Buildings may earn a rating of between one and four globes. 4 0 obj NYC °CoolRoofs is a New York City initiative to coat rooftops white with volunteers. [46] "Climate issues can affect cool roof performance. This project is co-financed by the European Union in the framework of the Intelligent Energy Europe Programme. 2 0 obj [21], Specifically, what works in California's Central Valley, such as cool roofs, does not necessarily provide the same benefits to other regions of the country, like Florida. %���� “The energy savings gained during the summer season, for some regions, is nearly entirely lost during the winter season,” Georgescu said. The program's outreach[64] has helped complete white roof projects in more than 20 US states and five countries, engaged thousands in volunteer projects, and sponsored the coating of hundreds of nonprofit and low-income rooftops. The reflectivity and emissivity ratings for over 500 reflective coatings can be found in the Cool Roofs Rating Council. As many as 10 points may be awarded for 1–100 percent roof coverage with either vegetation or highly reflective materials or both. [57] The program began in 2009 as part of PlaNYC,[58] and has coated over 5 million square feet of NYC rooftops white. In October 2013, the United States Department of Energy ranked Cool Roofs as a 53 out of 100 (0 to 100 weighted average) for a cost-effective energy strategy. White surfaces reflect more than half of the radiation that reaches them, while black surfaces absorb almost all. According to the U.S. Energy Information Administration, 2003 Commercial Buildings Energy Consumption Survey, heating accounts for 36% of commercial buildings' annual energy consumption, while air conditioning only accounts for 8% in United States. TARGET VAlUES . [50], Under the LEED 2009 version, to receive Sustainable Sites Credit 7.2 Heat Island Effect-Roof, at least 75% of the surface of a roof must use materials having a solar reflective index (SRI) of at least 78. [20], In 2014, a team of researchers, led by Matei Georgescu, an assistant professor in Arizona State University's School of Geographical Sciences and Urban Planning and a senior sustainability scientist in the Global Institute of Sustainability, explored the relative effectiveness of some of the most common adaptation technologies aimed at reducing warming from urban expansion. This is because a 93-square-metre (1,000 sq ft) white roof will offset 10 tons of carbon dioxide over its 20-year lifetime. Cool roofs are more beneficial in warmer climates and may cause energy consumption for heating applications to rise in colder climates. [14], A 2012 study by researchers at Concordia University included variables similar to those used in the Stanford study (e.g., cloud responses) and estimated that worldwide deployment of cool roofs and pavements in cities would generate a global cooling effect equivalent to offsetting up to 150 gigatonnes of carbon dioxide emissions – enough to take every car in the world off the road for 50 years. High-reflectivity, low-emissivity roofs maintain a temperature very close to ambient at all times preventing heat gains in hot climates and minimizing heat loss in cold climates. The value of the solar reflectance index varies from 0 to 1. The program does not, however, specify minimum requirements for solar reflectance or thermal emittance. The average daily summertime temperature of the black roof surface was 75 °C (167 °F), but once retrofitted with a white reflective surface, it measured 52 °C (126 °F). If all urban, flat roofs in warm climates were whitened, the resulting 10% increase in global reflectivity would offset the warming effect of 24 gigatonnes of greenhouse gas emissions, or equivalent to taking 300 million cars off the road for 20 years. building owners) may believe that the Energy Star label means their roof is energy-efficient; however, the testing is not as stringent as their appliance standard and does not include the additional components of a roof (i.e. Results of the study indicate that the performance of urban adaptation technologies can counteract this increase in temperature, but also varies seasonally and is geographically dependent. Volunteers use paintbrushes and rollers to apply an acrylic, elastomeric coating to the roof membrane. ��x�3re�]~���7�0��l�&�v2�1F�vmS�u� �:��g�|j3Q��݅~@_��0-r��]��V��7���kt���q_���; ����{�z��{ The US department of energy defines the Solar Reflectance Index (SRI.) For Florida, cool roofs may not be the optimal way to battle the urban heat island because of these unintended consequences.” Overall, the researchers suggest that judicious planning and design choices should be considered in trying to counteract rising temperatures caused by urban sprawl and greenhouse gases. Highly reflective, low-emittance materials are much better at reducing energy consumption. However, during winter, these same urban adaptation strategies, when deployed in northerly locations, further cool the environment, and consequently require additional heating to maintain comfort levels. 3 0 obj In sunny conditions, this could cause uncomfortable glare and unwanted heat for you or your neighbors. These guides were aimed at improvements to existing Retail and Office buildings which could improve their energy efficiency. For low-slope roof applications, a roof product qualifying for the Energy Star label under its Roof Products Program must have an initial solar reflectivity of at least 0.65, and weathered reflectance of at least 0.50, in accordance with EPA testing procedures. TSR is usually displayed as a percentage between 0% and 100%. In tropical Australia, zinc-galvanized (silvery) sheeting (usually corrugated) do not reflect heat as well as the truly "cool" color of white, especially as metallic surfaces fail to emit infrared back to the sky. High emissivity roofs have much higher heat loss in cold climates for the same insulation values. 4. This criterion can also be met by installing a vegetated roof for at least 50% of the roof area, or installing a high albedo and vegetated roof in combination that meets this formula: (Area of Roof meeting Minimum SRI Roof/0.75) + (Area of vegetated roof/0.5) ≥ Total Roof Area. High temperatures and large variations, seasonally or daily, at the roofing level are detrimental to the longevity of roof membranes.

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