(The provisions contained in this appendix are not mandatory unless specifically referenced in the adopting ordinance.)
This appendix contains requirements for new construction in jurisdictions where radon-resistant construction is required. 
Inclusion of this appendix by jurisdictions shall be determined through the use of locally available data or determination of Zone 1 designation in Figure AF101 and Table AF101(1).
a. pCi/L standard for picocuries per liter of radon gas. The U.S. Environmental Protection Agency (EPA) recommends that all homes that measure 4 pCi/L and greater be mitigated.
The EPA and the U.S. Geological Survey have evaluated the radon potential in the United States and have developed a map of radon zones designed to assist building officials in deciding whether radon-resistant features are applicable in new construction.
The map assigns each of the 3,141 counties in the United States to one of three zones based on radon potential. Each zone designation reflects the average short-term radon measurement that can be expected to be measured in a building without the implementation of radon-control methods. The radon zone designation of highest priority is Zone 1. Table AF101 lists the Zone 1 counties illustrated on the map. More detailed information can be obtained from state-specific booklets (EPA-402-R-93-021 through 070) available through State Radon Offices or from EPA Regional Offices.
FIGURE AF101
EPA MAP OF RADON ZONES
TABLE AF101(1)
HIGH RADON-POTENTIAL (ZONE 1) COUNTIESa
| ALABAMA Calhoun Clay Cleburne Colbert Coosa Franklin Jackson Lauderdale Lawrence Limestone Madison Morgan Talladega CALIFORNIA Santa Barbara Ventura COLORADO Adams Arapahoe Baca Bent Boulder Chaffee Cheyenne Clear Creek Crowley Custer Delta Denver Dolores Douglas El Paso Elbert Fremont Garfield Gilpin Grand Gunnison Huerfano Jackson Jefferson Kiowa Kit Carson Lake Larimer Las Animas Lincoln Logan Mesa Moffat Montezuma Montrose Morgan Otero Ouray Park Phillips Pitkin Prowers Pueblo Rio Blanco San Miguel Summit Teller Washington Weld Yuma | CONNECTICUT Fairfield Middlesex New Haven New London GEORGIA Cobb De Kalb Fulton Gwinnett IDAHO Benewah Blaine Boise Bonner Boundary Butte Camas Clark Clearwater Custer Elmore Fremont Gooding Idaho Kootenai Latah Lemhi Shoshone Valley ILLINOIS Adams Boone Brown Bureau Calhoun Carroll Cass Champaign Coles De Kalb De Witt Douglas Edgar Ford Fulton Greene Grundy Hancock Henderson Henry Iroquois Jersey Jo Daviess Kane Kendall Knox La Salle Lee Livingston Logan Macon Marshall Mason McDonough McLean Menard Mercer | Morgan Moultrie Ogle Peoria Piatt Pike Putnam Rock Island Sangamon Schuyler Scott Stark Stephenson Tazewell Vermilion Warren Whiteside Winnebago Woodford INDIANA Adams Allen Bartholomew Benton Blackford Boone Carroll Cass Clark Clinton De Kalb Decatur Delaware Elkhart Fayette Fountain Fulton Grant Hamilton Hancock Harrison Hendricks Henry Howard Huntington Jay Jennings Johnson Kosciusko LaGrange Lawrence Madison Marion Marshall Miami Monroe Montgomery Noble Orange Putnam Randolph Rush Scott Shelby St. Joseph Steuben Tippecanoe Tipton Union Vermillion | Wabash Warren Washington Wayne Wells White Whitley IOWA All Counties KANSAS Atchison Barton Brown Cheyenne Clay Cloud Decatur Dickinson Douglas Ellis Ellsworth Finney Ford Geary Gove Graham Grant Gray Greeley Hamilton Haskell