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Title: Cooler paving materials for heat-island mitigation

Abstract

Many cities suffer summer daytime temperatures greater than their suburban or rural surroundings. One of the causes of this heat island phenomenon is the absorption of sunlight by dark pavements. In warm climates, the urban heating damages the environment by adding to air-conditioning demand and creating smog. If urban roads, driveways and walkways were paved with light colored, and consequently cooler, materials these penalties would be diminished. However, lighter materials may cost more than the usual asphalt materials, In this report, the dollar value of potential air conditioning and smog savings from lighter pavements is estimated, and compared to the extra cost of such roads. The extra cost is minimized if the lighter-colored coating is applied as a thin layer when normal maintenance is performed. The authors find that, in Los Angeles, increasing the albedo from 0.1 to 0.35, could produce an air-conditioning saving of $$0.012/m{sub 2}-yr. and smog savings of about $$0.06/m{sub 2}-yr. The present value of these savings, for the 5 year lifetime of the resurfacing, is about 5 times the annual saving, or about $0.36/m{sub 2}. (The particular climate and smog problem clearly influence this result.) Thus one could purchase a cooler material whose extra cost is this amount, with no net expense. If roads are cooler they may also last longer and thus save money.

Authors:
;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab., CA (US)
Sponsoring Org.:
USDOE; Environmental Protection Agency
OSTI Identifier:
20006373
Report Number(s):
CONF-980815-
TRN: IM200007%%429
DOE Contract Number:
AC03-76SF00098
Resource Type:
Conference
Resource Relation:
Conference: 1998 ACEEE Summer Study on Energy Efficiency in Buildings, Pacific Grove, CA (US), 08/23/1998--08/28/1998; Other Information: 10 volume set available for $200.00; PBD: 1998; Related Information: In: 1998 ACEEE summer study on energy efficiency in buildings: Proceedings, [3100] pages.
Country of Publication:
United States
Language:
English
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; 54 ENVIRONMENTAL SCIENCES; URBAN AREAS; THERMAL POLLUTION; AIR POLLUTION ABATEMENT; PAVEMENTS; MATERIAL SUBSTITUTION; COLOR; ECONOMICS; AIR CONDITIONING; ENERGY CONSERVATION; SMOG

Citation Formats

Pomerantz, M., and Akbari, H.. Cooler paving materials for heat-island mitigation. United States: N. p., 1998. Web.
Pomerantz, M., & Akbari, H.. Cooler paving materials for heat-island mitigation. United States.
Pomerantz, M., and Akbari, H.. 1998. "Cooler paving materials for heat-island mitigation". United States. doi:.
@article{osti_20006373,
title = {Cooler paving materials for heat-island mitigation},
author = {Pomerantz, M. and Akbari, H.},
abstractNote = {Many cities suffer summer daytime temperatures greater than their suburban or rural surroundings. One of the causes of this heat island phenomenon is the absorption of sunlight by dark pavements. In warm climates, the urban heating damages the environment by adding to air-conditioning demand and creating smog. If urban roads, driveways and walkways were paved with light colored, and consequently cooler, materials these penalties would be diminished. However, lighter materials may cost more than the usual asphalt materials, In this report, the dollar value of potential air conditioning and smog savings from lighter pavements is estimated, and compared to the extra cost of such roads. The extra cost is minimized if the lighter-colored coating is applied as a thin layer when normal maintenance is performed. The authors find that, in Los Angeles, increasing the albedo from 0.1 to 0.35, could produce an air-conditioning saving of $0.012/m{sub 2}-yr. and smog savings of about $0.06/m{sub 2}-yr. The present value of these savings, for the 5 year lifetime of the resurfacing, is about 5 times the annual saving, or about $0.36/m{sub 2}. (The particular climate and smog problem clearly influence this result.) Thus one could purchase a cooler material whose extra cost is this amount, with no net expense. If roads are cooler they may also last longer and thus save money.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1998,
month = 7
}

