Solar-reflective building envelope surfaces, such as cool roofs and walls, can be especially helpful in disadvantaged communities that often have poorly insulated older homes, aging or absent air conditioning units, steep utility bills, polluted air, and high vulnerability and exposure to extreme heat. Our project seeks to dramatically increase the climate-appropriate deployment of cool surfaces across the United States with an emphasis on their application to disadvantaged communities. First, we sought to identify cool-surface deployment barriers, opportunities, and models by (a) reviewing the history of cool-surface deployment activities, (b) interviewing cool-surface stakeholders, (c) researching successful energy-efficiency/green building deployment models; and (d) interviewing the actors who have implemented these models. Second, we conducted a workshop to engage stakeholders in the development of a deployment plan. Third, we asked several U.S. federal agencies (a) how cool surfaces and cool surface stakeholders could support their missions and (b) how agency activities could support cool-surface deployment. Fourth, we identified a set of transformative ideas that form the core of the deployment plan. Transformative ideas include but are not limited to initiatives to (a) launch an educational campaign to make the general public and building professionals aware of how cool roofs and walls exclude unwanted solar heat; (b) create a "Cool Roof Prize" stimulating the development of affordable, high-performance cool asphalt roofing shingles; (c) conduct high-profile, large-scale demonstration programs that bring cool surfaces to disadvantaged hotclimate communities; and (d) support local, regional, and state climate action (heat mitigation) plans with cool surfaces.

Solar-reflective building envelope surfaces, such as cool roofs and walls, can be especially helpful in disadvantaged communities that often have poorly insulated older homes, aging or absent air conditioning units, steep utility bills, polluted air, and high vulnerability and exposure to extreme heat.With support from the U.S. Department of Energy, our project seeks to dramatically increase the climate-appropriate deployment of cool surfaces across the United States with an emphasis on their application to disadvantaged communities.First, we sought to identify cool-surface deployment barriers, opportunities, and models by (a) reviewing the history of cool-surface deployment activities, (b) interviewing cool-surface stakeholders, (c) researching successful energy-efficiency/green building deployment models; and (d) interviewing the actors who have implemented these models.Second, we conducted a workshop to engage stakeholders in development of a deployment plan.Third, we asked six U.S. federal agencies (a) how cool surfaces and cool surface stakeholders could support their missions and (b) how agency activities could support coolsurface deployment.Fourth, we identified a set of transformative ideas that form the core of the deployment plan.Transformative ideas include but are not limited to initiatives to (a) launch an educational campaign to make the general public and building professionals aware of how cool roofs and walls exclude unwanted solar heat; (b) create a "Cool Roof Prize" stimulating the development of affordable, high-performance cool asphalt roofing shingles; (c) conduct high-profile, large-scale demonstration programs that bring cool surfaces to disadvantaged heat-vulnerable communities; and (d) support local, regional, and state climate action (heat mitigation) plans with cool surfaces.

Photocatalytic self-cleaning "cool" roofs and walls can maintain high albedos, saving building cooling energy, reducing peak power demand, and mitigating the urban heat island effect. Other environmental benefits result from their de-polluting properties. Specimens from two different photocatalytic architectural membranes and a non-photocatalytic control were exposed alongside vertically, facing west, for two years at three California sites, and retrieved quarterly for testing. Photocatalytic materials showed excellent self-cleaning performance, retaining albedos of 0.74 - 0.75. By contrast, the control material exhibited an albedo loss of up to 0.10, with appreciable soiling observed by scanning electron microscopy. De-pollution capacity was assessed by quantifying NO removal and NOx deposition rates at 60 degrees C. Efficacy varied with exposure location, weather conditions, and the nature of the photocatalytic material. Seasonal effects were observed, with partial inhibition during the dry season and reactivation during the rainy season.

To understand spatial air-temperature variations in local urban heat islands (UHIs) and urban cool islands (UCIs), and their relationship to land-use and land-cover (LULC) properties in the Los Angeles Basin, we sought to (a) use fine-resolution climate models to identify UHI / UCI areas, (b) relate observed intra-urban temperature variations (from mobile transects and stationary monitors) to LULC and surface physical properties, and (c) calibrate/validate the fine-resolution meso-urban climate models that were used in identifying the UHI / UCI.We conducted a multidimensional assessment of urban temperature variations based on numerical modeling and several types of observations, including mobile transects, dense networks of personal weather stations, and sparse but more accurate research-grade stationary weather monitors.To identify the causative factors of the UHI / UCI at the neighborhood scale, we collected detailed LULC datasets, such as 1-m resolution roof albedo and tree canopy cover, as inputs for the meteorological modeling and analysis.The fine-scale meteorological model was used to design mobile-transect routes and to site the stationary monitors based on the definition of UHI / UCI areas.This study provides the first observational evidence from analysis of high spatial density weather stations that increases in roof albedo at neighborhood scale are associated with reductions in near-surface air temperature.This was corroborated with the analysis from mobile transect measurements and correlation of observed air temperature with neighborhood-scale albedo and vegetation canopy cover, which revealed a cooling effect from area-wide increase in albedo and/or canopy cover.

