White roof - two abstracts. The first is climatic, the second practical/experimental.
A Environmental Research Letters Volume 7 Number 2 Create an alert RSS this journal Hashem Akbari et al 2012 Environ. Res. Lett. 7 024004 doi:10.1088/1748-9326/7/2/024004 The long-term effect of increasing the albedo of urban areas IOPSELECT Hashem Akbari, H Damon Matthews and Donny Seto Show affiliations Tag this article Full text PDF (2.60 MB) Enhanced article HTML AbstractReferences Letter Solar reflective urban surfaces (white rooftops and light-colored pavements) can increase the albedo of an urban area by about 0.1. Increasing the albedo of urban and human settlement areas can in turn decrease atmospheric temperature and could potentially offset some of the anticipated temperature increase caused by global warming. We have simulated the long-term (decadal to centennial) effect of increasing urban surface albedos using a spatially explicit global climate model of intermediate complexity. We first carried out two sets of simulations in which we increased the albedo of all land areas between ±20° and ±45° latitude respectively. The results of these simulations indicate a long-term global cooling effect of 3 × 10-15 K for each 1 m2 of a surface with an albedo increase of 0.01. This temperature reduction corresponds to an equivalent CO2 emission reduction of about 7 kg, based on recent estimates of the amount of global warming per unit CO2 emission. In a series of additional simulations, we increased the albedo of urban locations only, on the basis of two independent estimates of the spatial extent of urban areas. In these simulations, global cooling ranged from 0.01 to 0.07 K, which corresponds to a CO2 equivalent emission reduction of 25-150 billion tonnes of CO2. Environmental Research Letters Volume 7 Number 1 Create an alert RSS this journal S R Gaffin et al 2012 Environ. Res. Lett. 7 014029 doi:10.1088/1748-9326/7/1/014029 Bright is the new black--multi-year performance of high-albedo roofs in an urban climate IOPSELECT S R Gaffin1, M Imhoff2, C Rosenzweig1, R Khanbilvardi3, A Pasqualini1, A Y Y Kong1, D Grillo4, A Freed5, D Hillel1 and E Hartung1 Show affiliations Tag this article Full text PDF (1.73 MB) Enhanced article HTML AbstractReferences Letter High-albedo white and cool roofing membranes are recognized as a fundamental strategy that dense urban areas can deploy on a large scale, at low cost, to mitigate the urban heat island effect. We are monitoring three generic white membranes within New York City that represent a cross section of the dominant white membrane options for US flat roofs: (1) an ethylene-propylene-diene monomer (EPDM) rubber membrane; (2) a thermoplastic polyolefin (TPO) membrane; and (3) an asphaltic multi-ply built-up membrane coated with white elastomeric acrylic paint. The paint product is being used by New York City's government for the first major urban albedo enhancement program in its history. We report on the temperature and related albedo performance of these three membranes at three different sites over a multi-year period. The results indicate that the professionally installed white membranes are maintaining their temperature control effectively and are meeting the Energy Star Cool Roofing performance standards requiring a three-year aged albedo above 0.50. The EPDM membrane shows evidence of low emissivity; however this had the interesting effect of avoiding any 'winter heat penalty' for this building. The painted asphaltic surface shows high emissivity but lost about half of its initial albedo within two years of installation. Given that the acrylic approach is such an important 'do-it-yourself', low-cost, retrofit technique, and, as such, offers the most rapid technique for increasing urban albedo, further product performance research is recommended to identify conditions that optimize its long-term albedo control. Even so, its current multi-year performance still represents a significant albedo enhancement for urban heat island mitigation. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
