Dallas Urban Heat Island Options 1 W AYS TO E FFECTIVELY R EDUCE U RBAN H EAT I SLAND E FFECTS 2009
Background Dallas, like most cities, is hotter than comparable rural areas an urban heat island. 2 Urban development reduces trees and vegetation, which have a cooling effect, and add heat absorbing surfaces roofs, paving, and buildings. Heat is added from other sources - fuel combustion and air conditioning units. The urban heat island negatively affects Dallas energy use, air quality, water quality, and public health.
Dallas Surface Temperatures 3 Downtown Dallas Surface Temperatures Kinetic Thermal Corrected Aster Image: September 28, 2006, 5:25 pm NOTE: darkest blue areas are clouds and cloud shadows.
Reducing Urban Heat Island Effects Three Basic Strategies Expand and protect urban tree cover Plant Protect Increase roof reflectivity Cool roofing Green roofing Reduce paving reflectivity Cool paving Pervious paving 4
Trees Trees help cool the city and are a defining feature of many parts of Dallas. Trees are valuable assets. Trees... Add value to property. Contribute to human health. Reduce air conditioning costs. Are attractive urban features. 5
Options for Dallas Trees Set high goals Dallas Million Trees Initiative Provide outreach and education Consolidate city information. Actively engage other organizations. Manage urban forest data Tree inventory Urban forest analysis project Fund tree planting and conversation Expand Dallas Reforestation Fund. Establish capital improvement set-aside for trees/landscaping. Support utility-based tree planting for energy savings. Improve regulations and incentives Include trees in SIP. Modify current ordinances to protect larger trees, increase tree placement, and increase tree planting during development. 6
Dallas Urban Tree Canopy 7 Trees planted early in the development process are the future tree canopy for Dallas.
Cool Roofing Roofing is perhaps the hottest of all urban surfaces, and covers 20 to 30 percent of the city s developed area. Cool roofing reflects solar radiation and reduces energy demand for air conditioned buildings, providing immediate benefits to building owners. Green roofs are planted with vegetation and help cool the city and save energy. 8
Cool Roofing in Dallas 9 Cool roofs are fairly common in Dallas, but are not the dominant type of low-slope roofs. Cool roofing examples are easy to see on Dallas aerial photos. These examples of reflective roofing include a building supply retailer and an elementary school.
Outreach Cool Roof Options for Dallas Inform target audiences of Dallas cool roof requirements for low-slope roofs. Emphasize cool roofing replacement for existing low-slope buildings. Showcase green roofs for energy and stormwater benefits. Cool Roof Policies Encourage others in the region to adopt cool roof requirements. Consider inclusion of EPA ENERGY STAR standards for sloped roofs. Incentives and Regulations Include cool roof requirements for re-roofing. Encourage utilities to provide cool roof and green roof rebates. Create green roof provisions in the building code. Use stormwater fees for greenroof and porous paving demonstration projects. Support inclusion of cool roofs in State energy code. 10
Dallas Cool Paving Paved surfaces make up 30 to 40% of developed areas of Dallas. Reflective paving reflects solar energy helping to lower area temperatures. Porous paving cools through increased evaporation and reduced thermal storage. These pavements benefit water quality by reducing runoff temperatures and removing pollutants, and stormwater management, by slowing stormwater release. 11
Paving and Temperatures 12 This industrial/warehouse area along I-635 illustrates the impact of extensive heat absorbing pavement and roofing on surface temperatures. The surface temperatures of the residential areas to the southwest are 10 to 20ºF cooler.
Thermal Image of Street 13 This street photo shows the effect of shade on paved surface temperatures. Surfaces in the shade are 30 to 50ºF hotter that paved surfaces.
Cool Paving Options Demonstration and outreach Foster and support cool paving demonstration projects. Create cool paving database of current examples. Conduct cool paving workshops. Policies Create a unified cool paving policy in city plans, green building program, landscape requirements, and stormwater regulations. Incentives and regulations Add points in green building program for cool paving. 14 Add supportive provisions in stormwater management regulations. Add provisions in zoning ordinance.
Summary Dallas has many options for effectively reducing urban heat island impacts, while contributing to the area s economic and environmental qualities. Heat island options include setting goals, outreach, education, policies, regulations, and incentives. The basic tools for reducing urban heat island impacts are: An expanded and healthy urban tree population. Cool roofing that helps lower temperatures, saves energy, and reduces air pollution. Cool paving that reduces surface temperatures, improves water quality, and helps with stormwater management. 15
EPA Urban Heat Island http://www.epa.gov/heatisland EPA Compendium of UHI Reports For More Information http://www.epa.gov/heatisland/resources/compendium.htm EPA ENERGY STAR Cool Roofs http://www.energystar.gov/index.cfm?c=roof_prods.pr_roof_products Cool Roof Rating Council http://www.coolroofs.org/index.html SMART Innovations for Urban Climate and Energy, EPA Center of Excellence http://www.asusmart.org/ 16 This presentation was prepared by the Houston Advanced Research Center as part of the Dallas Sustainable Skylines Initiative, through the support of the U.S. Environmental Protection Agency, September 2009.