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United States EPA/402-K-01-002Environmental April 2001Protection Agency

Office of Air and Radiation

Building Radon OutA Step-by-Step Guide On How ToBuild Radon-Resistant Homes


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Building Radon Out

Building Radon Out: A Step-By-Step Guide on How to Build Radon-Resistant Homes was developed by the IndoorEnvironments Division in the Office of Radiation and Indoor Air at the U.S.Environmental Protection Agency. The

lead EPA staff on the document wasPaulina Chen. Other staff contributingto the development of this documentwere: Greg Brunner, Brenda Doroski,Gene Fisher, Matt Hiester, WendyKammer, Jennifer Keller, Mike Rogers,and David Rowson.

Much of the description of building

techniques in this document is basedon training materials prepared byDouglas Kladder of the Center forEnvironmental Research and

Technology, Inc., including the bookProtecting Your Home from Radon byKladder, Burkhart, and Jelinek.

Contributions from training sessions of Dave Murane of Sanford Cohen andAssociates are also acknowledged.

In addition, EPA would like to gratefullyacknowledge the review and

contributions of Terry Brennan,Camroden Associates; Robert Brown,International Code Council; ThomasDickey, City of East Moline, Illinois;Ken Ford, National Association of HomeBuilders; Douglas Kladder, WesternRegional Radon Training Center; andBrad Turk, Mountain West TechnicalAssociates.

Disclaimer Acknowledgements

The U.S. Environmental ProtectionAgency (EPA) strives to provideaccurate, complete, and usefulinformation. However, neither EPA norany person contributing to thepreparation of this document makes

any warranty, express or implied, withrespect to the usefulness oreffectiveness of any information,method, or process disclosed in thismaterial. Nor does EPA assume anyliability for the use of, or for damagesarising from the use of, anyinformation, method, or processdisclosed in this document.

Mention of firms, trade names, orcommercial products in this documentdoes not constitute endorsement orrecommendation for use.


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Table of Contents

Building the Framework: IntroductionDoes It Make Sense To Build Homes Radon-Resistant?

Digging Deeper: Questions and AnswersWhat Is Radon?Is Radon a Significant Health Risk?Is Radon a Problem In Homes?Is There a Safe Level Of Radon?

How Does Radon Enter a House?How Does Air Pressure Affect Radon Entry?Does Foundation Type Affect Radon Entry?What Can You Do To Reduce Radon New Homes?What Are The Radon-Resistant Features?Is There a Way To Test The Lot Before Building?Would I Incur Liability By Installing The Features?Should All New Homes Be Built Radon-Resistant?EPA Map of Radon ZonesList of Zone 1 Counties

56

910111213

14151617182021222324


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Nuts and Bolts: Installation GuidePlanning Answer The Question: To Intall Or Not To Install?Determine What Type Of System To InstallDetermine Vent Pipe Location And Size

Installation Basement and Slab-On-Grade Construction: Sub-Slab PreparationGravelPerforated Pipe

Soil Gas Collection MatPlastic SheetingSeal Off And Label Riser StubLay FoundationCrawlspace ConstructionSeal OpeningsInstall Vent PipeSealing Ducts and Air Handling UnitsInstall Electrical Junction BoxPost-Occupancy TestingActivate the System

Sold: Working With HomebuyersGet An Edge On The MarketMake a Name For Yourself What To Tell Homebuyers

Appendix A: Architectural DrawingsAppendix B: GlossaryAppendix C: For More InformationAppendix D: State Radon Contacts

27

293032

34353638

4042434445515558596062

64646668

72767880


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Building the Framework: Introduction

Should You Be Concerned AboutRadon?

Yes.

Radon is a colorless, odorless gas thatcan cause lung cancer. Yourcustomers rely on you to construct ahigh quality, safe home. You can easilymake a difference in how much radon

gets into the homes you build. Byusing a handful of simple buildingpractices and common materials, youcan effectively lower the radon level inthe homes that you build, and buildmost radon problems right out of thehouse.


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Does it make sense to build homes radon-resistant?

Absolutely. There are a number of reasons why you should considerinstalling radon-resistant features. Offering homes with radon-resistant

features can attract more potentialhome buyers, which can translate intoclosing more sales and greater profits.Consumers are becoming more awarethat radon is a health risk, andbuilding a home with radon-resistantfeatures could give buyers one morereason to purchase a home from you.About one in every six homes is beingbuilt radon-resistant in the UnitedStates every year, averaging about200,000 homes annually, according toannual surveys of home builderpractices conducted by the NationalAssociation of Home Builders (NAHB)Research Center over the past decade.In high radon areas, about one in everythree homes is built with the features.

Industry surveys continue todemonstrate a rapidly growing marketfor more energy-efficient,environmentally-friendly, comfortable,and healthy homes. Radon-reductiontechniques are consistent with state-of-the-art energy-efficient construction.

The features can also decreasemoisture and other soil gases enteringthe home, reducing molds, mildews,methane, pesticide gases, volatileorganic compounds, and other indoorair quality problems. When using thesetechniques, follow the Model EnergyCode (or other applicable energy codes)for weatherization, which will result inenergy savings and lower utility bills forthe homeowner.

You can gain a marketing advantage


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Building Radon Out

It is a good investment for ahome buyer

It is simple to install

It is effective Upgrading is easy

It is cheaper to install a radon-reduction system during constructionthan to go back and fix a radon problemidentified later. On average, installingradon-resistant features duringconstruction costs about $350 - $500,or even less if you already use some of the techniques for moisture control orenergy efficiency. (Many builders whouse the techniques have reportedactual costs of $100 or less.) Incontrast, retrofitting an existing homewill typically cost between $800 and$2500.

All of the techniques and materials arecommonly used in construction. Nospecial skills or materials are required.

A basic radon reduction system, calleda passive sub-slab depressurizationsystem, effectively reduces radon levelsby an average of about 50% and, inmost cases, to levels below EPA s actionlevel. An upgraded system, called anactive sub-slab depressurizationsystem, includes an in-line fan toprovide even further reductions.

After occupancy, all homes should betested for radon, even those built withradon-resistant features. EPArecommends that homes with radonlevels at or above 4 picocuries per literof air (pCi/L) be fixed. Homes with apassive system can be upgraded to anactive system with the simpleinstallation of a special in-line fan tofurther reduce the radon level.

Typically, the passive system includes a junction box in the attic to make the

future installation of the fan easy. Thisupgrade is also used by some buildersto control moisture in basements andcrawlspaces.


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Digging Deeper: Questions and Answers

This chapter digs deeper into some of the more commonly asked questionsconcerning radon-resistant new

construction.


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Questions and Answers

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What Is Radon?

Radon is a radioactive gas. It comesfrom uranium and radium in soils,which can be found everywhere in theworld. Uranium is present in rockssuch as granite, shale, phosphate andpitchblende. Uranium breaks down to

radium, which then decays into radon. This gas can easily move up throughthe soil into the atmosphere. Naturaldeposits of uranium and radium, notman-made sources, produce most of the radon present in the air.

Radon is in the soil and air everywherein varying amounts.

People cannot see, taste, feel, or smellradon. There is no way to sense thepresence of radon.

Radon levels are commonly expressedin picocuries per liter of air (pCi/L),where a picocurie is a measure of radioactivity.

The national average of indoor radonlevels in homes is about 1.3 pCi/L.Radon levels outdoors, where radon isdiluted, average about 0.4 pCi/L.

Radon in the soil can be drawn into abuilding and can accumulate to highlevels. Every building or home has thepotential for elevated levels of radon.All homes should be tested for radon,even those built with radon-resistantfeatures. EPA recommends takingaction to reduce indoor radon levelswhen levels are 4 pCi/L or higher.


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Building Radon Out

Is Radon A Significant Health Risk?

When radon enters a home, it decaysinto radioactive particles that have astatic charge, which attracts them toparticles in the air. These particles canget trapped in your lungs when youbreathe. As the radioactive particles

break down further, they release burstsof energy which can damage the DNA inlung tissue. In some cases, if the lungtissue does not repair the DNAcorrectly, the damage can lead to lungcancer.

Not everyone exposed to elevated levelsof radon will develop lung cancer, but

your risk of getting radon-induced lungcancer increases as your exposure toradon increases (either because theradon levels are higher or you live inthe home longer). Smokers who havehigh radon levels in their homes are atan especially high risk for gettingradon-induced lung cancer.

The evidence that radon causes lungcancer is extensive and based on:human data taken from studies of underground miners carried out overmore than 50 years in five countries,including the United States and

Canada; human data from studies inhomes in many different nations,including the U.S. and Canada; andbiological and molecular studies.

Energy released fromradon decay products

damages DNA

Radon decay particlesare breathed into thelungs

Radon is classified as aClass A carcinogen (known to

cause cancer in humans).

Some other Class Acarcinogens are arsenic,asbestos, and benzene.


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The following is a sample of organizations which state that radon isa health threat in homes:

" U.S. Surgeon General"

American Medical Association" American Lung Association" Centers for Disease Control" National Cancer Institute" National Academy of Sciences" Environmental Protection Agency

The risk of developing lung cancer fromradon has been clearly demonstrated inunderground miners. Did you knowthat the average lifetime radonexposure for the general population isabout the same as the levels of exposure at which increased risk hasbeen demonstrated in undergroundminers?