Conference:
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  • This report summarizes paving materials suitable for urban streets, driveways, parking lots and walkways. The authors evaluate materials for their abilities to reflect sunlight, which will reduce their temperatures. This in turn reduces the excess air temperature of cities (the heat island effect). The report presents the compositions of the materials, their suitability for particular applications, and their approximate costs (in 1996). Both new and resurfacing are described. They conclude that, although light-colored materials may be more expensive than conventional black materials, a thin layer of light-colored pavement may produce energy savings and smog reductions whose long-term worth is greatermore » than the extra cost.« less
  • Part of the urban heat island effect can be attributed to dark pavements that are commonly used on streets and parking lots. In this paper we consider two light colored, hence cooler, alternative paving materials that are in actual use in cities today. These are Portland cement concrete (PCC) pavements and chip seals. We report measurements of the albedos of some PCC and chip sealed pavements in the San Francisco Bay Area. The albedos of the PCC pavements ranged from about 0.18 to 0.35. The temperatures of some PCC pavements are also measured and calculated. We then consider how themore » albedos of the constituent materials of the PCC (stone, sand and cement) contribute to the albedos of the resulting finished concrete. The albedos of a set of chip sealed pavements in San Jose, CA, were measured and correlated with the times of their placement. It is found that the albedos decrease with age (and use) but remain higher than that of standard asphalt concrete (AC) for about five years. After t hat, the albedos of the chip seals are about 0.12, similar to aged AC. The fact that many PCC pavements have albedos at least twice as high as aged AC suggests that it is possible to have pavement albedos that remain high for many years.« less
  • Urban heat islands increase the demand for cooling energy and accelerate the formation of smog. They are created when natural vegetation is replaced by heat-absorbing surfaces such as building roofs and walls, parking lots, and streets. Through the implementation of measures designed to mitigate the urban heat island, communities can decrease their demand for energy and effectively cool the metropolitan landscape. In addition to the economic benefits, using less energy leads to reductions in emission of CO{sub 2}--a greenhouse gas--as well as ozone (smog) precursors such as NOx and VOCs. Because ozone is created when NOx and VOCs photochemically combinemore » with heat and solar radiation, actions taken to lower ambient air temperature can significantly reduce ozone concentrations in certain areas. Measures to reverse the urban heat island include afforestation and the widespread use of highly reflective surfaces. To demonstrate the potential benefits of implementing these measures, EPA has teamed up with NASA and LBNL to initiate a pilot project with three US cities. As part of the pilot, NASA will use remotely-sensed data to quantify surface temperature, albedo, the thermal response number and NDVI vegetation of each city. This information will be used by scientists at Lawrence Berkeley National Laboratory (LBNL) along with other data as inputs to model various scenarios that will help quantify the potential benefits of urban heat island mitigation measures in terms of reduced energy use and pollution. This paper will briefly describe this pilot project and provide an update on the progress to date.« less
  • Urban areas tend to have higher air temperatures than their rural surroundings as a result of gradual surface modifications that include replacing the natural vegetation with buildings and roads. The term ''Urban Heat Island'' describes this phenomenon. The surfaces of buildings and pavements absorb solar radiation and become extremely hot, which in turn warm the surrounding air. Cities that have been ''paved over'' do not receive the benefit of the natural cooling effect of vegetation. As the air temperature rises, so does the demand for air-conditioning (a/c). This leads to higher emissions from power plants, as well as increased smogmore » formation as a result of warmer temperatures. In the United States, we have found that this increase in air temperature is responsible for 5-10% of urban peak electric demand for a/c use, and as much as 20% of population-weighted smog concentrations in urban areas. Simple ways to cool the cities are the use of reflective surfaces (rooftops and pavements) and planting of urban vegetation. On a large scale, the evapotranspiration from vegetation and increased reflection of incoming solar radiation by reflective surfaces will cool a community a few degrees in the summer. As an example, computer simulations for Los Angeles, CA show that resurfacing about two-third of the pavements and rooftops with reflective surfaces and planting three trees per house can cool down LA by an average of 2-3K. This reduction in air temperature will reduce urban smog exposure in the LA basin by roughly the same amount as removing the basin entire onroad vehicle exhaust. Heat island mitigation is an effective air pollution control strategy, more than paying for itself in cooling energy cost savings. We estimate that the cooling energy savings in U.S. from cool surfaces and shade trees, when fully implemented, is about $5 billion per year (about $100 per air-conditioned house).« less