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Urbant klimat & U ba t at &klimatanpassad urban design

Erik JohanssonBoende och Bostadsutveckling

Urbant klimat & klimatanpassadUrbant klimat & klimatanpassad urban design

• Urbant klimatTemperatur– Temperatur

– VindE empel• Exempel

– Fez (Marocko)Colombo (Sri Lanka)– Colombo (Sri Lanka)

• Inverkan av urbana normer

Lund University / Dept. of Architecture & Built Environment / Housing Development & Management / 2012-01-18

Global, regional and localgclimate phenomena


Urban climate

Source: Boundary Layer Climates by T R Oke


Urban microclimate


Characteristics of the urbanCharacteristics of the urban climate

Mean air temperature 1-3°C warmer (occasionally up to 12°C)12 C)

Pollution 10-25% higher concentrations

Cloudiness 5-10% more

Solar radiation 5-25% lessSolar radiation 5-25% less

Mean wind speed 20–50% of rural wind speed

Turbulence 10–50% greater


Värmeön (the Urban Heat Island)Värmeön (the Urban Heat Island)

S B d L Cli b T R Ok



Värmeön (the Urban Heat Island)



Temperaturvariationer för stadTemperaturvariationer för stadoch landsbygd


Fuente: Boundary Layer Climates por T R Oke

Maximum heat island effect

• 3–5 hours after sunset3 5 hours after sunset• Calm weather

Cl dl ki• Cloudless skies


Causes ofCauses of the urban heat island

Geometry of the built environment• Geometry of the built environment• Thermal properties of building materials• Heat from traffic, buildings etc• Lack of vegetationac o ege a o• Air pollution


Radiation balance – dayy

UrbanUrban


Radiation balance – night


H/W ratio – sky view factor

Sky View Factor (SVF) = cos


Heat island as a function of H/W



Surface material properties

Reflection Thermal capacity Reflection (MJ/m3°C)

Dry soil 0.4 1.3Dry soil 0.4 1.3

Humid soil 0.05 3.0Grass 0 15 0 25Grass 0.15-0.25 --Asphalt 0.05–0.20 1.9

Concrete 0.10–0.35 2.1


Andra orsakertill värmeön

• Värme från trafik, b dbyggnader

• Brist på vegetation

• Luftföroreningar


Effect of water bodies

• Large water bodies (seas, big lakes andLarge water bodies (seas, big lakes and rivers) may cause cooling through the sea breeze effectbreeze effect

• Smaller water bodies may cause cooling through evaporationthrough evaporation


P k h ö ådParker och grönområden• Lägre temperatur på grund av skuggning och

evapotranspirationevapotranspiration• Större parker kan vara 1–4ºC svalare än

i d b b lomgivande bebyggelse• Fler träd ger större

effekt• Parkens klimat på-p

verkar angränsande bebyggda områden


ygg

Fördelar med vegetationFördelar med vegetationG k• Ger skugga

• Evapotranspiration medför temperatursänkning

• Absorberar regnvatten

• Vindskydd (viktigt under• Vindskydd (viktigt under kalla årstider)

Filt l ftfö i• Filtrerar luftföroreningar

• Biologisk mångfald

• Estetiskt tilltalande

• Motverkar stress


• Motverkar stress

Effect of shading treesEffect of shading trees

• Protection againstgdirect solar radiation

• Less reflectedLess reflectedradiation

• Lower surface• Lower surfacetemperatures


P bl fPermeable surfaces

• Increased infiltration • Increased evaporation (cooling)

Lund University / Dept. of Architecture & Built Environment / Housing Development & Management / 2012-01-1827 jan-10 Erik Johansson, HDM 24

Wind in urban areas


Wi d d tWind data

Urban winds 25-50% of rural wind speeds

Lund University / Dept. of Architecture & Built Environment / Housing Development & Management / 2012-01-1827 jan-10 Erik Johansson, HDM 26

Urban wind more turbulent


Wi d i bWind in urban areas



Wi d ff t f hi h i b ildiWind: effect of highrise buildings



Point Hyllie, Malmö (30 våningar)


Scandinavian Tower, Hotell, VästraScandinavian Tower, Hyllie (17 våningar)

Hotell, Västra Hamnen, Malmö (85 m)(85 m)


Exempel på problem iExempel på problem i kallt klimat• Vindproblem

id hö b d– vid höga byggnader– Raka gator


Ways to reduce wind speeds nearWays to reduce wind speeds near high-rise buildings

Use of podium


Increased wind speeds betweenIncreased wind speeds between buildings

funnel effectfunnel effect

High Higher HighestHigh Higher HighestHigh Higher HighestHigh Higher Highest


Urban climate field studiesUrban climate field studies

Fez

Colombo

Fez, Morocco: Colombo, Sri Lanka: 1 4 illi i h b


1 million inhab. 1.4 million inhab.