A study released by the NationalAcademy of Sciences on February 19,1998 called The Health Effects of Exposure to Indoor Radon is the mostdefinitive accumulation of scientificdata on indoor radon. The reportconcludes that radon causes 15,000 -22,000 deaths per year, making it thesecond leading cause of lung cancer inthe U.S. and a serious public healthconcern.

Is Radon A Health Problem In Homes?

Stanley J. Watras was a constructionengineer at the Limerick nuclear powerplant in Pottstown, Pennsylvania. Oneday, on his way to work, he entered the

plant and set off the radiation monitoralarms which help protect workers bydetecting exposure to radiation. Safetypersonnel checked him out, but couldnot find the source of the radiation.Interestingly, because the plant wasunder construction at the time, therewas no nuclear fuel at the plant. Theydiscovered the source of radiationexposure when Watras s home wastested and was measured to have veryhigh radon levels (2,700 pCi/L). Afterinstalling a radon-reduction system,radon levels in the home tested below4 pCi/L.

Radon is the second leadingcause of lung cancer in the

United States.

Radon causes about 20,000

lung cancer deaths per year.

Have You Heard Of Stanley Watras?


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Building Radon Out

There is no known safe level of radon.As your exposure to radon is increased,so is your risk for developing lungcancer. Even radon levels below 4pCi/L pose some risk.

Homes have been found with radonlevels above 20, 100, and in rare caseseven 2000 pCi/L. High indoor radonlevels have been found in every state.

EPA, the Surgeon General, the Centersfor Disease Control, and many otherhealth organizations recommend thataction be taken to reduce indoor radonlevels at or above 4.0 pCi/L, which is areasonably achievable level of radon inhomes using currently available cost-effective techniques.

Radon is a significant risk. Morepeople die from lung cancer caused byradon each year than from many otherhighly publicized causes of death.

Is There A Safe Level Of Radon?

* data from the National Safety Council, 1999


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How Does Radon Enter A House?

Four main factors drive radon entryinto homes. All of these factors exist

in most homes throughout the country.

1. Uranium is present in the soilnearly everywhere in the United States.

2. The soil is permeable enough toallow radon to migrate into the homethrough the slab, basement orcrawlspace.

3. There are pathways for the radon toenter the basement, such as small

holes, cracks, plumbing penetrations,or sumps. All homes have radon entrypathways.

4. An air pressure difference betweenthe basement or crawlspace and thesurrounding soil draws radon into thehome.

Common Radon Entry Points


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Building Radon Out

The air pressure in a house is generallylower than in the surrounding air andsoil, particularly in the basement andfoundation levels. This difference inpressure causes a house to act like avacuum, drawing air containing radonand other soil gases in throughfoundation cracks and other openings.Some of the replacement air comesfrom the underlying soil and cancontain radon.

One reason why this pressuredifference occurs is because exhaustfans remove air from inside the house.When this air is exhausted, outside airenters the house to replace it. Anothercause for a pressure difference is that

warm air rises and will leak fromopenings in the upper portion of thehouse when temperatures are higherindoors than outdoors. This condition,known as stack effect, causesunconditioned replacement air to enterthe lower portion of the house.

How Does Air Pressure Affect Radon Entry?

Warm air rises upand out through

leaks in the buildingenvelope. Air is

also drawn out bymechanicalventilation (e.g.

bathroom fans andclothes dryers) and

combustionexhaust.

Replacement air entersthe house by

infiltration in lowerlevels. Soil gases are

also drawn into thehome where the housecontacts the ground.

Mechanical systems, such as thefurnaces or central air conditioners,may also contribute to the difference inair pressure. In areas with very shortmild winters, mechanical systems can

be the dominant driving force. Airhandlers and leaky return ducts cannot only draw in radon, they can alsodistribute it throughout a home.


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The vacuums thatexist within a homeare exerted on thecrawlspaces causing

radon and othergases to enter the

home from the earthen area below.Even with crawlspace vents, a slightvacuum is still exerted on thecrawlspace. Measurements in homeswith crawlspaces have shown elevatedradon levels.

Radon can enterthrough floor-to-wall

joints and control joints and cracks inthe slab.

Does Foundation Type Affect Radon Entry?

Because radon can literally be suckedinto a home, any home can potentiallyhave a radon problem. All conventionalhouse construction types have beenfound to have radon levels exceedingthe action level of 4 pCi/L.

Basement Slab-On-Grade

Crawlspace Manufactured Homes

Radon can enter ahome regardless of whether or not there isa basement. Slabsbuilt on grade can

have just as many openings to allowradon to enter as do basements.

Unless thesebuildings are set upon piers without anyskirting placed

around them,interior vacuums can

cause radon to enter these types of homes as well.


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Building Radon Out

What Can You Do To Reduce Radon In New Homes?

Sealing large cracks and openings isimportant to do when you build ahome, both in the lower portion of thehome to reduce radon entry points, and

in the upper portion of the home toreduce stack effect. However, fieldresearch has shown that attempting toseal all of the openings in a foundationis both impractical and ineffective as astand-alone technique. Radon canenter through very small cracks andopenings. These small cracks andopenings are too small to locate andeffectively seal. Even if all cracks couldbe sealed during construction, whichwould be costly, building settlementmay cause new cracks to occur.

Therefore, sealing large cracks andopenings is one of the key componentsof radon-resistant construction, but notthe only technique that should beemployed.

Can we keep radon out by sealingthe cracks?

You can easily draw radon away and help prevent radon from entering thehome by with the following basic steps.

Reduce stack effect Sealing and caulking reduce stack effect,and thus reduce the negative pressure inlower levels in the home.

Install air distribution systems so that soil air is not mined Air-handling units and all ducts inbasements and, especially, in crawlspacesshould be sealed to prevent air, andradon, from being drawn into the system.Seamless ducts are preferred for runsthrough crawlspaces or beneath slabs.Any seams or joints in ducts should besealed.

You may already be employing many of these techniques in the homes that youbuild. All of the techniques haveadditional benefits associated with

them and they are very easy to install.

Install a sub-slab (or sub-membrane) depressurization system

The objective of these systems is tocreate a vacuum beneath thefoundation which is greater in strengththan the vacuum applied to the soil bythe house itself. The soil gases that arecollected beneath the home are pipedto a safe location to be vented directlyoutside.

Use mechanical barriers to soil gas entry Plastic sheeting and foundation sealingand caulking can serve as barriers toradon entry, entry of other soil gases,and moisture.


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What Are The Radon-Resistant Features?

The techniques may vary for differentfoundations and site requirements, butthe basic elements of the passive sub-

slab depressurization system areshown on the opposite page.

In many parts of the country, thegravel beneath the slab (gas-permeablelayer), plastic sheeting, and sealing andcaulking are already employed formoisture reduction. In these cases,simply adding the vent pipe and

junction box is extremely cost-effectivefor reducing radon, and so cost-effective that even a cost-consciousbuilder like Habitat for Humanity hasbeen adding these features in many of its homes.

There are more in-depth discussionsabout installing the features in the nextchapter.

If the pipe is routed through warmspace (such as an interior wall or thefurnace flue chase, following local firecodes), the stack effect can create anatural draft in the pipe. Because thismethod requires no mechanicaldevices, it is called a passive soil depressurization system .

If further reduction is necessary tobring radon levels in a home below theaction level of 4 pCi/L or even lower, anin-line fan can be installed in the pipeto activate the system. The system isthen called an active soil depressurization system . The futureinstallation of the fan can be madeeasier with a little planning during

What pulls the soil gas throughthe pipe?


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A. Gas Permeable LayerUsually a 4-inch layer of clean, coarsegravel is used beneath the slab to allowthe soil gas to move freely underneaththe house. Other options are to installa loop of perforated pipe or soil gascollection mat (also known as drainagemat or soil gas matting).

B. Plastic SheetingPolyethylene sheeting is placed on top

of the gas permeable layer to helpprevent the soil gas from entering thehome. The sheeting also keepsconcrete from clogging the gaspermeable layer when the slab ispoured.

C. Vent PipeA 3- or 4-inch (recommended) PVC or

other gas-tight pipe (commonly used forplumbing) runs from the gas permeablelayer through the house and roof tosafely vent radon and other soil gasesabove the house. Although somebuilders have used 3-inch pipe, fieldresults have indicated that passivesystems tend to function better with4-inch pipe.

D. Junction BoxAn electrical junction box is wired incase an electric venting fan is neededlater to activate the system.

E. Sealing and CaulkingAll openings in the concrete foundationfloor are sealed to prevent soil gas fromentering the home. Also, sealing andcaulking the rest of the buildingenvelope reduces stack effect in thehome.


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Soil testing for radon is notrecommended for determining whethera house should be built radon-resistant. Although soil testing can bedone, it cannot rule out the possibilitythat radon could be a problem in thehouse you build on that lot. Even if soil testing reveals low levels of radongas in the soil, the amount of radonthat may enter the finished housecannot be accurately predicted becauseone cannot predict the impact that thesite preparation will have onintroducing new radon pathways or theextent to which a vacuum will beproduced by the house. Furthermore,the cost of a single soil test for radonranges from $70 to $150, and at least 4

to 8 tests could be required toaccurately characterize the radon in thesoil at a single building site. Therefore,the cost to perform soil testing is veryhigh when compared with installing thepassive radon system in high radonpotential areas (see page 22 on highradon potential areas).

