Urbant Uba klimat at& klimatanpassad urban design Erik Johansson Boende och Bostadsutveckling
Urbant klimat & klimatanpassad urban design Urbant klimat Temperatur Vind Exempel Fez (Marocko) Colombo (Sri Lanka) Inverkan av urbana normer
Global, regional and local climate phenomena
Urban climate Source: Boundary Layer Climates by T R Oke
Urban microclimate
Characteristics of the urban climate Mean air temperature Pollution Cloudiness Solar radiation Mean wind speed Turbulence 1-3 C warmer (occasionally up to 12 C) 10-25% higher concentrations 5-10% more 5-25% less 20 50% of rural wind speed 10 50% greater
Värmeön (the Urban Heat Island) Source: Boundary Layer Climates by TROk Oke
Värmeön (the Urban Heat Island) Source: Boundary Layer Climates by T R Oke
Temperaturvariationer för stad och landsbygd Fuente: Boundary Layer Climates por T R Oke
Maximum heat island effect 3 5 hours after sunset Calm weather Cloudless skies
Causes of the urban heat island Geometry of the built environment Thermal properties of building materials Heat from traffic, buildings etc Lack of vegetation Air pollution
Radiation balance day Urban
Radiation balance night
H/W ratio sky view factor Sky View Factor (SVF) = cos
Heat island as a function of H/W Source: Boundary Layer Climates by T R Oke
Surface material properties Reflection Thermal capacity (MJ/m3 C) Dry soil 0.4 1.3 Humid soil 0.05 3.0 Grass 015025 0.15-0.25 -- Asphalt 0.05 0.20 1.9 Concrete 0.10 0.35 2.1
Andra orsaker till värmeön Värme från trafik, byggnader Brist på vegetation Luftföroreningar
Effect of water bodies Large water bodies (seas, big lakes and rivers) may cause cooling through the sea breeze effect Smaller water bodies may cause cooling through evaporation
Parker och grönområden Lägre temperatur på grund av skuggning och evapotranspiration Större parker kan vara 1 4ºC svalare än omgivande bebyggelseb Fler träd ger större effekt Parkens klimat på- verkar angränsande bebyggda områden 21
Fördelar med vegetation Ger skugga Evapotranspiration medför temperatursänkning Absorberar regnvatten Vindskydd (viktigt under kalla årstider) Filtrerar luftföroreningar Biologisk mångfald Estetiskt tilltalande Motverkar stress 22
Effect of shading trees Protection against direct solar radiation Less reflected radiation Lower surface temperatures
Permeable surfaces Increased infiltration Increased evaporation (cooling) 27 jan-10 Erik Johansson, HDM 24
Wind in urban areas
Wind data Urban winds 25-50% of rural wind speeds 27 jan-10 Erik Johansson, HDM 26
Urban wind more turbulent
Wind in urban areas Source: Boundary Layer Climates by T R Oke
Wind: effect of highrise h i buildings Source: Boundary Layer Climates by T R Oke
Point Hyllie, Malmö (30 våningar)
Scandinavian Tower, Hyllie (17 våningar) Hotell, Västra Hamnen, Malmö (85 m)
Exempel på problem i kallt klimat Vindproblem vid höga byggnader Raka gator
Ways to reduce wind speeds near high-rise buildings Use of podium
Increased wind speeds between buildings funnel effect High Higher Highest
Urban climate field studies Fez Colombo Fez, Morocco: Colombo, Sri Lanka: 1 million inhab. 1.4 million inhab.
Methods 1. Microclimate measurements and calculation of thermal comfort 2. Simulations of how urban design influences microclimate and comfort 3. Analysis of urban regulations and interviews with urban planners and designers
Climate measurements in street canyons Air and surface temperatures Humidity Wind speed H W
Calculation of outdoor thermal comfort Air temperature Physiologically i ll Mean radiant Equivalent temperature Temperature (PET) Humidity Wind Assumed upper comfort limit: PET = 33 C Assumed lower comfort limit: PET = 18 C
Climate of Fez, Morocco 40 Temp. ( C) Max. temp. Min. temp 30 20 10 0 J F M A M J J A S O N D Month Relative humidity: 40 70%
Measurement sites Fez
Plot coverage of the neighbourhoods Compact, traditional Dispersed, modern (deep canyon) (shallow canyon)
Measured air temperature in Fez Summer C 38 36 34 32 30 28 26 24 22 20 18 Old city New city Rural Height/Width ratio: Old city 10 New City 0.6 16 00:00 06:00 12:00 18:00 24:00
Measured air temperature in Fez Winter C 18 Old city 16 New city 14 Rural Height/Width ratio: Old city 10 12 10 8 New City 0.6 6 4 00:00 03:0000 06:0000 09:0000 12:00 15:00 18:00 21:00 24:00
PET fysiologiskt ekvivalenta temperaturen PET inkluderar kyleffekt från vinden och värmetillskott från solstrålning. Temp. Solförhållanden Vindförhållanden d PET 20 C molnigt vindstilla 20 C 20 C soligt vindstilla 30 C 20 C molnigt blåsigt 10 C
Comfort comparison Summer (PET) C 50 45 Old city New city 40 35 30 25 20 15 00:00 06:00 12:00 18:00 00:00
Comfort comparison Winter (PET) C 25 20 Deep Shallow 15 10 5 0 00:00 06:00 12:00 18:00 00:00
Conclusion from measurements in Fez Urban areas were found to be both warmer (heat island) and cooler (cool island) than the rural surroundings There are big variations in thermal comfort within the city, both in summer and winter
Climate of Colombo Temp. ( C) 40 Temp. max Temp. min 30 20 10 0 J F M A M J J A S O N D Month Relative humidity: 75 90%
Measurement sites: Colombo
C Day 38 36 34 32 30 Measured air temperature, Colombo 28 26 24 07:00 10:00 13:00 16:00 19:00 C Night 32 30 28 26 24 20:00 23:00 02:00 05:00 C 38CBD - high rise 36 34Old city (dense) 32 30Centre - big avenue 28 26Suburb (inland) 24 07:00 10:00 13:00 16:00 19:00 Rural
Sea breeze Sunny afternoons Erik Johansson, HDM 52
Results from measurements in Colombo Large climate variations within the city Max. PET decreases with increasing height-to-width (H/W) ratio of urban canyons Lower PET near the coast due to the sea- breeze Lower PET under colonnades and shading trees
Results from interviews Climate is rarely considered in urban planning and ddesign Lack of knowledge about climate-conscious design Lack of tools and guidelines
Current urban codes in Fez and Colombo Introduced during the colonial time Based on principles from western countries low density to encourage solar access and fresh air as well as daylight in buildings
Lack of shade for pedestrians Wide streets Low buildings No shade trees, arcades or other overhead shading
How to promote a climate- conscious urban design Improvements of urban codes: Allow higher H/W ratios Allow ventilation around buildings (hot humid) Prescriptions for shading Development of design guidelines Training of urban planners/designers in climate-conscious design Development of design tools