green design at any size urban heat island effect & tod - Rail~Volution

What is an Urban Heat Island?• In denser cities, UHI's can get up to 8 degrees warmer during theday time and 12 degrees warmer at night then their surroundingareas.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 2008

What is an Urban Heat Island?• The Urban Heat Island Effect (UHIE) is more prominent at nightthen the daytime.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 2008

What is an Urban Heat Island?• It has long been recognized that the excessive heat and smog inmany cities in the Summer is partly due to the Urban Heat Islandand choices of building materials, vegetation and urban design.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 2008

Elements that contribute to the Urban Heat Island(‏UHIE‏)‏ Effect• Buildings block the view to the cool sky - air is not circulated• Lack of Vegetation = loss of evapotranspirationGREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 2008

Elements that contribute to the Urban Heat Island(‏UHIE‏)‏ Effect• Thermal properties of building materials such as roads, concrete,etc. (dark and dense mater absorb rather than reflect)GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 2008

Elements that contribute to the Urban Heat Island(‏UHIE‏)‏ Effect• Increases in density and amount of building materials• Automobiles and other machines ejecting heatGREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 2008

Energy Use• The rise in heat creates higherdemand for air conditioning• Demand for electric power risesnearly 2% for every degreeFahrenheit the daily maximumtemperature rises.• It is estimated that in LosAngeles, UHIE accounts forincreased city AC costs of 100million dollars.• Increases in temperature =decrease pedestrian and bicycleriding= increase in car usage =increase in pollutants,mechanical heat emissions, anda need for more roads.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200810

Air Quality• The formation of smog is highly sensitive to temperatures; thehigher the temperature, the higher the formation.• The probability of smog increases by 5% for every 0.5°F rise indaily maximum temperature above 70°F.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200811

UHI misconceptions• UHIE has been adopted by someglobal warming critics.• The claims: In the mostsimplistic terms, the world is notgrowing warmer; rather,weather measuring stations,generally located closer to cities,are picking up the increasedheat of the UHI as opposed toactual global warming. Theseclaims have proven largelyfallacious.• UHIE has also been used as away for suburban sprawladvocates to justify less density.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200812

The Density Paradox• UHI is caused by increased density; even though density is nowgenerally considered the most environmentally responsibleform of urbanizationGREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200813

The Density Paradox• Should increased density be a more important considerationthen UHI? Yes and No.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200814

The Density Paradox• Density alleviates many other environmental impacts.• Transit Oriented Development seems the most sensible modelwith which to begin.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200815

Transit Oriented Development and and UHI• Transit Oriented Development does create density but reduces theproportion of land devoted to roads and parking lots.• TOD suggests all important city functions should be within 1/4-1/2mile of transit; this requires a lot of density.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200816

Transit Oriented Development and and UHI• Reduced parking ratios in TOD allow for increased opportunities forUHI mitigation.• The integration of UHI mitigation in TOD planning isessential for its effectiveness.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200817

Mitigation Techniques: Albedo Mitigation• The albedo of an object is theextent to which it diffuselyreflects light from the sun.• Way to improve reduce highurban albedo rates: CoolRooftops.• Up to 80% of the solar heatreflected by cool roofs passesback through the atmosphereand out into space, leaving thecity unaffected.• 90% of roofs in USA are black.Lighter colors are morereflective.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200818

Mitigation Techniques: Cool Roofing Options• White vinyl• Cool Coating: Paint withhigher glass quantity• Green Roofing: RooftopGardensGREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200819

Other benefits of green roofing• In San Francisco, the largerooftop on the CaliforniaAcademy of Sciences is beingused as a habitat for thethreatened bay checkerspotbutterfly.• Environment Canada found a26% reduction in summercooling needs and a 26%reduction in winter heat losseswhen a green roof is used.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200820

Mitigation Techniques: Vegetative Mitigation• Any increase in urban vegetation,trees, rooftop gardens, publicparks, will have a cooling effectthrough evapotranspiration.• Trees should be plantedstrategically, to east and west ofbuildings. Optimally they wouldshade AC condenser units,windows, and roofing.• Trees are the preferred shadingmethod for pedestrians as theydon't trap hot air, allowing forincreased air circulation.• Trees may block useful solar energyin the winter particularly on thesouth side.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200821

