Residential Roof Albedos in Tucson, Arizona: A Model for the Southwest

Abstract:

Growing concern over energy efficiency and expected increases in ambient temperature due to global warming drive the search for mitigation strategies that are both sustainable and cost-effective. These issues are keenly felt in the desert Southwest of the U.S., particularly in low-income communities or neighborhoods where residents cannot afford the capital expenditures and operating costs of refrigerated air conditioning. Low-efficiency evaporative coolers, fans, or simply open windows are the minimal-cost alternatives, with consequent negative morbidity and mortality outcomes, particularly among the elderly and the infirm. According to CLIMAS (Climate Assessment for the Southwest), an ongoing vulnerability assessment has been conducted for the community of Tucson, Arizona regarding the anticipated climate change impact. Projections within this assessment indicate that Tucson is especially vulnerable to extreme temperature risks, and these risks correlate to socio-economic status. When considering energy and cooling efficiency, roof solar reflectance (albedo) is often overlooked; style and cosmetics of residential buildings are the more typical priorities of both developers and buyers. Although light-colored roofs can reduce energy consumption for cooling, data recorded from companion studies indicate that many residential buildings have been built and continue to be built with dark-colored roofs in Southwest cities. However, our preliminary data suggest that Tucson, unlike several of its desert neighbors, has not followed this trend. Of 2,270 roofs counted, about 69% fall within the light category (white or light gray), with the remainder being darker shades. In comparison, a companion study found that approximately 51% of residential roofs in El Paso, TX fell in the light category. We now are focused on roof colors from different socio-economic areas in Tucson to determine whether there is a correlation between socio-economic status and roof albedo. Similarly, we also are examining the age of residential housing at the neighborhood level to determine whether there is any secular trend in roof color choices in Tucson.