'Cool pavement' technologies studied to address hot urban surfaces - 0 views
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n a typical city, pavements account for 35 to 50 percent of surface area,
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half is comprised of streets and about 40 percent of exposed parking lots
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Most of these
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are constructed with dark materials
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"Because dark pavements absorb almost all of the sun's energy, the pavement surface heats up, which in turn also warms the local air
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Berkeley Lab scientists have been studying "cool pavement" technologies
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Like cool roofs, which are lighter-colored roofs that keep the air both inside and outside the building cooler by reflecting more of the sun's energy
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pavements reflect as much as 30 to 50 percent of the sun's energy, compared to only 5 percent for new asphalt (and 10 to 20 percent for aged asphalt)
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Heat Island Group has converted a portion of a new temporary parking lot at Berkeley Lab into a cool pavement exhibit that will also allow them to evaluate the products over time
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provides an opportunity to feature cool pavement coatings that are applied directly to existing paved surfaces
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the exhibit features six coatings donated by two manufacturers
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Emerald Cities Cool Pavement and StreetBond.
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Cool pavements can either be made from traditional pavement materials that are lighter in color
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such as cement concrete
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or can consist of cool-colored coatings or surface treatments for asphalt surfaces
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An ideal design goal would be a pavement with solar reflectance of at least 35 percent
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Sealcoats are a common maintenance practice for parking lots and schoolyards since the asphalt pavement structure degrades over tim
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asphalt
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can be used in lieu of a sealcoat, and are a good strategy for cities looking to introduce cool pavement technologies
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Cool pavements come in different hues, including green, blue and yellow, and their solar reflectance value depends on both color and material
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some colors that look dark but are actually more reflective in the near infrared spectrum
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scientists will be collecting data to see how the coatings fare over time
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At some point they will reach an equilibrium at which the solar reflectance won't degrade much anymore
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very interested to see what happens when it rains, which may help the coatings self-clean and restore higher reflectance
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"Across an entire city, small changes in air temperature could be a huge benefit as it can slow the formation of smog
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Just a couple of degrees can also reduce peak power demand, by reducing the energy load from air-conditioning
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Chicago has reported energy savings from using solar-reflective pavements in its alleys
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more reflective parking lots could allow building owners and cities to save on energy needed to illuminate streets and parking lots
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field studies are needed to verify and quantify the results.
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many of these benefits have been confirmed by scientific models
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leading a study
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will closely monitor the solar reflectance values and temperatures of 20 x 24 square-foot pavement sections of six different materials on a residential street on the UC Davis campu
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scientists hope to better understand how changes in solar reflectance over time affect heat transfer throughout the pavement structure
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may assist policymakers and pavement professionals in making informed decisions regarding cool pavement requirements for building codes and project specifications
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may also help sell cool pavement coatings since they tend to be more expensive than traditional sealants
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hurdle is that the benefits of cool pavements are more for the public rather than the building owner
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benefits are less immediately tangible than for cool roofs
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initial cost premium can potentially be offset over the lifespan of the product with increased durability and less need for ongoing maintenance
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schoolyards are a particular target because of the negative health implications of hot blacktops for schoolchildren
