Section 502 – Building Envelope Requirements

502.1 General (Prescriptive).
502.1.1 Insulation and fenestration criteria. The bUilding
thermal envelope shall meet the requirements of Tables
502.2(1) and 502.3 based on the climate zone specified in
Chapter 3. Commercial buildings or portions of commercial
buildings enclosing Group R occupancies shall use the
R-values from the “Group R” column of Table 502.2(1).
Commercial buildings or portions of commercial buildings
enclosing occupancies other than Group R shall use the
R-values from the “All other” column of Table 502.2(1).
Buildings with a vertical fenestration area or skylight area
that exceeds that allowed in Table 502.3 shall comply with
the building envelope provisions ofASHRAE/IESNA 90.1.
502.1.2 V-factor alternative. An assembly with aU-factor,
C-factor, or F-factor equal or less than that specified in
Table 502.1.2 shall be permitted as an alternative to the
R-value in Table 502.2(1) . Commercial buildings or portions
of commercial buildings enclosing Group R occupancies
shall use the U-factor, C-factor, or F-factor from the
“Group R” column of Table 502.1.2. Commercial buildings
or portions of commercial buildings enclosing occupancies
other than Group R shall use the U-factor, C-factor or F-factor
from the “All other” column of Table 502.1.2.
502.2 Specific insulation requirements (Prescriptive).
Opaque assemblies shall comply with Table 502.2(1).
502.2.1 Roof assembly. The minimum thermal resistance
(R-value) of the insulating material installed either between
the roof framing or continuously on the roof assembly shall
be as specified in Table 502.2(1), based on construction
materials used in the roof assembly.
Exception: Continuously insulated roof assemblies where
the thickness of insulation varies 1inch (25 mm) or less and
where the area-weighted Ufactor is equivalent to the same
assembly with the R-value specified in Table 502.2(1).
Insulation installed on a suspended ceiling with removable
ceiling tiles shall not be considered part of the minimum
thermal resistance of the roof insulation.
502.2.2 Classification of walls. Walls associated with the
building envelope shall be classified in accordance with
Section 502.2.2.1 or 502.2.2.2.
502.2.2.1 Above-grade walls. Above-grade walls are
those walls covered by Section 502.2.3 on the exterior of
the building and completely above grade or walls that are
more than 15 percent above grade.
502.2.2.2 Below-grade walls. Below-grade walls covered
by Section 502.2.4 are basement or first-story walls
associated with the exterior of the building that are at
least 85 percent below grade.
502.2.3 Above-grade walls. The minimum thermal resistance
(R-value) of the insulating material(s) installed in the
wall cavity between the framing members and continuously
on the walls shall be as specified in Table 502.2(1), based on
framing type and construction materials used in the wall
assembly. The R-value of integral insulation installed in concrete
masonry units (CMU) shall not be used in determining
compliance with Table 502.2(1). “Mass walls” shall include
walls weighing at least (1) 35 pounds per square foot (170
kg/m2) of wall surface area or (2) 25 pounds per square foot
(120 kg/m2) of wall surface area if the material weight is not
more than 120 pounds per cubic foot (1900 kg/m3).
502.2.4 Below-grade walls. The minimum thermal resistance
(R-value) of the insulating material installed in, or
continuously on, the below-grade walls shall be as specified
in Table 502.2(1), and shall extend to a depth of 10 feet
(3048 mm) below the outside finished ground level, or to the
level of the floor, whichever is less.
502.2.5 Floors over outdoor air or unconditioned space.
The minimum thermal resistance (R-value) ofthe insulating
material installed either between the floor framing or continuously
on the floor assembly shall be as specified in Table
502.2 (1), based on construction materials used in the floor
assembly.
“Mass floors” shall include floors weighing at least (1) 35
pounds per square foot (170 kg/m2) of floor surface area or
(2) 25 pounds per square foot (120 kg/m2) of floor surface
area if the material weight is not more than 12 pounds per
cubic foot (1,900 kg/m3).
502.4 Air leakage (Mandatory).
502.4.1 Window and door assemblies. The air leakage of
window and sliding or swinging door assemblies that are
part of the building envelope shall be determined in accordance
with AAMA/WDMA/CSA 101/I.S.2/A440, or
NFRC 400 by an accredited, independent laboratory, and
502.2.6 Slabs on grade. The minimum thermal resistance
(R-value) of the insulation around the perimeter ofunheated
or heated slab-on-grade floors shall be as specified in Table
502.2 (1). The insulation shall be placed on the outside ofthe
foundation or on the inside of a foundation wall. The insulation
shall extend downward from the top of the slab for a
minimum distance as shown in the table or to the top of the
footing, whichever is less, or downward to at least the bottom
of the slab and then horizontally to the interior or exterior
for the total distance shown in the table.
