Radon Resistant Construction Standard for Commercial Buildings
Florida Standard for Radon-Resistant New
Commercial Building Construction
January 23, 1996
State of Florida Florida Department of Community Affairs Radon Program 2555
Shumard Oak Blvd Tallahassee, FL 32399-2100 James F. Murley, Secretary
TABLE OF CONTENTS
Chapter Description ONE GENERAL 101 General 102 Intent 103 Scope 104 Compliance
TWO DEFINITIONS 201 General 202 Definitions THREE CONSTRUCTION REQUIREMENTS
FOR PASSIVE CONTROLS 301 General 302 Soil-Gas-Retarder Membrane 303 Concrete
floors In Contact With Soil-Gas 304 Walls In Contact With Soil-Gas 305 Buildings
with Crawl Spaces 306 Space Conditioning Systems and Ventilating 307 Air Distribution
Systems FOUR ACTIVE SOIL-DEPRESSURIZATION SYSTEMS 401 General 402 System Components
403 ASD System Design Requirements
The design and construction requirements set forth in the following chapters
and sections shall constitute and be known as the Florida Standard For Radon-Resistant
Commercial Building Construction, hereinafter referred to as "this standard".
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This standard was developed in accordance with Section 553.98, Florida Statutes,
to minimize radon entry into newly constructed commercial buildings, in compliance
with the state health standard. The design, construction, and operation of buildings
are governed by a variety of codes, standards, guidelines, and regulations.
Nothing in this standard is intended to create a conflict with existing health
and life-safety regulations.
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103.1 Applicability The provisions of this standard shall apply to the design
and construction of new commercial buildings and additions to existing commercial
buildings, except single family and multi-family residential buildings of three
or fewer stories above grade and those identified in Section 104.3. When adopted
by county and local government, this standard shall be applied uniformly countywide.
This standard shall not be modified by a local government or building-regulatory
103.2 Additions When the cost of an addition to an existing building exceeds
50% of the current value of the building; only the addition must be brought
into compliance with all applicable portions of this standard, as defined in
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104.1 General Buildings designed and constructed in accordance with all the
applicable provisions of this standard are deemed to comply.
104.2 New Buildings and Additions All new commercial buildings and additions
to existing buildings shall meet the following compliance requirements of this
(1) Compliance with existing local building codes and the current edition of
the "Florida Energy Efficiency Code for Building Construction".
(2) Use of methods described in Chapters 3 and 4 of this standard.
104.3 Exemptions All buildings described below in items (1) through (5) are
exempted from compliance with this standard. Buildings described in item (6)
are exempted from compliance with Sections 306 and 307, and Chapter 4 of this
standard. Elevated buildings that comply with all provisions of item (7) are
exempted from compliance with other portions of this standard.
(1) Temporary Structures
(2) Free-standing greenhouses used exclusively for the cultivation of live
(3) Open-air reviewing stands, grandstands and bleachers
(4) Farm structures used only for storage or to shelter animals
(5) Residential buildings defined as one-or two-family detached houses or townhouse
apartments with no more than three stories
(6) Buildings of occupancy classification S, Storage, or H, Hazardous (Standard
Building Code designations).
(7) Elevated buildings that satisfy all the following conditions:
(a) The structure shall be separated from the ground by a vertical separation,
measured between the final grade and the lower surface of the floor, of at least
18 inches, and (b) all pilings, posts, piers or other supports shall be solid,
or if hollow, shall be capped by a solid masonry unit or sealed at the surface
of the soil with a construction complying with all applicable portions of Chapter
3 of this standard, and (c) enclosures of any kind, including but not limited
to chases, storage rooms, elevator shafts and stairwells, that connect between
the soil and the structure, shall comply with all applicable provisions of Chapter
3 and shall have a soil contact area of less than five percent (5%) of the projected
building floor area, and (d) the perimeter of the structure, from the ground
plane to the lower surface of the lowest floor shall be totally open for ventilation.
104.4 Required Documentation In order to comply with this standard, all structures
must include in the construction documents provided for permitting, a summary
of the radon-resistant design strategies being implemented in the structure.
Additionally, the building owner shall be provided with a manual substantiating
the radon resistance features. This manual shall include: a summary of the radon-resistant
design strategies incorporated into the structure, a listing of the design specifications
for all relevant motor-driven systems; a maintenance schedule for maintaining
design specifications, including active soil depressurization and heating, ventilating,
and air conditioning systems; and a listing of all critical adjustments, such
as intake-air damper settings.
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For the purpose of this Standard, certain abbreviations, terms, phrases, words
and their derivatives shall be construed as set forth in this chapter. Words
not defined herein shall have the meanings stated in the Standard Building Code,
Standard Mechanical Code, Standard Plumbing Code, Standard Gas Code, Standard
Fire Prevention Code, or the current edition of the "Florida Energy Efficiency
Code For Building Construction". Words not defined in these Codes shall
have the meanings in Webster's Ninth New Collegiate Dictionary, as revised.
When cited throughout this Standard, ASTM and ACI standards refer to the latest
Table of Contents
ACTIVE SOIL-DEPRESSURIZATION - the lowering of air-pressure in the soil, relative
to the atmospheric pressure immediately above ground level.
ACTIVE SOIL-DEPRESSURIZATION SYSTEM - a system designed to lower the air-pressure
in the soil beneath a building, relative to the atmospheric pressure immediately
above ground level, by continuously withdrawing air from below a membrane covering
the soil. An active soil-depressurization system consists of a pressure distribution
manifold, one or more radon vents, an operating fan, and a fan-failure indicator.
ADDITION - an extension or increase in floor area that can be occupied or that
exchange air with the conditioned space of the building.
AND/OR - when referring to a choice of two or more provisions of this standard,
signifies that use of any one provision is acceptable, and that two or more
provisions may also be used together.
APPROVED - accepted by the Building Official or other authority having jurisdiction.
AREA - the maximum horizontally projected area of a building or space, measured
to the outside surface of the enclosing walls.
AUTOMATIC - self- acting, providing an emergency function without human intervention,
and activated as a result of a predetermined event such as an interruption of
air-flow, a change in air-pressure, or the loss of electrical supply.
BACKER ROD - see backup
BACKUP - a compressible material used in the bottom of sealant reservoirs to
reduce the depth of the sealant, thus improving its shape factor. Backup also
serves to support the sealant against sag or indentation while curing.