Author(s): Levinson, Ronnen; Ban-Weiss, George; Berdahl, Paul; Chen, Sharon; Destaillats, Hugo; Dumas, Nathalie; Gilbert, Haley; Goudey, Howdy; Houze de l’Aulnoit, Sebastien; Kleissl, Jan; Kurtz, Benjamin; Li, Yun; Long, Yan; Mohegh, Arash; Nazarian, Negin; Pizzicotti, Matteo; Rosado, Pablo; Russell, Marion; Slack, Jonathan; Tang, Xiaochen; Zhang, Jiachen; Zhang, Weilong | Abstract: Raising the albedo (solar reflectance) of a building’s walls reduces unwanted solar heat gain in the cooling season. This saves electricity and lowers peak power demand by decreasing the need for air conditioning. It can also cool the outside air, which can mitigate the urban heat island effect and also improve air quality by slowing the reactions that produce smog. This project quantified the energy savings, peak demand reduction, urban cooling, and air quality improvements attainable from solar-reflective “cool” walls in California; collaborated with industry to assess the performance of existing cool-wall technologies, and to develop innovative cool-wall solutions; and worked with state and federal government agencies, utilities, and industry to create a cool-wall infrastructure, including application guidelines, a product rating program, incentives, and building code credits. Simulations indicate that cool walls provide annual energy savings, peak demand reduction, annual emission reduction, and summer heat island mitigation benefits comparable to those yielded by cool roofs, and are helpful across California and in most of the southern half of the United States (that is, in U.S. climate zones 1—4). Natural exposure trials conducted at three sites in California and another three sites across the United States indicate that cool-wall materials tend to stay clean and reflective. Significant advances were made in novel cool-wall technologies, such as fluorescent cool pigments that expand the color palette for cool-wall products. We prepared guidelines for the climate- and building-appropriate use of cool walls, convened a stakeholder workshop, and created a working group. Ongoing efforts seek to introduce or expand cool-wall provisions in building energy standards, green building programs, and energy efficiency incentive programs, and to develop a cool-wall product rating system.

Lawrence Berkeley National Laboratory partnered with Mid-America Regional Council (MARC) to quantify the costs and benefits from the adoption of urban heat island (UHI) countermeasures in the Kansas City region (population 1.5 million), and identify the best regional implementation pathway for MARC. The team selected cool (high-albedo) roofs and increased vegetation as the two countermeasures to evaluate. For vegetation, there were two strategies: (1) planting new trees to shade building surfaces, and (2) increasing urban irrigation (a surrogate for the use of vegetation to manage stormwater) to increase evapotranspiration. Using the Weather Research and Forecasting (WRF) model we simulated selected weeks during summer time, across five years (2011 2015) representing a range of normal summer conditions. We also simulated six of the most intense heatwaves that occurred between 2004 and 2016. We found under typical summer conditions (non-heatwave) average daytime (07:00 19:00 local standard time) regional near-ground air temperature reductions of 0.08 and 0.28 C for cool roofs and urban irrigation, respectively. We calculated the building electricity, electricity cost, and emission savings that result from the reduction in outdoor air temperature (indirect savings) and found maximum regional annual indirect electricity savings of 42.8 GWh for cool roofs and 85.6 GWh for urban irrigationyielding maximum regional annual indirect electricity cost savings of $5.6M ($0.05/m2 roof) and $11.1M ($0.01/m2 irrigated land), respectively, and maximum regional annual CO2 savings of 43.4 kt and 80 kt, respectively.We next evaluated the building energy, energy cost, and emission savings from reducing direct absorbed radiation on the building surfaces using cool roofs and shade trees (direct savings). For cool roofs, we found regional annual direct energy cost savings of $10.9M ($0.15/m2 roof) with regional annual CO2 savings of 66.4 kt. For shade trees, the regional annual direct energy cost savings were $21M ($21/tree) with regional annual CO2 savings of 126 kt. We investigated cool roof cost premiums (the additional cost for selecting a cool roof product in lieu of a conventional roof product, estimated to be zero to $2.15/m2) and shade tree first costs (assumed to be $100 per tree). The regional cool roof cost premium was calculated using the regional roof area per roofing material type and the range of cool roof product premiums for each material type. The extra cost of selecting cool roofs across the region ranged from $4.33M to $87.1M, while the additional shade trees planted across the region were assumed to cost $102M. When we compared the regional annual direct cost savings to the regional cool-roof cost premium and the regional shade-tree first cost, we found regional simple payback times up to 8.0 years for cool roofs and 4.9 years for trees, respectively.Since this comprehensive assessment of UHI countermeasures is a valuable methodology for other local governments to apply, we developed a step-by-step guide for others to follow. Based on the benefits and costs of the UHI countermeasures, MARC will pursue the inclusion of these countermeasures in existing regional plans where they can complement other regional priorities for transportation, climate resiliency, clean air, and hazard mitigation. They hosted a local workshop in 2016 for stakeholders to introduce the topic and will continue to share these resources to further appropriate adoption of UHI countermeasures.