Mitigation Techniques: Wind Circulation• Increased wind circulation patterns diffuse the UHI.CITY OF PHOENIX / STUDIO MA• Large cities that plan “street canyons” to coincide with the windpatterns will see a drop in UHI.• While narrow roads may be preferable to increase density, widerstreet canyons are preferable towards heat reduction.• Best practice would be checkerboard building mass patterns.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200822

Mitigation Techniques: Wind Circulation• Increased wind circulation patterns diffuse the UHI.CITY OF PHOENIX / STUDIO MA• Large cities that plan “street canyons” to coincide with the windpatterns will see a drop in UHI.• While narrow roads may be preferable to increase density, widerstreet canyons are preferable towards heat reduction.• Best practice would be checkerboard building mass patterns.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200823

Mitigation Techniques: Opaque Vented Walls• An opaque ventilated wall is aspecial façade case where theouter face consists of a detachedlayer that forms a naturallyventilated cavity.• Construction of walls that canventilate air is an essentialtechnique in mitigating heatinside buildings and helps thecirculation of surface air.CITY OF PHOENIX / STUDIO MAGREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200824

TOD Best Practices• Good TOD can mitigateUHIE while remainingfunctional and aesthetic.• Mixture of shadingmethods both vegetativeand man-made atdiffering heights. Toomuch shading will be badfor winter months.• Open air, multifunctionalwater systems.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200825

TOD Best Practices• “Cool corridors” allowingincreased levels ofpedestrianship in hotclimates.• Color schemes that promotecooling effects.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 2008CITY OF PHOENIX / DYETT & BHATIA / STUDIO MA26

What other Cities are doing to mitigate UHIE• Phoenix and Scottsdale, AZplans call for providing “coolcorridors” for pedestriansthrough the provision of shade,landscaping, street furniture andother elements of human scaleand comfort to extend perceivedwalking distance and maketravel safe and enjoyable.• Policies and standards requiringbuildings, streets, and publicspaces to be designed withmaterials and forms that createcomfortable temperatures forpedestrians and minimize theUrban Heat island Effect.CITY OF SCOTTSDALEGREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200827

What other Cities are doing to mitigate UHIE• Seattle Policy Statement:Strive to increase the amountof permeable surface andvegetative cover in the city inorder to mitigate the heatisland effect of developedareas, control storm waterflows and reduce pollution.• City of Houston has a policyof reflective roofing for allnew buildings and reroofings.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200828

What other Cities are doing to mitigate UHIE:Green Roofs• Portland and Chicago havezoning incentives for theinstallation of rooftopgardens by allowingdevelopers to buildadditional square footageon the same building site.• In Washington DC: addingmore water-retainingsurfaces including greenroofs will lower a buildingowner’s city fees.• Some cities in Europe(mostly in Switzerland)require green roofing.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200829

What other Cities are doing to mitigate UHIE:Parking Lot Tree Planting Policies• Trees in parking lots not onlymitigate UHIE but also help cleancarbon dioxide emissions.• Sacramento has one of the moreaggressive ordinances requiringnew parking lots to have enoughshade for 50% of the lot after 15years.• Orlando’s ordinance requires treecoverage specified as 1 “treepoint” per 100 square feet. Treepoints are earned according totree size.GREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 200830

What other Cities are doing to mitigate UHIE:Transit Oriented Development + UHIE MitigationTOD/Smart Growth StrategiesGreen Design/Green Building to minimize environmental impactsand mitigate climate changeUrban Heat Island Effect design strategies to mitigate effects ofhigher density and ensure human comfortGREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 2008CITY OF PHOENIX / DYETT & BHATIA / STUDIO MA31

More Information• Lawrence Berkeley Labs Heat Island Group:http://heatisland.lbl.gov/• Arizona State University National Center forExcellence (ASU Smart): http://asusmart.com• U.S. EPA Website:http://www.epa.gov/hiri/index.htm• Wikipedia:http://en.wikipedia.org/wiki/Urban_heat_island• Phoenix Urban Form Project:http://phoenix.gov/urbanformproject/Kevin Gardiner, AICPkevin@kevingardinerassociates.comAmitai Helleramitai@kevingardinerassociates.comGREEN DESIGN AT ANY SIZE – URBAN HEAT ISLAND EFFECTRAIL~VOLUTION 2008