BLEACHERS - tiered or stepped seating facilities without backrests in which
an area of 3 square feet or less is assigned per person.
BUILDING - any structure that encloses a space used for sheltering any occupancy.
Each portion of a building separated from other portions by a fire wall shall
be considered as a separate building.
BUILDING OFFICIAL - the officer or other designated authority, or their duly
authorized representative, charged with the administration and enforcement of
BUTT JOINT - a non-bonded plain, square joint a keyed joint or a doweled joint
between two members, where primarily movement is at right angles to the plane
of the joint. Sealant in a butt joint will generally be in tension or compression,
but not shear.
CAVITY WALL - a wall built of any combination of materials, so arranged as
to provide a vertical air space within the wall.
COMMERCIAL BUILDING - a structure or building classified according to use by
the Standard Building Code as occupancy groups: A - Assembly, B - Business,
E - Educational, F - Factory Industrial, I - Institutional, M - Mercantile,
and R- Residential (except those already covered by the Florida Standard for
Passive Radon-Resistant New Residential Building Construction).
CONTRACTION JOINT - a formed or sawed groove in a concrete structure, extending
normal to the surface and to a depth of at least one-fourth the thickness of
a concrete element, for the purpose of creating a weakened plane that induces
a crack as internal stresses develop due to drying shrinkage.
CONSTRUCTION JOINT - the surface where two successive placements of concrete
meet and are to be bonded; reinforcement is not interrupted and tie bars are
used as required.
CONTROL JOINT - see contraction joint
CRAWL SPACE - the unconditioned space between the bottom surface of the lowest
floor of a structure and the earth, that is created when the lowest floor of
the structure spans between structural supports rather than being directly supported
by the earth beneath the floor.
CURING - for concrete, the maintenance of a satisfactory moisture content and
temperature during its early stages so that desired properties may develop.
For sealants, the maintenance of a satisfactory moisture content and temperature
while the physical properties of the sealant are changed by chemical reaction.
CURING COMPOUND - a liquid that can be applied as a coating to the surface
of newly placed concrete to retard the loss of water, or in the case of pigmented
compounds, also to reflect heat so as to provide an opportunity for the concrete
to develop its properties in a favorable temperature and moisture environment.
DETERIORATION - the physical manifestation of failure of a material or assembly
(e.g. cracking, delamination, flaking, pitting, scaling) caused by environmental
or internal autogenous influences during testing or service.
DIFFUSION - the movement of radon from areas of high concentration to areas
of low concentration.
ELASTOMERIC SEALANT - a sealant whose macromolecular material returns rapidly
to approximately its initial dimensions and shape after substantial deformation
by a weak stress and release of the stress.
EMANATION - the gaseous elements produced by and given off from the radioactive
disintegration of radium.
EQUILIBRIUM - the condition where the rate of decay of a radioactive parent
isotope is exactly matched by the rate of decay of every intermediate daughter
EXISTING - as applied to a building or structure, one which was erected or
permitted prior to the adoption of this standard.
FOUNDATION WALL - a wall below the first floor extending below the adjacent
ground level and serving as a structural support for a wall, pier, column or
other structural element.
FIELD-MOLDED SEALANT - a liquid or semi-solid material molded into the desired
shape in the joint into which it is installed.
FOOTING - that portion of the foundation of a structure which spreads and transmits
load directly to the piles, or to the soil or supporting grillage.
GASKET - a deformable material clamped between essentially stationary faces
to prevent the passage of air through an opening or joint.
GRADE - the top surface of the ground adjoining the exterior of a building.
GRADE BEAM - a reinforced concrete beam, usually at ground level, to form a
foundation for the walls of a superstructure.
GRANDSTANDS - tiered or stepped seating facilities where an area of more than
3 square feet is provided for each person.
GRANULAR SOIL - a soil with an air permeability greater than or equal to 10-12
GROUT - a mixture of cementitious material and water, with or without aggregate,
proportioned to produce a pourable consistency without segregation of the constituents.
HIGH-RANGE WATER REDUCER - a chemical admixture capable of reducing the water
content of concrete at least 12%. This admixture shall conform to ASTM C494
Type F and/or Type 0.
HOLLOW MASONRY WALL - a wall built of masonry units so arranged as to provide
an air space within the wall.
HONEYCOMB - voids left in concrete due to failure of the mortar to effectively
fill the spaces among course aggregate particles.
ISOLATION JOINT - a non-bonded separation between adjoining parts of a structure,
usually in a vertical plane, designed to allow relative movement in three directions
in order to accommodate differential horizontal or vertical movement without
the development of cracks elsewhere in the structure. May be either a butt joint
or a lap joint, used to structurally separate the floor slab from other building
KEYED - fastened or fixed in position in a notch or other recess.
KEYWAY - a recess or groove in one lift or placement of concrete which is filled
with concrete of the next placement, providing improved shear resistance at
LAITANCE - a layer of weak and nondurable material containing cement and fines
from aggregates, brought by bleeding water to the outer surface of concrete.
LAP - the length by which one material overlays another at a lap joint.
LAP JOINT - a non-bonded joint in which the materials being joined override
each other so that any movement of the materials is primarily parallel to the
plane of the joint, putting sealants in shear rather than tension or compression.
Formed slab joints that are not attached with a keyway are considered to be
MEMBRANE-FORMING CURING COMPOUND - a liquid material that, when applied over
the surface of freshly placed concrete, forms a solid, impervious layer which
holds the mixing water in the concrete.
MANUFACTURED SANDS - sands resulting from the crushing of rock, gravel or slag.
MASONRY - construction composed of shaped or molded units, usually small enough
to be handled by one person and composed of stone, ceramic brick or tile, concrete,
glass, adobe, or the like.
MASTIC - a sealant with putty-like properties.
MEMBRANE - a flexible, continuous sheet. See also: membrane-forming wring compound;
soil-gas-retarder membrane; waterproofing membrane.
MID-RANGE WATER REDUCER - a chemical admixture capable of reducing the water
content of concrete from 6 - 15%. This admixture shall conform to ASTM C494
Type A and/or Type F.
NATURAL SANDS - sands resulting from the natural disintegration and abrasion
NET FREE AREA - when referring to foundation vents, the area determined by
multiplying the overall width and height of the object and subtracting the total
area obstructed by any solid object, such as screen, mesh, louvers, and frame
of the vent.
