klimatanpassad urban design Erik Johansson Boende och Bostadsutveckling

Transcription

1 Urbant Uba klimat at& klimatanpassad urban design Erik Johansson Boende och Bostadsutveckling

2 Urbant klimat & klimatanpassad urban design Urbant klimat Temperatur Vind Exempel Fez (Marocko) Colombo (Sri Lanka) Inverkan av urbana normer

3 Global, regional and local climate phenomena

4 Urban climate Source: Boundary Layer Climates by T R Oke

5 Urban microclimate

6 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

7 Värmeön (the Urban Heat Island) Source: Boundary Layer Climates by TROk Oke

8 Värmeön (the Urban Heat Island) Source: Boundary Layer Climates by T R Oke

9 Temperaturvariationer för stad och landsbygd Fuente: Boundary Layer Climates por T R Oke

10 Maximum heat island effect 3 5 hours after sunset Calm weather Cloudless skies

11 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

12 Radiation balance day Urban

13 Radiation balance night

14 H/W ratio sky view factor Sky View Factor (SVF) = cos

15 Heat island as a function of H/W Source: Boundary Layer Climates by T R Oke

16 Surface material properties Reflection Thermal capacity (MJ/m3 C) Dry soil Humid soil Grass Asphalt Concrete

17 Andra orsaker till värmeön Värme från trafik, byggnader Brist på vegetation Luftföroreningar

18 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

19 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

20 Fördelar med vegetation Ger skugga Evapotranspiration medför temperatursänkning Absorberar regnvatten Vindskydd (viktigt under kalla årstider) Filtrerar luftföroreningar Biologisk mångfald Estetiskt tilltalande Motverkar stress 22

21 Effect of shading trees Protection against direct solar radiation Less reflected radiation Lower surface temperatures

22 Permeable surfaces Increased infiltration Increased evaporation (cooling) 27 jan-10 Erik Johansson, HDM 24

23 Wind in urban areas

24 Wind data Urban winds 25-50% of rural wind speeds 27 jan-10 Erik Johansson, HDM 26

25 Urban wind more turbulent

26 Wind in urban areas Source: Boundary Layer Climates by T R Oke

27 Wind: effect of highrise h i buildings Source: Boundary Layer Climates by T R Oke

28

29 Point Hyllie, Malmö (30 våningar)

30 Scandinavian Tower, Hyllie (17 våningar) Hotell, Västra Hamnen, Malmö (85 m)

31 Exempel på problem i kallt klimat Vindproblem vid höga byggnader Raka gator

32 Ways to reduce wind speeds near high-rise buildings Use of podium

33 Increased wind speeds between buildings funnel effect High Higher Highest

34 Urban climate field studies Fez Colombo Fez, Morocco: Colombo, Sri Lanka: 1 million inhab. 1.4 million inhab.

35 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

36 Climate measurements in street canyons Air and surface temperatures Humidity Wind speed H W

37 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

38 Climate of Fez, Morocco 40 Temp. ( C) Max. temp. Min. temp J F M A M J J A S O N D Month Relative humidity: 40 70%

39 Measurement sites Fez

40 Plot coverage of the neighbourhoods Compact, traditional Dispersed, modern (deep canyon) (shallow canyon)

41 Measured air temperature in Fez Summer C Old city New city Rural Height/Width ratio: Old city 10 New City :00 06:00 12:00 18:00 24:00

42 Measured air temperature in Fez Winter C 18 Old city 16 New city 14 Rural Height/Width ratio: Old city New City :00 03: : : :00 15:00 18:00 21:00 24:00

43 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

44 Comfort comparison Summer (PET) C Old city New city :00 06:00 12:00 18:00 00:00

45 Comfort comparison Winter (PET) C Deep Shallow :00 06:00 12:00 18:00 00:00

46 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

47 Climate of Colombo Temp. ( C) 40 Temp. max Temp. min J F M A M J J A S O N D Month Relative humidity: 75 90%

48 Measurement sites: Colombo

49 C Day Measured air temperature, Colombo :00 10:00 13:00 16:00 19:00 C Night :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

50 Sea breeze Sunny afternoons Erik Johansson, HDM 52

51 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

52 Results from interviews Climate is rarely considered in urban planning and ddesign Lack of knowledge about climate-conscious design Lack of tools and guidelines

53 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

54 Lack of shade for pedestrians Wide streets Low buildings No shade trees, arcades or other overhead shading

55 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