502.2.7 Opaque doors. Opaque doors (doors having less
than 50 percent glass area) shall meet the applicable requirements
for doors as specified in Table 502.2(1) and be considered
as part ofthe gross area ofabove-grade walls that are
part of the building envelope.
502.3 Fenestration (Prescriptive). Fenestration shall comply
with Table 502.3.
502.3.1 Maximum area. The vertical fenestration area (not
including opaque doors) shall not exceed the percentage of
the gross wall area specified in Table 502.3. The skylight
area shall not exceed the percentage of the gross roof area
specified in Table 502.3.
502.3.2 Maximum V-factor and SHGe. For vertical fenestration,
the maximum V-factor and solar heat gain coefficient
(SHGC) shall be as specified in Table 502.3, based on
the window projection factor. For skylights, the maximum
PF = AlB (Equation 5-1)
labeled and certified by the manufacturer and shall not
exceed the values in Section 402.4.2.
Exception: Site-constructed windows and doors that are
weatherstripped or sealed in accordance with Section
502.4.3.
502.4.2 Curtain wall, storefront glazing and commercial
entrance doors. Curtain wall, storefront glazing and commercial-
glazed swinging entrance doors and revolving
doors shall be tested for air leakage at 1.57 pounds per
square foot (psf) (75 Pa) in accordance with ASTM E 283.
For curtain walls and storefront glazing, the maximum air
leakage rate shall be 0.3 cubic foot per minute per square
foot (cfm/ft2) (5.5 m3/h x m2) of fenestration area. For commercial
glazed swinging entrance doors and revolving
doors, the maximum air leakage rate shall be 1.00 cfm/ft2
(18.3 m3/h x m2) of door area when tested in accordance
with ASTM E 283.
502.4.3 Sealing of the building envelope. Openings and
penetrations in the building envelope shall be sealed with
caulking materials or closed with gasketing systems compatible
with the construction materials and location. Joints
and seams shall be sealed in the same manner or taped or
covered with a moisture vapor-permeable wrapping material.
Sealing materials spanningjoints between construction
materials shall allow for expansion and contraction of the
construction materials.
502.4.4 Hot gas bypass limitation. Cooling systems shall
not use hot gas bypass or other evaporator pressure control
systems unless the system is designed with multiple steps of
unloading or continuous capacity modulation. The capacity
of the hot gas bypass shall be limited as indicated in Table
502.4.4.
Exception: Unitary packaged systems with cooling
capacities not greater than 90,000 Btu/h (26 379 W) .
502.4.5 Outdoor air intakes and exhaust openings. Stair
and elevator shaft vents and other outdoor air intakes and
exhaust openings integral to the building envelope shall be
equipped with not less than a Class I motorized, leakage-
rated damper with a maximum leakage rate of 4 cfm per
square foot (6.8 Lis• C m2) at 1.0 inch water gauge (w.g.)
(1250 Pa) when tested in accordance with AMCA 500D.
Exception: Gravity (nonmotorized) dampers are permitted
to be used in buildings less than three stories in
height above grade.
502.4.6 Loading dock weatherseals. Cargo doors and
loading dock doors shall be equipped with weatherseals to
restrict infiltration when vehicles are parked in the doorway.
502.4.7 Vestibules. A door that separates conditioned space
from the exterior shall be protected with an enclosed vestibule,
with all doors opening into and out of the vestibule equipped
with self-closing devices. Vestibules shall be designed so that
in passing through the vestibule it is not necessary for the interior
and exterior doors to open at the same time.
Exceptions:
1. Buildings in climate Zones 1 and 2 as indicated in
Figure 301.1 and Table 301.1.
2. Doors not intended to be used as a building
entrance door, such as doors to mechanical or
electrical equipment rooms.
3. Doors opening directly from a sleeping unit or
dwelling unit.
4. Doors that open directly from a space less than
3,000 square feet (298 m2) in area.
5. Revolving doors.
6. Doors used primarily to facilitate vehicular movement
or material handling and adjacent personnel
doors.
502.4.8 Recessed lighting. Recessed luminaires installed in
the building thermal envelope shall be sealed to limit air
leakage between conditioned and unconditioned spaces. All
recessed luminaires shall be IC-rated and labeled as meeting
ASTM E 283 when tested at 1.57 psf (75 Pa) pressure
differential with no more than 2.0 cfm (0.944 L/s) of air
movement from the conditioned space to the ceiling cavity.
All recessed luminaires shall be sealed with a gasket or
caulk between the housing and interior wall or ceiling covering.

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