OPEN-AIR - when referring to reviewing stands, grandstands and bleachers, indicates
a seating facility in which the side toward which the audience faces is without
an enclosing wall.
PICOCURIES PER GRAM - pCi/g, a measure of radioactivity corresponding to 0.037
radioactive disintegrations per second per gram of dry weight of a sample.
PICOCURIES PER LITER - pCi/L, a measure of radioactivity corresponding to 0.037
radioactive disintegrations per second per liter of volume.
PLASTICIZER - see mid-range water-reducer.
POLYETHYLENE - a thermo-plastic high-molecular-weight organic compound often
used in sheet form as a water-vapor retarder.
POLYURETHANE SEALANT - a building sealant consisting primarily of a polyurethane
POLYVINYL CHLORIDE - a synthetic resin used in the manufacture of pipes and
PREFORMED SEALANT - a sealant functionally preshaped by the manufacturer so
that only a minimum of field fabrication is required prior to installation.
PRESSURE SENSITIVE - capable of adhering to a surface without the application
of additional adhesives, when pressed against it.
PSI - pounds force per square inch.
RADIUM (Ra) - a naturally occurring radioactive element resulting from the
decay of uranium. For the purposes of this standard, radium applies to radium-226.
It is the parent of radon gas.
RADON - a naturally occurring, chemically inert, radioactive gas. It is part
of the uranium-238 decay series. For the purposes of this standard radon applies
to radon-222; thus, it is the direct decay product of radium-226.
RADON POTENTIAL - a measure of the potential of soils at a building site for
contributing to indoor radon concentrations.
SEALANT - any material used to seal joints or openings against passage of solids,
liquids, or gases.
SHAFT - a vertical opening extending through one or more stories of a building,
for utilities, an elevator, dumbwaiter, light, ventilation, plumbing or electrical
installation or a similar purpose.
SHAPE FACTOR - the relationship between the depth and width of a field-molded
SOIL-GAS-RETARDER MEMBRANE - a durable, flexible and non-deteriorating material,
installed in a continuous sheet to retard the pressure-driven flow of soil gas
through elements of a structure.
SOLID REINFORCED MASONRY - masonry construction in which mortar, grout or concrete
completely fills all joints and voids and in which steel reinforcement is embedded
in such a manner that the materials act together in resisting forces.
STORY - that portion of a building between the upper surface of a floor and
the upper surface of the floor or roof next above.
STRUCTURE - that which is built or constructed. A structure may contain one
or more buildings separated by fire-rated construction elements in accordance
with prevailing building codes.
SUBGRADE - the soil prepared and compacted to support a structure
SUPERPLASTICIZER - see high-range water reducer
SUPERSTRUCTURE - all of that part of a structure that is above grade.
TEMPORARY STRUCTURE - a structure which is erected, occupied, and disassembled
or otherwise removed from the site within a total time period of 90 calendar
days or less.
WATER-REDUCING ADMIXTURE - a chemical additive to concrete conforming to ASTM
C94 capable of producing a reduction in mixing water or increase in flowability
without causing undue set retardation or entrainment of air in the mortar or
WATERPROOFING MEMBRANE - a liquid sealing compound (e.g., bituminous and paraffinic
emulsions, coal tar cut-backs, etc.) or non-liquid protective coatings (e.g.,
sheet plastics, etc.) used separately or together in a manner which renders
the structural surface to which they are applied essentially impervious to water
in either the liquid or vapor state.
WATERSTOP - a diaphragm used across a joint as a sealant, usually manufactured
specifically to prevent the passage of water through joints in concrete structures.
WORKING LEVEL (WL) - a measure of radioactive exposure equal to the total quantity
of radon decay products in one liter of air that will result in the ultimate
emission of 1.3 x 105 MeV (million electron volts) of energy from alpha particles.
In perfect equilibrium, 1 WL equals 100 pCi/L (picoCuries per liter). It is
often assumed that the air inside buildings is not in equilibrium, and that
only half the radon daughters are moving freely in the air, while half are attached
to dust or building surfaces. When this condition exists, an equilibrium ratio
of 0.5 is said to exist. At an equilibrium ratio of 0.5, 1 WL = 200 pCi/L. For
purposes of this standard, 1 WL is defined as equal to 200 pCi/L.
ZONE - that portion of a building in which the HVAC system is controllable
from a single point.
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FOR PASSIVE CONTROLS
Construction to these standards will limit radon entry points through building
floors, walls, and foundations and will limit mechanical depressurization of
buildings, which can enhance radon entry. Structural radon barriers are primarily
intended to stop the pressure-driven flow of soil-gas through unsealed cracks
and openings in the foundation and/or floor and into the building. Barriers
can also be effective in controlling the diffusion of radon through materials
and the emanation of radon from materials. An acceptable degree of redundancy
and reliability is achieved only when these components are implemented as part
of an integrated system of radon-resistance as prescribed by this standard.
All structures shall be isolated from the soil by an approved structural barrier
as defined by the applicable portions of this standard. No crack, joint, duct,
pipe, conduit, chase or other opening in the building foundation or floor shall
be allowed to connect soil-gas to a conditioned space or to the interior space
of an enclosed space that is either adjacent to, or connected to, a conditioned
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302 Soil-Gas-Retarder Membrane
302.1 Membrane Materials Acceptable soil-gas-retarder membranes shall consist
of a single layer of polyethylene, not less than 0.006-inch (6 mils) thick with
a maximum perm rating of 0.3. Polyvinyl chloride (PVC), ethylene propylene diene
ter polymer (EPDM), neoprene or other non-deteriorating, non-porous material
may be used instead of polyethylene, provided the installed thickness of the
alternate material has greater or equal tensile strength, resistance to water-vapor
transmission, resistance to puncture, and resistance to deterioration determined
in accordance with ASTM E 154. The membrane shall be placed to minimize seams
and to cover all of the soil below the building floor.
302.2 Tape Tape used to install the soil-gas retarder shall have a minimum
width of 2 inches and shall be pressure sensitive vinyl or other non-deteriorating
pressure sensitive tape compatible with the surfaces being joined. Paper tape
and/or cloth tape shall not be used for these purposes.