Is There A Way To Test The Lot Before Building?

operating costs by planning to routethe pipe through warm space tomaximize passive operation of thesystem.

The best way to determine the radonlevel in a home: test the home for radon after occupancy .

It is much easier and far less costly toprepare the sub-grade to improve soilgas flow before the slab is cast. Also,the pipe itself can be run more easilythrough the house before it is finished.

This significantly improves aestheticsand can reduce subsequent system

Why not wait to install thefeatures until after the home iscompleted and a radon test isperformed?


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New homes built in the United Statesare not required to meet a specifiedradon level. You are not required totest a home, nor to guarantee that ahome will meet a specified radon level.By installing radon-resistant features,

you are proactively offering your homebuyers features designed to reduceradon levels. Adopting radon-resistantbuilding techniques should notincrease your liability risks in any

jurisdiction as long as due care isexercised in following the properconstruction techniques. Especially inhigh radon areas, radon-resistantfeatures may actually help you marketand sell the homes you build.

Once you have decided to build radon-resistant, you will want to make sure toinstall the features properly. If yourbuilding code includes provisions forthe radon features, follow your coderequirements. Otherwise, follow theguidance provided in this document orin any of the following documents:

Model Standards and Techniques for Control of Radon in New Residential Buildings , EPA, March 1994

Appendix F: One and Two-Family Dwelling Code , 1995 Edition, Councilof American Building Officials

Appendix D: International One and Two-Family Dwelling Code , 1998Edition, International Code Council

Appendix F: International Residential Code , 2000 Edition, InternationalCode Council

Standard Guide for Radon Control Options for the Design and

Construction of New Low Rise Residential Buildings , E 1465-92,American Society for Testing andMaterials

Would I Incur Liability By Installing The Features?


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Should All New Homes Be Built Radon-Resistant?

All homes could benefit from having aradon reduction system. However, it isespecially cost effective to install thefeatures in homes with the greatestpotential for high radon levels.

The potential for elevated radon levelsis not uniform throughout the UnitedStates. EPA and the U.S. GeologicalSurvey have identified areas of thecountry with the greatest potential forhigh radon levels. The map shown onthe next page is the result of indoorradon measurements, local geology,and population densities in a combinedeffort to rank radon potentials in allcounties across the U.S. The mapindicates three radon potential zonesdefined by the likelihood of findingradon measurements within certainranges when a short-term closedbuilding radon test is performed.

If you are building in a Zone 2 or 3area, the homes you build could stillhave high radon levels, particularly if there is a radon hot spot in yourcounty. According to an annual surveyby the NAHB Research Center, about

60,000 homes in Zone 2 and 3 are builtwith radon-resistant techniques each year. You may want to considerapplying the techniques in these areastoo. Since the map was developed,many States have acquired additionalinformation on high radon areas.Contact your state radon office for moreinformation.

Consumers have asked for the radon-reduction features in many differentparts of the country and in all threeradon zones.

EPA recommends that allhomes built in Zone 1 (highradon potential) areas haveradon reduction systems.

NAHB also recommends using the

passive system in homes in high radonpotential areas (Zone 1). Zone 1counties are listed by state on pages 24and 25.


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List of Zone 1 CountiesALABAMACalhounClayCleburneColbertCoosaFranklin

JacksonLauderdaleLawrenceLimestoneMadisonMorgan

Talladega

CALIFORNIASanta BarbaraVentura

COLORADOAdamsArapahoeBacaBentBoulderChaffeeCheyenneClear CreekCrowleyCusterDeltaDenverDoloresDouglasEl PasoElbertFremontGarfieldGilpinGrandGunnisonHuerfano

Jackson JeffersonKiowaKit CarsonLakeLarimerLas AnimasLincolnLogan

MesaMoffatMontezumaMontroseMorganOteroOurayParkPhillipsPitkinProwersPuebloRio BlancoSan MiguelSummit

TellerWashingtonWeldYuma

CONNECTICUT FairfieldMiddlesexNew HavenNew London

GEORGIACobbDe KalbFultonGwinnett

IDAHOBenewahBlaineBoiseBonnerBoundaryButteCamasClarkClearwaterCusterElmoreFremontGoodingIdahoKootenaiLatahLemhiShoshoneValley

ILLINOISAdamsBooneBrownBureauCalhounCarrollCassChampaignColesDe KalbDe WittDouglasEdgarFordFultonGreeneGrundyHancockHenderson

HenryIroquois Jersey Jo DaviessKaneKendallKnoxLa SalleLeeLivingstonLoganMaconMarshallMasonMcDonoughMcLeanMenardMercerMorganMoultrieOglePeoriaPiattPikePutnamRock IslandSangamonSchuylerScottStarkStephenson

TazewellVermilionWarrenWhitesideWinnebagoWoodford

INDIANAAdamsAllenBartholomewBentonBlackfordBooneCarrollCassClarkClintonDe KalbDecatur

DelawareElkhartFayetteFountainFultonGrantHamiltonHancockHarrisonHendricksHenryHowardHuntington

Jay Jennings JohnsonKosciuskoLagrangeLawrenceMadisonMarionMarshallMiamiMonroeMontgomeryNobleOrangePutnamRandolphRushScott

ShelbySteubenSt. Joseph

Tippecanoe TiptonUnionVermillionWabashWarrenWashingtonWayneWellsWhiteWhitley

IOWAAll Counties

KANSASAtchison

BartonBrownCheyenneClayCloudDecaturDickinsonDouglasEllisEllsworthFinneyFordGearyGoveGrahamGrantGrayGreeleyHamiltonHaskellHodgeman

Jackson Jewell JohnsonKearnyKingmanKiowaLaneLeavenworthLincolnLogan

MarionMarshallMcPhersonMeadeMitchellNemahaNessNortonOsborneOttawaPawneePhillipsPottawatomiePrattRawlinsRepublicRiceRileyRooksRush

RussellSalineScottSheridanShermanSmithStanton

Thomas TregoWallaceWashingtonWichitaWyandotte

KENTUCKY AdairAllenBarrenBourbonBoyleBullittCaseyClarkCumberlandFayetteFranklinGreenHarrisonHart

Jefferson Jessamine

LincolnMarionMercerMetcalfeMonroeNelsonPendletonPulaskiRobertsonRussellScott

TaylorWarrenWoodford

MAINEAndroscogginAroostookCumberlandFranklin

HancockKennebecLincolnOxfordPenobscotPiscataquisSomersetYork

MARYLANDBaltimoreCalvertCarrollFrederickHarfordHowardMontgomeryWashington

MASSACHUSETTSEssexMiddlesexWorcester

MICHIGANBranchCalhounCassHillsdale

JacksonKalamazoo

LenaweeSt. JosephWashtenaw

MINNESOTABeckerBig StoneBlue EarthBrownCarverChippewaClayCottonwoodDakotaDodgeDouglasFaribaultFillmoreFreebornGoodhue

GrantHennepinHoustonHubbard

JacksonKanabecKandiyohiKittsonLac Qui ParleLe SueurLincolnLyonMahnomenMarshallMartinMcLeodMeekerMowerMurrayNicolletNoblesNormanOlmstedOtter TailPenningtonPipestonePolkPopeRamseyRed LakeRedwood

RenvilleRiceRockRoseauScottSherburneSibleyStearnsSteeleStevensSwift

Todd TraverseWabashaWadenaWasecaWashingtonWatonwanWilkinWinona

WrightYellow Medicine

MISSOURIAndrewAtchisonBuchananCassClayClintonHoltIron

JacksonNodawayPlatte

MONTANABeaverheadBig HornBlaineBroadwaterCarbonCarterCascadeChouteauCusterDanielsDawsonDeer LodgeFallonFergus

FlatheadGallatinGarfieldGlacierGraniteHill

Jefferson Judith BasinLakeLewis and ClarkLibertyLincolnMadisonMcConeMeagherMineralMissoulaParkPhillipsPondera

Powder RiverPowellPrairieRavalliRichlandRooseveltRosebudSandersSheridanSilver BowStillwater

Teton TooleValleyWibauxYellowstoneNational Park

NEBRASKAAdamsBooneBoydBurtButlerCassCedarClayColfaxCumingDakotaDixon


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DodgeDouglasFillmoreFranklinFrontierFurnasGageGosperGreeleyHamiltonHarlanHayesHitchcockHurston

Jefferson JohnsonKearneyKnoxLancasterMadison

NanceNemahaNuckollsOtoePawneePhelpsPiercePlattePolkRed WillowRichardsonSalineSarpySaundersSewardStanton

ThayerWashingtonWayneWebsterYork

NEW HAMPSHIRECarroll

NEW JERSEY HunterdonMercerMonmouthMorris

SomersetSussexWarren

NEW MEXICOBernalilloColfaxMoraRio ArribaSan MiguelSanta Fe

Taos

NEVADACarson CityDouglasEurekaLanderLincolnLyon

MineralPershingWhite Pine

NEW YORKAlbanyAlleganyBroomeCattaraugusCayugaChautauquaChemungChenangoColumbiaCortlandDelawareDutchessErieGeneseeGreeneLivingstonMadisonOnondagaOntarioOrangeOtsegoPutnamRensselaerSchoharieSchuylerSeneca