The effects of neighborhood-scale land use and land cover (LULC) properties on observed air temperatures are investigated in two regions within Los Angeles County: Central Los Angeles and the San Fernando Valley (SFV). LULC properties of particular interest in this study are albedo and tree fraction. High spatial density meteorological observations are obtained from 76 personal weather-stations. Observed air temperatures were then related to the spatial mean of each LULC parameter within a 500 m radius “neighborhood” of each weather station, using robust regression for each hour of July 2015. For the neighborhoods under investigation, increases in roof albedo are associated with decreases in air temperature, with the strongest sensitivities occurring in the afternoon. Air temperatures at 14:00–15:00 local daylight time are reduced by 0.31 °C and 0.49 °C per 1 MW increase in daily average solar power reflected from roofs per neighborhood in SFV and Central Los Angeles, respectively. Per 0.10 increase in neighborhood average albedo, daily average air temperatures were reduced by 0.25 °C and 1.84 °C. While roof albedo effects on air temperature seem to exceed tree fraction effects during the day in these two regions, increases in tree fraction are associated with reduced air temperatures at night.

To identify and characterize localized urban heat- and cool-island signals embedded within the temperature field of a large urban-climate archipelago, fine-resolution simulations with a modified urbanized version of the WRF meteorological model were carried out as basis for siting fixed weather monitors and designing mobile-observation transects. The goal was to characterize variations in urban heat during summer in Los Angeles, California. Air temperatures measured with a shielded sensor mounted atop an automobile in the summers of 2016 and 2017 were compared to model output and also correlated to surface physical properties focusing on neighborhood-scale albedo and vegetation canopy cover. The study modeled and measured the temperature response to variations in surface properties that already exist in the real world, i.e., realistic variations in albedo and canopy cover that are attainable through current building and urban design practices. The simulated along-transect temperature from a modified urbanized WRF model was compared to the along-transect observed temperature from 15 mobile traverses in one area near downtown Los Angeles and another in an inland basin (San Fernando Valley). The observed transect temperature was also correlated to surface physical properties characterizations that were developed for input to the model. Both comparisons were favorable, suggesting that (1) the model can reliably be used in siting fixed weather stations and designing mobile-transect routes to characterize urban heat and (2) that except for a few cases with opposite co-varying influences, the correlations between observed temperature and albedo and between observed temperature and canopy cover were each negative, ranging from −1.0 to −9.0 °C per 0.1 increase in albedo and from −0.1 to −2.2 °C per 0.1 increase in canopy cover. Observational data from the analysis domains pointed to a wind speed threshold of 3 m/s. Below this threshold the variations in air temperature could be explained by land use and surface properties within a 500-m radius of each observation point. Above the threshold, air temperature was influenced by the properties of the surface within a 1-km upwind fetch. Of relevance to policy recommendations, the study demonstrates the significant real-world cooling effects of increasing urban albedo and vegetation canopy cover. Based on correlations between the observed temperature (from mobile transects) and surface physical properties in the study domains, the analysis shows that neighborhood-scale (500-m) cooling of up to 2.8 °C during the daytime can be achieved by increasing albedo. A neighborhood can also be cooled by up to 2.3 °C during the day and up to 3.3 °C at night by increasing canopy cover. The analysis also demonstrates the suitability of using fine-resolution meteorological models to design mobile-transect routes or site-fixed weather monitors in order to quantify urban heat and the efficacy of albedo and canopy cover countermeasures. The results also show that the model is capable of accurately predicting the geographical locations and the magnitudes of localized urban heat and cool islands. Thus the model results can also be used to devise urban-heat mitigation measures.