302.3 Mastic Mastic used to install the soil-gas retarder shall be compatible
with the surfaces being joined, and shall be installed in accordance with the
manufacturer's recommendations for the materials, surface conditions and temperatures
involved. Mastic may be used to join sections of membrane to one another or
to elements of the building foundation, or to seal penetrations in the membrane.
302.4 Installation The soil-gas retarder shall be placed under the entire soil-contact
area of the floor in a manner that minimizes the required number of joints and
seams. Care shall be taken to prevent damage to the membrane during the construction
process. In buildings incorporating the sub-slab portions of an active soil-depressurization
system, the soil-gas retarder serves an important second purpose: to prevent
mastic, cement or other materials from blocking the pressure distribution manifolds
302.5 Seams Seams between portions of the soil-gas retarder shall maintain
a minimum of 12 inches of lap when concrete is placed. This may be accomplished
by securing the lapped edges of the membrane with tape or mastic or using larger
unsecured overlaps prior to placing concrete.
302.6 Slab Edges and Joints The soil-gas retarder shall fully cover the soil
beneath the building floor. Where the slab edge is cast against a foundation
wall or grade beam, the soil-gas retarder shall contact the foundation element,
and shall not extend vertically into the slab more than one half the slab thickness.
302.7 Penetrations At all points where pipes, conduits, reinforcing bars or
other objects pass through the soil-gas-retarder membrane, the membrane shall
be fitted to within ½ inch of the penetration and sealed to the penetration.
When penetrations occur within 24 inches of a soil-depressurization-system mat
or pit, the gap between the penetrating object and the soil-gas-retarder shall
be taped closed. When necessary to meet this requirement a second layer of the
membrane, cut so as to provide a minimum 12-inch lap on all sides, shall be
placed over the object and shall be sealed to the soil-gas retarder with a continuous
band of tape.
302.8 Punctures, Cuts and Tears All damaged portions of the soil-gas-retarder
membrane within 24 inches of any portion of a soil-depressurization-system mat
or pit shall be sealed with tape or with a patch made from the same or compatible
material, cut so as to provide a minimum 12-inch lap from any opening, and taped
continuously about its perimeter.
302.9 Mastics Mastic may be used to join sections of soil-gas retarder to one
another or to elements of the building foundation, or to seal penetrations in
the soil-gas retarder, provided that mastic is kept at least 24 inches from
any portion of a soil-depressurization-system mat or pit. Only tape may be used
to seal the soil-gas-retarder membrane within 24 inches of a soil-depressurization-system
mat or pit.
302.10 Repairs Where portions of an existing slab have been removed and are
about to be replaced, a soil-gas-retarder membrane shall be carefully fitted
to the opening, and all openings between the membrane and the soil closed with
tape or mastic. Special care must be exercised to assure that mastic does not
enter any portion of a soil-depressurization system located beneath the slab.
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303 Concrete Floors in Contact with Soil-Gas
Concrete slabs supported on soil or spanning over exposed soil, that are used
as floors for conditioned space or enclosed spaces adjacent to or connected
to conditioned spaces, shall be constructed in accordance with the following
provisions of Section 303. 303.2 Concrete for Slabs
303.2.1 Compressive Strength Design strength for all concrete mixes used in
the construction of slab-on-grade floors shall be a minimum of 3,000 psi at
28 days and shall be designed, delivered and placed in accordance with ASTM
303.2.2 Shrinkage Control In order to limit the uncontrolled cracking of floor
slabs, the concrete mix design, placing practices, and curing practices prescribed
in this section shall be followed. All concrete slabs-on-grade or slabs spanning
above exposed soil shall be designed, placed, finished, and cured in accordance
with local governing codes and applicable portions of ACI 318, "Building
Code Requirements for Reinforced Concrete"; ACI 302, "Guide for Concrete
Floor and Slab Construction"; and if fiber-reinforced concrete is used,
the recommendations of the ACI Committee 544, "State of the Art Report
on Fiber Reinforced Concrete". ACI 302 and 544 may not be incorporated
by reference for design.
303.2.3 Mix Design Mix design for all concrete used in the construction of
slab on grade floors shall specify a maximum design slump not to exceed four
(4) inches. On-site slumps shall not exceed five (5) inches, provided that the
total water added to the mix, including plant, transit, and site added water
does not exceed the total following parameters:
(1) For mixes using only natural sands, water content shall not exceed 275
pounds per cubic yard of concrete.
(2) For mixes using manufactured sands, water content shall not exceed 292
pounds per cubic yard of concrete.
303.2.4 Slump and Workability For concretes that do not contain mid-range or
high-range water-reducers, concrete slump measured at the point of placement
in accordance with ASTM C 172, shall not exceed 5-inches. For concretes designed
and mixed containing mid-range or high-range water-reducers conforming with
ASTM C 494, slump measured at the point of placement in accordance with ASTM
C 172, shall not exceed 7-inches for mid-range and 8-inches for high-range water
303.2.5 Hot Weather Placing and Finishing All concrete shall be placed and
finished in accordance with the provisions of ACI 301, Specifications for Structural
Concrete for Buildings. When necessary, provision for wind breaks, shading,
fog spraying, sprinkling, ponding or wet covering with a light colored material
shall be made in advance of placement, and such protective measures shall be
taken as quickly as concrete hardening and finishing operations will allow.
303.2.6 Curing Concrete floors shall be cured by one of the means described
below and shall not be subjected to loading until the architect or engineer
has determined the slab to be structurally adequate for the loads imposed.
(1) Concrete floor slabs shall be cured by covering the entire slab surface
for a period of 7 days with clean, ponded water.
(2) Concrete floor slabs shall be cured by covering the entire slab surface
for a period of 7 days with a continuous mist or spray of clean, potable water.
(3) Concrete floor slabs shall be cured by covering the entire slab surface
for a period of 7 days with an impermeable sheet material conforming to ASTM
(4) Concrete floor slabs shall be cured by covering the entire slab surface
with a liquid membrane-forming compound that conforms with ASTM C 309. Curing
compounds shall be compatible with materials specified in Section 303.3.1.
303.3 Sealing of Construction Joints, Penetrations, Cracks, and Other Connections
303.3.1 Sealants Sealants shall be selected and installed in compliance with
ASTM C 920 "Standard Specification for Elastomeric Joint Sealants"
and ASTM C 1193 "Standard Guide for Use of Joint Sealants."
(1) Sealant materials shall be compatible with the materials they join, including
curing compounds and admixtures, and with materials that will be applied over
them, including floor finishing materials.
