CitySpeak X: Green City. Cool City: Edward Ng - Urban heat and air ventilation – what are the implications for public health?

Green space, what for? Professor Edward Ng 3 March 2010

Background 3 March 2010

Background Global warming and urban heat island 3 March 2010

Background Courtesy Professor Janet Nicole of PolyU 3 March 2010

Background France's largest undertaker service says 15,000 died in August heat wave 3 March 2010

Background This city is heading towards a hot, stuffy state of atmosphere. In future summers, the old and the weak living in their tiny rooms in the urban areas will have to face the increasing number of hot nights with no air-conditioning, little wind and the dampness arising from little sun and little evaporation. They also have to fear the attack of more germs than used to be since their natural enemies, viz. fresh air and sunshine, have been reduced in strength. Unfortunately the underprivileged have to look forward to even more tall buildings along the shore or even right at the heart of the urban areas to block the little wind and sunshine left. CY Lam, ex-Director of HKO 3 March 2010

Due to Climate change and global warming, couple that with more intense UHI, heat stress, heat wave and heat spell will be more frequent, more intensive and will last longer. The elderly are particularly at risk 3 March 2010

Examples and References What influences Urban Climate? Urban Boundary Layer Time • day • season Weather City location • wind • climate • Cloud • topography • Temperature Urban Canopy Layer • rural surrounds • RH Roughness sub-layer Urban • Radiation City metabolism Climate • energy/water use Modified after Oke (1997) • waste & emissions City form • material & fabric • structure • building cover City size Every city is different, for sub- • size tropical climate, optimising the • density of land uses Oke, 1980, unpubl. city for human thermal comfort ‘Fixed’ – Location in the summer months and providing air ventilation are ‘Modulators’ – Time, Weather essential considerations for ‘Manageable’ (policy, planning, design) – Size, Form, Metabolism planners 3 March 2010

Examples and References Different Levels of Urban Climatic Planning Actions Objectives Strategies Planning Actions Planning Time Scale Spatial Scale • Cool material-building & Immediate pavement; city Effect Albedo Material & Surface • Cool roof & facade; • Water retention paving; Level Intervention UHI • Planting & greeneries; Thermal Vegetation • Parks & open spaces; Comfort • Building geometric design; • Shelter design; Building Level + Shading • Street orientation; Intervention • H/W ratio; Wind • Trees; Dynamic • Air paths; Potential • Building ground cover & building bulks; Ventilation • H/W ratio; Urban & Planning • Street orientation; Level Intervention Local Effect • Open spaces; Long term (neighbourhood • Building disposition; scale) 3 March 2010

Examples and References What is Urban Climatic Map? Urban Climatic Map integrates urban climatic factors and town planning considerations. It provides a spatial information platform to planners for making informed environmental / planning decisions. It has 2 components • The Urban Climatic Analysis Map • The Urban Climatic Planning Recommendation Map Berlin UC-Maps 1988-1992 3 March 2010

Examples and References UCMap Studies in Stuttgart, Germany (late 1980s - ) Urban Climatic Analysis Map Urban Climatic Recommendation Map Climatic Analysis Map Recommendation Map for Urban Planning VDI 3787 Part 1: Environmental Meteorology, Climate and Air Pollution Maps for Cities and Regions Key Lessons Learnt: Heat and Wind for Human Comfort; The use of “Climatopes” and Urban Climatic Planning Classes; Generic Planning recommendations 3 March 2010

Examples and References 3 March 2010

Examples and References UCMap Studies in Tokyo, Japan (2000 - ) Key Lessons Learnt: Greening; Sea Breezes & Mountain winds; air paths; building volume and coverage; anthropogenic heat 3 March 2010

The draft HK Urban Climatic Analysis Map The concept of ( ) 度 Physiological Equivalent Temperature (PET) as the synergizing variable for the HK Urban Climatic Analysis Map Humidity, solar radiation and Survey on Thermal other physiological factors Sensations PHYSIOLOGICAL EQUIVALENT AIR AIR VENTILATION TEMPERATURE TEMPERATURE Dynamic potentials PET Thermal load *note* Human Thermal Comfort evaluated Physiological Equivalent Temperature (PET) is the temperature of a reference environment based on a heat balance model that combines various climatic and physiological variables including air temperature, relative humidity, solar radiation, air movement, clothing and metabolic rate to give a synergetic indication of human thermal comfort. It is an index widely used to understand the Urban Climatic Analysis Map (PET) thermal comfort environment 3 March 2010

The draft HK Urban Climatic Analysis Map Technical input to HK UC-AnMap User urban thermal comfort survey Field measurements Wind tunnel studies Computational Fluid Dynamics (CFD) studies Wind (MM5 / CALMET) studies Wind Tunnel Study Thermal Comfort Study CFD Study 3 March 2010

The draft HK Urban Climatic Analysis Map Layer structure of UC-AnMap Buildings Landuse Topography Building Volume Topography Green Space Ground Coverage Natural Landscape Proximity to Openness + Thermal Load Dynamic Potential Draft UC-AnMap Further Wind Information Final UC-AnMap + = 3 March 2010

The draft HK Urban Climatic Analysis Map 3 March 2010

The draft HK Urban Climatic Analysis Map (UC-AnMap) 3 March 2010

The draft HK Urban Climatic Planning Recommendation Map Building setback & permeability, Air paths, Open spaces (air ventilation connectivity) + greenery 3 March 2010

The draft HK Urban Climatic Planning Recommendation Map Green Spaces: Ground (site) Coverage: Water – sea breezes Proximity to Openness + connectivity: Vegetated hill slopes 3 March 2010

The draft HK Urban Climatic Analysis Map (UC-AnMap) Urban climatically Open spaces increase urban porosity and air volume at the pedestrian level, thus allowing better urban ventilation penetration. Linkage of open spaces allows better connectivity and improves air mass exchange. Furthermore Greening lower the urban mean radiant temperature, increase trans-evaporation and hence improve urban human thermal comfort. Tree canopy also provide shading. 3 March 2010

So, … happy “spacing” and “greening”, … Thank you 5 , “ ” A sketch by a 5 years old, titled “my Hong Kong”. 3 March 2010

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CitySpeak X: Green City. Cool City: Edward Ng - Urban heat and air ventilation – what are the implications for public health?

by DesigningHongKong on Mar 14, 2010

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CitySpeak X: Green City. Cool City: Edward Ng - Urban heat and air ventilation – what are the implications for public health? — Presentation Transcript