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Building Code Information
SECTION R202
DEFINITIONS
CLOSED CRAWL SPACE
A foundation without wall
vents that uses air sealed walls, ground and foundation moisture
control, and mechanical drying potential to control crawl space
moisture. Insulation may be located at the floor level or at the
exterior walls.
CONDITIONED CRAWL SPACE
A conditioned crawl space is
a foundation without wall vents that encloses an intentionally
heated and/or cooled space. Insulation is located at the exterior
walls.
WALL VENTED CRAWL SPACE
A foundation that uses
foundation wall vents as a primary means to control space moisture.
Insulation is located at the floor level.
SECTION R318
FOAM PLASTIC
R318.2.3 Attics and crawl spaces.
Within attics and crawl
spaces where entry is made only for service of utilities, foam
plastic shall be protected against ignition by 1 ½ -inch –thick
(38mm) mineral fiber insulation, ¼ -inch thick (6.4mm) wood
structural panels, 3/8 –inch (9.5mm) particleboard, ¼ –inch (6.4mm)
hardboard, 3/8 –inch (9.5mm) gypsum board, or corrosion-resistant
steel having a base metal thickness of 0.016 inch (0.406). Within
crawl spaces, foam plastic use is governed by R409.8.2.
SECTION 324
PROTECTION AGAINST TERMITES
R324.4 Crawl spaces.
The use of foam plastic insulation inside of crawl spaces is
governed by R409.8.1.1.
SECTION R408
WALL VENTED CRAWL SPACES
R408.1 Space moisture vapor control.
Vented crawl space
foundations shall be provided with foundation vent openings through
the exterior foundation walls.
R408.1.1 Foundation vent sizing.
The minimum net area of ventilation
openings shall be not less than 1 square foot (0.0929 m2) for each
150 square feet (13.9 m2) of crawl space ground area.
Exception:
The total area of ventilation
openings may be reduced to 1/1,500 of the crawl space ground area
where the required openings are placed so as to provide
cross-ventilation of the crawl space. The installation of operable
louvers shall not be prohibited.
R408.1.2 Foundation vent location.
One foundation vent shall be
within 3 feet (914mm) of each corner of the building. To prevent
rainwater entry when the crawl space is built on a sloped site, the
uphill foundation walls may be constructed without wall vent
openings. Vent dams shall be provided when the bottom of the
foundation vent opening is less than 4 inches above the finished
exterior grade.
R408.1.3 Covering material.
To prevent rodent entry, foundation
vents shall be covered with any of the following materials provided
that the ventilation holes through the covering material shall not
exceed ¼ inch (6.4mm) in any direction:
1. Perforated sheet metal plates not less than 0.070 inch (1.8 mm)
thick.
2. Expanded sheet metal plates not less than 0.047 inch (1.2 mm)
thick.
3. Cast iron grills or grating.
4. Extruded load-bearing brick vents.
5. Hardware cloth of 0.035 inch (0.89 mm) wire or heavier.
6. Corrosion-resistant mesh, with the least dimension being 1/8
inch (3.2 mm)
R408.1.4 Drains and vent terminations.
Drains (including but not
limited to pressure relief and drain pans) shall terminate outdoors,
to crawl space floor drains or interior pumps, and shall not
intentionally discharge water into the crawl space. Crawl space
drains shall be separate from roof gutter drain systems and
foundation perimeter drains. Dryer vents shall terminate outdoors.
R408.1.5 Space separation.
Wall vented crawl spaces shall be
separated from adjoining basements, porches and garages by permanent
solid wall surfaces with all utility penetrations thru the
separating wall sealed. Latched, weather-stripped doors or access
panels shall provide access between the crawl space and such
adjoining spaces.
R408.2. Ground vapor retarder.
Requires full coverage ground vapor
retarders for all wall vented crawl spaces. Wall vented crawl spaces
shall be protected from water entry by the evaporation of water from
the ground surface. A minimum 6-mil (0.15 mm) polyethylene vapor
retarder or equivalent shall be installed to nominally cover all
exposed earth in the crawl space, with joints lapped not less than
12 inches. Where there is no evidence that the groundwater table can
rise to within 6 inches (152 mm) of the floor of the crawl space, it
is acceptable to puncture the ground vapor retarder at low spots to
prevent water puddles from forming on top of the vapor retarder due
to condensation. The floor of the crawl space shall be graded so
that it drains to one or more low spots. Install a drain to daylight
or sump pump at each low spot. Crawl space drains shall be kept
separate from roof gutter drain systems and foundation perimeter
drains.