(2) Field-molded sealants shall be installed in sealant reservoirs proportioned,
cleaned of laitance and prepared in accordance with the manufacturer's recommendations.
For elastomeric sealants, this generally requires the installation of a bond
breaker or backer rod.
(3) When the installed sealant is not protected by a finished floor or other
protective surface, it shall be suitable to withstand the traffic to which it
will be exposed.
(4) Waterstops shall be preformed from Polyvinyl chloride or other non-corrosive
material and shall be selected and installed in compliance with ACI 504R
303.3.2 Joints All joints between sections of concrete floor slabs, between
the floor slab and a wall or other vertical surface, or between a section of
floor and another object that passes through the slab, shall be sealed to prevent
soil-gas entry in accordance with the provisions of this section. Joint design
depends upon the amount and type of movement that the joint must withstand.
Ideally, sealing should occur as late in the construction process as possible.
No portion of any joint shall be covered or rendered inaccessible unless the
seal has first been inspected and approved by the building official. All such
joints shall be sealed prior to the structure being certified for occupancy.
(1) Butt joints. All non-bonded butt joints shall be sealed to prevent radon
entry using an elastomeric sealant or a waterstop as specified above. The sealant
reservoir shall be sufficiently large to prevent failure of the sealant or waterstop,
but in no case shall the sealant reservoir be less than ¼-inch by ¼-inch
(2) Lap joints. All non-bonded lap joints shall be sealed with either a field-molded
or preformed elastomeric sealant or with a flexible waterstop as specified above.
The lap joint shall be sufficiently large to prevent failure of the sealant
or waterstop, but in no case shall the sealant reservoir be less than ½-inch
by ½-inch in cross-section.
(3) Isolation joints. All non-bonded isolation joints shall be sealed with
either a field-molded or preformed elastomeric sealant or with a flexible waterstop
as specified above. Isolation joints shall be sufficiently large to prevent
failure of the sealant or waterstop, but in no case shall the sealant reservoir
be less than ½-inch by ½-inch in cross-section.
(4) Control or contraction joints may be used to limit unplanned cracking of
floor slabs. In locations where continued movement of the slab portions can
be reasonably expected, flexible sealants must be installed in reservoirs complying
with the requirements of above section on Butt Joints, or a flexible waterstop
must be used.
(5) Construction joints. All bonded construction joints shall be sealed to
prevent radon entry using either a rigid or an elastomeric sealant or a waterstop
as specified above. Where movement of the joint is not prevented by continuous
reinforcing and tie bars, flexible sealants must be installed in reservoirs
complying with the requirements of above section on Lap Joints, or a flexible
waterstop must be used.
303.3.3 Cracks All cracks in concrete slabs supported on soil or spanning over
exposed soil, that are used as floors for conditioned space or enclosed spaces
adjacent to or connected to conditioned spaces, shall be sealed against radon
entry in accordance with the provisions of this section and Section 303.3.1.
Ideally, sealing should occur as late in the construction process as possible.
(1) Cracks greater than ¼-inch wide; all cracks that exhibit vertical
displacement; all cracks that connect weakened zones in the slab such as vertical
penetrations or re-entrant corners; and, all cracks that cross changes in materials
or planes in the structure, shall be sealed with a flexible field-molded elastomeric
sealant installed in accordance with above section on Isolation Joints.
(2) Cracks greater than 1/16 inch in width, that do not meet any of the conditions
described in Item (1) above, shall be enlarged to contain a sealant reservoir
not less than ¼-inch x ¼-inch in cross-section along the entire
length of the crack; and shall be sealed with a flexible, field-molded elastomeric
sealant installed in accordance with above section on Butt Joints.
(3) Cracks less than 1/16 inch in width, that do not meet any of the conditions
described in item (1) above, may be left unsealed.
303.3.4 Stakes, Pipe Penetrations and Other Small Objects All objects that
pass through the slab shall be sealed gas tight. A sealant reservoir, appropriately
dimensioned to accommodate any differential movement between the object and
the concrete, shall be formed continuously around the object, and the joint
shall be sealed with a field molded elastomeric sealant as prescribed for Isolation
Joints and in accordance with the provisions of Section 303.3.1. Where pipes
or other penetrations are separated from the concrete by flexible sleeves, the
sleeve shall be removed to provide bonding of the sealant to the object. Where
stakes are used to support plumbing, electrical conduits or other objects that
will penetrate the slab, the stakes shall be solid, non-porous and resistant
to decay, corrosion and rust. Special care must be taken to avoid honeycombing
between multiple or ganged penetrations.
(1) Large utility service openings through the slab shall be sealed gas-tight.
For slab-on-grade construction, this can be accomplished by fully covering the
exposed soil with a vapor-retarder membrane, covered to a minimum depth of 1
inch with an elastomeric sealant. Alternatively, the opening may be closed with
an expansive concrete or hydraulic cement to within ½ inch of the top
of the slab, and the remaining ½ inch filled with an elastomeric sealant.
When the opening connects to a crawlspace, the opening shall be closed with
sheet metal or other rigid impermeable materials and sealed with an elastomeric
sealant compatible with the materials and conditions.
(2) For openings made through existing slabs, they must be sealed to meet the
appropriate provisions of this Section. If the opening is partially repaired
with concrete, any resulting crack shall be sealed in accordance with the Section
(3) Any sump located in a habitable portion of a building and connecting to
the soil, either directly or through drainage piping, shall be fined with a
gasketed lid. The lid shall be attached so as to provide a gas-tight seal between
the sump and the access space above.
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304 Walls in Contact with Soil-Gas
Walls separating below-grade conditioned space from the surrounding earth or
from a crawlspace or other enclosed volume with an exposed earth floor, shall
be isolated from the soil by an approved structural baffler as described in
Section 302 of this standard. Foundation walls consisting of cavity walls, or
constructed of hollow masonry products or of any material in such a way as to
create an air-space within the wall, shall be capped at the floor-level of the
first finished floor they intersect. The cap shall be either at least 8 inches
of solid concrete or concrete filled block, or a cap that provides air-flow
resistance at least equal to the adjacent floor. No crack, honeycomb, joint
duct, pipe, conduit chase or other opening in the wall shall be allowed to connect
soil-gas to a conditioned space or to an enclosed space adjacent to or connected
to a conditioned space. 304.2 Materials Walls governed by the provisions of
this section shall be constructed of reinforced concrete, or solid reinforced
Walls governed by the provisions of this section shall be constructed with
a continuous waterproofing membrane applied (1) either to the exterior surface
from the top of the footing to not less than 6 inches above the finished grade,
or where the wall separates interior space and a crawl space; or
(2) from the top of the footing to the bottom of the floor above.