Hodgeman Jackson Jewell Johnson Kearny Kingman Kiowa Lane Leavenworth Lincoln Logan Marion Marshall McPherson Meade Mitchell Nemaha Ness Norton Osborne Ottawa Pawnee Phillips Pottawatomie Pratt Rawlins Republic Rice Riley Rooks Rush Saline Scott Sheridan Sherman Smith Stanton Thomas | Trego Wallace Washington Wichita Wyandotte KENTUCKY Adair Allen Barren Bourbon Boyle Bullitt Casey Clark Cumberland Fayette Franklin Green Harrison Hart Jefferson Jessamine Lincoln Marion Mercer Metcalfe Monroe Nelson Pendleton Pulaski Robertson Russell Scott Taylor Warren Woodford MAINE Androscoggin Aroostook Cumberland Franklin Hancock Kennebec Lincoln Oxford Penobscot Piscataquis Somerset York MARYLAND Baltimore Calvert Carroll Frederick Harford Howard Montgomery Washington MASS. Essex Middlesex Worcester MICHIGAN Branch Calhoun Cass | Hillsdale Jackson Kalamazoo Lenawee St. Joseph Washtenaw MINNESOTA Becker Big Stone Blue Earth Brown Carver Chippewa Clay Cottonwood Dakota Dodge Douglas Faribault Fillmore Freeborn Goodhue Grant Hennepin Houston Hubbard Jackson Kanabec Kandiyohi Kittson Lac Qui Parle Le Sueur Lincoln Lyon Mahnomen Marshall Martin McLeod Meeker Mower Murray Nicollet Nobles Norman Olmsted Otter Tail Pennington Pipestone Polk Pope Ramsey Red Lake Redwood Renville Rice Rock Roseau Scott Sherburne Sibley Stearns Steele Stevens Swift Todd Traverse Wabasha Wadena Waseca Washington | Watonwan Wilkin Winona Wright Yellow Medicine MISSOURI Andrew Atchison Buchanan Cass Clay Clinton Holt Iron Jackson Nodaway Platte MONTANA Beaverhead Big Horn Blaine Broadwater Carbon Carter Cascade Chouteau Custer Daniels Dawson Deer Lodge Fallon Fergus Flathead Gallatin Garfield Glacier Granite Hill Jefferson Judith Basin Lake Lewis and Clark Madison McCone Meagher Missoula Park Phillips Pondera Powder River Powell Prairie Ravalli Richland Roosevelt Rosebud Sanders Sheridan Silver Bow Stillwater Teton Toole Valley Wibaux Yellowstone |
(continued)
TABLE AF101(1)—continued
HIGH RADON-POTENTIAL (ZONE 1) COUNTIESa
| NEBRASKA Adams Boone Boyd Burt Butler Cass Cedar Clay Colfax Cuming Dakota Dixon Dodge Douglas Fillmore Franklin Frontier Furnas Gage Gosper Greeley Hamilton Harlan Hayes Hitchcock Hurston Jefferson Johnson Kearney Knox Lancaster Madison Nance Nemaha Nuckolls Otoe Pawnee Phelps Pierce Platte Polk Red Willow Richardson Saline Sarpy Saunders Seward Stanton Thayer Washington Wayne Webster York NEVADA Carson City Douglas Eureka Lander Lincoln Lyon Mineral Pershing White Pine NEW HAMPSHIRE Carroll NEW JERSEY | Hunterdon Mercer Monmouth Morris Somerset Sussex Warren NEW MEXICO Bernalillo Colfax Mora Rio Arriba San Miguel Santa Fe Taos NEW YORK Albany Allegany Broome Cattaraugus Cayuga Chautauqua Chemung Chenango Columbia Cortland Delaware Dutchess Erie Genesee Greene Livingston Madison Onondaga Ontario Orange Otsego Putnam Rensselaer Schoharie Schuyler Seneca Steuben Sullivan Tioga Tompkins Ulster Washington Wyoming Yates N. CAROLINA Alleghany Buncombe Cherokee Henderson Mitchell Rockingham Transylvania Watauga N. DAKOTA All Counties OHIO Adams Allen Ashland Auglaize | Belmont Butler Carroll Champaign Clark Clinton Columbiana Coshocton Crawford Darke Delaware Fairfield Fayette Franklin Greene Guernsey Hamilton Hancock Hardin Harrison Holmes Huron Jefferson Knox Licking Logan Madison Marion Mercer Miami Montgomery Morrow Muskingum