Raising the albedo (solar reflectance) of streets can lower outside air temperature, reduce building energy use, and improve air quality in cities. However, the production and installation of pavement maintenance and rehabilitation treatments with enhanced albedo ("cool" pavements) may entail more or less energy consumption and carbon emission than that of less-reflective treatments. We developed several case studies in which a cool surface treatment is substituted for a more typical treatment (that is, a cool technology is selected instead of a more typical technology). We then assessed over a 50-year analysis period the changes in primary energy demand (PED, excluding feedstock energy) and global warming potential (GWP, meaning carbon dioxide equivalent) in Los Angeles and Fresno, California. The analysis considers two stages of the pavement life cycle: materials and construction (MAC), comprising material production, transport, and construction; and use, scoped as the influence of pavement albedo on cooling, heating, and lighting energy consumption in buildings. In Los Angeles, substituting a styrene acrylate reflective coating or a chip seal for a slurry seal in routine maintenance, or a bonded concrete overlay on asphalt (BCOA) without supplementary cementitious materials (SCM) for mill-and-fill asphalt concrete in conventional or long-life rehabilitation, induced MAC-stage PED and GWP penalties that substantially exceeded use-stage savings, primarily due to material production. Modified rehabilitation cases in which SCM comprised 21% to 50% of the BCOA's total cementitious content by mass (portland cement+SCM) yielded smaller total (MAC + use) PED and GWP penalties, or even total PED and GWP savings. Trends in Fresno were similar, with some differences in GWP outcomes that result from Fresno's longer heating season. The modified rehabilitation cases using BCOA with high SCM content yielded total GWP savings in each city; all other cases yielded total GWP penalties. The magnitude of the one-time GWP offset offered by global cooling from the increased albedo itself always, and sometimes greatly, exceeded the 50-year total GWP penalty or savings. In Los Angeles, the annual building conditioning (cooling+heating) PED and energy cost savings intensities yielded by cool pavements were each about an order of magnitude smaller than the corresponding savings from cool roofs. (C) 2017 Elsevier B.V. All rights reserved.

As the least expensive category of high-slope roofing in the U.S., shingles are found on the roofs of about 80% of U.S. homes, and constitute about 80% (by product area) of this market. Shingles are also among the least reflective high-slope roofing products, with few cool options on the market. The widespread use of cool roofs in the two warmest U.S. climate zones could reduce annual residential cooling energy use in these zones by over 7%. This project targets the development of high-performance cool shingles with initial solar reflectance at least 0.40 and a cost premium not exceeding US$0.50/ft². Phase 1 of the current study explored three approaches to increasing shingle reflectance. Method A replaces dark bare granules by white bare granules to enhance the near-infrared reflectance attained with cool pigments. Method B applies a white basecoat and a cool-color topcoat to a shingle surfaced with dark bare granules. Method C applies a visually clear, NIR-reflecting surface treatment to a conventionally colored shingle. Method A was the most successful, but our investigation of Method B identified roller coating as a promising top-coating technique, and our study of Method C developed a novel approach based on a nanowire mesh. Method A yielded red, green, brown, and black faux shingles with solar reflectance up to 0.39 with volumetric coloration. Since the base material is white, these reflectances can readily be increased by using less pigment. The expected cost premium for Method A shingles is less than our target limit of $0.50/ft², and would represent less than a 10% increase in the installed cost of a shingle roof. Using inexpensive but cool (spectrally selective) iron oxide pigments to volumetrically color white limestone synthesized from sequestered carbon and seawater appears to offer high albedo at low cost. In Phase 2, we plan to refine the cool shingle prototypes, manufacture cool granules, and manufacture and market high-performance cool shingles.

Since 1999, there have been advancements in the use of life cycle assessment (LCA) in Mexico. Many of the efforts, such as training, research, and application of life cycle thinking for decision-making, have been carried out across the government, industrial, and academic sectors, but mostly as independent initiatives, without communication or cooperation between the LCA practitioners. This independent approach to LCA has resulted in the perception that LCA advances in Mexico are minimal. However, there have been advancements and notable achievements. This paper presents a review of the history of the application of LCA in Mexico over the past 15 years.

