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HomeMy WebLinkAboutItem08-A City of Miami Gardens Agenda Cover Memo Council Meeting Date: March 2, 2011 Item Type: Resolution Ordinance Other x Fiscal Impact: (Enter X in box) Yes No Ordinance Reading: 1st Reading 2nd Reading x x Public Hearing: Yes No Yes No x Funding Source: Advertising Requirement: Yes No x Contract/P.O. Required: (Enter X in box) Yes No RFP/RFQ/Bid #: x N/A Strategic Plan Related (Enter X in box) Yes No Strategic Plan Priority Area: Enhance Organizational Bus. & Economic Dev Public Safety Quality of Education Qual. of Life & City Image x Communcation Strategic Plan Obj./Strategy Objective: Enhance overall quality of life for residents and businesses of CMG. X Sponsor Name Councilman Andre’ Williams Department: Mayor and Council Short Title: AN ORDINANCE OF THE CITY COUNCIL OF THE CITY OF MIAMI GARDENS, FLORIDA, AMENDING ARTICLE XIII OF CHAPTER 34 (“ZONING AND LAND DEVELOPMENT CODE”) TO CREATE SECTION 34-421 ENTITLED “HEAT ISLAND EFFECT-NON ROOF” AND TO PROVIDE REGULATIONS RELATING TO ENVIRONMENTALLY RESPONSIBLE METHODS FOR COOLING AND SHADING OF HARDSCAPES IN THE CITY OF MIAMI GARDENS; PROVIDING FOR ADOPTION OF REPRESENTATIONS; REPEALING ALL ORDINANCES IN CONFLICT; PROVIDING A SEVERABILITY CLAUSE; PROVIDING FOR INCLUSION IN CODE; PROVIDING AN EFFECTIVE DATE. Summary At the February 2, 2011 Zoning Meeting the City Council deferred this ordinance to the March 2, 2011 Zoning Meeting. ITEM 8-A) ORDINANCE FIRST READING Heat Island Effect 1515 NW 167 Street, Building 5 Suite 200 Miami Gardens, Florida 33169 The City of Miami Gardens is committed to doing its part to reduce energy consumption. One mechanism for doing this is to reduce the heat island effect from hardscapes in the City. It has been shown that elevated temperatures from heat island effects in urban areas result in increased energy consumption for cooling; increased greenhouse gas emissions associated with building and vehicle usage; and deterioration in air quality. Hardscape management methods, such as tree planting, shading and use of reflective light colored paving materials, will contribute to decreasing the urban heat island effect, which can thereby reduce the energy consumption of buildings. The City Council previously adopted Resolution No. 2008-27-714 whereby the City Council committed to implemented measures to become a “green local government.” Councilman Andre’ Williams is proposing that the City Council enact this Ordinance in an effort to mitigate the urban heat island effect within the City thereby improving the energy consumption in new commercial structures. At the February 2, 2011 Zoning Meeting the City Council requested Staff to provide an analysis of the proposed ordinance’s potential effect upon development. That analysis is attached. Based on discussion with the LDR Stakeholders on February 16, 2011, the proposed ordinance was revised so that it does not impact existing businesses and only applies to new construction. Proposed Action: Councilman Williams is recommending that the City Council adopt the attached Ordinance. Attachment: Smart Growth Heat Island Brochure Staff Analysis of Heat Island Effect Ordinance – Cost Analysis 1 Added language is underlined. Deleted language is stricken through. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 ORDINANCE NO. 2011 ____ AN ORDINANCE OF THE CITY COUNCIL OF THE CITY OF MIAMI GARDENS, FLORIDA, AMENDING ARTICLE XIII OF CHAPTER 34 (“ZONING AND LAND DEVELOPMENT CODE”) TO CREATE SECTION 34-421 ENTITLED “HEAT ISLAND EFFECTNON ROOF” AND TO PROVIDE REGULATIONS RELATING TO ENVIRONMENTALLY RESPONSIBLE METHODS FOR COOLING AND SHADING OF HARDSCAPES IN CERTAIN DISTRICTS WITHIN THE CITY OF MIAMI GARDENS; PROVIDING FOR ADOPTION OF REPRESENTATIONS; REPEALING ALL ORDINANCES IN CONFLICT; PROVIDING A SEVERABILITY CLAUSE; PROVIDING FOR INCLUSION IN CODE; PROVIDING AN EFFECTIVE DATE WHEREAS, the City of Miami Gardens is committed to doing its part to reduce energy consumption, and WHEREAS, one mechanism for doing this is to reduce the heat island effect from hardscapes in the City, and WHEREAS, the United States Environmental Protection Agency advises that it has been shown that elevated temperatures from heat island effects in urban areas result in increased energy consumption for cooling; increased greenhouse gas emissions associated with building and vehicle usage; and deterioration in air quality, and WHEREAS, hardscape management methods, such as tree planting, shading and use of reflective paving materials, will contribute to decreasing the urban heat island effect, which can thereby reduce the energy consumption of buildings, and WHEREAS, City Council previously adopted Resolution No. 2008-27-714 whereby the City Council committed to implement measures to become a “green local government”, and 2 Added language is underlined. Deleted language is stricken through. 