R408.3 Wall dampproofing.
Where the outside grade is higher than
the inside grade the exterior walls shall be dampproofed from the
top of the footing to the finished grade as required by R406.1.
R408.4 Site grading.
Building site shall be graded to drain
water away from the crawl space foundation per the requirements of
R401.3.
R408.5 Insulation.
The thermal insulation in a wall vented
crawl space shall be placed in the floor system. Wall insulation is
not allowed as the only insulation system in a wall vented crawl
space. The required insulation value can be determined from Table
N1102.1.
R408.6 Floor air leakage control.
All plumbing, electrical,
duct, plenum, phone, cable, computer wiring and other penetrations
through the subfloor shall be sealed with non-porous materials,
caulks or sealants. The use of Rockwool or fiberglass insulation is
prohibited as an air sealant.
R408.7 Duct air leakage control.
All heating and cooling ductwork
located in the crawl space shall be sealed with mastic or other
industry approved duct closure systems.
R408.8 Access.
A minimum access opening measuring 18
inches by 24 inches (457 mm by 610 mm) shall be provided to the
crawl space. See the North Carolina Mechanical Code for access
requirements where mechanical equipment is located under floors.
R408.9 Removal of debris.
The crawl space floor shall be cleaned
of all vegetation and organic material. All wood forms used for
placing concrete shall be removed before a building is occupied or
used for any purpose. All construction materials shall be removed
before a building is occupied or used for any purpose.
R408.10 Finished grade.
The finished grade of the crawl space
may be located at the bottom of the footings; however, where there
is evidence that the groundwater table can rise to within 6 inches
(152 mm) of the finished grade of the crawl space at the perimeter
or where there is evidence that the surface water does not readily
drain from the building site, the grade in the crawl space shall be
as high as the outside finished grade, unless an approved drainage
system is provided.
R408.11 Flood resistance.
For buildings located in areas prone to
flooding as established in Table R301.2 (1), the walls enclosing the
crawl space shall be provided with flood openings in accordance with
Section R327.2.2.
SECTION R409
CLOSED CRAWL SPACES
R409.1 Air sealed walls.
Closed crawlspaces shall be built to
minimize the entry of outdoor air into the crawl space. Specifically
prohibited are foundation wall vents and wall openings to ventilated
porch foundations. When outdoor packaged heating and cooling
equipment is used, solid blocking and sealants shall be used to seal
gaps between the exterior wall opening and the smaller supply and
return ducts that pass through the opening.
R409.1.1 Caulking and sealants.
Air sealing caulk, gaskets or
sealants shall be applied to the foundation wall and floor assembles
that separate the crawl space from outside and other ventilated
areas such as joints around access door and frame, between
foundation and sill plate, at penetrations for plumbing, mechanical,
electrical and gas lines and at duct penetrations.
R409.1.2 Access panel/door.
A minimum access opening measuring 18
inches by 24 inches (457 mm by 610 mm) shall be provided to the
crawl space. See the North Carolina Mechanical Code for access
requirements where mechanical equipment is located under floors. To
minimize air entry, provide a tight fitting access panel/door with a
latch mechanism. Access panels or doors shall be insulated to a
minimum of R-2.
R409.2 Ground vapor retarder.
Closed crawl spaces shall be
protected from water entry by the evaporation of water from the
ground surface.
R409.2.1 Ground vapor retarder.
A minimum 6-mil (0.15 mm)
polyethylene vapor retarder or equivalent shall be installed and
secured to nominally cover all exposed earth in the crawl space,
with joints lapped not less than 12 inches. Minor pockets or
wrinkles that prevent total drainage across the surface of the vapor
retarder are allowed. The floor of the crawl space shall be graded
so that it drains to one or more low spots. Install a drain to
daylight or sump pump at each low spot. Crawl space drains shall be
kept separate from roof gutter drain systems and foundation
perimeter drains.
R409.2.2 Liner.
The ground vapor retarder may be installed as a full interior liner
by sealing the edges to the walls and beam columns and sealing the
seams. Single piece liner systems are approved. The top edge of the
wall liner shall terminate 3 inches below the top edge of the
masonry foundation wall. The top edge of liner shall be brought up
the interior columns a minimum of 4 inches above the crawl space
floor. The floor of the crawl space shall be graded so that it
drains to one or more low spots. Install a drain to daylight or sump
pump at each low spot. Crawl space drains shall be separate from
roof gutter drain systems and foundation perimeter drains.