304.3.1 Application The waterproofing membrane shall be applied in accordance
with the applicable local building code and shall be sealed to the top of the
footing so as to waterproof the joint between the footing and the wall. When
installed in compliance with Section 304.3 Item (2), the membrane shall be attached
to the bottom of the floor above to fully seal the joint between the floor and
304.3.2 Utility Penetrations All below-grade utility penetrations through walls
in partial or full contact with the soil shall be closed and sealed with an
approved sealant material (see Section 303.3.1). This seal shall be made on
both faces of the wall. Where conduits or ducts do not provide a continuous
and gas-tight separation from the soil, the end of the conduit or duct must
be sealed in accordance with the provisions of Section 303.3.1 to prevent soil-gas
304.4 Doors and Service Openings Doors, hatches, or removable closures of any
kind that can create an opening between the interior and a crawlspace should
be avoided, but when required, shall be gasketed and installed with a latch
or other permanent fastening device.
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305 Buildings with Crawl Spaces
305.1 General For the purpose of this standard, buildings with crawl spaces
include all buildings with the floor supported above grade.
305.1.1 Reinforced Concrete Floor Systems A reinforced concrete floor constructed
over crawl spaces shall conform to all applicable provisions of Section 303.
305.1.2 Wood-framed Floor Systems Wood-framed floors spanning over soil, that
are used as floors for conditioned space or enclosed spaces adjacent to or connected
to conditioned spaces, shall be constructed in accordance with the provisions
of this section.
305.2 Materials Wood-framed floors constructed over a crawl space shall be
constructed of American Plywood Association (APA) certified tongue-in-groove
plywood, and otherwise comply with Paragraph 4.1.2 of Appendix "C"
to the 1993 Energy Efficiency Code for Building Construction. Oriented structural
board shall not be an acceptable substitute material.
305.3 Utility Penetrations All penetrations through the floor, including but
not limited to plumbing pipes and wiring, shall be fully sealed to the floor
structure with approved sealant materials as per Section 303.3.1. Large service
openings through the slab, such as beneath bath tub drains, shall be sealed
gas-tight. Where large openings are created, sheet metal or other rigid materials
shall be used in conjunction with sealants to close and seal the openings.
305.4 Vertical Joints All vertical joints between the subfloor and foundation
wall or the subfloor and any vertical plane of the building which extends from
the crawlspace to the top of the subfloor, shall be sealed with an approved
sealant (see Section 303.3.1).
305.5 Doors and Service Openings Doors, hatches, or removable closures of any
kind that can create an opening in the floor-plane should be avoided, but when
required, shall be gasketed and installed with a latch or other permanent fastening
305.6 Other Radon-Entry Paths All openings which connect a crawlspace and construction
cavities, such as the space between wall studs, hollow masonry or precast concrete
units, or floor and ceiling planes, shall be closed and sealed with an approved
sealant (see Section 303.3.1).
305.7 Crawl Space Ventilation Crawl spaces shall be passively ventilated or
shall be constructed with an active soil-depressurization system in compliance
with Chapter 4. No portion of an air-distribution system shall pass trough a
305.7.1 Required Ventilation Crawl spaces shall be ventilated by openings through
the perimeter wall connecting to the exterior of the foundation. Required vents
shall have a combined net free area not less than 1 square inch per 1 square
foot of crawl space, and shall conform to the following conditions:
(1) Openings shall be distributed uniformly around the outside walls of the
(2) Vents shall be fitted with corrosion- and decay-resistant wire mesh or
grilles with openings not less than ¼ inch nor more than ½ inch
in size. Vents shall not be fitted with operable louvers, dampers, or other
(3) Plumbing located in a ventilated crawlspace shall be protected from freezing
with insulation and/or heat tape.
305.7.2 Prohibited Uses Crawl spaces shall not be used as an air-duct or plenum
or to house any duct or fan that is part of a heating, ventilating or air-conditioning
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306 Space Conditioning Systems and Ventilating
All heating, ventilating and air-conditioning systems shall be designed, installed,
inspected and maintained in accordance with ANSI/ASHRAE 62-1989, Ventilation
for Acceptable Indoor Air Quality, the current "Florida Energy Efficiency
Code For Building Construction", and with the provisions of this Section.
Construction to the provisions of this Section will limit radon entry points
through mechanical depressurization of buildings, which can enhance radon entry.
Additionally, ventilating systems shall be designed to meet all applicable codes
and the provisions of this Section for use of outside air of low radon concentration.
306.2 Condensate Drains All joints in condensate piping shall be solvent welded,
soldered, or otherwise connected in a leak-proof and gas-tight manner. Condensate
drains shall be trapped and terminate in the building sewer or outside the building,
a minimum of 6 inches above finished grade. If the condensate piping penetrates
a floor or wall separating enclosed space from the soil or from a crawl space,
the penetration shall be sealed in accordance with the applicable provisions
of Chapter 3. The condensate drain piping shall not terminate in a return plenum.
306.3 Other Piping When any piping penetrates a floor or wall separating enclosed
space from the soil or from a crawl space, the penetration shall be sealed in
accordance with the applicable provisions of Chapter 3. In the case of insulated
piping, the insulation must be removed at the point of the seal, and required
seal must be made between the pipe and the building structure. Sealant must
be compatible with the materials and anticipated operating temperatures. Piping
shall not terminate in a return plenum.
306.4 Plumbing and Wiring Chases Wherever piping or wiring is installed in
a chase that is at any point in contact with the soil or a crawl space, the
chase shall be sealed to the floor or wall where it first enters the structure,
in accordance with the applicable portions of Chapter 3. Piping contained in
such a chase shall be sealed to the chase at the interior plane of that floor
or wall. No portion of any chase shall terminate in a return air duct or plenum.