32 33 34 35 36 37 38 39 40 41 WHEREAS, Councilman Andre’ Williams is proposing that the City Council enact this Ordinance in an effort to mitigate the urban heat island effect within the City thereby improving the energy consumption in new commercial structures, NOW, THEREFORE, BE IT ORDAINED BY THE CITY COUNCIL OF THE CITY OF MIAMI GARDENS, FLORIDA, AS FOLLOWS: Section 1. ADOPTION OF REPRESENTATIONS: The foregoing Whereas paragraphs are hereby ratified and confirmed as being true, and the same are hereby made a specific part of this Ordinance. Section 2. AMENDMENT: Article XIII of Chapter 34 of the City’s Zoning and Land Development Code is hereby amended to add Section 34-421 as follows: 42 Sec. 34-421. Heat Island Effect -Non-Roof 43 44 A. Intent 45 46 The requirements of this ordinance are intended to reduce the “heat island effect” 47 from hardscapes in the City of Miami Gardens and to consequently reduce 48 energy consumption and electric bills for buildings within the City. 49 50 B. Definitions 51 52 1. Hardscape means the nonliving portions of a building's landscaping, such 53 as roads, sidewalks, courtyards and parking lots. 54 2. Heat Island Effect is an elevated temperature over an urban area when 55 compared to rural areas, typically caused by the increased presence of dark, heat-absorbing materials, such as asphalt and dark roofs in urban areas. 56 57 58 3. Solar reflectance is the fraction of solar energy reflected by a material. 59 4. Pervious Pavement System is a porous surface system with a stabilized 60 base that allows water from precipitation and other sources to pass 61 directly through, thereby reducing the runoff from a site, allowing 62 groundwater recharge, and naturally cooling the surface through 63 evaporation of water from pavement voids or from beneath. 64 3 Added language is underlined. Deleted language is stricken through. 65 C. Applicability 66 67 The provisions of this section are applicable in all zoning designations except the 68 I-1 and I-2 Zoning Districts. All newly constructed buildings shall comply with 69 these requirements, provided that, single family, duplex, townhouse dwelling 70 units, and industrial parks, are exempt from these requirements. Additionally, 71 new developments, where asphalt and paving already exist, or where compliance 72 would otherwise require the removal of existing asphalt, are exempt from these 73 requirements. New construction that is a part of an overall larger site plan, with 74 existing asphalt shall be permitted to match the hardscape to the existing asphalt 75 to create a cohesive development. All new and replacement hardscape shall be 76 reviewed by the Planning & Zoning Department for compliance with this 77 Ordinance. 78 79 D. Solar reflectance 80 81 Solar reflectance shall be determined as follows: 82 83 a. For For parking lot roofing covering materials, all roof exterior surfaces and 84 building materials used to comply with Section 34-421(D) shall have a 85 minimum solar reflectance as specified in Sections 34-421(D) when (i) tested in accordance with American Society for Testing and Materials (“ASTM E1918”), (ii) tested with a portable reflectometer at near 86 87 88 ambient conditions, (iii) labeled by the Cool Roof Rating Council, or (iv) 89 labeled as an Energy Star qualified roof product. Any product that has 90 been rated by the Cool Roof Rating Council or by Energy Star shall 91 display a label verifying the rating of the product. 92 93 b. For paving materials, all paving materials used to comply with Section 94 34-421(D) shall have a minimum solar reflectance as specified in 95 Sections 34-421(D) when (i) tested in accordance with ASTM E903 or 96 ASTM E1918, (ii) tested with a portable reflectometer at near ambient 97 conditions, or (iii) default values of solar reflectance for listed materials 98 may be used as follows: 99 100 TABLE INSET: 101 102 Material Solar Reflectance 103 104 Typical new gray concrete 0.35 105 Typical weathered gray concrete 0.20 106 Typical new white concrete 0.70 107 Typical weathered white concrete 0.40 108 New asphalt 0.05 109 Weathered asphalt 0.10 4 Added language is underlined. Deleted language is stricken through. 