R409.2.1.1 Wall liner termite
inspection gap. Provide a
clear and unobstructed 3” minimum inspection gap between the top of
the wall liner and the bottom of the wood sill. This inspection gap
may be ignored with regards to energy performance and is not
intended to create an energy penalty.
R409.2.3 Concrete floor surfacing.
The ground vapor retarder
may be protected against ripping and displacement by pouring an
un-reinforced, minimum 2-inch thick, concrete surface directly over
the vapor barrier. A base coarse of gravel or other drainage
material under the ground moisture barrier is not required. The
floor of the crawl space shall be graded so that the concrete
surface drains to one or more low spots. Install a drain to daylight
or sump pump at each low spot. Crawl space drains shall be separate
from roof gutter drain systems and foundation perimeter drains.
R409.2.4 Drains and vent terminations.
Drains (including but not
limited to hot water tank pressure relief and drain pans, and
condensate drain pipes) shall terminate outdoors, to crawl space
floor drains or interior pumps, and shall not intentionally
discharge water into the crawl space. Crawl space drains shall be
separate from roof gutter drain systems and foundation perimeter
drains. Dryer vents shall terminate outdoors.
R409.3 Wall dampproofing.
Where the outside grade is higher than
the inside grade the exterior walls shall be dampproofed from the
top of the footing to the finished grade as required by R406.1.
R409.4 Site grading.
The building site shall be graded to
drain water away from the crawl space foundation per the
requirements of R401.3.
R409.5 Space moisture vapor control.
Closed crawl spaces shall be
provided with a mechanical drying capability to control space
moisture levels. The allowed methods are listed below in R409.5.1 –
R409.5.5. At least one method shall be provided; however,
combination systems shall be allowed.
R409.5.1 Dehumidifier.
A permanently installed dehumidifier
shall be provided in the crawl space. The minimum rated capacity per
day is 15 pints (7.1 Liters). Condensate discharge shall be drained
to daylight or interior condensate pump. Permanently installed
dehumidifier shall be provided with an electrical outlet.
R409.5.2 Supply air.
Supply air from the dwelling air
conditioning system shall be ducted into the crawl space at the rate
of 1 cubic foot per minute (0.5 L/s) per 30 square feet (4.6m2) of
crawl space floor area. No return air duct from the crawl space to
the dwelling air conditioning system is allowed. The crawl space
supply air duct shall be fitted with a backflow damper to prevent
the entry of crawl space air into the supply duct system when the
system fan is not operating. An air relief vent to the outdoors may
be installed. Crawl spaces with moisture vapor control installed in
accordance with this section are not to be considered plenums.
R409.5.3 House air.
House air shall be blown into the crawl
space with a fan at the rate of 1 cubic foot per minute (0.5 L/s)
per 50 square feet (4.6 m2) of crawl space floor area. The fan motor
shall be rated for continuous duty. No return air duct from the
crawl space back to the dwelling air conditioning system is allowed.
An air relief vent to the outdoors may be installed. Crawl spaces
with moisture vapor control installed in accordance with this
section are not to be considered plenums.
R409.5.4 Exhaust fan.
Crawl space air shall be exhausted to
outside with a fan at the rate of 1 cubic foot per minute (0.5 L/s)
per 50 square feet (4.6 m2) of crawl space floor area. The fan motor
shall be rated for continuous duty. There is no requirement for
make-up air.
R409.5.5 Conditioned space.
The crawl space shall be designed as a
heated and/or cooled, conditioned space with wall insulation
installed per the requirements of R409.8.1. Intentionally returning
air from the crawl space to space conditioning equipment that serves
the dwelling shall be allowed. Foam plastic insulation located in a
crawl space plenum shall be protected against ignition by an
approved thermal barrier.
R409.6 Plenums.
Closed crawl spaces used as supply or
return air plenums for distribution of heated or cooled air shall
comply with the requirements of the NC Mechanical Code. Crawl space
plenums shall not contain plumbing cleanouts, gas lines or other
prohibited components. Foam plastic insulation located in a crawl
space plenum shall be protected against ignition by an approved
thermal barrier.
R409.7 Combustion air.
The air sealing requirements of a
closed crawl space may result in a foundation which can not provide
adequate combustion air for fuel-burning appliances; therefore,
fuelburning appliances located in the crawl space such as furnaces
and water heaters shall obtain combustion air from outdoors as per
the NC Mechanical Code.
R409.8 Insulation.