Where it is impractical or prohibited by another code to seal wiring into an
electrical chase or conduit, the chase shall comply with all applicable portions
of Chapter 3 or the conduit shall be entirely fabricated of gas-tight components
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307 Air Distribution Systems
307.1 Air Distribution Systems Any air duct, plenum, fan enclosure, or fan
that is part of a building's heating, ventilating or air-conditioning system
shall be completely isolated from the soil-gas by a structural barrier complying
with the provisions of Chapter 3. Heating, ventilating, and air conditioning
systems supplying spaces that have floors or walls in contact with soil or soil-gas
shall be designed to minimize air-pressure differences and eliminate negative
pressures, that cause significant flow of soil-gas through the structural barrier
and into the building. Return ducts, plenums, and air-handlers shall not be
located in a crawl space.
307.2 Exhaust Fans, Hoods, Equipment, and Appliances For each zone, the required
volume of outside ventilation air shall be equal to or greater than the combined
volume of air capable of being exhausted by all exhaust fans, hoods, equipment,
and appliances installed in the zone. This amount may not be reduced by use
factors unless devices are wired and switched in a manner that prevents their
307.3 Combustion Air Ducts Ducts that provide combustion air to fuel-burning
appliances and equipment shall be completely isolated from the soil-gas by a
structural barrier complying with the provisions of Chapter 3.
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ACTIVE SOIL-DEPRESSURIZATION SYSTEMS
A soil-depressurization system maintains a lower air-pressure in the soil directly
beneath the building floor and foundation than exists within the building. This
not only draws radon away, but also causes the direction of the air-flow through
any possible failure in the structural barrier to be out of the building and
into the soil-depressurization system. Soil depressurization systems may be
installed beneath concrete slabs supported directly on the soil, or beneath
the soil-gas-retarder membrane in crawl spaces.
401.1 Prohibited Uses Soil depressurization systems components may not extend
beneath areas that are required to be depressurized by other codes for the protection
of public health, for example rooms containing general anesthesia, pathogens,
or poisonous chemicals. Soil depressurization systems may be installed beneath
rooms that are required to be depressurized for other reasons, such as toilets
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402 System Components
An active soil-depressurization (ASD) system is comprised of the following
components: pressure distribution system porous media or manifolds); a soil
cover; one or more vents; a suction fan; and a system failure indicator.
402.1 Pressure Distribution Media or Manifolds A wide variety of means can
be utilized to extend the low-pressure zone across the entire area beneath the
structure. Acceptable means include synthetic ventilation mats, a system of
perforated pipe, and an air-permeable gravel layer. Different types of pressure
distribution media may be used in the same system, provided each complies with
the installation requirements of this chapter. Pressure distribution media must
be installed is such a way as to assure that they are never blocked by water.
(1) Ventilation mats shall have a soil contact area of at least 216 square
inches per lineal foot and provide a cross-section profile of at least 9 square
(2) Perforated pipe may be used to construct pressure extension manifolds.
These pipes may be installed directly under the soil cover or in gravel or a
similar porous medium that provides an adequate air-flow connection between
the pipe and the sub-soil and that protects the pipe from becoming blocked by
(3) Continuous gravel layers of at least 4-inches thickness are an acceptable
pressure distribution medium, provided they completely cover the area of soil
to be depressurized.
402.2 Soil Cover In slab-on-grade construction, the soil cover consists of
the soil-gas-retarder membrane and the concrete slab. In crawl spaces, the concrete
slab may be omitted, providing the soil-gas-retarder membrane will not be subjected
to wear and damage due to required maintenance procedures. In all instances,
the soil-gas-retarder membrane shall be fully sealed to the radon vents in accordance
with the provisions of Section 302.
402.3 Radon Vents Radon vents are gas-tight pipes that carry the soil-gas to
an area above and away from the building. Radon vent pipes shall be of a material
approved by the governing local building code for plumbing vents.
402.4 Suction Fans Suction fans create the critical pressure difference between
the sub-slab and indoors. Suction fans shall be designed for continuous operation.
Fan performance is determined by the soil characteristics, the air-flow characteristics
of the pressure distribution system, and the system layout, and shall comply
with the air-flows and operating pressures determined by the system design,
as determined using the Large-Building Active Soil-Depressurization Model, or
with criteria below for Alternate Compliance Method. The computer model program
is available through the Department of Community Affairs, Codes and Standards,
2740 Centerview Drive, Tallahassee, Florida, 32399-2100, telephone (904) 487-1824.
402.5 Fan-Failure Indicator Each soil-depressurization system shall have a
failure indicator labeled with the words "Radon Reduction System Fan Failure
Indicator" mounted so as to be conveniently visible to the building occupants.
The fan-failure indicator may be either a visual device consisting of a light
of not less than 1/5 footcandle at the floor level, or an alarm that produces
a minimum 60 db audible signal. The indicator shall be made to operate automatically
when the pressure inside any radon vent pipe fitted with an operable fan is
less than 0.40-inch water column (100 pascals) lower than the air pressure inside
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403 ASD System Design Requirements
403.1 General All ASD systems must comply with a design shown by the Large-Building
Active Soil-Depressurization Model to be capable of maintaining a 0.02-inch
(5-pascal) pressure differential over 90% of the slab or crawlspace area.
403.2 Ventilation Mat Systems Mat systems may be designed and installed in
accordance with a design shown by the Large-Building Active Soil-Depressurization
Model to be capable of maintaining a 5-pascal pressure differential over 90%
of the slab area or with Section 503.2.2.
403.2.1 Installation Radon ventilation mats shall be installed immediately
prior to placing the soil-gas-retarder membrane, to reduce the chance for soil
to enter and block the mat. Mats shall be arranged in a pattern that provides
at least two possible flow paths from any point on the mat to a radon vent pipe.
Mats shall be placed with the filter material facing the compacted soil. Where
sections of mat join, a minimum 6-inch long section of filter material at the
end of one of the mats shall be loosened and the other piece of mat inserted
between the loosened filter material and the first section of mat. The mats
will be pressed tightly together at this lap and mechanically attached together
with hog rings or metal pins driven through the mat and into the soil. Wire
ties, which will puncture or tear the soil-gas-retarder membrane, shall not
be used to join the mats. When properly joined, the filter material will extend
continuously across the joint and the full cross-sectional area of the mat will
be preserved across the splice.
403.2.2 Alternate Compliance Method Systems installed on sand or granular soil,
can demonstrate compliance by meeting the following design limits:
(1) Mats shall be located at least 15 feet and not more than 25 feet from the
outside edge of the floor.