110 111 E. Requirements 112 113 Sites with new construction, except as provided under Section C above, shall be 114 required to comply with the following: 115 116 (a) Provide any combination of the following strategies for fifty percent 117 (50%) of the site hardscape: 118 119 (i) Shade from solar panels or roofing materials with a solar 120 reflectance of at least 0.30 121 (ii) Shade from trees within five (5) years of occupancy 122 (iii) Paving materials with a solar reflectance of at least 0.30 123 (iv) Pervious pavement system; OR 124 125 (b) Place a minimum of fifty-percent (50%) of parking spaces under 126 cover (defined as underground, under deck, under roof, or under 127 building). Any roof used to shade or cover parking must have a 128 solar reflectance of at least 0.30. 129 130 131 132 133 134 135 136 137 138 139 140 141 Section 3. CONFLICT: All ordinances or Code provisions in conflict herewith are hereby repealed. Section 4. SEVERABILITY: If any section, subsection, sentence, clause, phrase or portion of this Ordinance is for any reason held invalid or unconstitutional by any court of competent jurisdiction, such portion shall be deemed a separate, distinct and independent provision and such holding shall not affect the validity of the remaining portions of this Ordinance. Section 5. INCLUSION IN CODE: It is the intention of the City Council of the City of Miami Gardens that the provisions of this Ordinance shall become and be made a part of the Code of Ordinances of the City of Miami Gardens and that the section of this Ordinance may be renumbered or relettered and the word “Ordinance” may be changed to “Chapter,” “Section,” “Article” or 5 Added language is underlined. Deleted language is stricken through. 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 such other appropriate word or phrase, the use of which shall accomplish the intentions herein expressed. Section 6. EFFECTIVE DATE: This Ordinance shall become effective immediately upon its final passage. PASSED ON FIRST READING ON THE _____ DAY OF __________, 2011. PASSED ON SECOND READING ON THE ____ DAY OF _________, 2011. ADOPTED AND PASSED BY THE CITY COUNCIL OF THE CITY OF MIAMI GARDENS AT ITS ZONING MEETING HELD ON THE _____ DAY OF FEBRUARY, 2011. ________________________________ SHIRLEY GIBSON, MAYOR ATTEST: ________________________ _________ RONETTA TAYLOR, MMC, CITY CLERK PREPARED BY: SONJA K. DICKENS, ESQ., CITY ATTORNEY SPONSORED BY: COUNCILMAN ANDRE’ WILLIAMS Moved by: ____________________ Second by: ____________________ VOTE: _________ 6 Added language is underlined. Deleted language is stricken through. 176 Mayor Shirley Gibson ____ (Yes) ____(No) 177 Vice Mayor Aaron Campbell, Jr. ____ (Yes) ____(No) 178 Councilwoman Lisa Davis ____ (Yes) ____(No) 179 Councilman Oliver Gilbert, III ____(Yes) ____(No) 180 Councilwoman Sharon Pritchett ____ (Yes) ____(No) 181 182 183 Councilwoman Felicia Robinson ____(Yes) ____(No) Councilman Andre’ Williams ____(Yes) ____(No) 1EPA United States Environmental Protection Agency EPA 430-F-03-001 Smart Growth and Urban Heat Islands Development patterns of the last 50 years have had both positive and negative impacts on communities across the country. One concern has been steadily increasing urban temperatures due to the effects of “urban heat islands.” A heat island is an umbrella of air, often over a city or built-up area, that is warmer than the air surrounding it. The urban heat island profile shown here demonstrates that heat islands are typically most intense over dense urban areas. The profile also shows how parks and other vegetated sections within a downtown area may help to reduce heat islands. In general, summertime heat islands raise air conditioning demand, air pollution levels (particularly smog), and greenhouse gas emissions. They also increase the incidence of heatrelated illness and mortality. In fact, in an average year, approximately 1,100 Americans die from extreme heat --the leading weather-related killer in the United States. 2 Heat islands augment this public health threat by directly increasing temperature and indirectly raising ground-level ozone concentrations. Those at significant risk from extreme heat and ozone exposure include the elderly, children, and individuals with pre-existing respiratory disease. Residents who live in homes with dark-colored roofs and no air conditioning may also be more vulnerable than the general population. S m a r t G r o w t h F a c t s h e e t S e r i e s Because urban design plays a large role in heat island formation, smart growth development strategies provide an opportunity to reduce heat islands. Smart growth is development that enhances both a community’s economy and environment through strategies to help citizens make informed decisions about how and where they want to grow. In addition to mitigating the heat island effect, smart growth provides a framework for increasing regional environmental protection, enhancing community character, and strengthening local economies. economies. Here are four smart growth solutions that can achieve these goals: 􀁺 Reducing off-street parking and using porous paving materials: Surface parking lots replace natural vegetation with pavements that transfer heat to the surroundings. Providing on-street parking and planning compact, pedestrianoriented development promotes transportation choices and can minimize the size and number of parking lots. 