Highly reflective roofs can decrease the energy required for building air conditioning, help mitigate the urban heat island effect, and slow global warming. However, these benefits are diminished by soiling and weathering processes that reduce the solar reflectance of most roofing materials. Soiling results from the deposition of atmospheric particulate matter and the growth of microorganisms, each of which absorb sunlight. Weathering of materials occurs with exposure to water, sunlight, and high temperatures. This study developed an accelerated aging method that incorporates features of soiling and weathering. The method sprays a calibrated aqueous soiling mixture of dust minerals, black carbon, humic acid, and salts onto preconditioned coupons of roofing materials, then subjects the soiled coupons to cycles of ultraviolet radiation, heat and water in a commercial weatherometer. Three soiling mixtures were optimized to reproduce the site-specific solar spectral reflectance features of roofing products exposed for 3 years in a hot and humid climate (Miami, Florida); a hot and dry climate (Phoenix, Arizona); and a polluted atmosphere in a temperate climate (Cleveland, Ohio). A fourth mixture was designed to reproduce the three-site average values of solar reflectance and thermal emittance attained after 3 years of natural exposure, which the Cool Roof Rating Council (CRRC) uses to rate roofing products sold in the US. This accelerated aging method was applied to 25 products–single ply membranes, factory and field applied coatings, tiles, modified bitumen cap sheets, and asphalt shingles–and reproduced in 3 days the CRRC's 3-year aged values of solar reflectance. This accelerated aging method can be used to speed the evaluation and rating of new cool roofing materials.

In 2006, California introduced the Global Warming Solutions Act (Assembly Bill 32), which requires the state to reduce greenhouse gas emissions to 1990 levels by 2020. "Cool community" strategies, including cool roofs, cool pavements, cool walls and urban vegetation, have been identified as voluntary measures with potential to reduce statewide emissions. In addition, cool community strategies provide co-benefits for residents of California, such as reduced utility bills, improved air quality and enhanced urban livability. To achieve these savings, Lawrence Berkeley National Laboratory (LBNL) has worked with state and local officials, non-profit organizations, school districts, utilities, and manufacturers for 4 years to advance the science and implementation of cool community strategies. This paper summarizes the accomplishments of this program, as well as recent developments in cool community policy in California and other national and international efforts. We also outline lessons learned from these efforts to characterize successful programs and policies to be replicated in the future. Published by Elsevier B.V.

The use of highly reflective "cool" roofing materials can decrease demand for air conditioning, mitigate the urban heat island effect, and potentially slow global warming. However, initially high roof solar reflectance can be degraded by natural soiling and weathering processes. We evaluated solar reflectance losses after three years of natural exposure reported in two separate databases: the Rated Products Directory of the US Cool Roof Rating Council (CRRC) and information reported by manufacturers to the US Environmental Protection Agency (EPA)'s ENERGY STAR (R) rating program. Many product ratings were culled because they were duplicative (within a database) or not measured. A second, site-resolved version of the CRRC dataset was created by transcribing from paper records the site-specific measurements of aged solar reflectance in Florida, Arizona and Ohio.Products with high initial solar reflectance tended to lose reflectance, while those with very low initial solar reflectance tended to become more reflective as they aged. Within the site-resolved CRRC database, absolute solar reflectance losses for samples of medium-to-high initial solar reflectance were 2-3 times greater in Florida (hot and humid) than in Arizona (hot and dry); losses in Ohio (temperate but polluted) were intermediate. Disaggregating results by product type factory-applied coating, field-applied coating, metal, modified bitumen, shingle, single-ply membrane and tile revealed that absolute solar reflectance losses were largest for field-applied coating, modified bitumen and single-ply membrane products, and smallest for factory-applied coating and metal products.The 2008 Title 24 provisional aged solar reflectance formula overpredicts the measured aged solar reflectance of 0-30% of each product type in the culled public CRRC database. The rate of overprediction was greatest for field-applied coating and single-ply membrane products and least for factory-applied coating, shingle, and metal products. New product-specific formulas of the form rho'(a)= 0.20+beta(rho(i)-0.20) can be used to estimate provisional aged solar reflectance rho'(a) from initial solar reflectance rho(i) pending measurement of aged solar reflectance. The appropriate value of soiling resistance beta varies by product type and is selected to attain some desired overprediction rate for the formula. The correlations for shingle products presented in this paper should not be used to predict aged solar reflectance or estimate provisional aged solar reflectance because the data set is too small and too limited in range of initial solar reflectance. (C) 2011 Elsevier B.V. All rights reserved.