SteubenSullivan

Tioga TompkinsUlsterWashingtonWyomingYates

N. CAROLINAAlleghanyBuncombeCherokeeHendersonMitchellRockingham

TransylvaniaWatauga

N. DAKOTAAll Counties

OHIOAdamsAllenAshlandAuglaizeBelmontButlerCarrollChampaignClarkClintonColumbianaCoshoctonCrawfordDarkeDelawareFairfieldFayetteFranklinGreeneGuernseyHamiltonHancockHardin_ HarrisonHolmesHuron

JeffersonKnox

LickingLoganMadisonMarionMercerMiamiMontgomeryMorrowMuskingumPerryPickawayPikePrebleRichlandRossSenecaShelbyStarkSummit

Tuscarawas

UnionVan WertWarrenWayneWyandot

PENNSYLVANIAAdamsAlleghenyArmstrongBeaverBedfordBerksBlairBradfordBucksButlerCameronCarbonCentreChesterClarionClearfieldClintonColumbiaCumberlandDauphinDelawareFranklinFultonHuntingdon

Indiana JuniataLackawannaLancasterLebanonLehighLuzerneLycomingMifflinMonroeMontgomeryMontourNorthamptonNorthumberlandPerrySchuylkillSnyderSullivanSusquehanna

Tioga

UnionVenangoWestmorelandWyomingYork

RHODE ISLANDKentWashington

S. CAROLINAGreenville

S. DAKOTAAuroraBeadleBon HommeBrookingsBrownBruleBuffaloCampbellCharles MixClarkClayCodingtonCorsonDavisonDayDeuelDouglas

EdmundsFaulkGrantHamlinHandHansonHughesHutchinsonHyde

JerauldKingsburyLakeLincolnLymanMarshallMcCookMcPhersonMinerMinnehahaMoody

PerkinsPotterRobertsSanbornSpinkStanleySully

TurnerUnionWalworthYankton

TENNESSEEAndersonBedfordBlountBradleyClaiborneDavidsonGilesGraingerGreeneHamblenHancockHawkinsHickmanHumphreys

Jackson JeffersonKnoxLawrence

LewisLincolnLoudonMarshallMauryMcMinnMeigsMonroeMoorePerryRoaneRutherfordSmithSullivan

TrousdaleUnionWashingtonWayneWilliamsonWilson

UTAHCarbonDuchesneGrandPiuteSanpeteSevierUintah

VIRGINIAAlleghanyAmeliaAppomattoxAugustaBathBlandBotetourtBristolBrunswickBuckinghamBuena VistaCampbellChesterfieldClarkeClifton ForgeCovingtonCraigCumberlandDanvilleDinwiddie

FairfaxFalls ChurchFluvannaFrederickFredericksburgGilesGoochlandHarrisonburgHenryHighlandLeeLexingtonLouisaMartinsvilleMontgomeryNottowayOrangePagePatrickPittsylvania

PowhatanPulaskiRadfordRoanokeRockbridgeRockinghamRussellSalemScottShenandoahSmythSpotsylvaniaStaffordStaunton

TazewellWarrenWashingtonWaynesboroWinchesterWythe

WASHINGTONBerkeleyBrookeClarkFerryGrantGreenbrierHampshireHancockHardy

JeffersonMarshallMercerMineralMonongaliaMonroeMorganOhioOkanoganPend OreillePendletonPocahontasPrestonSkamaniaSpokaneStevensSummersWetzel

WISCONSINBuffaloCrawfordDaneDodgeDoorFond du LacGrantGreenGreen LakeIowa

JeffersonLafayetteLangladeMarathonMenomineePepinPiercePortageRichlandRockShawanoSt. CroixVernonWalworthWashingtonWaukeshaWaupacaWood

WYOMINGAlbany

Big HornCampbellCarbonConverseCrookFremontGoshenHot Springs

JohnsonLaramieLincolnNatronaNiobraraParkSheridanSubletteSweetwater

TetonUintaWashakie


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Nuts and Bolts: Installation Guide

As you ll see in this chapter, installingradon-resistant features is simple,because you use common buildingpractices and materials.

Proper installation of the radon-resistant features is very important.Improper installation could actuallyincrease indoor radon levels.

This section gives you step-by-stepinstructions - the nuts and bolts - on

how to install radon-resistant features.

The techniques in this document applyprimarily to new one- and two- familydwellings and other residentialbuildings three stories or less inheight.

Installation is easy.


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Step-By-Step Installation Guide

28

Answer The Question: To Install Or Not To Install?

Planning Step 1

? Do you want to reap the benefits

of installing the features? The features not only protect yourcustomer s health, they also affect yourbottom line: your profit. A smallinvestment up front on your part maymake a big difference in return downthe road, particularly as home buyersare increasingly looking forenvironmentally-conscious builders andhealthy homes.

Are you building in a Zone 1 area?

Check the radon potential map and thelist of Zone 1 counties in the previouschapter. Some states and countieshave done further research on radonpotential, and you can check with yourstate or county government to find outwhether additional information isavailable.

If you are building in a Zone 1 area, youshould install radon-resistant featuresin the homes that you build. Somebuilders also choose to install thefeatures in Zone 2 and 3 areas,particularly if radon-resistantconstruction is a common practice intheir area.

?

Planning To help you answer this question,consider the following points:


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Building Radon Out

? ? ? Are you required by code to use

radon-resistant techniques?Some states and local juridisdictionshave adopted Appendix F of the 1995CABO One & Two Family Dwelling Code,Appendix D of the 1998 International One & Two Family Dwelling Code , or asimilar code requiring installation of the radon-resistant features. TheInternational Code Council s newInternational Residential Code,published in early 2000, also contains avoluntary appendix for radon-resistantconstruction requirements thatbecomes effective if the appendix isadopted with the code. If you don talready know what is required in yourarea, check with your local code officialfor more information.

Are other builders in your area

installing radon-resistantfeatures?

If so, you may want to find out why theyare installing the features, how much itcosts to install the features in yourarea, and what the market responsehas been.

Are the home buyers in your area

interested in features thatimprove indoor air quality orenergy efficiency?

A sub-slab depressurization system notonly helps to reduce indoor radon levels,but also may help to reduce moistureand other soil gases. The techniquesalso improve energy-efficiency, which

can translate into energy savings forthe home buyer.


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Passive Systemin Crawlspace

Passive Systemin Basement or with

Slab-on-grade

Planning Step 2

There are three general types of radon-reduction systems that builders haveinstalled.

Passive sub-slab or sub-membrane depressurization system

It is cost-effective and recommended toinstall a complete passive sub-slab orsub-membrane depressurizationsystem, which would be fully-functioning as soon as construction isfinished. The home should be testedafter occupancy, and the passivesystem should be activated if post-occupancy testing reveals radon levelsat or above 4 pCi/L.

Recommended Option

Determine What Type Of System To Install


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Building Radon Out

Active Systemin Basement or with

Slab-on-gradeActive sub-slab or sub-membrane depressurization system

Activating a passive system by addingan in-line fan would be an effectiveupgrade during construction. Virtuallyall homes with an active system haveradon levels below the 4 pCi/L actionlevel.

Passive system rough-in

Some builders perform only the sub-slabpreparation and stub the vent pipeabove the slab. A vent pipe can beconnected and routed through the homeand roof later if radon levels are high.This is not the recommendedapproach. It is much more cost-effective to run the vent pipe throughthe house during construction ratherthan after the walls have been closedup. However, if you elect to rough in a radon-reduction system, it is important to be clear with the home buyer that the home is not equipped with a functioning system. Be sure to seal off the riser stub so that radon is not being vented into the living space. Also, label the stub so it is not used as a plumbing waste line.

Upgraded Option Not Recommended


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Planning Step 3

The vent pipe exhausts radon collectedfrom beneath the slab or crawlspace.One objective of a radon system in anew home is to install it in such a

manner that a natural draft occurs inthe pipe to draw the radon from the soilwithout the use of a fan. To accomplishthis, route the pipe up through a warmpart of the house and exhaust itthrough the roof.

Ideally, the vent pipe should beinstalled in a vertical run, with the

least number of elbows which couldrestrict air flow. A radon vent pipe canalso be run through the same chase asthe furnace and water heater flue. Donot tie them together, but rather allowfor enough room to route the radonvent pipe up alongside the flues with

proper clearances consistent with localbuilding and fire codes. This meansthat the riser should be brought upthrough the slab within the same room

as the furnace or water heater. Thisrequires a little planning on your partto identify this location before the slabis poured and to allow for sufficientroom in the chase.

In cold climates, do not route the pipeup through an outside wall. Routing thepipe up an outside wall will reduce the

natural thermal stack effect in the ventpipe, reducing its effectiveness. It willalso make it difficult to install a fan inthe attic if it is needed later on. Abetter option is to route the pipe upthrough an interior wall.

Route Pipe Through Warm Spaces

Determine Vent Pipe Location And Size

In hot climates and predominantly air-conditioned houses, the passive stackwill depend more on wind, a hot attic,and sun heating the pipe.


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Building Radon Out

To prevent radon from re-entering thehouse or any other nearby buildings,make sure the vent pipe exhausts:

" a minimum of 12 inches above thesurface of the roof

" a minimum of 10 feet away from anywindows or other openings in thebuilding

" a minimum of 10 feet away from anywindows or other openings in

adjoining or adjacent buildings

When deciding between 3-inch and4-inch pipe (PVC or ABS), the 3-inchpipe size is the minimum you shoulduse. However, 4-inch pipe is the

preferred choice for a couple of reasons.Field results have indicated thatpassive systems tend to function betterwith 4-inch pipe. A 4-inch pipe will alsoallow for a quieter system if the systemis activated.