􀁺 Planting, preserving, and maintaining trees and vegetation: Trees and vegetation contribute to the beauty, distinctiveness, and material value of communities by incorporating the natural environment into the built environment. In addition, they cool surrounding areas by increasing evapotranspiration – a natural process that draws heat from the air to convert water in the leaf structure to water vapor. Planted adjacent to homes and buildings, trees provide shade, cool the interior, and reduce air conditioning energy demand. Trees and vegetation planted along medians and sidewalks can decrease evaporative emissions from cars and filter pollution from the air. Rooftop gardens, or green Everyone wins. Residents get better homes, lower energy bills, and cooler neighborhoods with plenty of green space. Narrower streets and a shorter pipeline means lower installation costs, so the developer gets a subdivision that’s cheaper to build. And the City ends up with less streets to maintain and a standard for future development that maintain the community’s existing high quality of life. J.D. Hightower, City Planner for Escalon, CA Currents – An Energy Newsletter for Local Governments January/February 1999 Source: EPA 1992 1 S m a r t G r o w t h F a c t s h e e t S e r i e s “EPA's mission is to protect public health and the environment. EPA works with state and local decision makers to evaluate, promote, and implement integrated, common-sense strategies that capitalize on public health and air quality improvements, while encouraging economic growth. Studies have demonstrated that mitigating heat islands provide clear environmental and financial benefits including improved local and global air quality, reduced heatrelated illness and death, and increased energy savings.” Case Study Chicago is a leader in urban forestry and heat island mitigation. The city has adopted an open space impact fee ordinance that requires new residential development to contribute a proportionate amount of open space or recreational facilities, or to pay fees that ensure community residents of continued access to greenspace. Chicago also replaced a 10,080 ft² conventionally paved alley with a light-colored permeable gravel pave system, which has eliminated chronic flooding without requiring the installation of a sewer system. In addition, between 1991 to 1998 Chicago planted over 500,000 trees and achieved a citywide tree count of 4.1 million. Chicago's Bureau of Forestry now plants a minimum of 5,000 new trees per year and plans to install --in addition to 120 miles of existing median planters --280 miles of new median planters by 2005. In June 2001, Chicago amended its energy code to include requirements for reflective or green roofs. See: http://www.cityofchicago.org/Environment/To learn more about Smart Growth and the Smart Growth Network, please go to http://www.smartgrowth.org. roofs, can also mitigate urban heat islands while increasing the energy efficiency and attractiveness of commercial and residential buildings. 1 “Cooling Our Communities – A Guidebook On Tree Planting and Light-Colored Surfacing” U.S. Environmental Protection Agency 22P-2001, January 1992. 2 Kalkstein, LS, 1993. Health and Climate Change: Direct Impacts in Cities. The Lancet Lancet 342:1397-99. 3 Stone, B., and M.O. Rodgers. 2001. “Urban Form and Thermal Efficiency: How the Design of Cities Influences the Urban Heat Island Effect.” Journal of the American Planning Association 67 (2) 186-198. Resources For more information on heat islands, see www.epa.gov/heatisland, www.hotcities.org, and http://eetd.lbl.gov/HeatIsland. For more information on smart growth, see www.smartgrowth.org and www.epa.gov/smartgrowth. Additional information on the relationship between the environment and the built environment can be found in “Our Built and Natural Environments: A Technical Review of the Interactions between Land Use, Transportation, and Environmental Quality.” EPA 231-R-01-002. 