SKY GARDEN DESIGN IN HIGH-DENSITY HIGH-RISE RESIDENTIAL DEVELOPMENT

Transcription

1 SKY GARDEN DESIGN IN HIGH-DENSITY HIGH-RISE RESIDENTIAL DEVELOPMENT Tony Ip 1 B.Eng., B.BltEnv.(Dist.), M.Sc., M.Arch.(Dist.), M.UrbanDesign(Dist.), M.St.IDBE RA(HK), AP(Architect), HKIA, HKIUD, BEAM Pro Ronald Lu & Partners (Hong Kong) Ltd., Hong Kong 1 Tony Ip - Address: Ronald Lu & Partners (Hong Kong) Ltd., 33/F., Wu Chung House, 213 Queen s Road East, Wanchai, Hong Kong, tonyip@rlphk.com / tony_7699@yahoo.com, Tel: (852) , Fax: (852)

2 SKY GARDEN DESIGN IN HIGH-DENSITY HIGH-RISE RESIDENTIAL DEVELOPMENT ABSTRACT The Hong Kong government issued green incentives for sky gardens in domestic buildings in 2001, including gross floor area exemptions and relaxation of the allowable overall building height in regard to provision of sky gardens. Such incentives were conceived to encourage developers to incorporate greening measures in new residential high-rise buildings; however, these incentives have been criticized due to uncertainty of whether these sky gardens provide benign effects to the local micro-environment. Further criticism has been directed against whether the sky gardens are underused due to windy conditions, poor connectivity or access, and lack of recreational facilities to suit their intended purpose. Case studies of twenty sky gardens in high-rise residential developments inform that the location and openness of sky gardens are not optimized to alleviate air flow at the street level and improve microclimate in the existing urban contexts. A survey on residents experiences in sky gardens is conducted in three residential developments with distinctive characters of sky gardens in terms of sky garden locations and connectivity, amenity provisions, design themes, surrounding urban contexts, and property completion years. One-third of the residents never visit their sky gardens and no daily visitors are found, whilst the elderly and children are infrequent users of sky gardens. It reveals that misunderstanding of the values of sky gardens and personal perceptions may cause the low occupancy rate but more positive experiences are reported as a result after residents visit the sky gardens. Residents habits and living patterns affect decisions on whether to utilize outdoor communal spaces and spend time for enjoyment in sky gardens. The study evaluates the effectiveness of existing sky gardens and discusses design of effective sky gardens for improving environmental quality and social interaction in densely occupied, high-rise contexts. Keywords: High-rise; Residents Experience; Sky Garden; Urban Living. 1. BACKGROUND Sky gardens have been promoted by the Hong Kong government since 2001 as a design strategy to improve the quality of the living environment by balancing social, environmental, and economic concerns. A decade later, the benefits and functions of sky gardens are not obvious, leading to only a limited number of new residential buildings in Hong Kong being provisioned with sky gardens. In the high-density urban environment, the scarcity of land squeezes development of high-rise greenery away from the ground level. In Hong Kong, there are three types of gardens in high-rises: podium gardens, sky gardens, and roof gardens. Sky gardens are scattered at various levels of a tower, while podium gardens and roof gardens are situated on the roof of a podium and a tower respectively. This paper investigates the characteristics of existing sky gardens, analyses their environmental, social and economic performances, evaluates residents experiences, and discusses design of effective sky gardens in high-density, high-rise residential developments. It focuses on sky gardens at storeys of densely-populated residential high-rises in urban areas. 2