Discharge Location Use 4-inch Pipe When Possible

If you are routing the pipe through thesame chase as the furnace flue, thevent pipe needs to exit the roof at least10 feet away from the furnace flue.

Plan to elbow the pipe away from theflue in the attic to maintain thisseparation above the roof. However,the additional elbows and horizontalpipe length will restrict air flow throughthe pipe if the system is activated. Use45 degree joints to reduce friction.


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See page 45 Treat each foundationseparately and use theappropriatetechniques for eachfoundation segment.Pay special attentionto the points at which

different foundationtypes join, becausesoil-gas entry routesexist in suchlocations. For analternative, seepage 43.

See page 35

Basement or Slab-on-Grade Crawlspace Combination Foundation

The type of system you installalso depends on foundation type. Pleasesee the pages listed below whichcorrespond to the type of foundation youwill be using.

Installation


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Building Radon Out

Basement and Slab-on-Grade Construction:Sub-Slab Preparation

Installation Step 1

If the house you are building has a slab-on-grade or basement foundation, theradon gas must be able to move laterallybeneath the slab to the location wherethe vent pipe collects the gas. Thereare three basic methods for improvingsoil gas collection beneath slabs.

This option is generally chosen inregions of the country where gravel isplentiful and economical or wheregravel is required by the building codefor water drainage. A continuous four-inch layer of -inch to -inch clean (nofines) gravel placed beneath a slabprovides a largely unrestricted path forradon to be collected. This size gravelprovides a drainage layer and capillarybreak for moisture control.

In some regions of the country, gravelis not a feasible option, either becausenative soils are sufficiently permeable

and gravel is not required for waterdrainage, or because lack of local supplymakes gravel very expensive. Onealternative is to use the native fillsbeneath the slab and lay in a loop of perforated pipe to improve soil gasmovement. This method is alreadyemployed in some homes with the useof a drain tile loop. The loop of perforated pipe works well because thesoil gases need only move to the looprather than all the way across the slabas in the case of a single collectionpoint.

In some areas, the perforated pipeoption may not be feasible if the laborneeded to dig a trench for the pipe loop

is too expensive, or if sub-grade soilsare compacted or frozen. The thirdoption is to install interconnected stripsof drainage mats (soil gas mats) on topof the sub-grade and beneath the slab.Drain mats consist of plastic materialthat resembles an egg crate. Wrappedaround the egg crate is a geotextilefilter fabric that allows for the passageof air but prevents the infiltration of wetconcrete. The mat can be laid directlyon top of the prepared sub-grade, whichshould be a uniform layer of sand(native or fill) a minimum of fourinches thick. The concrete can bepoured directly over the soil gascollection mat.

For installation guidance, see page 36. For installation guidance, see page 38. For installation guidance, see page 40.

Gravel

Perforated Pipe Alternative Soil Gas Collection MatAlternative


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GravelInstallation Step 1A

Place a uniform layer of clean aggregateunder all concrete slabs or floor systemsthat directly contact the ground and arewithin the walls of the living spaces.

Use a minimum 4-inch thick layer. The gravel should be about - to -inchsize. Smaller or fine gravel, or gravelthat is not as uniform in size, willrestrict air movement under the slab.

Grade Beam Obstructions

A grade beam or intermediate footing isoften installed beneath a slab to

support a load-bearing wall, presentinga barrier to the lateral flow of airbeneath the slab to the soil gascollection point. There are a fewoptions that can be used to avoid gradebeam obstructions to soil gas air flow.

Option 1Use post and beam construction bysetting teleposts that support overheadbeams on pads rather than continuousfootings.

Option 2 Provide a means for air to flow throughthe grade beam. This is can be done byinserting at least two 4-inch pipesleeves between the form boards ortrench and pouring the grade beam overthem. A minimum of two pipes shouldbe installed at opposite ends of thegrade beam. One pipe should beinstalled every 10 feet. Tape the endsso concrete does not enter the ends of the pipe while pouring the footing.Remove the tape when forms areremoved and before connecting to pipe

loop if a pipe loop is used.

Option 3Add a second riser on the other side of the grade beam. Tie the riser into thevertical vent stack or run a second ventstack.


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Building Radon Out

Inserting Vent Pipe In Gravel

Place a 3- or 4-inch TEE fitting at thelocation where you want the riser to

extend through the slab. The size of the TEE or elbow will depend upon thediameter of vent pipe you will beinstalling.

Connect a short stub, at least 8 inches,of 3- or 4-inch PVC pipe vertically intothe TEE.

Soil gas air flow can besomewhat restricted if thepipe is inserted into thegravel, and the gravel fills thepipe, especially if the systemis later activated. To allowfor airflow over a larger area,lay 3- or 4-inch perforatedand corrugated pipe(recommended minimumlength of 10 feet) in thegravel and connect it to theradon vent riser TEE fitting.Depending on the location of

the riser, an elbow fittingmay be used in place of a TEEfitting when using additionalpiping in the gravel. Makesure that the concrete doesnot plug up the pipe duringpour.

RecommendedImprovement


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Lay a 3- or 4-inch diameter perforateddrain pipe in a trench around thefoundation perimeter just inside thefoundation footing. This could be thesame pipe loop used for under-slabdrainage. Be sure the pipe is coveredby at least one inch of fill to keepconcrete from filling perforations.

What Kind Of Pipe WorksBest?

Perforated and corrugated pipe isflexible, which makes it easy to laydown in a trench. The perforations also

allow for good soil gas collection. It isrecommended that the pipe be coveredwith a geotextile cloth to prevent finesfrom clogging the holes.

How Much Pipe Do I Need?

Based on field work, it is recommendedto lay a continuous loop of 3- or 4-inchdiameter perforated pipe in the sub-grade with the top of the pipe located anominal one inch below the concreteslab, for slab areas less than 2,000square feet. The pipe loop should belocated approximately 12 inches fromthe inside of the exterior perimeterfoundation walls. For slab areas greaterthan 2,000 square feet, but less than4,000 square feet, the sameconfiguration may be used but the pipesize should be a minimum of 4 inchesin diameter. Slab designs in excess of 4,000 square feet should have separateloops for each 2,000 to 4,000 square feetdepending upon the size of pipe utilized(3-inch or 4-inch).

Pipe Alternative

Perforated Pipe


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Building Radon Out

For a more secure connection, when3-inch corrugated pipe is used forthe loop, the corrugated pipe can beinserted into a 4-inch PVC TEE bysecuring with sheet metal screws.When 4-inch corrugated pipe isused, 4-inch by 4-inch rubbercouplings can be used to connect theperforated pipe to the solid PVC pipestubs.

Install In Loops Rather ThanStraight Sections

The reason for laying out the pipe in aloop is to allow for the soil gas to enterthe collection pipe from two sides.

Also, if the pipe is crushed at one pointduring the construction, the soil gaswill still be drawn to the vent pipe.

Crossing Grade Beams

In buildings where interior footings orother barriers separate the sub-gradearea, the loop of pipe shouldpenetrate, or pass beneath, theseinterior footings and barriers. Lay theloop before the grade beams arepoured, or lay a length of non-perforated but corrugated pipe acrossthe trench before pouring a gradebeam. If the latter method is used,tape off the ends of the pipe beforepouring the beam, remove the tapeafter pouring, and finish connecting theloop.

Connecting Pipe Loop To Riser

Close the loop by connecting the endsto short pipe stubs and to oppositelegs of a 3- or 4-inch PVC TEE.Connect a short stub of 3- or 4-inchPVC pipe vertically into the TEE.

InstallationTip


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First, install a uniform layer of sand, aminimum of four inches thick. Next,place a layer of drainage matting overthe sand, or lay a loop of matting insidethe exterior perimeter foundation walls(no farther than a nominal 12 inchesfrom the perimeter foundation walls).

In buildings where interior footings orother barriers separate the sub-gradearea, the matting should penetratethese interior footings or barriers toform a continuous loop around theexterior perimeter.

Slabs larger than 2,000 sq. ft., but less

than 4,000 sq. ft., should have anadditional strip of matting that bisectsthe loop, forming two areas equallyimpacted by the two halves of therectilinear loop. Slab designs in excessof 4,000 sq. ft. should have successiveloops of drain mat with one riser per4,000 sq. ft. of area.

Some mats that are sold for radonreduction are only -inch high and onlyhave one side covered with a geotextile

cloth. If this material is used, use aminimum width of 24 inches. To keepconcrete from entering the matrix, itwill need to be covered with geotextilecloth. Do not cover with plastic stripsbecause differential concrete dryingcan occur and cause a crack in theconcrete along the edge of the plastic.

Mat material

Use a soil gas collection mat ordrainage mat having minimumdimensions of one inch in height by 12inches wide, and a nominal cross-sectional air flow area of 12 squareinches. The mat matrix should allow

for the movement of air through it and yet be capable of supporting the weightof the concrete above it. The matrixshould be covered by a geotextile filtercloth on all four sides to prevent dirt orwet concrete from entering the matrix.Repair all breaches and joints in thegeotextile cloth prior to the pouring of the slab.