2) Mats shall be spaced not more than 50 feet on center.
3) No portion of a building floor shall be isolated from a mat by a construction
feature, such as an internal footing, grade beam, foundation wall, or other
obstacle having a depth greater than the exterior foundation walls.
4) No portion of a building floor shall be more than 35 feet from a mat.
5) Mats shall be run parallel to the longest slab dimension unless obstructed
by a construction feature, and arranged in a pattern that provides at least
two possible flow paths from any point on the mat to a radon vent pipe.
403.2.3 Radon Vent Connection The radon vent pipe shall join to the mat in
a manner that does not restrict the full air-flow capacity of the pipe. Depending
upon the thickness and effective net-free-area of the ventilation mat, this
may require enlarging the diameter of the vent pipe at the connection with a
suitable flange, or increasing the net-free-area of the mat by installing additional
layers of mat or a layer of gravel beneath the connection point. The soil-gas-retarder
membrane shall be fully sealed to the radon vents in accordance with the provisions
of Section 302.
403.3 Perforated Pipe Systems Perforated pipes shall be of a material approved
by the governing local building code for foundation drainage, and sized according
to the air-flow estimated from the Large-Building Active Soil-Depressurization
Model. Where perforated pipes are installed in gravel meeting ASTM D 448, numbers
4 or 5 gravel, with not more than 5% passing a 3/8-inch screen.
403.3.1 Installation Perforated pipe pressure distribution manifolds shall
be installed only after the installation of all other utilities has been completed,
and immediately prior to the soil-gas-retarder membrane. Pipes shall be installed
with a row of perforations located at the bottom of the pipe, in order to allow
condensate to drain from the system. Pipes shall be arranged in a pattern that
provides at least two possible flow paths from any point in the system to a
radon vent pipe. Separate sections of pipe shall be solvent welded or mechanically
403.3.2 Radon Vent Connection The radon vent pipe shall join to the perforated
pipe with a fitting that allows for the fill air-flow capacity of the vent pipe.
The soil-gas-retarder membrane shall be fully sealed to the radon vents in accordance
with the provisions of Section 302.
403.4 Continuous Gravel Layer Systems Gravel used as the pressure distribution
medium shall be installed only after the installation of all other utilities
has been completed, and immediately prior to the soil-gas-retarder membrane.
Where regions of gravel are isolated from one another by interior foundation
elements, separate suction points shall be provided in each region, or regions
shall be interconnected with pipes run horizontally through the obstruction.
The size and number of such pipes shall be sufficient to provide at least two-times
the anticipated air-flow. In no case shall fewer than two pipes be used to interconnect
one gravel area with another. These pipes shall be separated by a horizontal
distance not less than one-half the length of the boundary between the connecting
403.4.1 Radon Vent Connection The radon vent pipe shall join to the gravel
layer with a "T" fitting that allows for the full air-flow capacity
of the vent pipe from either side of the "T". The fitting shall be
installed with two arms in the gravel and a single arm connected to the radon
vent pipe. The soil-gas-retarder membrane shall be fully scaled to the radon
vents in accordance with the provisions of Section 302.
403.5 Radon Vent Pipe Installation Radon vent pipes shall be solvent welded
or otherwise joined to create a gas-tight connection from the soil-suction point
to the vent termination point. They shall be sloped a minimum of 1/8 inch per
foot in a manner that will drain all rain and condensate back to the soil, and
shall be supported in compliance with regulations for plumbing vents.
403.5.1 Labeling All portions of the radon vent pipe not permanently encased
in a wall or chase shall be labeled to prevent accidental misuse. Labels shall
consist of a pressure sensitive 2-inch yellow band with the words "Radon
Reduction System" printed in black letters at least 1 inch in height. These
labels shall be placed on every visible portion of the vent pipe at a spacing
of not more than 3 feet. The labels shall be placed so as to be visible from
403.5.2 Sizing The size of vent pipes shall be determined by application of
appropriate engineering principles, based on air-flow rates predicted with the
Large-Building Active Soil-Depressurization Model. For systems that comply with
the Alternate Compliance Method, Section 403.2.2, and are installed in buildings
with straight runs of vent pipes no more than 50 feet in height the required
number and size of vent pipes may be determined as follows:
1) For up to 100 linear feet of ventilation mat use one 2-inch diameter pipe.
2) For up to 200 linear feet of ventilation mat use one 3-inch diameter pipe,
or two 2- inch diameter pipes.
3) For up to 400 linear feet of ventilation mat use one 4-inch diameter pipe,
or two 3- inch diameter pipes, or four 2-inch diameter pipes.
403.5.3 Terminals Radon vent pipes shall terminate with a rain cap, installed
above the roof of the structure, and shall be located in accordance with existing
codes for toxic or noxious exhausts. If not specifically addressed or applicable,
vent pipes shall be terminated in locations that minimize human exposure to
their exhaust air, such that the location is:
(1) at least 12 inches above the surface of the roof;
(2) at least ten feet from any window, door, or other opening (e.g., operable
skylight or air intake) to conditioned spaces of the structure; and
(3) 10 feet from any opening into an adjacent building.
The total required distance (ten feet) shall be measured either directly between
the two points or be the sum of measurements made around the intervening obstacles.
If the discharge point is within two feet of elevation of the opening into conditioned
space, the distance (ten feet) shall be the horizontal distance between the
403.6 Suction Fans Soil-depressurization system fans shall be designed to maintain
the following minimum air-pressure differences at the lower opening of the radon
vent pipe, as compared to the air pressure of the conditioned space above:
1) For Systems using ventilation mats, 0.5 inches water column.
2) For systems using perforated pipe, 0.5 inches water column.
3) For systems using continuous gravel layers, 1.0 inches water column.
403.6.1 Fan Sizing Soil-depressurization systems that comply with the Alternative
Compliance Method, Section 403.2.2, and Sizing, Section 403.5.2, may comply
by sizing the fan as follows:
1) For up to 100 lineal feet of ventilation mat the fan shall be rated for
50 cfm at 1-inch water column.
2) For 100 to 200 lineal feet of ventilation mat, the fan shall be rated for
at least 100 cfm at 1-inch water column.
3) For 200 to 400 lineal feet of ventilation mat, the fan shall be rated for
at least 175 cfm at 1-inch water column.
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End of Standard
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