3 2. GARDENS IN URBAN LIVING Sense of community is only evoked with profound opportunities of social interaction. The demand for a peaceful and natural environment in the urban areas has increased; people desire such environments where they can stay, chat, and otherwise interact with their family, friends, neighbours, and passers-by (Connell, 2004; Kaplan and Matsuoka, 2008). Green spaces have direct and indirect benefits on environmental, social, and economic aspects in urban living (Givoni, 1991; Goddard et al., 2009; HKSAR, 2009). Can sky gardens be an option of bridging nature with urban living? Residents of high-rises have a strong desire for pleasant communal green spaces that can encourage social interaction and communal activities amongst neighbours in proper circumstances (Chien and Wang, 1999; Huang, 2006). For urban dwellers, the opportunity to breathe clean air and exercise is their main driver to visit green spaces; and they are willing to pay more for residences with more green spaces (Chen and Jim, 2010; Jim and Lo, 2010). Unfortunately, a survey in Singapore showed that green spaces in high-rises, such as roof gardens, were under-utilized due to a lack of people s awareness of such green spaces (Wong and Yuen, 2005). Green spaces are essential in a child s healthy development. Children in the city may develop nature-deficiency disorders with physical inactivity, thus eliciting social and psychological ramifications and an increase in the trend of chronic diseases. Green environments and pleasant outdoor spaces can encourage children to be more active and improve their health (Lee and Min, 2006; Kuo et al., 2002; McCurdy et al., 2010). Meanwhile, elderly residents prefer garden apartments and have a greater sense of community there. Green common spaces benefit the social integration of older adults in the inner-city, which can also indirectly lessen public expenditure on individual elderly services (Delvin and Zaff,1998; Kweon et al., 1998). 3. SKY GARDENS Sky garden is a form of micro-environmental design meant for improving wind conditions in urban districts and providing a recreational garden space. Research findings on the topic of sky gardens are limited. However, available research regarding sky gardens in Hong Kong (Niu, 2004) states that sky gardens provide better thermal comfort in the summer. There is only one set of available guidelines for the design of sky gardens in Hong Kong (HKSAR, 2001). Some key points extracted are listed as follows:- i. Locations of sky gardens are recommended to be determined by wind tunnel testing or computation fluid dynamic modelling but it is not compulsory. ii. The maximum number of sky gardens provided is equal to or less than the number of residential storeys divided by 15. Such a garden can be split into multi-levels but it occupies not less than one-third of the area of the floor plate. iii. The first sky garden is located at not more than 10 storeys where more than iv. one sky garden is provided and where there is no podium garden. The minimum headroom is 4.5m and it is open-sided above safe parapet height on at least two opposite sides for cross ventilation. v. Sky gardens can be coupled with refuge floor. vi. Not less than 25% of the area of the floor plate is to be vegetated. 3

4 4. CHARACTERISTICS OF SKY GARDENS IN HIGH-RISE RESIDENTIAL DEVELOPMENTS IN HONG KONG According to the government statistics in (HKSAR, 2008), only 14 residential buildings completed within that time were provisioned with sky gardens, equalling only 3% of the 520 new buildings completed in that period. Case studies of twenty sky gardens in high-rise residential buildings were carried out. These buildings were built after the Hong Kong government s implementation of the green incentives of sky gardens in Some common characteristics of sky gardens in Hong Kong are identified as follows:- i. With the effects of green incentives, height concession is the main driver for the provision of sky gardens such that units above sky gardens can be elevated with better distant views, resulting in higher property prices. ii. Most of the sky gardens at mid-levels are mainly designed for the purpose of refuge floors. For those at low- and high-levels, sky gardens are usually adjoined to podiums or sky clubhouses that act as an extension of the clubhouses area or serve as main circulations to the clubhouses from individual tower blocks. iii. The total opening of sky gardens in proportion to the overall building height is merely 2-3%. Two-thirds of the gardens are located at mid- and high-levels about m from the street that impose insignificant effects on improving air flow at the pedestrian street-level and microclimate in the old urban context of high-density built environments at 60m or below. In considering most of the sky gardens located at 60m or below, the ratio of openness to its level from the street is about 5%, which is not comparable to 22% of one case that 14.5m high sky garden is purposely designed for alleviating air ventilation. iv % of the net floor areas are vegetated in sky garden. About 45% of outdoor areas serve as circulation and event spaces. Structural configuration and fire service installations restrained the spatial planning in sky gardens. Amenities mainly facilitated passive activities such as leisurely sitting areas, viewing platforms, strolling paths and foot massage trails. 5. RESIDENTS EXPERIENCES IN SKY GARDENS To investigate the values of sky gardens from the residents perspectives, a survey was conducted in three residential developments with distinctive typology of sky gardens as shown in Table 1. The questionnaires were completed through face-to-face interviews with individuals and the number of successful respondents was ninety in total (thirty per development typology). Table 1 Sky gardens selected for the survey on residents experiences. Typology One mid-level sky garden One low-level and one mid-level sky garden Location Sai Wan Ho, HK (Harbour Front) Quarry Bay, HK (Urban Area) Completion Property 5 blocks, storeys, 2 blocks, 38 storeys, Description 2020 units 442 units One high-level sky garden connecting to a sky clubhouse Cheung Sha Wan, HK (An Old District) 2 blocks, 37 storeys, 400 units Occupancy Rate & Pattern 33.3% of residents never visit their sky gardens, 40% visit during festivals or special occasions, and 26.7% visit regularly on a weekly or monthly basis, but none on a daily basis. Residents between the age of are both the main group of respondents and sky-garden users simultaneously. The elderly and children are not the most 4