Mat Alternative

Soil Gas Collection Mat


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Building Radon Out

Connecting Soil GasCollection Mat To Vent Pipe

There is a special adaptor fitting thatwill accept the flat mat and adapt to around vent pipe (see graphic on right).

This type of adaptor is available fromsoil gas collection mat and drainagemat suppliers, and from radonmitigation equipment suppliers. Themat is inserted into the flat ends andthe geotextile fabric is taped to theedges to prevent wet concrete fromentering the TEE. The top of the TEE ismolded plastic to keep wet concrete out.

After the concrete is poured, the top canbe cut with a hacksaw and a 4-inchriser inserted and glued or cementedinto place.

Making SplicesWhen making splices, slit the fabricof the two ends to be joined. Lay thecore from one end on top of the corefrom the other end with a three inchoverlap. Lay the fabric back over thetop of the splice and thoroughly sealwith duct tape to keep the wetconcrete from seeping in. Drive atleast two 8-inch long staples throughthe mat at this point, being sure todrive them through the point wherethe two ends overlap.

Making TEEs in MatIf you need to connect a length of mat in the middle of another lengthof mat, make a TEE by: cutting backthe geotextile cloth, overlapping theinterior matrix, replacing the cloth,securing with nails or landscape

staples, and using duct tape to sealopenings in the geotextile cloth.

Securing the Mat To keep the mat in place while theconcrete is being poured, the matshould be nailed down with 8-inchlandscape staples, or 60 penny nails,about every seven feet.

Seal Cloth Tears WithDuct Tape

To insure that wet concrete does notenter the mat interior, cuts and tearsshould be sealed with duct tape.

InstallationTip


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Laying plastic sheeting between the gaspermeable layer and the concrete slabor floor assembly serves severalimportant purposes. The sheeting canprevent concrete from flowing downand clogging the gas permeable layer.It can also bridge any cracks that maydevelop in the slab or floor assembly,thereby reducing soil gas entry.Finally, the plastic sheeting can act asa vapor barrier to reduce moisture andother soil gas entry into the home.

Prior to pouring the slab or placing thefloor assembly, lay a minimum 6-mil(or 3-mil cross laminated) polyethylene

or equivalent flexible sheeting materialon top of the gas permeable layer. Thesheeting should cover the entire floorarea.

Installation Step 1B

Separate sections of sheeting should beoverlapped by at least 12 inches. Belowa slab, it is not necessary to seal the

joint between overlapping sheets of plastic.

The sheeting should fit closely around

any pipe, wire or other penetrations.

Repair punctures or tears in thematerial. Duct tape may work forsmall, uniform tears or holes. Forlarger tears, cover with an additionalpiece of overlapping sheeting.

Plastic Sheeting

Below: Thomas Dickey of the EastMoline, IL Health Department inspectsplastic sheeting installed for a group of townhomes.


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Building Radon Out

Regardless of the sub-grade collection methodused, you will have ashort stub of pipesticking up to which thevent piping system willlater be attached. Careshould be taken tocover the end of thepipe so that it does notbecome filled withconcrete when the slabis poured.

Label this stub so thatsomeone does not

mistakenly think it istied to the sewer andset a commode on it.

Support the stub,perhaps off a wall, so thatit stays vertical as the wetconcrete is poured.

Installation Step 1C

Seal Off And Label Riser Stubs

Alternative For CombinationFoundations

Some builders have found itto be more economical to tiethe different foundationstogether into a single riser.Place a pipe to connect thesub-grade area to the crawlspace in the trench of theintervening footing prior topouring the foundation walls.

This pipe should be 4-inchperforated and corrugatedpipe to prevent accumulation

of water, which could blockair flow. Cover withgeotextile cloth. Tape theends of the cross-over to keepfrom getting debris in it untilthe pipe can be connected tothe slab and crawlspacesystems.


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Installation Step 1D

Lay Foundation

Foundation walls and slabs should beconstructed to reduce potential radonentry routes. In general, openings inwalls and slabs should be minimized,and necessary openings and jointsshould be sealed.

Foundation WallsIn poured concrete walls, all control

joints, isolation joints, and any other joints should be caulked with anelastomeric sealant such aspolyurethane caulk.

Hollow block masonry walls typicallyhave cavities that can allow radonmovement. To prevent this, hollowblock walls should be topped with acontinuous course of solid block or begrouted solid on the top. Alternatively,use a solid concrete beam at or abovethe finished ground level or a full sillplate.

Dampproof foundation walls, and sealany penetrations through the walls.

SlabPour a strong slab, and take steps tocontrol cracking. Although concrete

slabs will almost inevitably crack,control joints can help the concrete tocrack in planned locations. As with thefoundation walls, all control joints orother joints should be sealed withpolyurethane caulk to reduce radonentry.

Do not deliberately puncture holes inthe plastic sheeting prior to pouring theslab. Some contractors will do this toallow excess water to drain from the wetconcrete. Putting holes in the plasticsheeting decreases (but does noteliminate) its effectiveness as a soil-gas retarder. It is preferable to useconcrete with a lower water-to-cementratio (low slump concrete).

Similarly, some contractors will put alayer of sand on top of the polyethylene,both to protect it and to absorb waterfrom the concrete mix. This practice isnot recommended. The sand maybecome wet, from the concrete or risingground water, and would have to dry tothe interior through the concrete. Thepresence of the polyethylene sheetingduring this drying process may causemoisture problems above the slab.

Trap any condensate or floor drainswhich pass through the slab, or routethem through non-perforated pipe todaylight. Mechanical traps should be

used rather than wet traps which candry out.

Sump pits which are open to the soil orfed by drain tile loops should becovered with a gasketed lid. For moreinformation on sumps, see page 52.


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Building Radon Out

Installation Step 2

Crawlspaces are best treated bycovering the entire crawlspace floorwith plastic sheeting, laying a

perforated collection pipe beneath theplastic sheeting, and connecting thepipe to the radon vent riser.

Crawlspaces should be constructedconsistent with applicable buildingcodes.

Access doors and other openings orpenetrations between basements andadjoining crawlspaces should beclosed, gasketed, or otherwise sealedwith materials that prevent airleakage.

Crawlspace Construction


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Location Of Riser

The riser can be located anywhere inthe crawlspace. It does not need to bein the center, so plan on placing itanywhere in the crawlspace that will beconvenient for crawlspace access andfor routing the pipe up through thehouse.

Install Pipe

Lay a length (usually five feet or more)of 3- or 4-inch diameter corrugated andperforated pipe or a strip of geotextiledrain matting on the soil at the locationwhere you will run the radon vent pipeup.

Amount Of Plastic

Plan enough plastic to allow you tooverlap seams by 12 inches. Theedges should also be brought up onthe foundation walls about 12 inchesto allow for proper adhesion. It iscritical to allow for enough excessplastic so if a vacuum is drawnunderneath the plastic, the plastic canconform to the surface of thecrawlspace floor (like vacuumpackaging). If the amount of excessplastic is insufficient, the plastic maystretch over a depression in the dirtlike a trampoline.

Install Plastic Sheeting

Clear the crawlspace area of objectswhich may puncture the plasticsheeting.

Lay a continuous layer of minimum6-mil (or 3-mil cross-laminated)polyethylene sheeting or equivalentmembrane material to cover the entirecrawlspace area.

Crawlspaces Continued


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Building Radon Out

Type Of Plastic

The minimum thickness of plastic is a 6-mil polyethylene sheeting.However, this material is not very durable if the crawlspace will be accessedfrequently or if occupants would like to use this area as storage. Regular 8-to 10-mil sheeting would provide better puncture resistance. High-density,cross-laminated polyethylene has even greater puncture resistance and isstronger and more durable. Unlike the regular polyethylene sheeting, whichcan be torn by hand even with a thickness of 10 mil, the high-density cross-laminated material cannot be torn by hand, even though its thickness may

be only 4 mil. Due to its significantly increased puncture resistance, thecross-laminated polyethylene is recommended. The high-density sheetingis also available in white, making the crawlspace brighter and most suitablefor use as storage space.

Special Precautions

It may be necessary to take specialprecautions to ensure that the plasticsheeting will not be damaged afteroccupancy. In high traffic areas, thepolyethylene should be overlain byheavier material along expected trafficroutes. Various materials have beenused for this purpose, including roofingfelt, EPDM rubberized roofingmembrane, and drainage mat. Also, if there may be foot traffic over the entirecrawlspace floor, or if the crawlspacehas very irregular floors, such as sharpprotruding rocks, it may be advisableto use thicker cross-laminated plasticsheeting or to lay a heavier materialunderneath the polyethylene, betweenthe sheeting and the crawlspace floor.

OptionalImprovement


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Sealing The Sheeting

Although not required in current radon-resistant construction building codes,increasing the air-tightness of theseams in the plastic sheeting mayenhance the system s effectiveness andintegrity. Sealing should be sufficientlydurable to withstand anticipated trafficthrough the crawlspace. To effectivelyseal the plastic sheeting, use a -inchwide bead of caulk.

Type Of Caulk

Polyurethane caulk will provide someadhesion to the polyethylene sheeting.However acoustical sealant, butylrubber, or butyl acrlyic caulks form amore durable bond with the plastic.Field work suggests that otherproprietary sealants are also effective,such as Proflex by GeoCel.

Sealing Seams

Seams between adjoining sheets of sheeting are usually sealed by

applying a continuous bead of sealantbetween the sheets in the 12-inch stripwhere the sheets overlap. Firmly pressthe overlapping sheets together.


