b'T&R Update Field Study Results of Reflective Modified Bitumen Roofs Matt Dupuis At every MRCA conference, the technical programs are well attended andKeys continue to trigger discussions long after everyone returns home. TheFindingpresentation on the results of the MRCA Technology and Research ( ) Most of the CRRC-listed membranes studied did not meet their T&R published value, although some came closerothers. Committee\'smeasurements of highly reflective modified bitumenthan field Many of the membranes fell close to or below their published the 63rdproved3-year-aged reflectivity- some within months of installation. roofs atAnnual Conference in Grapevine, TX,no different. The field study results were presented, installation of these systemsWhen the reflecti\\1ty of the samewas sampled on was discussed, and aof manufacturers responded to conferencemembrane panel different buildings and different cities we find awithin attendees\' questions.variation Asyou know, cool roofing is no longer aproduct or trend in thethe results. This suggests service conditions have an important newinfluence on reflectivity performance. roofing industry.Itis here to stay, and itfinding its way into building is and codes for municipalities largesmall. Modified bitumen roofing membranes have proved they can compete with other roofing systems(Forground and methodology of the field testing,"Examining back see in reflectivity and thennal perfonnanceinereflective category.Highly Reflective Modified Bitumen Systems" in the2012 issue of th highlyAugust However, the results of the field study suggest there are large variationsMidwest Roofer.) The roofs were provided by member contractors of the in reflectivity performance over time for the highlymodifiedMRCA. In total, there are 28 roofs varying in age from several months to reflective bitumen membranes.more than 5 years. Field Re ectivity MeasurementsDevices The reflectance measurements were conducted with aand flThe MRCA T&R Committee recognizes a lack of available infonnationServices Company Solar Spectrum Reflectometer Model SSR with version 5. Aof 30 readings were taken from each roof, on.fieldvalues for highlyve modified bitumens. Onfirmware minimumand reflectivityreflecti eachgtaken from a random location. Theof these most modified bitumen membrane data sheets and marketing literature,readin wasresults one will find the initialvalues for reflectivity. The initial valuereadings are available for download in the Technical section ofwww and agedmrca.org. The membrane names and ages in this table are listed from is what we would expectreflectivity to be as it unro on the roof. thelledthe infonnation provided by the participating contractors. Thevalue gets more interesting and is typically reported after agedThe field reflectivity readings provided theles to produce prescribed aging via the Cool Roof Rating Council\'s CRRC-1 methodsampconfidence intervals presented in the table. Ainterval may (http:/ roofs.org/documents/ lStandard-finalANSI.pdf). Thisconfidence /cool CRRC- require aof explaining.intervals are based on the more than standard dictates that manufacturers\' samples must be exposed outdoorsbitThese 30 random reflectivity readings taken onroof. These readings for 3before the reflectivityismeasured again. CRRC-1 requires thateach yearswere taken from all types of areas on these roofs\' high areas, the manufacturer\'s samples are placedthree different climates withinlow inareas, crickets, saddles,flashings. But the areas selected were as the United States, are 24 square inches in size or larger,and/or and are mountedrandomly chosen as possible on these roofs varying from asquares at a five-degree(1:slope.few 12)toou of squares.largeof samples and their random For aaging protocol,1well tho o th sandsThenumber prescribedCRRC- appearsughtut.selection from the entire roof allows us to calculate ainterval. But the largeof environmental variables that roofs face areconfidence numbersWhat is ainterval? For ourhere, suffice to say difficult to replicate w aaging process.confidencepurposes ithprescribedthat ifcould hypothetically measure the reflectivity of every square In May-June 2012, the T&R Committee conducted field readingswe inch of the roof (population) and then calculate thefor the roof of highly reflective modified bitumen roofs inand Austin, TX.average Dallasfrom all these individual readings, we are99%confident that the interval we report in the tableaverage. contains this What does it mean ifanufacturer X\'s m CRRC-reported reflectivity does not fall within the reported confidence interval?it mean Does manufacturer Xis providing bad infonnation?remember the No,CRRC value is aaging standard/process and is conducted by an prescribed The independent laboratory, not the manufacturer.values we report here are from in-service roofs. Aspecifier, or building owner should definitely not contractor, choose aghlymodified bitumen roof membrane based hi reflective solely on these field reflectivity numbers. These numbers should be taken as onlyan indicator of reflectivity. They represent only one of as many pieces of information that should be considered in the total life The field study findings are presented and discussed at conference.cost of the roof system. 16www.mrca.org- Midwest Roofer'