The thermal insulation in a closed
crawl space may be located in the floor system or at the exterior
walls. The required insulation value can be determined from Table
N1102.1
Exception:
Insulation shall be placed at the
walls when the following condition exists: 1. The closed crawl
space is designed to be an intentionally heated or cooled,
conditioned space.
R409.8.1 Wall Insulation.
Where the floor above a closed crawl
space is not insulated, the walls shall be insulated. Wall
insulation can be located on any combination of the exterior and
interior surfaces and within the structural cavities or materials of
the exterior crawl space walls. Wall insulation systems require that
the band joist area of the floor frame be insulated. Wall insulation
shall begin 3 inches below the top of the masonry foundation wall
and shall extend down to 3 inches above the top of the footing or
concrete floor, 3 inches above the interior ground surface or
24-inches below the outside finished ground level, whichever is
less. No insulation shall be required on masonry walls of 9 inches
height or less.
R409.8.1.1 Foam plastic termite
inspection gap. For outside
wall Section R324 governs applications. When expanded polystyrene,
extruded polystyrene, polyisocyanurate, or other foam plastic
insulation is installed on the inside surface of the exterior
foundation walls, provisions R409.8.1.1.1 – 2 below apply.
R409.8.1.1.1 Earth floored crawl
spaces. Provide a clear and
unobstructed 3- inch minimum termite inspection gap between the top
of the foam plastic wall insulation and the bottom of the wood sill.
Because Insulation ground contact is not allowed, provide a
continuous 3-inch minimum clearance gap between the bottom edge of
the foam plastic wall Insulation and the earth floor surface. Refer
to N1102.1.7 to determine maximum allowances for insulation gaps.
R409.8.1.1.2 Concrete floor surfaced
crawl spaces. Provide a
clear and unobstructed 3-inch minimum termite inspection gap between
the top of the foam plastic wall insulation and the bottom of the
wood sill. Provide a continuous 3-inch minimum clearance gap between
the bottom edge of the foam plastic wall Insulation and the concrete
floor surface. Refer to N1102.1.7 to determine maximum allowances
for insulation gaps.
R409.8.1.2 Porous insulation materials.
When fiberglass, rockwool, cellulose or other porous insulation
materials are installed on the inside wall surface of a closed crawl
space, provide a clear and unobstructed 3-inch minimum termite
inspection gap between the top of the porous wall insulation and the
bottom of the wood sill. To reduce wicking potential, porous
insulation ground contact is not allowed in earth floored or
concrete surfaced crawl spaces. Provide a continuous 3-inch minimum
wicking gap between the bottom edge of the porous wall Insulation
and the earth or concrete floor surface. Refer to N1102.1.7 to
determine maximum allowances for insulation gaps.
R409.8.2 Foam plastic fire safety.
Foam plastic insulation may
be installed inside crawl spaces without a thermal cover when the
insulation product has been tested in accordance with ASTM E 84 to
have a flame-spread rating of not more than 25 and a smoke developed
rating of not more than 450. Foam plastics that have not been tested
to meet these ratings shall be protected against ignition by
covering them with a thermal barrier. Acceptable thermal barriers
include but are not limited to ½ inch cement board, metal foil
sheets, metal foil tape, steel or aluminum metal sheets or other
approved materials installed in such a manner that the foam is not
exposed.
Exception:
Foam plastic insulation located in
closed crawl spaces used as conditioned spaces or plenums shall be
protected against ignition by an approved thermal barrier.
R409.9 Floor air leakage control.
All plumbing, electrical,
duct, plenum, gas line and other wiring penetrations through the
subfloor shall be sealed with non-porous materials, caulks or
sealants. The use of rockwool or fiberglass insulation is prohibited
as an air sealant.
R409.10 Duct air leakage control.
All heating and cooling
ductwork located in the crawl space shall be sealed with mastic or
other industry approved duct closure systems.
R409.11 Removal of debris.
The crawl space floor shall be cleaned
of all vegetation and organic material. All wood forms used for
placing concrete shall be removed before a building is occupied or
used for any purpose. All construction materials shall be removed
before a building is occupied or used for any purpose.
R409.12 Finished grade.
The finished grade of the crawl space
floor may be located at the bottom of the footings; however, where
there is evidence that the groundwater table can rise to within 6
inches (152 mm) of the finished grade of the crawl space at the
perimeter or where there is evidence that the surface water does not
readily drain from the building site, the floor in crawl space shall
be as high as the outside finished grade, unless an approved
drainage system is provided.
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