􀁺 Promoting infill and higherdensity development: Development within existing communities can preserve open space and help offset heat islands and their consequences. A 2001 report found that for every acre of brownfield redevelopment, 4.5 acres of open space is preserved. Additional research found that compact development contributes less heat energy to the surrounding air than low-density dispersed growth patterns.3 􀁺 Increasing public education and outreach: Heat island mitigation strategies should reflect local variation in the built environment, as well as local preferences and attitudes. Policies should be tailored to meet these needs, based on stakeholder input, and effectively communicated to the public. Committees formed to address urban heat mitigation should include representatives from citizen groups, local government, non-governmental organizations, universities, and others concerned about how the community grows. A lead organization should be appointed to disseminate information to the community, solicit feedback, and incorporate issues and concerns Office of Air and Radiation (MC 6205J) Office of the Administrator (MC 1808) EPA 430-F-03-001 into action plans. Working together, communities can address urban heat islands while enhancing the quality and character of their neighborhoods. 2Printed on 100% recycled/recyclable paper with a minimum 50% post-consumer fiber using vegetable-based ink. The City of Miami Gardens Planning and Zoning Department 1515 N.W. 167th Street ● Bldg. 5 ● Suite 200 ● Miami Gardens, Florida 33169 ● Tel: (305) 622-8023 ● Fax: (305) 622-8857 ● www.miamigardens-fl. gov DATE: February 23, 2011 TO: Mayor and City Council VIA: Danny Crew, City Manager FROM: Jay R. Marder, AICP, Development Services Director CC: Daniel Rosemond, Assistant City Manager/Community Development Director Sonja Dickens, City Attorney Shellie Ransom, Building Official Tom Ruiz, Public Works Director SUBJECT: Heat Island Effect Ordinance – Cost Analysis BACKGROUND AND PURPOSE Councilman Andre’ Williams has sponsored a Heat Island Effect ordinance that is based on similar City of Miami regulatory provisions. The provisions are proposed to be incorporated into the Zoning Code by amending Design Standards section. The draft ordinance was deferred at the Zoning Meeting of February 2, 2011 to allow City Staff to develop a more comprehensive analysis of the issues and to give Council more time to review the proposed ordinance. The ordinance will be heard on first reading at the Zoning Meeting of March 2, 2011. Staff has been asked to analyze the Heat Island Effect ordinance in terms of its potential cost impact upon businesses and the City’s development review process. A Brief Explanation of the Proposed Ordinance What is the “Heat Island Effect” – A definition by the United Stated Environmental Protection Agency is attached. The proposed ordinance regulates the hardscape of a given development which primarily includes parking and traffic circulation areas. The ordinance does not affect the principal building or buildings. The proposed specifications require hardscape/pavement to provide and maintain a minimum 30% reflective surface per the national standards established by Leadership in Energy & Environmental Design (LEED: an internationally recognized green building certification system). In short, that means that hardscape must be white concrete material or other similarly reflective surfaces such as pervious concrete pavement that meet the 30% requirement. Grey concrete is not considered because over time it will diminish in the percentage of reflection and will no longer provide the required reflectance. In general asphalt is not known to meet the 30% requirement unless the asphalt is coated with a 30% reflective coating. 􀁺 Page 2 February 25, 2011 Cost Comparison and Estimates of White Concrete and Asphalt Paving Cost Analysis/Comparison • Asphalt Paving in a Typical Parking and Traffic Surface: o Total to Install Asphalt per Square Yard (SY): $22.00 o Includes Subgrade, Limerock, and Asphalt • White Concrete Paving in a Typical Parking and Traffic Surface: o Total to install white concrete per SY: $34.32 o Includes Subgrade, Forming, Concrete, Finishing and Sawcutting • Cost Difference: White concrete costs 56% more than asphalt in the typical parking and traffic surface calculation. * Source: Miami Gardens Public Works Department, Miami Gardens Building Services Sample Estimates: These projects are currently permitted and under construction. • Mariner Parking Lot, 1100 Park Center Boulevard/NW 12 Avenue (Adjacent to Roma Hotel) o Number of Spaces: 126 o Surface Parking Area: 4,284 SY o Estimated Cost of Asphalt: $94,248 o Estimated Cost of White Concrete: $147,027 • FMU Dormitories, Florida Memorial University o Number of Spaces: 189 o Surface Parking Area: Approximately 9,000 SY o Estimated Cost of Asphalt: $198,000 o Estimated Cost of White Concrete: $308,880 • Again, as noted above, there is a 56% cost differential between white concrete and asphalt. Potential Future Development Projects – Specific developments that could be impacted by the proposed Heat Island Effect ordinance: • Solabella: 13 buildings; 92 new units • Planned Projects by the City of Miami Gardens: o Paving Projects such as Vista Verde o City Hall o Rolling Oaks Park: 600 spaces o Bunche Park Pool Redevelopment 􀁺 Page 3 February 25, 2011 DEVELOPMENT REVIEW IMPACT (Potential Costs to the City of Miami Gardens) • Development Review – Plan review by the Planning and Zoning Department to confirm that heat island specifications are met will not increase development review costs. • Inspections -The cost of inspecting concrete parking lots will be covered in the permit cost. Thus, there is no initial financial impact to the City. City of Miami -Per Staff’s research, the City of Miami’s Zoning Division reviews plans to insure that the heat island effect standards are included on the plans. As with other projects, the project engineer ensures that the project is built according to plan. According to LEED references, white concrete maintains its reflective quality for many years and does not need to be inspected. CONCLUSIONS Based on the information gathered from various sources, the following are staff’s conclusions: • The City of Miami Gardens does not meet the Environmental Protection Agency’s definition of an Urban Heat Island. This definition is more in line with condensed downtown developments such as City of Miami or Fort Lauderdale. • The City’s Zoning Code provides for a landscape provision requiring additional tree canopies in both residential and commercial districts. It has been well documented that providing additional shading through the use of tree canopies is just as effective as the proposed amendments to the Zoning Code. • The cost implication of this ordinance is indicated in the above analysis. Any significant increase in development costs to private sector commercial developers would seem to work in stark contrast to the City’s goal of maintaining and increasing its tax base. Moreover, the ordinance as proposed would also create a cost burden to existing commercial developments during the maintenance of their hardscape areas. • Finally, a stand-alone ordinance related to reducing heat island effect is limited in its true environmental impact as compared to a more comprehensive amendment of our Building and Zoning Codes to include Green Design Standards. These anticipated amendments will incentivize property owners to make these improvements, rather than simply requiring them. Staff anticipates bringing this recommendation to Council once the consultant completes all the related tasks tied to the scope of work. 􀁺 Page 4 February 25, 2011 Attachment 1: Heat Island Definition Heat Island Effect Contact Us Search: ( ) All EPA (X) This Area [Go] • You are here: EPA Home • Heat Island Effect • Basic Information <hr size=0 width=11 style='width:7.9pt' align=center> Basic Information You will need the free Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more. More Information on Urban Heat Islands • Heat Island Basics Chapter from EPA’s Reducing Urban Heat Islands: Compendium of Strategies (PDF) (22 pp, 1.5MB) • Measuring Heat Islands • Heat Island Video Segments What Is an Urban Heat Island? As urban areas develop, changes occur in their landscape. Buildings, roads, and other infrastructure replace open land and vegetation. Surfaces that were once permeable and moist become impermeable and dry.1 These changes cause urban regions to become warmer than their rural surroundings, forming an "island" of higher temperatures in the landscape. Heat islands occur on the surface and in the atmosphere. On a hot, sunny summer day, the sun can heat dry, exposed urban surfaces, such as roofs and pavement, to temperatures 50–90°F (27– 50°C) hotter than the air,2 while shaded or moist surfaces—often in more rural surroundings— remain close to air temperatures. Surface urban heat islands are typically present day and night, but tend to be strongest during the day when the sun is shining. In contrast, atmospheric urban heat islands are often weak during the late morning and throughout the day and become more pronounced after sunset due to the slow release of heat from urban infrastructure. The annual mean air temperature of a city with 1 million people or more can be 1.8– 5.4°F (1–3°C) warmer than its surroundings.3 On a clear, calm night, however, the temperature difference can be as much as 22°F (12°C).3 􀁺 Page 5 February 25, 2011 view a larger version of this image Surface and atmospheric temperatures vary over different