It is the purpose of this chapter to promote the public health, safety,
and general welfare and to provide construction standards to resist the entry
of radon and prepare buildings for postconstruction radon mitigation. These
radon control methods shall apply only to new construction of homes and buildings
intended for occupancy
For the purpose of this chapter, the terms used shall be defined as
follows:
DRAIN TILE LOOP
A continuous length of drain tile or perforated pipe extending around
all or part of the internal or external perimeter of a basement or crawl space
footing.
SOIL-GAS RETARDER
A continuous membrane of six mil (0.15 mm) polyethylene or other
equivalent material used to retard the flow of soil gases into a building.
SUB-MEMBRANE DEPRESSURIZATION SYSTEM
A system designed to achieve lower sub-membrane air pressure relative
to crawl space air pressure by use of a vent drawing air from beneath the
soil-gas-retarder membrane.
SUB-SLAB DEPRESSURIZATION SYSTEM (PASSIVE)
A system designed to achieve lower sub-slab pressure relative to
indoor air pressure by use of a vent pipe routed through the conditioned space
of a building and connecting the sub-slab area with outdoor air, thereby relying
on the convective flow of air upward in the vent to draw air from beneath
the slab.
The following construction techniques are intended to resist radon entry
and prepare the building for postconstruction radon mitigation, if necessary.
A. Subfloor preparation. A layer of gas permeable material
shall be placed under all concrete slabs and other floor systems that directly
contact the ground and are within the walls of the living spaces of the building
to facilitate future installation of a sub-slab depressurization system, if
needed. The gas-permeable layer shall consist of one of the following:
(1) A uniform layer of clean aggregate, a minimum of four
inches (102 mm) thick. The aggregate shall consist of material that will pass
through a two-inch (51-mm) sieve and be retained by a one-fourth-inch (6.4-mm)
sieve.
(2) A uniform layer of sand (native or fill) a minimum of
four inches (102 mm) thick, overlain by a layer or strips of geotextile drainage
matting designed to allow the lateral flow of soil gases.
(3) Other materials, systems or floor designs with demonstrated
capability to permit depressurization across the entire sub-floor area.
B. Ground cover. A minimum six-mil (0.15-mm) [or three-mil
(0.075-mm) cross-laminated] polyethylene or equivalent flexible sheeting material
shall be placed on top of the gas-permeable layer prior to casting the slab
or placing the floor assembly to serve as a soil-gas retarder by bridging
any cracks that develop in the slab or floor assembly and to prevent concrete
from entering the void spaces at the aggregate base material. The sheeting
shall cover the entire floor area with separate sections of sheeting lapped
at least 12 inches (305 mm). The sheeting shall fit closely around any pipe,
wire or other penetrations of the material. All punctures or tears in the
material shall be sealed or covered with additional sheeting.
C. Entry routes. Potential radon entry routes shall be closed in accordance with Subsection
C(1) through
(10).
(1) Floor openings. Openings around bathtubs, showers, water
closets, pipes, wires or other objects that penetrate concrete slabs or other
floor assemblies shall be filled with a polyurethane caulk or equivalent sealant
applied in accordance with the manufacturer's recommendations.
(2) Concrete joints. All control joints, isolation joints,
construction joints and any other joints in concrete slabs or between slabs
and foundation walls shall be sealed with a caulk or sealant. Gaps and joints
shall be cleared of loose material and filled with polyurethane caulk or other
elastomeric sealant applied in accordance with the manufacturer's recommendations.
(3) Condensate drains. Condensate drains shall be trapped
or routed through nonperforated pipe to daylight.
(4) Sumps. Sump pits open to soil or serving as the termination
point for sub-slab or exterior drain tile loops shall be covered
with a gasketed or otherwise sealed lid. Sumps used as the suction point in
a sub-slab depressurization system shall have a lid designated to accommodate
the vent pipe. Sumps used as a floor drain shall have a lid equipped with
a trapped inlet.
(5) Foundation walls. Hollow block masonry foundation walls
shall be constructed with either a continuous course of solid masonry, one
course of masonry grouted solid, or a solid concrete beam at or above finished
ground surface to prevent passage of air from the interior of the wall into
the living space. Where a brick veneer or other masonry ledge is installed,
the course immediately below that ledge shall be sealed. Joints, cracks or
other openings around all penetrations of both exterior and interior surfaces
of masonry block or wood foundation walls below the ground surface shall be
filled with polyurethane caulk or equivalent sealant. Penetrations of concrete
walls shall be filled. Channel-type drains are not recommended; however, if
used, the joint between the foundation wall and floor slab should be sealed
with backer rods and an elastomeric joint sealant, below the top of the floor
slab, to form a channel. The channel shall be sloped toward the sump in a
manner that retains the channel feature and does not interfere with the effectiveness
of the drain as a water control measure.