Optional Improvement: Sealing seamsand edges of plastic sheeting


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Building Radon Out

Sealing Edges And Seams

Brush the walls with a wire brush at 6to 12 inches above the crawlspace floorto remove any dirt or loose deposits.

Makesure thesheetinglays flaton thecrawlspacefloor rightup to the wall. Leave several inches of slack on the vertical section of theplastic rising up the wall to help prevent

the plastic from pulling on the seamdue to foot traffic or by the system itself when it is functioning.

Secure plastic to the wall at 6 to 12inches above the crawlspace floor witha -inch wide bead of acousticalsealant or butyl caulk along the wall.

Keeping Plastic In PlaceWhile the caulk is curing, use duct tape along the seam to hold the sheetstogether. The tape can secure the seam to keep the seam from breakingduring the cure as workers complete the installation. When sealing edges,it is also a good idea to temporarily tape the free edge of the plastic so it willstay in place as the caulk cures. Place weights on the plastic to keep it frombeing pulled off the walls as you work on the balance of the crawlspace.

Vertical Pentrations The sheeting needs to be sealed around posts and plumbing lines. It iseasier to seal a large sheet to a flat apron section than to try to fit itaround the obstacle. You can use scraps of plastic to form an apron to fitaround these obstructions. Also, try to plan your seams along rows of piers. When sealing around plumbing risers, make sure that the clean-out is accessible.

Plan on using one11-ounce tube of caulkto attach an 8-footlength of plastic to

the wall.

For a more durable connection,consider using mechanical fasteners,such as strapping, to hold the plastic tothe wall. If there is an obstruction tothe wall within six to 12 inches of thefloor, such as a crawlspace access door,

trim the sheeting to pass beneath theobstruction and caulk the sheeting tothe wall around the obstruction. Atcorners, cut and tuck plastic sheetingneatly, and make sure that the sealingis also airtight.

InstallationTip


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Riser Installation

The vent pipe needs to be connectedto the perforated pipe beneath theplastic in a manner that prevents airleakage. The plastic sheeting can bewrapped around the vent pipe andtaped to the pipe securely.

Another way to prevent air leakagearound the joint is to use two roof flashing hoods. One roof flashing goesbelow the plastic and one is placedabove the plastic to provide a flat areato which the plastic can be sealed. Theriser is sealed by the rubber grommet

on the roof flashing. The two roof flashings are then secured by sheetmetal screws. Depending on thelocation of the riser, there may beeither a PVC TEE or an elbow beneaththe plastic that has a short 4-inch stubof pipe to which the corrugated andperforated pipe will be connected.


Label Riser And Plastic

It is a very good idea to label the riserwithin the crawlspace so it is notconfused with any other plumbing. Itis also a good idea to label the plasticto state that the plastic should not beremoved and, if cut, it should bepatched or replaced.

After home construction is completed,inspect the sheeting for damage andrepair as necessary.


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Building Radon Out

After you pour the slab or place the floorassembly, seal major openings in theslab to retard soil gas entry throughopenings in the slab or floor assembly.

Use materials that provide apermanent airtight seal such as non-shrink mortar, grouts, expanding foam,or similar materials. When caulkingslab openings, it is best to utilize apolyurethane caulk which hasexcellent adhesion characteristics forconcrete. The following are someexamples of locations to be caulkedafter the concrete slab has cured andbefore framing is installed.

Joint Type Feet per11 oz. Tube

Cold 12

Expansion 8

Installation Step 3

Seal Floor-To-Wall-Joints

Floor-to-wall joints are critical places toseal. Brush debris away from the jointbefore applying caulk. Apply enoughcaulk so when smoothed with a piece of cardboard cut in a convex form, thecaulk will come out onto the floor andup on the wall about 3/8-inch. Thetable on this page indicates theapproximate length of joint that an11-ounce tube of caulk will cover.

Seal Openings

Seal control joints

Control joints in the concrete slab,whether they are saw cut or made withgrooving tools, should be cleaned andfilled with caulk. Even if they are notcracked initially, they will likelydevelop cracks in the future andcaulking them before the floor finishesare in place makes sense. A gun-gradepolyurethane or a flowable polyurethanecan be used. This seal does notinterfere with the expansion of thecontrol joint, but does block radon entry.


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Installation Step 3 Continued

Seal Open Sumps

An open sump may allow radon into thehouse from beneath the entire housefoundation. Make sure to cover andseal the sump. The sump cover, whichmust be removable to allow for regularmaintenance and inspection of thesump pump, is usually sealed by boltingit directly to the slab or sump-liner lip

and made airtight through the use of agasket or silicone-caulk seal.

If the sump is intended as a floor drain,make sure the lid is equipped with atrapped drain to handle surface wateron the slab.

Alternative: Tie Into Sumps

The sump can also be incorporatedinto the radon system.

If the sump is used without a draintile loop, install a sump pit coverspecifically designed toaccommodate a radon vent pipe andrun the vent pipe directly from thesump. These sump covers areavailable from numerous buildingsupply stores, as well as catalogfirms dealing in equipment andsupplies for radon migitationcontractors.

If the sump pit where the radon ventpipe will be located also includes apump, a cover can be ordered thatincludes both an opening for theradon vent pipe as well as holes forthe pump s water discharge line andelectrical connection. Becausesump-cover removal and resealing isrequired every time pump

maintenance is performed, considerusing a sump cover with atransparent door or see-throughviewing window. These doors, whichare usually screwed into the coverand sealed with a gasket, aregenerally large enough to permitlimited access to the pump switchwithout removing the sump coverand breaking the seal. Windowedsump covers are available for lessthan $50.

If the sump is connected to a draintile loop, the radon vent pipe could beinserted directly into the sump orinto any convenient section of the

drain tile loop (then cover and sealthe open sump). Although installingthe radon vent pipe in a remotesection of the drain tile loop isslightly more difficult than directlyinto the sump, it may offer a betterexhaust route through the home sinterior spaces and may offer thehomeowner simplified access to thesump.


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Building Radon Out

Seal hollow block foundation walls at

the top. Use at least one continuouscourse of solid masonry, one course of masonry grouted solid, or a pouredconcrete beam at or above finishedground surface. Where a brick veneeror other masonry ledge is installed, thecourse immediately below that ledgeshould be sealed.

Caulk joints, cracks, or other openingsaround all penetrations of both exteriorand interior surfaces of masonry blockor wood foundation walls below theground surface. Penetrations of poured concrete walls should also besealed on the exterior surface. Thisincludes sealing wall tie penetrations.

Other Places To Seal The SlabAnd Foundation

Use a polyurethane caulk around

locations where plumbing and otherutility service lines pass through slaband below-grade walls.

Use a full sill plate over the upper row of block walls in basements or make theupper row solid block.


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Placing air handling ducts in orbeneath a concrete slab floor, or inother areas below grade is notrecommended unless the air handlingsystem is designed to maintaincontinuous positive pressure withinthe ductwork. This is to prevent radonfrom being drawn into the ductwork andthen distributed throughout the house.

If ductwork does pass through acrawlspace or beneath a slab, it shouldbe of seamless material or sealedtightly. Where joints in the ductworkare unavoidable, seal to prevent air

leakage.


Avoid using floor drains and airconditioning condensate drains whichdischarge directly into the soil belowthe slab or into the crawlspace. If installed, these drains should berouted through solid pipe to daylight orthrough a trap approved for use in floordrains. Mechanical traps should beused rather than wet traps which candry out.

The bottom of channel-type (French)drains should be sealed with a backerrod and caulking. Water drainageshould be directed to a suitable drain.

Placing air handling units incrawlspaces, or in other areas belowgrade and exposed to soil gas, is notrecommended . However, if they areinstalled in these areas, make surethat they are designed or sealed in adurable manner to prevent airsurrounding the unit from being drawninto the unit.

Other Considerations


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Building Radon Out

Be sure to run the pipe up through theroof before the roofer installs the roof system. This will allow the roofer toproperly flash around the pipe. Avoidangles in the pipe, if possible, toincrease air flow through the vent pipeand maximize radon reduction.

Type Of Pipe

Use Schedule 40 PVC or ABS pipe. The pipe does not need to be pressurerated, so a pipe rated for Drain, Wasteand Vent (DWV) applications will be themost cost effective. Do not use a pipethinner than Schedule 40. Do not use

sheet-metal ductwork due to thelikelihood of breakage or leaks at joints.

All joints should be primed and gluedin a similar manner as indoorplumbing.

Use either PVC or ABS pipe,not both. The two types of pipe require differentcleaners and cements.

Installation Step 4

Do Not Trap Pipe

Plan your pipe routing to minimize thelength of pipe and fittings and tocontain no traps.

Do not install traps, intentional oraccidental, in the pipe that will collectwater and restrict or stop airmovement. Air from the soil will havesome moisture in it. As this air movesthrough sections of the vent pipelocated in cold spaces, such as an attic,some moisture can condense. It isimportant that this water can drainback down to the soil. Insulating the

pipe in the attic will reduce moisturecondensation and maintain upwardthermal draft in the pipe as it passesthrough unconditioned space.

Piping should also slope back to thesuction pipe at a minimum angle of 1/8 inch per foot.

