Section 140.3 Prescriptive Requirements for Building Envelopes

A building complies with this section by being designed with and having constructed to meet all prescriptive requirements in Subsection (a) and the requirements of Subsection (c) where they apply.

(a) Envelope component requirements.

1. Exterior roofs and ceilings. Exterior roofs and ceilings shall comply with each of the applicable requirements in this subsection:

   1. Roofing products. Shall meet the requirements of Section 110.8 and the applicable requirements of Subsections i through ii:

      1. Nonresidential buildings:

         1. Low-sloped roofs in climate zones 1 through 16 shall have:

            1. A minimum aged solar reflectance of 0.63 and a minimum thermal emittance of 0.75; or
            2. A minimum solar reflectance index (SRI) of 75.

            Exception 1 to Section 140.3(a)1Aia: Wood-framed roofs in climate zones 3 and 5 are exempt from the requirements of Section 140.3(a)1Aia if the roof assembly has a U-factor of 0.034 or lower.

            Exception 2 to Section 140.3(a)1Aia: Roof constructions that have thermal mass with a weight of at least 25 lb/ft² over the roof membrane are exempt from the requirements of Section 140.3(a)1Aia.

            Exception 3 to Section 140.3(a)1Aia: An aged solar reflectance less than 0.63 is allowed provided the maximum roof/ceiling U-factor in Table 140.3 is not exceeded.

         2. Steep-sloped roofs in climate zones 1 through 16 shall have a minimum aged solar reflectance of 0.20 and a minimum thermal emittance of 0.75, or a minimum SRI of 16.

      2. High-rise residential buildings and hotels and motels:

         1. Low-sloped roofs in Climate Zones 9, 10, 11, 13, 14 and 15 shall have a minimum aged solar reflectance of 0.55 and a minimum thermal emittance of 0.75, or a minimum SRI of 64.

            Exception to Section 140.3(a)1Aiia: Roof constructions that have thermal mass with a weight of at least 25 lb/ft² over the roof membrane.

         2. Steep-sloped roofs in climate zones 2 through 15 shall have a minimum aged solar reflectance of 0.20 and a minimum thermal emittance of 0.75, or a minimum SRI of 16.

         Exception to Section 140.3(a)1A: Roof area covered by building integrated photovoltaic panels and building integrated solar thermal panels are not required to meet the minimum requirements for solar reflectance, thermal emittance, or SRI.

   2. Roof insulation. Roofs shall have an overall assembly U-factor no greater than the applicable value in Table 140.3-B, C or D, and where required by Section 110.8(e), insulation shall be placed in direct contact with a continuous roof or drywall ceiling.
2. Exterior walls. Exterior walls shall have an overall assembly U-factor no greater than the applicable value in Table 140.3-B, C or D.
3. Demising walls. Demising walls shall meet the requirements of Section 120.7(b)7.
4. Exterior floors and soffits. Exterior floors and soffits shall have an overall assembly U-factor no greater than the applicable value in Table 140.3-B, C or D.

5. Fenestration.Vertical windows shall:

   1. Have (1) a west-facing area no greater than 40 percent of the gross west-facing exterior wall area, or 6 feet times the west-facing display perimeter, whichever is greater; and (2) a total area no greater than 40 percent of the gross exterior wall area, or 6 feet times the display perimeter, whichever is greater; and

      Exception to Section 140.3(a)5A: Window area in demising walls is not counted as part of the window area for this requirement. Demising wall area is not counted as part of the gross exterior wall area or display perimeter for this requirement.

   2. Have an area-weighted average U-factor no greater than the applicable value in Table 140.3-B, C or D.

      Exception to Section 140.3(a)5B: For vertical fenestration containing chromogenic type glazing:

      1. The lower-rated labeled U-factor shall be used with automatic controls to modulate the amount of heat flow into the space in multiple steps in response to daylight levels or solar intensity; and
      2. Chromogenic glazing shall be considered separately from other fenestration; and
      3. Area-weighted averaging with other fenestration that is not chromogenic shall not be permitted.

   3. Have an area-weighted average relative solar heat gain coefficient, RSHGC, excluding the effects of interior shading, no greater than the applicable value in Table 140.3-B, C or D.

      For purposes of this paragraph, the relative solar heat gain coefficient, RSHGC, of a vertical window is:

      1. the solar heat gain coefficient of the windows; or
      2. Relative solar heat gain coefficient is calculated using Equation 140.3-A, if the window has an overhang that extends beyond each side of the window jamb by a distance equal to the overhang’s horizontal projection.

      Exception 1 to Section 143(a)5C: An area-weighted average relative solar heat gain coefficient of 0.56 or less shall be used for windows:

      1. that are in the first story of exterior walls that form a display perimeter; and
      2. for which codes restrict the use of overhangs to shade the windows.