(6) Damp-proofing. The exterior surfaces of portions of concrete
and masonry block walls below the ground surface shall be damp-proofed.
(7) Air-handling units. Air-handling units in crawl spaces
shall be sealed to prevent air from being drawn into the unit. Exception:
units with gasketed seams or units that are otherwise sealed by the manufacturer
to prevent leakage.
(8) Ducts. Ductwork passing through a crawl space or beneath
a slab shall be of seamless material unless the air-handling system is designed
to maintain continuous positive pressure within such ducting. Joints in such
ductwork shall be sealed to prevent air leakage.
(9) Crawl space floors. Openings around all penetrations
through floors above crawl spaces shall be caulked or otherwise filled to
prevent air leakage.
(10) Crawl space access. Access doors and other openings or
penetrations between basements and adjoining crawl spaces shall be closed,
gasketed or otherwise filled to prevent air leakage.
D. Passive sub-membrane depressurization system. In buildings
with crawl space foundations, the following components of a passive sub-membrane
depressurization system shall be installed during construction. Exception:
buildings in which an approved mechanical crawl space ventilation system or
other equivalent system is installed.
(1) Ventilation. Crawl spaces shall be provided with vents
to the exterior of the building.
(2) Ground cover. The soil in crawl spaces shall be covered
with a continuous layer of minimum six-mil (0.15-mm) polyethylene ground cover.
The ground cover shall be lapped a minimum of 12 inches (305 mm) at joints
and shall extend to all foundation walls enclosing the crawl space area.
(3) Vent pipe. A plumbing tee or other approved connection
shall be inserted horizontally beneath the sheeting and connected to a three-inch
or four-inch diameter (76 mm or 102 mm) fitting with a vertical vent pipe
installed through the sheeting. The vent pipe shall be extended up through
the building floors, terminate at least 12 inches (305 mm) above the roof
in a location at least 10 feet (3,048 mm) away from any window or other opening
into the conditioned spaces of the building that is less than two feet (610
mm) below the exhaust point, and 10 feet (3,048 mm) from any window or other
opening in adjoining or adjacent buildings.
E. Passive sub-slab depressurization system. In basement
or slab-on-grade buildings, the following components of a passive sub-slab
depressurization system shall be installed during construction.
(1) Vent pipe.
(a) A minimum three-inch diameter (76 mm) ABS, PVC, or equivalent
gas-tight pipe shall be embedded vertically into the sub-slab aggregate or
other permeable material before the slab is cast. A "T" fitting or equivalent
method shall be used to ensure that the pipe opening remains within the sub-slab
permeable material. Alternatively, the three-inch (76-mm) pipe shall be inserted
directly into an interior perimeter drain tile loop or through a sealed sump
cover where the sump is exposed to the sub-slab aggregate or connected to
it through a drainage system.
(b) The pipe shall be extended up through the building floors,
terminate at least 12 inches (305 mm) above the surface of the roof, in a
location at least 10 feet (3,048 mm) away from any window or other opening
into the conditioned spaces of the building that is less than two feet (610
mm) below the exhaust point, and 10 feet (3,048 mm) from any window or other
opening in adjoining or adjacent buildings.
(2) Multiple vent pipes. In buildings where interior footings
or other barriers separate the sub-slab aggregate or other gas-permeable material,
each area shall be fitted with an individual vent pipe. Vent pipes shall connect
to a single vent that terminates above the roof or each individual vent pipe
shall terminate separately above the roof.
F. Vent pipe drainage. All components of the radon vent
pipe system shall be installed to provide positive drainage to the ground
beneath the slab or soil-gas retarder.
G. Vent pipe accessibility. Radon vent pipes shall be accessible
for future fan installation through an attic or other area outside the habitable
space. Exception: The radon vent pipe need not be accessible in an attic space
where an approved rooftop electrical supply is provided for future use.
H. Vent pipe identification. All exposed and visible interior
radon vent pipes shall be identified with at least one label on each floor
and in accessible attics. The label shall read: "Radon Reduction System."
I. Combination foundations. Combination basement/crawl space
or slab-on-grade/crawl space foundations shall have separate radon vent pipes
installed in each type of foundation area. Each radon vent pipe shall terminate
above the roof or shall be connected to a single vent that terminates above
the roof.
J. Building depressurization. The construction shall include
joints in air ducts and plenums in unconditioned spaces, thermal envelope
air infiltration requirements and fire stopping.
K. Power source. To provide for future installation of an
active sub-membrane or sub-slab depressurization system, an electrical circuit
terminated in an approved box shall be installed during construction in the
attic or other anticipated location of vent pipe fans. An electrical supply
shall also be accessible in anticipated locations of system failure alarms.