5 frequent users although they spend the longest time in residential buildings on weekdays. Residents, who live in sq.ft & sq.ft flats, visit sky gardens more frequently and on a more regular basis. Daytime visitors are not the majority. 42.6% of residents visit sky gardens after 8pm, 34.9% between 3-8pm and 13.4% between noon-3pm. Different typologies pose slight variations of residents experiences and their occupancy patterns. Reasons for Visiting Sky Gardens The most agreed reason why residents visit sky-gardens is landscaped garden with scenic views. The second reason is self-retreat / reading in a peaceful environment. The third is leisure walk with family & friends, and the least is children play / doing exercise & stretching. The reason of communal space for chatting with neighbours is disregarded. Compared with those visiting sky gardens occasionally, residents who visit on a regular basis have a higher degree of satisfaction for leisure walk with family & friends and self-retreat / reading in a peaceful environment. Reasons for Not or Seldom Visiting Sky Gardens For residents who never visit sky gardens, they consider lack of amenity facilities as the main reason. Other reasons for not visiting sky gardens, including too windy, difficult to access, safety concerns and insecure sense, are quite distinctive amongst the three developments. More positive comments on sky gardens, except for too windy, are received from residents after they have visited there. Values of Sky Gardens Most of the residents agree that the values of sky gardens is to provide more outdoor communal spaces, provide more green spaces, and enhance property value. More seating and recreational facilities, especially for children playing, should be provided. In summary, residents misunderstanding of the values of sky gardens and personal perceptions may cause low occupancy rate, but more positive experiences resulted after residents visited the sky gardens. Residents habits and living patterns affect decisions on whether to utilize outdoor communal spaces and spend time to have enjoyment in sky gardens. Social interactions amongst neighbours are relatively difficult to achieve, but sky gardens have a definite positive impact to urban living for individuals and families in Hong Kong. 6. DISCUSSION ON EFFECTIVENESS OF SKY GARDENS IN HIGH- DENSITY HIGH-RISE RESIDENTIAL DEVELOPMENT Can the existing sky gardens improve the quality of urban living? Only few developments with sky gardens and low occupancy rates have been observed. It may relate that either developers or residents do not understand or fully experience the merits of sky gardens. On the other hand, the government policy has not effectively encouraged good quality of sky garden design in optimizing its environmental, social, and economic performances. Environmental Performance With sky gardens, the building permeability and greenery ratio increase, but the magnitude is not obvious. The ratio of clear openings at sky gardens to the overall building height is merely 2-3%. Two-thirds of sky gardens are located in the mid- and high-levels of buildings, about m from the street. These sky gardens impose an insignificant effect on improving air flow at the pedestrian street-level or in the existing urban context where old buildings are at 60m or below. Furthermore, the actual 5

