b'The Cool Roof Rating Council-S100study.roofs, as a whole. However, the MRCA standard is the one which roofingMember roofing contractors ofdid request a target age of three years manufacturers almost universallythe CRCA, FRSA and or WSRCAfrom the participating contractors in use and report as their initial solarprovided all of the subject roofseach climate. Figure 1 is a histogram of reflectivity value and three-year-agedutilized in this study. A strictthe ages for all the measured roofs, in solar reflectivity value. In this standard,distribution of roof membrane typesall climates.manufacturer submitted specimensor building occupancies were not are prepared and mounted outdoorsprescribed to these contractors. These on sloped racks. These racks arecontractors were only asked to provide positioned in three climates aroundhighly reflective single ply membranes, the United States. These climates, peri.e. White TPO, White PVC and the CRRC-S100 standard, includeWhite EPDM. From this directive, Hot/Humid climate, Cold/Temperatethese contractors merely provided a climate and a Hot/Dry climate. Oncesampling of their local roof membrane the samples have been exposed for three years they are measured for their solar reflectance. Given the prescribed aging locations in the CRRC standard, it was obvious that this current study should utilize these same climates. The CRRC standard gives examples of cities that meet the prescribed climates. This study utilized examples cited in this standard; for a Hot/Humid climate, Miami, Florida, for a Cold/Dry climate, Chicago, Illinois and a Hot/Dry climate, Phoenix, AZ was used.Incorporated by reference into the Photo 5CRRC-S100 standard is ASTM C1549Dust from manufacturing operations under the roof are ejected onto the roof by the vent unit. - 09(2014) Standard Test Method forOnce the air velocity drops sufficiently the dust is dropped and solar reflectivity suffers. Determination of Solar Reflectance Near Ambient Temperature Usingpopulation. Table 1 details theFigure 1Histogram of all a Portable Solar Reflectometer. Thedistribution of membrane types in eachroofs measured in this study. Ages are portable solar reflectometer thatclimate zone for this study.truncated to the year.is described in the ASTM C1549 standard is the Solar SpectrumOn each of these 90 roofs, 30 random Reflectometer (SSR) from Devicesreadings were taken with the SSR and Services Company, Dallas, TX.reflectometer. An important aspect of This reflectometer has been in use forthis research was the random nature of decades and is the basis for almost allthese readings. The majority of these published data on roof membrane solarrandomly selected areas may fall in reflectivity. The NRCA provided thethe field of the roof, but could also MRCA with their SSR and an operator,be near drains, near wall flashings, for this study. Immediately prior to thearound roof top ventilators, or around testing program the SSR unit had beenany other roof top feature. In essence, returned from the manufacturer forno horizontal (low-slope) area of the calibration and updates.actual roof membrane surface was Single-Ply roof membranes currentlyTable 1. Inventory of Single-Ply Roofconsidered out of bounds for random dominate the United States low slopeMembranes Measured sampling. Vertical surfaces covered roofing market. The three membranesIt would be preferred to measure in- in roof membrane, such as parapet that are the current predominateservice roofs that exactly match thewalls and equipment curbs, were not choices are TPO, PVC and EPDM.three years of exposure that is specifiedsampled.This dominance in the low-slopeon product data sheets. However,For each roof, the 30 random readings roofing market made these single-plythis constraint is impractical whenwere averaged to give the sample membranes the obvious choice for thisdiscussing the in-service population ofmean. In Figure 2 the sample means www.mrca.orgMidwest Roofer 33'