Perry Pickaway Pike Preble Richland Ross Seneca Shelby Stark Summit Tuscarawas Union Van Wert Warren Wayne Wyandot PENNSYLVANIA Adams Allegheny Armstrong Beaver Bedford Berks Blair Bradford Bucks Butler Cameron Carbon Centre Chester Clarion Clearfield Clinton Columbia Cumberland Dauphin | Delaware Franklin Fulton Huntingdon Indiana Juniata Lackawanna Lancaster Lebanon Lehigh Luzerne Lycoming Mifflin Monroe Montgomery Montour Northampton Northumberland Perry Schuylkill Snyder Sullivan Susquehanna Tioga Union Venango Westmoreland Wyoming York RHODE ISLAND Kent Washington S. CAROLINA Greenville S. DAKOTA Aurora Beadle Bon Homme Brookings Brown Brule Buffalo Campbell Charles Mix Clark Clay Codington Corson Davison Day Deuel Douglas Edmunds Faulk Grant Hamlin Hand Hanson Hughes Hutchinson Hyde Jerauld Kingsbury Lake Lincoln Lyman Marshall McCook | McPherson Miner Minnehaha Moody Perkins Potter Roberts Sanborn Spink Stanley Sully Turner Union Walworth Yankton TENNESEE Anderson Bedford Blount Bradley Claiborne Davidson Giles Grainger Greene Hamblen Hancock Hawkins Hickman Humphreys Jackson Jefferson Knox Lawrence Lewis Lincoln Loudon Marshall Maury McMinn Meigs Monroe Moore Perry Roane Rutherford Smith Sullivan Trousdale Union Washington Wayne Williamson Wilson UTAH Carbon Duchesne Grand Piute Sanpete Sevier Uintah VIRGINIA Alleghany Amelia Appomattox Augusta Bath | Bland Botetourt Bristol Brunswick Buckingham Buena Vista Campbell Chesterfield Clarke Clifton Forge Covington Craig Cumberland Danville Dinwiddie Fairfax Falls Church Fluvanna Frederick Fredericksburg Giles Goochland Harrisonburg Henry Highland Lee Lexington Louisa Martinsville Montgomery Nottoway Orange Page Patrick Pittsylvania Powhatan Pulaski Radford Roanoke Rockbridge Rockingham Russell Salem Scott Shenandoah Smyth Spotsylvania Stafford Staunton Tazewell Warren Washington Waynesboro Winchester Wythe WASHINGTON Clark Ferry Okanogan Pend Oreille Skamania Spokane Stevens W. VIRGINIA Berkeley Brooke Grant Greenbrier Hampshire | Hancock Hardy Jefferson Marshall Mercer Mineral Monongalia Monroe Morgan Ohio Pendleton Pocahontas Preston Summers Wetzel WISCONSIN Buffalo Crawford Dane Dodge Door Fond du Lac Grant Green Green Lake Iowa Jefferson Lafayette Langlade Marathon Menominee Pepin Pierce Portage Richland Rock Shawano St. Croix Vernon Walworth Washington Waukesha Waupaca Wood WYOMING Albany Big Horn Campbell Carbon Converse Crook Fremont Goshen Hot Springs Johnson Laramie Lincoln Natrona Niobrara Park Sheridan Sublette Sweetwater Teton Uinta Washakie |
a. The EPA recommends that this county listing be supplemented with other available State and local data to further understand the radon potential of a Zone 1 area.
FIGURE AF102
RADON-RESISTANT CONSTRUCTION DETAILS FOR FOUR FOUNDATION TYPES
For the purpose of these requirements, 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.
RADON GAS. A naturally occurring, chemically inert, radioactive gas that is not detectable by human senses. As a gas, it can move readily through particles of soil and rock, and can accumulate under the slabs and foundations of homes where it can easily enter into the living space through construction cracks and openings.
SOIL-GAS-RETARDER. A continuous membrane of 6-mil (0.15 mm) polyethylene or other equivalent material used to retard the flow of soil gases into a building.