land use areas. Surface temperatures vary more than air temperatures during the day, but they both are fairly similar at night. The dip and spike in surface temperatures over the pond show how water maintains a fairly constant temperature day and night, due to its high heat capacity. * Note: The temperatures displayed above do not represent absolute temperature values or any one particular measured heat island. Temperatures will fluctuate based on factors such as seasons, weather conditions, sun intensity, and ground cover. To view images of surface and atmospheric heat islands, and to learn more about how scientists measure them, visit the Measuring Heat Islands page. The heat island sketch pictured here shows how urban temperatures are typically lower at the urban-rural border than in dense downtown areas. The graphic also show how parks, open land, and bodies of water can create cooler cooler areas within a city. For additional information on urban heat islands: • read the Heat Island Basics chapter (PDF) (22 pp, 1.5MB) from EPA's Reducing Urban Heat Islands: Compendium of Strategies, which explains the different types of urban heat islands and their causes, describes the impacts of heat islands, and provides resources for more information; • learn how heat islands are measured; and • watch two short video segments that EPA developed in partnership with The Weather Channel cable television network. Why Do We Care About Heat Islands? Elevated temperature from urban heat islands, particularly during the summer, can affect a community's environment and quality of life. While some heat island impacts seem positive, such as lengthening the plant-growing season, most impacts are negative and include: • Increased energy consumption: Higher temperatures in summer increase energy demand for cooling and add pressure to the electricity grid during peak periods of demand. One 􀁺 Page 6 February 25, 2011 study estimates that the heat island effect is responsible for 5–10% of peak electricity demand for cooling buildings in cities.3 • Elevated emissions of air pollutants and greenhouse gases: Increasing energy demand generally results in greater emissions of air pollutants and greenhouse gas emissions from power plants. Higher air temperatures also promote the formation of ground-level ozone. • Compromised human health and comfort: Warmer days and nights, along with higher air pollution levels, can contribute to general discomfort, respiratory difficulties, heat cramps and exhaustion, non-fatal heat stroke, and heat-related mortality. • Impaired water quality: Hot pavement and rooftop surfaces transfer their excess heat to stormwater, which then drains into storm sewers and raises water temperatures as it is released into streams, rivers, ponds, and lakes. Rapid temperature changes can be stressful to aquatic ecosystems. For more information on the effects of heat islands, visit the Heat Island Impacts page. What Can Be Done? Communities can take a number of steps to reduce the heat island effect, using four main strategies: • increasing tree and vegetative cover; • creating green roofs (also called "rooftop gardens" or "eco-roofs"); • installing cool—mainly reflective—roofs; and • using cool pavements. Typically heat island mitigation is part of a community's energy, air quality, water, or sustainability effort. Activities to reduce heat islands range from voluntary initiatives, such as cool pavement demonstration projects, to policy actions, such as requiring cool roofs via building codes. Most mitigation activities have multiple benefits, including cleaner air, improved human health and comfort, reduced energy costs, and lower greenhouse gas emissions. For more information on heat island mitigation strategies and activities: • visit the Urban Heat Island Mitigation page; • read the Heat Island Reduction Activities chapter (PDF) (23 pp, 2.7 MB) from EPA's Reducing Urban Heat Islands: Compendium of Strategies; • use the Community Actions Database to see what communities around the United States are doing to reduce the urban heat island effect; and • learn about EPA's Clean Energy-Environment State and Local Program. Footnotes and References 1. This change in landscape may differ in regions such as deserts, where moisture may increase in urban areas if development introduces grass lawns and other irrigated vegetation. 􀁺 Page 7 February 25, 2011 2. Berdahl P. and S. Bretz. 1997. Preliminary survey of the solar reflectance of cool roofing materials. Energy and Buildings 25:149-158. 3. Akbari, H. 2005. Energy Saving Potentials and Air Quality Benefits of Urban Heat Island Mitigation (PDF) (19 pp, 251K). Lawrence Berkeley National Laboratory.