BUILDING ENVELOPE FENESTRATION MAXIMUM U-FACTOR AND SHGC REQUIREMENTS
|CLIMATE ZONE||1||2||3||4 EXCEPT|
|PF < 0.2||0.25||0.33||0.25||0.33||0.25||0.33||0.40||0.53||0.40||0.53||0.40||0.53||0.45||NR||0.45||N|
|0.2 ≤ PF < 0.5||0.30||0.37||0.30||0.37||0.30||0.37||0.48||0.58||0.48||0.58||0.48||0.58||NR||NR||NR||NR|
|PF ≥ 0.5||0.40||0.40||0.40||0.40||0.40||0.40||0.64||0.64||0.64||0.64||0.64||0.64||NR||NR||NR||NR|
- “N” indicates vertical fenestration oriented within 45 degrees of true north. “SEW” indicates orientations other than “N.” For buildings in the southern hemisphere, reverse south and north. Buildings located at less than 23.5 degrees latitude shall use SEW for all orientations.
In Climate Zones 1 through 6, not more than 40 percent of the gross above-grade wall area shall be permitted to be vertical fenestration, provided all of the following requirements are met:
- In buildings not greater than two stories above grade, not less than 50 percent of the net floor area is within a daylight zone.
- In buildings three or more stories above grade, not less than 25 percent of the net floor area is within a daylight zone.
- Daylight responsive controls complying with Section C405.2.3.1 are installed in daylight zones.
- Visible transmittance (VT) of vertical fenestration is not less than 1.1 times solar heat gain coefficient (SHGC).
Exception: Fenestration that is outside the scope of NFRC 200 is not required to comply with Item 4.
In an enclosed space greater than 2,500 square feet (232 m2) in floor area, directly under a roof with not less than 75 percent of the ceiling area with a ceiling height greater than 15 feet (4572 mm), and used as an office, lobby, atrium, concourse, corridor, storage space, gymnasium/exercise center, convention center, automotive service area, space where manufacturing occurs, nonrefrigerated warehouse, retail store, distribution/sorting area, transportation depot or workshop, the total daylight zone under skylights shall be not less than half the floor area and shall provide one of the following:
- A minimum skylight area to daylight zone under skylights of not less than 3 percent where all skylights have a VT of at least 0.40 as determined in accordance with Section C303.1.3.
- A minimum skylight effective aperture of at least 1 percent, determined in accordance with Equation 4-4.
|Skylight area||=||Total fenestration area of skylights.|
|Skylight VT||=||Area weighted average visible transmittance of skylights.|
|WF||=||Area weighted average well factor, where well factor is 0.9 if light well depth is less than 2 feet (610 mm), or 0.7 if light well depth is 2 feet (610 mm) or greater.|
|Light well depth||=||Measure vertically from the underside of the lowest point of the skylight glazing to the ceiling plane under the skylight.|
Exception: Skylights above daylight zones of enclosed spaces are not required in:
- Buildings in Climate Zones 6 through 8.
- Spaces where the designed general lighting power densities are less than 0.5 W/ft2 (5.4 W/m2).
- Areas where it is documented that existing structures or natural objects block direct beam sunlight on at least half of the roof over the enclosed area for more than 1,500 daytime hours per year between 8 a.m. and 4 p.m.
- Spaces where the daylight zone under rooftop monitors is greater than 50 percent of the enclosed space floor area.
- Spaces where the total area minus the area of daylight zones adjacent to vertical fenestration is less than 2,500 square feet (232 m2), and where the lighting is controlled according to Section C405.2.3.
Skylights in office, storage, automotive service, manufacturing, nonrefrigerated warehouse, retail store and distribution/sorting area spaces shall have a glazing material or diffuser with a haze factor greater than 90 percent when tested in accordance with ASTM D 1003.
Exception: Skylights designed and installed to exclude direct sunlight entering the occupied space by the use of fixed or automated baffles or the geometry of skylight and light well.
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 4-5.
|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.
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.