SUBMEMBRANE DEPRESSURIZATION SYSTEM. A system designed to achieve lower submembrane air pressure relative to crawl space air pressure by use of a vent drawing air from beneath the soil-gas-retarder membrane
SUBSLAB DEPRESSURIZATION SYSTEM (Active). A system designed to achieve lower subslab air pressure relative to indoor air pressure by use of a fan-powered vent drawing air from beneath the slab.
SUBSLAB DEPRESSURIZATION SYSTEM (Passive). A system designed to achieve lower subslab air pressure relative to indoor air pressure by use of a vent pipe routed through the conditioned space of a building and connecting the subslab 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 post-construction radon mitigation, if necessary (see Figure AF102). These techniques are required in areas where designated by the jurisdiction.
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 subslab 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 4 inches (102 mm) thick. The aggregate shall consist of material that will pass through a 2-inch (51 mm) sieve and be retained by a 1/4-inch (6.4 mm) sieve.
2. A uniform layer of sand (native or fill), a minimum of 4 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 subfloor area.
A minimum 6-mil (0.15 mm) [or 3-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 in 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.
Potential radon entry routes shall be closed in accordance with Sections AF103.4.1 through AF103.4.10.
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.
Sump pits open to soil or serving as the termination point for subslab or exterior drain tile loops shall be covered with a gasketed or otherwise sealed lid. Sumps used as the suction point in a subslab depressurization system shall have a lid designed to accommodate the vent pipe. Sumps used as a floor drain shall have a lid equipped with a trapped inlet.
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 the 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.
The exterior surfaces of portions of concrete and masonry block walls below the ground surface shall be dampproofed in accordance with Section R406.
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.
Ductwork passing through 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.
Ductwork located in crawl spaces shall have all seams and joints sealed by closure systems in accordance with Section M1601.4.1.
Openings around all penetrations through floors above crawl spaces shall be caulked or otherwise filled to prevent air leakage.
Access doors and other openings or penetrations between basements and adjoining crawl spaces shall be closed, gasketed or otherwise filled to prevent air leakage.
In buildings with crawl space foundations, the following components of a passive submembrane depressurization system shall be installed during construction.
Exception: Buildings in which an approved mechanical crawl space ventilation system or other equivalent system is installed.
Crawl spaces shall be provided with vents to the exterior of the building. The minimum net area of ventilation openings shall comply with Section R408.1.
The soil in crawl spaces shall be covered with a continuous layer of minimum 6-mil (0.15 mm) polyethylene soil-gas-retarder. 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.
A plumbing tee or other approved connection shall be inserted horizontally beneath the sheeting and connected to a 3- or 4-inch-diameter (76 or 102 mm) fitting with a vertical vent pipe installed through the sheeting. The vent pipe shall be extended up through the building floors, and terminate at least 12 inches (305 mm) above the roof in a location at least 10 feet (3048 mm) away from any window or other opening into the conditioned spaces of the building that is less than 2 feet (610 mm) below the exhaust point, and 10 feet (3048 mm) from any window or other opening in adjoining or adjacent buildings.
A minimum 3-inch-diameter (76 mm) ABS, PVC or equivalent gas-tight pipe shall be embedded vertically into the subslab 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 subslab permeable material. Alternatively, the 3-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 subslab aggregate or connected to it through a drainage system.
The pipe shall be extended up through the building floors, and terminate at least 12 inches (305 mm) above the surface of the roof in a location at least 10 feet (3048 mm) away from any window or other opening into the conditioned spaces of the building that is less than 2 feet (610 mm) below the exhaust point, and 10 feet (3048 mm) from any window or other opening in adjoining or adjacent buildings.
In buildings where interior footings or other barriers separate the subslab 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.
Joints in air ducts and plenums in unconditioned spaces shall meet the requirements of Section M1601. Thermal envelope air infiltration requirements shall comply with the energy conservation provisions in Chapter 11. Fireblocking shall meet the requirements contained in Section R302.11.
To provide for future installation of an active submembrane or subslab 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.