b'Photo 2Biological growth (mildew) on the surface of Single-ply membranes in hot humid southern climates, markedly decreases solar reflectivity. T&R UPDATE THE REAL DIRT ON REFLECTIVEPhoto 1ROOFS Biological growth has impeded full drainage. Reflectivity typically suffers in these areasSingle-Ply Membranes and Reflectivity Realityby Mathew Dupuis, PhD, PEI n increasingPhoto 4regularity,A close up view of a fastener head location from Photo roofing3. Is this due to temperature differences, from the air-conditioned interior? Perhaps electrostatic charges contractors areconveyed by the metal fastener to metal deck connection? finding theirPhoto 3 Interesting phenomena observed over and over. projects subjectInsulation levels to the solar reflectance requirements.on membranes appears to have These requirements are provided inan effect. Note model building codes. In addition,the rows of thermal short local codes and ordinances have beencircuits caused adopted or enacted in a number ofby the in-seam jurisdictions.metal fasteners. Each one of The codified requirements referencethese fasteners is clean, where solar reflectance ratings provided bythe field of the the ENERGY STAR Roof Productsmembrane Program and the Cool Roof Ratingcollected liberal Councils Products Rating Program.amounts of dirt.When these solar reflectivityin the roofing industry recognizesof 2013 and the NRCA conducted requirements first appeared, solarroof membranes can get very dirtya 5-year study of numerous roofs reflectivity compliance could bein-service, and have questioned howin the Chicago area, ending in substantiated on the basis of reflectivityaccurate a predictor the three-year- 2015.However, these studies were measurements for new materialsaged values for reflectivity are. geographically limited; looking only (initial values) or for materials exposedPrevious studies on the subject ofat roofs in a single geographic area. To to three years of weathering (three- in-service reflectivity have producedbetter explore this fundamental issue of year-aged values). The three-year- interesting results. The MRCAin-service long-term solar reflectance, aged values developed in accordanceundertook a study of in-servicethe MRCA undertook a field study with the CRRC-S100 standard havereflective polymer-modified bitumensolar reflectivity for single ply roof come to represent a proxy for in- roofs in Texas during the summermembranes in 2015. service performance. However, most 32 www.mrca.orgMidwest Roofer'