Install Vent Pipe

InstallationTip


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Label Radon Vent Pipe

Label the exposed portions of the pipeso other people will know that the pipeis not part of the sewer system duringconstruction. It is recommended thatthe radon vent system be labeled in aconspicuous location on each floorlevel. Also, occupants and futureoccupants will know that it is part of a

radon vent system.

Places to label include:

" Where riser exits slab" Where pipe is seen in closets" Pipe run through attic

Allow For Future InstallationOf Fan

Although passive radon systems areeffective for reducing radon levels byan average of about 50%, it is always agood idea to plan ahead in case addingan in-line fan is needed for furtherradon reduction to bring indoor levelsbelow 4.0 pCi/L, or in case the futureoccupant wants to lower the radonlevels as much as possible. Duringinstallation of the vent pipe, considerthese criteria for locating a future fan:" Fan cannot be inside the living space

of the house." Fan cannot be in the crawlspace

beneath the home." Fans are most often located in attics

or garages (unless there is livingspace above the garage).

" Fans require a 30-inch vertical runof pipe for installation.

" Fans require an unswitchedelectrical junction box.


Maintain Fire Resistive RatingOf Walls And Ceilings

If you route your vent pipe through thewall between the house and thegarage, you will need to put a fire-barrier around the pipe (on the insideof the garage) to maintain the integrityof the wall. Install a fire barrier with arating equal to the wall.

Note that some ceilings are also firerated ceilings and will require firebarriers as well.


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Support the pipeSupport the pipe usingplumbers strapping at leastonce every 6 feet inhorizontal runs and onceevery 8 feet in vertical runs.

Insulate the pipeIn cold climates, insulate thepipe where the pipe is routedthrough unheated spaces,such as the attic.

Recommended Improvement:Screen On Discharge

It is a good idea to put a 1/4-inch meshscreen on the discharge to keep birdsfrom nesting in the pipe.

Rain caps can reduce radon flow andcan force radon (if the system isactivated) back down towards theopenings into the living spaces. Inmost areas, they are not needed. Forvery high rainfall areas, use alternativespecial devices which prevent largeamounts of rain from entering thesystem while still allowing the air tovent up and away from the building.

These devices are available throughradon mitigation supply distributors.Another design option, which is morecommonly used with commercialapplications than with residentialinstallations, is an annular rain cap aspictured here.

InstallationTip


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HVAC systems should be carefullydesigned, installed and operated toavoid depressurization of basementsand other areas in contact with the soil.Ideally, ductwork should remain in theconditioned space of the home. It isvery important to seal joints in airducts and plenums passing throughunconditioned spaces such as attics,crawlspaces, or garages.

In addition to avoiding problems withunwanted air distribution, sealing ductscan save energy, make homes morecomfortable, and lower heating andcooling costs.

Installation Step 5

Seal Ducts andAir-Handling Units

ld d


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Installation Step 6

Install Electrical Junction Box

For Future Installation of Fan

Although in most cases the passivesystem alone is enough to keep radonlevels below 4 pCi/L, occasionally thehomeowner will want or need toactivate the system by adding a fan tofurther lower radon levels in the home.

To prepare for this possibility, pre-wirethe attic when installing a passivesystem. An unswitched electrical

junction box should be installed in theattic or garage within 6 feet of the ventpipe. (See page 56 for a discussionabout fan installation location.)

For attics with interior access, manybuilding codes require a light in theattic. In these cases, if the junctionbox for the light is located at anappropriate location for the fan,another junction box will not benecessary. If not, wiring the additionaloutlet will be simple. The fan outletdoes not require a dedicated circuit; itmay branch off the existing circuit forthe light.

S B S I ll i G id


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Testing is simple and easy.

After the home is complete andoccupied, it should be tested todetermine whether or not the passivesystem needs to be activated. Youshould recommend to the home buyerthat they test the home after they movein and activate the system if the radonlevel is at or above 4 pCi/L.

Some builders installing passivesystems are testing the homes theybuild and activating the passive radonsystems if radon levels are at or above 4pCi/L. In all cases you should advise

the homeowners to retest sometime inthe future to confirm radon levelsremain low.

Obtaining a Test Kit

Radon test kits can often be obtained at your local hardware store. There are

Installation Step 7

Post-Occupancy Testing

many kinds of low-cost "do-it-yourself"radon test kits you can get through themail and in hardware stores and otherretail outlets. Coupons for short-termand long-term radon test kits are alsoavailable from the National SafetyCouncil s web site atwww.nsc.org/EHC/indoor/coupon.htm.

Types Of Radon Tests

Short-term Tests

The quickest way to test is with short-term tests. Short-term tests remain in

the home for two days to 90 days,depending on the device. Becauseradon levels tend to vary from day to dayand season to season, a short-term testis less likely than a long-term test togive the home s year-round averageradon level. If you or the homeownerneed results quickly, a short-term test

Note: The above figure illustrates one exampleof a radon testing device. There are manyother types of radon testing devices available.

B ildi R d O t


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Building Radon Out

If you are conducting the radon testprior to sale of the home, you will likelywant to get results as quickly aspossible by following these testingsteps. If a homeowner is testing thehome for radon, he or she shouldfollow the longer steps on page 69.

Step 1Conduct a short-term test for at least48 hours. After the first test has beencompleted, conduct a follow-up short-term test for at least 48 hours.

Alternatively, take two short-term testsat the same time in the same locationfor at least 48 hours.

Step 2 If the average of the two tests is4 pCi/L or more, activate the passiveradon reduction system.

tests lasting just 2 or 3 days duringunusually severe storms or periods of unusually high winds, because theseconditions can affect the test results.

The test kit should be placed in thelowest lived-in level of the home, for

example, the basement if it is to befrequently used, otherwise the firstfloor. It should be put in a room that isused regularly, like a living room,playroom, den or bedroom but not thekitchen or bathroom. Place the kit atleast 20 inches above the floor in alocation where it won't be disturbed andaway from drafts, high heat, high

humidity, and exterior walls. Leave thekit in place for as long as specified inthe device instructions. Once the testis completed, reseal the package andsend it to the lab specified on thepackage right away for analysis. Youshould receive test results within a fewweeks.

followed by a second short-term testmay be used, or two short-term testsmay be performed simultaneously.

Long-term Tests

Long-term tests remain in a home for

more than 90 days. A long-term testwill give a reading that is more likely togive a home s year-round average radonlevel than a short-term test.

How To Use a Test Kit

Follow the test kit instructions. For

short-term tests, close all windows andoutside doors and keep them closedthroughout the test, except for normalentry and exit. If you are doing a short-term test lasting just 2 or 3 days, besure to also close windows and outsidedoors at least 12 hours before beginningthe test. Do not conduct short-term

Steps For Testing

Step By Step Installation Guide


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This section provides basic guidelines if you decide to install an in-line fan toactivate the system. Some states

require that in-line fans for radonreduction be installed by a

certified radon mitigationcontractor. Call your

state radon contactfor a list of certifiedcontractors (seeAppendix D for a listof phone numbers).

Location The fan and all positively pressurizedportions of the vent pipe should be

located outside habitable space in thebuilding.

The ideal location is in the attic, or,perhaps, in an attached garage, wherethe fan housing and vent pipe can besheltered from the elements, yet beoutside the building s conditionedspaces. Sheltering the fan maximizes

Optional Step 8

Activating the System

its efficiency and life expectancy byminimizing exposure to extremetemperatures and moisture.Placement in a non-conditioned spaceprevents the accidental pumping of radon directly into a home should aleak occur in the fan housing or at the

vent-pipe joints.

Building designs that call for a flat roof or cathedral ceiling, or some otherdesign feature that makes the atticinstallation unworkable, maynecessitate placing the fan on the roof or in an exterior venting pipe.

Appropriate fan locations:" Unoccupied attic" Outside the house" In garage

Inappropriate fan locations:% In crawlspace% In basement% In occupied attic

Building Radon Out


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Building Radon Out

How To Install

Install the fan in a vertical run of thevent pipe. This will prevent outdoorprecipitation from accumulating in thefan or fan housing. Do not use anangled portion of the pipe.

To reduce vibrations and noisetransmission, use flexible air-tightcouplings instead of rigid couplings.Secure couplings tightly to the fanusing circular hose clamps.

In regions with prolonged or extremecold, both fans and attic vent pipes

should be insulated to reducecondensation and the possibility of vent exhaust freeze up. Freeze-up ismost often found in regions withextremely cold winters and in systemshaving high air-flow rates as well ashigh moisture levels in the sub-slabsoil.

Type Of Fan

Although various types of fans aresuitable for this purpose, the mostcommonly-used fans are centrifugalfans often referred to as in-line,

tubular or tube fans.

The size and air movement capacity of the vent pipe fan should be sufficientto maintain a pressure field beneaththe slab or crawlspace membrane thatis lower than the ambient pressureabove the slab or membrane. Mostcontractors have found 90-watt in-linefans to be adequate for most home

styles, locations and sizes. You canalso look for a fan capable of moving100 cubic feet of air per minute atone inch of water column, which shouldbe sufficient for most applications.

Install A System FailureWarning Device

A system failure warning device shouldbe used to alert occupants to anymalfunction of the system or drop in itssuction flows. Types of warning devicesinclude pressure gauges, manometersand visual or audible alarms. Unlessthe indicator is integral to the fanpower supply, the audible or visualalarm should be connected to aseparate circuit so that it will activateif power to the fan is interrupted.

Working With Homebuyers


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