      Exception 2 to Section 140.3(a)5C: For vertical fenestration containing chromogenic type glazing:

      1. the lower-rate labeled RSHGC shall be used with automatic controls to modulate the amount of heat flow into the space in multiple steps in response to daylight levels or solar intensity to demonstrate compliance with this section; and
      2. chromogenic glazing shall be considered separately from other fenestration; and
      3. area-weighted averaging with other fenestration that is not chromogenic shall not be permitted.

   4. Have an area-weighted average visible transmittance (VT), no less than the applicable value in Tables 140.33-B and C, or Equation 140.3-B, as applicable.

      Exception 1 to Section 140.3(a)5D: When the fenestration’s primary and secondary sidelit daylit zones are completely overlapped by one or more skylit daylit zones, then the fenestration need not comply with Section 140.3(a)5D.

      Exception 2 to Section 140.3(a)5D: If the fenestration’s visible transmittance is not within the scope of NFRC 200, or ASTM E972, then the VT shall be calculated according to Reference Nonresidential Appendix NA6.

      Exception 3 to Section 140.3(a)5D: For vertical fenestration containing chromogenic type glazing:

      1. the higher-rate labeled VT shall be used with automatic controls to modulate the amount of light transmitted into the space in multiple steps in response to daylight levels or solar intensity; and
      2. chromogenic glazing shall be considered separately from other fenestration; and
      3. area-weighted averaging with other fenestration that is not chromogenic shall not be permitted.

   EQUATION 140.3-A

   RELATIVE SOLAR HEAT GAIN, COEFFICIENT, RSHGC
   

   where:

   RSHGC	=	Relative Solar Heat Gain Coefficient.
   SHGCwin	=	Solar Heat Gain Coefficient of the window.
   H	=	horizontal projection of the overhang from the surface of the window in feet, but no greater than V.
   V	=	vertical distance from the window sill to the bottom of the overhang, in feet.
   a	=	-0.41 for north-facing windows, -1.22 for south-facing windows and -0.92 for east- and west-facing windows.
   b	=	0.20 for north-facing windows, 0.66 for south-facing windows and 0.35 for east- and west-facing windows.

   EQUATION 140.3-B

   VERTICAL FENESTRATION MINIMUM VT
   

   where:

   WWR	=	Window wall ratio, the ratio of (i) the total window area of the entire building to (ii) the total gross exterior wall area of the entire building. If the WWR is greater than 0.40, then 0.40 shall be used as the value for WWR in Equation 140.3-B.
   VT	=	Visible transmittance of framed window.

6. Skylights. Skylights shall:

   1. Have an area no greater than 5 percent of the gross exterior roof area (SRR); and

      Exception to Section 140.3(a)6A: Atria over 55 feet high shall have a skylight area no greater than 10 percent of the gross exterior roof area.

   2. Have an area-weighted performance rating U-factor no greater than the applicable value in Table 140.3-B, C or D.

      Exception to Section 140.3(a)6B: For skylights containing chromogenic type glazing:

      1. the lower-rate labeled U-factor shall be used with automatic controls to modulate the amount of heat flow into the space in multiple steps in response to daylight levels or solar intensity; and
      2. chromogenic glazing shall be considered separately from other skylights; and
      3. area-weighted averaging with other skylights that is not chromogenic shall not be permitted.

   3. Have an area-weighted performance rating solar heat gain coefficient no greater than the applicable value in Table 140.3-B, C or D.

      Exception to Section 140.3(a)6C: For skylights containing chromogenic type glazing:

      1. the lower-rated labeled SHGC shall be used to demonstrate compliance with this section; and
      2. chromogenic glazing shall be considered separately from other skylights; and
      3. area-weighted averaging with other skylights that is not chromogenic shall not be permitted.

   4. Have an area-weighted performance rating VT no less than the applicable value in Table 140.3-B or C; and

      Exception to Section 140.3(a)6D: For skylights containing chromogenic type glazing:

      1. the higher-rated labeled VT shall be used with automatic controls to modulate the amount of light transmitted into the space in multiple steps in response to daylight levels or solar intensity and;
      2. chromogenic glazing shall be considered separately from other skylights; and
      3. area-weighted averaging with other skylights that are not chromogenic shall not be permitted.

   5. Have a glazing material or diffuser that has a measured haze value greater than 90 percent, determined according to ASTM D1003 or other test method approved by the Energy Commission.

      Exception to Section 140.3(a)6E: Skylights designed and installed to exclude direct sunlight entering the occupied space by the use of fixed or automated baffles or the geometry of the skylight and light well.

7. Exterior doors. All exterior doors that separate conditioned space from unconditioned space or from ambient air shall have a U-factor not greater than the applicable value in Table 140.3-B, C or D. Doors that are more than one-half glass in area are considered glazed doors.