M th dMethods

1. Microclimate measurements and calculation of thermal comfortcalculation of thermal comfort

2 Simulations of how urban design2. Simulations of how urban design influences microclimate and comfort

3. Analysis of urban regulations and interviews with urban planners andinterviews with urban planners and designers


Climate measurementsClimate measurements in street canyonsy

• Air and surface temperaturesH idit• Humidity

• Wind speed

H

W


W

Calculation of outdoor thermalCalculation of outdoor thermal comfort

• Air temperatureh i l i ll • Mean radiant

temperaturePhysiologically Equivalent

• HumidityTemperature(PET)

• 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

Relative humidity: 40 – 70%

0J F M A M J J A S O N D


40 70%Month

M t it FMeasurement sites Fez


Plot coverage of thePlot coverage of the neighbourhoods

Compact, traditional Dispersed, modern (deep canyon) (shallow canyon)


Measured air temperature inMeasured air temperature in Fez – Summer

36

38°C

Old city Height/Width ratio:

32

34 New city

Rural

Height/Width ratio:

Old city 10

26

28

30

22

24 New City 0.6

16

18

20


1600:00 06:00 12:00 18:00 24:00

Measured air temperature inMeasured air temperature in Fez – Winter

Height/Width ratio:18°C Height/Width ratio:

Old city 1016

18

Old city

New city

12

14 Rural

New City 0.6 8

10

4

6

00 00 03 00 06 00 09 00 12 00 15 00 18 00 21 00 24 00


00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 24:00

PET fysiologiskt ekvivalentaPET – fysiologiskt ekvivalentatemperaturen

• PET inkluderar kyleffekt från vinden och värmetillskott från solstrålningvärmetillskott från solstrålning.

T S lfö håll d Vi dfö håll d PETTemp. Solförhållanden Vindförhållanden PET

20°C molnigt vindstilla 20°C20 C molnigt vindstilla 20 C

20°C soligt vindstilla 30°C

20°C molnigt blåsigt 10°C


Comfort comparison –Summer (PET)

°C

45

50°C

Old city

40

New city

30

35

25

15

20


00:00 06:00 12:00 18:00 00:00

Comfort comparison – Winterp(PET)

°C25

Deep

15

20Shallow

10

15

5

000:00 06:00 12:00 18:00 00:00


00:00 06:00 12:00 18:00 00:00

Conclusion from measurementsConclusion 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 summercomfort within the city, both in summer and winter


Climate ofClimate of Colombo

40

Temp. (°C)

Temp. max Temp. min

30

40

20

30

10

Relative humidity: 75–90%0

J F M A M J J A S O N D


J F M A M J J A S O N DMonth

Measurement sites: Colombo


Measured air38°C

DayMeasured air temperature, 34

36

38

p ,Colombo30

32

24

26

28

36

38°C

CBD - high rise

2407:00 10:00 13:00 16:00 19:00

Night32

34

36

Old city (dense)

30

32°C Night

26

28

30Centre - big avenue

Suburb (inland)

24

26

2824

07:0

010

:00

13:0

016

:00

19:0

0

Rural


20:00 23:00 02:00 05:00

Sea breeze

• Sunny afternoons

Lund University / Dept. of Architecture & Built Environment / Housing Development & Management / 2012-01-18Erik 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 g ( )canyons

• Lower PET near the coast due to the sea-Lower PET near the coast due to the seabreeze

• Lower PET under colonnades and• Lower PET under colonnades and shading trees


Results from interviews

• Climate is rarely considered in urban planning d d iand design

• Lack of knowledge about climate-conscious design

• Lack of tools and guidelinesg


Current urban codes in Fez andCurrent urban codes in Fez and Colombo

• Introduced during the colonial timetime

• Based on principles from western countrieswestern countries

• low density to encourage solar access and fresh airsolar access and fresh air as well as daylight in buildingsbuildings


Lack of shadefor pedestriansfor pedestrians

• Wide streets• Low buildingsg• No shade trees,

arcades or otherarcades or other overhead shading


How to promote a climate-pconscious 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


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