6 vegetated areas within sky gardens are fragmented and occupy less than a quarter of the net floor area. The effectiveness of alleviating the wall effect and urban heat island effect is in question. Social Performance Residents generally agree that their sky gardens offer scenic and peaceful environments for self-retreat, resting, reading, and leisurely walks with family and friends; thus more greenery and garden areas are strongly requested. Residents within the age of are the main sky garden users while the elderly and children do not visit frequently. It is arguable that sky gardens are ideal places for children to play and the elderly to exercise, subject to appropriate amenities and parapet designs that are sensible and safe. Nonetheless, a sky garden is not considered as a communal space to encourage more social interactions among neighbours. Economic Performance The height concession to elevate the overall building height incentivizes the provision of sky gardens in new developments from the developers perspective. On the other hand, residents consider that sky gardens can enhance their property value by providing more pleasant communal spaces and greenery. However, it is not comparable to other communal facilities such as clubhouses or podium gardens. Current Design Guidelines The current design guidelines of sky gardens have not been thoroughly implemented. For instance, locations of sky garden are recommended to be determined by a wind tunnel testing or computation fluid dynamic modelling; however, none of the studied projects determined their sky garden locations by following published recommendations except where specific statutory planning conditions were imposed. Negation of testing and modelling recommendations may be due to implications of substantial costs and/or time. Although multi-level sky gardens are allowed, it is not uncommon that residential highrises of more than 30 storeys have only one single-level sky garden to satisfy green incentive credits. In the twenty case studies, only one-fifth of developments incorporate two sky gardens and none of them have split-level sky gardens. Reasons to explain this phenomenon are that either there is a lack of successful sky garden implementation, or that the building authority prevents the abuse of height recession and likely requests more deliberate justification for environmental improvement if more than one sky garden is proposed. A question arises in regard to what would be more appropriate to specify prescriptive building permeability requirements for environmental improvement by a podium garden, a sky garden or a combination of them? How can the design of sky gardens maximize benefits for urban living in highdensity high-rise residential developments? If we consider that a sky garden is an alternative communal space for leisure activities and a relaxing outdoor green environment that promotes healthy and sustainable living quality, then provisioning of such an appealing covered landscaping area is a perquisite rather than a by-product in the design of new residential developments. Greenery has positive effects in urban living in particular to the aging population and for children s healthy development. Furthermore, residents express their strong preference to the living environment with more planting. The green ratio is suggested to be determined in relation to population or gross floor areas instead of the ratio of the site area, which is of the similar approach in determining sufficient recreational facilities. 6

7 Building Permeability and Greenery To improve building permeability and alleviate urban ventilation, the sky garden should be located at low levels and of higher floor height. References can be made to the case of 14.5m high sky garden and to design guidelines of 13m high sky gardens in Singapore. A 6m floor height with 4.5m clear headroom is advisable for sky gardens at high levels and even for a sky garden that serves the purpose of a refuge floor; otherwise, daylight is not sufficient at the inner part of the garden area. Similarly, if greenery can effectively alleviate urban micro-climatic conditions, the green cover area at the sky garden should be large enough to incur positive environmental results. Trees and shrubs of various species and heights should be planted in order to achieve a desirable environmental comfort and create an authentic-feeling garden. Amenity and Spatial Quality The popularity of new private residential buildings with sky clubhouses has justified that recreational facilities at high levels may not be residents concern in residential highrises; however, how attractive the destination may be is an issue. More greenery and diversity in amenity facilities are expected by residents. To promote a low carbon living environment, a sky garden can act as a naturally-ventilated sky clubhouse which provides amenity facilities to residents in a more energy efficient way. Furthermore, the usage of a designated space like a refuge floor that is converted into a sky garden is encouraged, but its spatial quality has to be improved, including wider and higher event spaces and appropriate planter areas for a variety of plant species. Design of Effective Sky Gardens Three types of sky gardens are proposed in view of specific environmental and social functions. First, sky gardens are designed with high headroom located at or below 60m to emphasize improving upon a building s permeability and environmental quality. Second, sky gardens with larger event spaces and attractive elderly friendly facilities and children s play amenities above 60m can facilitate more outdoor recreational spaces for residents and act as naturally-ventilated sky clubhouses. Third, pocket-sized sky gardens with extensive planting are integrated within communal circulation spaces, such as lift lobbies and corridors on residential floors, and are scattered in the building at multiple levels, which offer more chances of social interactions amongst neighbours and physical contact with greenery and facilitate impromptu extension of living spaces. 7. CONCLUSION The higher we live from the ground level, the more disconnected we feel from the natural world and even from each other within a community. We can understand that sky gardens may provide beneficial impacts on environmental and social aspects in urban living, and supplement deficiencies and needs in highdensity, high-rise residential developments. Benefits to the environment derived from the implementation of sky gardens include improved human thermal comfort and urban microclimate, increased social cohesion through the provision of a community green space, provisioning of a place for individuals to escape from the busy city life, improved community integration for all age groups, and improved health and well-being. In practice, improving environmental quality and enhancing social interactions are not considered important factors by residents of developments. The case studies show that the location and openness of sky gardens are not optimized to alleviate air flow at pedestrian level and microclimate in the existing urban context. Moreover, the fragmented configuration of planters in sky gardens has not improved ambient cooling 7

