b'(} reduce rainfall runoff impacts;most region With alar reducs.simi reducesoundreflectionandtion in runoff rate, other d ices like evtransmission;stormwaterbasins,below-gradeprovide urbanhabitat forbirdsdetentionstorage,etc.,canbe and p ,imp ing airr in sizeor eliminated. In lants therebyrov educed ar tial quality and the local ecology;urbanized ~ easthepoten savreduce urban heat-island effects;ingsarethree-fold:r siteeduced anddevelopmentcosts,increasedenhance property values.commercial space (wh wouldichothExperienceEurope shows thate ise be consumedby stormwater inrwuniformly vegetated extensive greendetentionbasins) a lower public nd fo stormwroofswith3 inches(76mm)ofinfrastructure demandsramedia provide the highest benefit ter mitigation strategies. to-costImprovementsiratio.assocatedwiththickerandmoreStandards and Guidelines intensively landscaped systems areBecause the mark intheU.S. et marginal.forgreenroofsisin itsinfancy, rom F a heat-flowperspective,most Americans are unfamiliar with the performance of green roofs asthem. The combination of few cominsulatorsdependsgreatlyonapanieswithexten in lation sivestalnumberofvariables,includingexperience and the large number of moisturecontentandtemperaturedifferent systems now entering the regimen. T physicalprocessesmarketit d to obtain hecan makeifficult producing the benefit are many andgood information about green roof varied, but the general characteris systems.E ngthe claimso~ valuatindI ticofgreenroofmaterials a different providers can be cha lend Photograph by: Charlie Miller, PE, Roofscapes, Inc.foliage is ac to absorbing, especially sin there are nhighapacityceot heat (i.e., thermal mass effect).yetanyaccepiedstandardsof Green Roofs: AGreen roofs generallyameasures of per to referNewprovideformance greaterbenefit insummer than inence. American Building Systemthe winter. Their capacity to virtu In the a ence of Americ stanbs an ti stomers ally eliminate the daily varia on indards,many green roof cuby Charles D. Miller, P.E.temperature on the roof deck, how relyontheguidelinesandstanever, is aphenomen dardsd inGermany. In year-roundoneveloped Editor\'s note: The MRCA T&Rcover system. First popularized inthatservestoextendroofIbyparticular,thedetailed standards ife Committee is preparing an educa Europe, vegetated roof covers offerreducing thermalling. By way ofandguidelin published by FLLcyc es1, tionaltitled "Green Roofs awiderangeinfunctionandcom greenroofs are up tocovermostaspects of green roof sessionparison, Your Next Market Niche?" for theappearance. Greenroofs are tradi twice as efficient as white or reflec design.Theseincludetestsand MRCA54thAnnualConventiontionally divided into two categories:tiveroofsurfacesinreducingstandardsforassessing the root andTradeShow,October 22-24,"extensive" - 6-inches (152 mm)thermal gain, which is whyresistance of waterproofing materijurisdic2003 inCincinnati.Come tothethickless,"intensive" -10- tionslike the City of Chicago areals, determining the water retention orand MRCA convention to find out moreinches (254 mm) thick or more.advancinggreenroofsfortheirpropertiesof growingmedia, preabout the pitfalls and possibilitiespotential tointerior temper dictingthemaximumweightof reduce ottered by "green roofs. "Benefitsatures during thegreen roof systems, ensuring adesummer. ThebenefitsofgreenroofsG roofsalsop dra quate drainage capacity, etc.ese reenroduceThG roofs, sometimesinclude their capacity to:ofthematicinction inr the quantitystandardsaremostappropriately reenredu both alsoreferredtoas extendtheservicelifeof rainfallandtherate of runoff. 1applied intemperate northernarea "living"or"vegetated"underlyingwaterproofingsys This benefit has spu red the wide of North America. Severalgroups, roofs,arecompositetem;spreadimplementationofgreenmostnotably ASTMInternational, systemsthatcombinea water improvetheefficiencyofroofroofsGerm Onanann are working to adopt standards that any.ual proofing system with ainsulation;basis, rainfall runoff quantity will bewillbemorebroadlyapplicabl~ vegetated-reducedby 60 percent or more inthroughout the U . .S'