In full sun, the surface of a black low-slope roof may experience a temperature rise of as much as 50 to 90 degrees Fahrenheit (F), reaching midday temperatures of 150 to 190 F on a summer day. A white vinyl/PVC reflective roof on the same building typically increases only 10 to 25 degrees above ambient temperature under the same conditions. A differential of this magnitude begs the question: What makes one roofing material “cooler” than another?