8 and the overall occupancy rate for the gardens is low. The survey on residents experiences reveals that one-third of the residents never visit their sky gardens and no daily visitors are found, whilst the elderly and children were infrequent users of sky gardens. Still, residents expect more greenery, spacious garden spaces, and more amenity facilities in their sky gardens, and agree that sky gardens improve property prices. Nonetheless, more research is needed to confirm whether sky gardens can improve social outcomes and perceptions. Recommendations are that the design of sky gardens needs to include consideration of specific environmental and social functions. Sky gardens located at relatively low levels emphasize building permeability with sufficient headroom. Sky gardens at high levels serve the purposes of recreation, social gathering, and ambient cooling. Sky gardens with wider spaces and attractive amenities act like naturally-ventilated sky clubhouses, and those with extensive planting integrate well with circulation spaces at multi-levels of a building. REFERENCES Chen, W. Y. and Jim, C. Y., External Effects of Neighbourhood Parks and Landscape Elements on High-rise Residential Value Land Use Policy, 27, Chien H. T. and Wang M. S., Environmental Behaviour Analysis of High-rise Building Areas in Taiwan, Building and Environment, 34, Connell J., The Purest of Human Pleasures - The Characteristics and Motivations of Garden Visitors in Great Britain Tourism Management, 25, Delvin, A. S. and Zaff, J., 1998 Sense of Community in Housing for the Elderly, Journal of Community Psychology, 26(4), Givoni B., Impact of Planted Areas on Urban Environmental Quality - A Review, Atmospheric Environment, 25B(3), Goddard M. A., Dougill A. J. and Benton T.G., Scaling Up from Gardens - Biodiversity Conservation in Urban Environments, Trends in Ecology and Evolution, 25(2), HKSAR Buildings Department, Lands Department and Planning Department, Joint Practice Note No.1 Green and Innovative Buildings, HKSAR. HKSAR Development Bureau, Legislative Council Panel on Development Discussion Paper: Review of Measures to Promote Green Features in Building Developments, HKSAR. HKSAR Buildings Department, Consultancy Study on Building Design that Supports Sustainable Urban Living Space in Hong Kong, HKSAR. HKSAR Council on Sustainable Development, Invitation for Response Document: Building Design to Foster a Quality and Sustainable Built Environment, HKSAR. Huang, S. C. L., A Study of Outdoor Interaction Spaces in High-rise Housing, Landscape and Urban Planning, 76, Ip C. M., Sky Garden Design in High-density High-rise Residential Development. Thesis (MSt. IDBE). University of Cambridge. Jim C. Y. and Lo A. Y., Willingness of Residents to Pay & Motives for Conservation of Urban Green Spaces in the Compact City of HK, Urban Forestry & Urban Greening, 9, Kaplan R. and Matsuoka R. H., People needs in the urban landscape - Analysis of Landscape and Urban Planning contributions, Landscape and Urban Planning, 84, Kuo F. E., Sullivan W. C. and Taylor A. F., Views of Nature and Self-discipline- Evidence from Inner City Children, Journal of Environmental Psychology, 22, Kweon, B. S., Sullivan, W. C. and Wiley, A. R., Green Common Spaces and The Social Integration of Inner-city Older Adults, Environment and Behaviour, 30, Lee J. and Min B., Children s Neighbourhood Place as a Psychological and Behavioural Domain, Journal of Environmental Psychology, 26, McCurdy L. E., Winterbottom K. E., Mehta S. S., and Roberts J. R., Using Nature and Outdoor Activity to Improve Children s Health, Health Care, 5, Niu, J., Some Significant Environmental Issues in High-rise residential Building Design in Urban Areas, Energy and Buildings, 36, Wong, N. H. and Yuen, B., Resident Perceptions and Expectations of Rooftop Gardens in Singapore, Landscape and Urban Planning, 73,