separate space conditioning areas shall not be applied to the window-to-wall ratio and skylight-to-roof ratio calculations.
C402.4.1.1 Vertical fenestration maximum area withhigh performance alternates. For buildings that comply with Section C402.4.1.1.1 or C402.4.1.1.2, the total building vertical fenestration area is permitted to exceed 30 percent but shall not exceed 40 percent of the gross above grade wall area for the purpose of prescriptive compliance with Section C402.1.4.
When determining compliance using the component performance alternative in accordance with Section C402.1.5, the total building vertical fenestration area allowed in Equation 4-2 is 40 percent of the above grade wall area for buildings that comply with the vertical fenestration alternates described in this section.
C402.4.1.1.1 Optimized daylighting. All of the following requirements shall be met:
1. Not less than 50 percent of the total conditioned floor area in the building is within a daylight zone that includes daylight responsive controls complying with Section C405.2.4.1.
2. Visible transmittance (VT) of all vertical fenestration in the building is greater than or equal to 1.1 times the required solar heat gain coefficient (SHGC) in accordance with Section C402.4, or 0.50, whichever is greater. It shall be permitted to demonstrate compliance based on the area weighted average VT being greater than or equal to the area weighted average of the minimum VT requirements.
EXCEPTION: | Fenestration that is outside the scope of NFRC 200 is not required to comply with Item 2. |
C402.4.1.1.2 High-performance fenestration. All of the following requirements shall be met:
1. All vertical fenestration in the building shall comply with the following U-factors:
a. U-factor for Class AW windows rated in accordance with AAMA/CSA101/I.S.2/A440, vertical curtain walls and site-built fenestration products (fixed) = 0.34
b. U-factor for Class AW windows rated in accordance with AAMA/CSA101/I.S.2/A440, vertical curtain walls and site-built fenestration products (operable) = 0.36
c. Entrance doors = 0.60
d. U-factor for all other vertical fenestration = 0.28
2. The SHGC of the vertical fenestration shall be less than or equal to 0.35, adjusted for projection factor in compliance with C402.4.3.
An area-weighted average shall be permitted to satisfy the U-factor requirement for each fenestration product category listed in Item 1 of this section. Individual fenestration products from different fenestration product categories shall not be combined in calculating the area-weighted average U-factor.
[Statutory Authority: RCW
19.27A.020,
19.27A.025,
19.27A.160 and chapter
19.27 RCW. WSR 19-24-040, § 51-11C-40231, filed 11/26/19, effective 7/1/20. Statutory Authority: RCW
19.27A.025,
19.27A.160, and
19.27.074. WSR 16-03-072, § 51-11C-40231, filed 1/19/16, effective 7/1/16. Statutory Authority: RCW
19.27A.025,
19.27A.045, and
19.27.074. WSR 13-23-096, § 51-11C-40231, filed 11/20/13, effective 4/1/14. Statutory Authority: RCW
19.27A.020,
19.27A.025 and chapters
19.27 and
34.05 RCW. WSR 13-04-056, § 51-11C-40231, filed 2/1/13, effective 7/1/13.]