8. Relocatable public school buildings. In complying with Sections 140.3(a)1 to 7 shall meet the following:

   1. Relocatable public school buildings shall comply with Table 140.3-B for a specific climate zone when the manufacturer or builder of the relocatable public school building certifies that the building is intended for use only in a specific climate zone; or
   2. Relocatable public school buildings shall comply with Table 140.3-D for any climate zone when the manufacturer or builder of the relocatable public school building certifies that the building is intended for use in any climate zone; and

   3. The manufacturer or builder of a relocatable public school building shall certify that components of the building comply with requirements of this section by:

      1. The placement of two (2) metal identification labels on the building, one mechanically fastened and visible from the exterior and the other mechanically fastened to the interior frame above the ceiling at the end of the module, both labels stating (in addition to any other information by the Division of the State Architect or other law) “Complies with Title 24, Part 6 for all climate zones;” and
      2. Identification of the location of the two labels on the plans submitted to the enforcing agency.

9. Air barrier. To meet the requirement of Table 140.3-B, all buildings shall have a continuous air barrier that is designed and constructed to control air leakage into, and out of, the building’s conditioned space. The air barrier shall be sealed at all joints for its entire length and shall be composed of:

   1. Materials that have an air permeance not exceeding 0.004 cfm/ft², under a pressure differential of 0.3 in. w.g. (1.57 psf) (0.02 L/m² at 75 pa), when tested in accordance with ASTM E2178; or

      Exception to Section 140.3(a)9A: Materials in Table 140.3-A shall be deemed to comply with Section 140.3(a)9A, provided all joints are sealed and all of the materials are installed as air barriers in accordance with the manufacturer’s instructions.

   2. Assemblies of materials and components that have an average air leakage not exceeding 0.04 cfm/ft², under a pressure differential of 0.3 in. w.g (1.57 psf) (0.2 L/m² at 75 pa), when tested in accordance with ASTM E2357, ASTM E1677, ASTM E1680 or ASTM E283; or

      Exception to Section 140.3(a)9B: The following materials shall be deemed to comply with Section 140.3(a)9B if all joints are sealed and all of the materials are installed as air barriers in accordance with the manufacturer’s instructions:

      1. Concrete masonry walls that have at least two coatings of paint or at least two coatings of sealer coating.
      2. Concrete masonry walls with integral rigid board insulation.
      3. Structurally insulated panels.
      4. Portland cement or Portland sand parge, or stucco, or a gypsum plaster, each with a minimum ¹/₂ inch thickness.
   3. The entire building has an air leakage rate not exceeding 0.40 cfm/ft² at a pressure differential of 0.3 in w.g. (1.57 psf) (2.0 L/ m² at 75 pa), when the entire building is tested, after completion of construction, in accordance with ASTM E779 or another test method approved by the Commission.

   Exception to Section 140.3(a)9: Relocatable public school buildings.

(b) Reserved.

(c) Minimum daylighting requirement for large enclosed spaces. In climate zones 2 through 15, conditioned enclosed spaces, and unconditioned enclosed spaces that are greater than 5,000 square feet and that are directly under a roof with ceiling heights greater than 15 feet, shall meet the following requirements:

1. A combined total of at least 75 percent of the floor area, as determined in building floor plan (drawings) view, shall be within one or more of the following:

   1. Primary sidelit daylit zone in accordance with Section 130.1(d)1B, or
   2. The total floor area in the space within a horizontal distance of 0.7 times the average ceiling height from the edge of rough opening of skylights.
2. All skylit daylit zones and primary sidelit daylit zones shall be shown on building plans.
3. General lighting in daylit zones shall be controlled in accordance with Section 130.1(d).
4. The total skylight area is at least 3 percent of the total floor area in the space within a horizontal distance of 0.7 times the average ceiling height from the edge of rough opening of skylights; or the product of the total skylight area and the average skylight visible transmittance is no less than 1.5 percent of the total floor area in the space within a horizontal distance of 0.7 times the average ceiling height from the edge of rough opening of skylights.
5. All skylights shall have a glazing material or diffuser that has a measured haze value greater than 90 percent, tested according to ASTM D1003 (notwithstanding its scope) or other test method approved by the Commission.

6. Skylights for conditioned and unconditioned spaces shall have an area-weighted average visible transmittance (VT) no less than the applicable value required by Section 140.3(a)6D.

   Exception 1 to Section 140.3(c): Auditoriums, churches, movie theaters, museums and refrigerated warehouses.

   Exception 2 to Section 140.3(c): In buildings with unfinished interiors, future enclosed spaces for which there are plans to have:

   1. A floor area of less than or equal to 5,000 square feet, or

   2. Ceiling heights of less than or equal to 15 feet.

      This exception shall not be used for S-1 or S-2 (storage), or for F-1 or F-2 (factory) occupancies.

   Exception 3 to Section 140.3(c): Enclosed spaces having a designed general lighting system with a lighting power density less than 0.5 watts per square foot.

   Exception 4 to Section 140.3(c): Enclosed spaces where it is documented that permanent architectural features of the building, existing structures or natural objects block direct beam sunlight on at least half of the roof over the enclosed space for more than 1500 daytime hours per year between 8 a.m. and 4 p.m.