Greening the city

Discussion Greening of a city is the process of building a clean city from the viewpoint of energy efficiency, resource conservation, and environmental protection. Why is it necessary for greening a city? What are the possible benefits of greening a city? Discuss and explain the conditions favouring the greening process. Evaluate the possibilities and difficulties in achieving the purpose of greening in Hong Kong.

What is greening?

Why is it necessary for greening in a city? Urban heat island effect Energy shortage Pollution problems arising from power generation

Examples in Japan

Greening in Beijing 北京屋顶绿化协会是中国政府批准的第一家具有法人资格的屋顶绿化非盈利、非政府的民间社团。成立于2006年3月12日。致力于发挥好政府和企业之间的桥梁和纽带作用。它的宗旨是加强行业自律和对业主、对社会负责。口号是在屋顶上铺块绿，还北京一片蓝天。 北京屋顶绿化协会由谭天鹰先生出任会长，王仙民先生出任秘书长，中国工程院资深院士陈俊愉、原国家林业部副部长董志勇、原首都绿化委员会常务副主任单昭祥、原北京市人民政府常务副市长韩伯平出任名誉会长。

Greening in China 国内外屋顶绿化通常分为两大类： 屋顶草坪 (rooftop greening)：一般是不上人的屋面，荷载轻，适合种植管理粗放的景天科、多年生地被植物。 空中花园 (hanging gardens)：乔灌花草搭配，亭榭花架、小桥流水、体育设施综合在一起的，供人们休闲娱乐的绿色空间。

灣仔舊樓天台 首建降溫植物花園 (明報) 03月 25日 星期日 05:10AM 【明報專訊】愈來愈多新落成樓宇建設「空中花園」，以改善附近空氣質素。浸會愛群社會服務處率先於灣仔舊區建設全港首個「城市降溫植物花園」，綠化舊樓天台之餘，更可減少僭建物。 浸會愛群社會服務處的大樓設於灣仔舊區，樓高9層，該會特別花費1.6萬元於天台搭建花園，率先於舊區推行環保綠化。負責設計的    土木及結構工程學系副教授韋永康表示，花園面積約400平方呎，可種植海棠、菊花、西瓜和南瓜等植物，改善空氣質素之餘，亦可降低8樓的室內氣溫。 他解釋，由於花園的泥土層有水分，泥土溫度較低，直接令8樓的室內溫度一併降低，長遠可減少冷氣用電，有助環保。理大已設置儀器收集數據，研究空中花園對改善空氣質素和降低室溫的影響，若成效顯著，會向灣仔    建議，於區內舊樓廣泛建設空中花園。方便休憩 可減僭建出任浸會愛群社會服務處服務改善委員會主席的產業測量師曾家求表示，港人普遍認為新式樓宇才能興建空中花園，其實舊樓天台也可展開綠化工程。他說，灣仔舊區的樓宇較矮，方便居民隨時到空中花園休憩，更可減少居民胡亂僭建，提升舊區形象。

公屋設空中花園試點 葵聯路公屋首建 料2010落成 (明報) 10月 31日 星期二 05:05AM 【明報專訊】為配合施政報告中「推廣綠化屋」的項目，房屋署銳意以公共屋作試點，在東區海底隧道第三至六期的房屋用地樓宇和兩個油塘區商場屋頂，增設綠化環境，以減低室內氣溫。另外，房署 廣 告 會在葵聯路的公屋增設空中花園，每3層設有公用綠化平台，兩個項目分別最快於2008及2010落成，務求把公屋的平均綠化範圍由現時15%增至20%至30%。 消息人士透露，房屋署會選取葵涌區葵聯路30多層高的公共屋做試點，平均每3層設一半露天公眾休憩平台。「由於該地段面積較小，活動空間不多，所以我們希望增設綠化環境，擺放長椅，讓市民茶餘飯後有個地方聚腳談天。」 該屋苑將於2010年落成，屆時每幢樓宇會有約10個「空中花園」(elevated gardens)，該層的單位數目可能減少，走廊會伸延至「空中花園」，政府需解決保安及風力問題。「於20多樓設花園，風力較地面強近3倍，我們會種植適應這環境的植物。可能會參考日本的經驗，增設擋風板，以免市民因強風減少遊興。」

Greening in HK A green roof design is adopted in the site office to enhance thermal insulation. It is found that the temperature inside the ceiling void of the CED office nearby has a high temperature up to 52oC at 2:00 under sunshine on a day with 33oC, while for the green site office, the temperature of the ceiling void is around 33oC under sunshine at 3:00p.m. Thus, it can be concluded that the green roof have made significant effect to the thermal loading of the site office building. Moreover, when using green roof, their shallow soil reduce rainwater run off to less than 50% of normal, reducing the pressure on the ground level drainage system. The rainwater retained in the soil supports the plants, reduces the temperature, and through evaporation, it can humidifies the air and reduces the dust levels.

Hong Kong Waterproof Concrete in Asia Tuen Mun Town Plaza The 33,000-meter membrane-free podium deck of the Tuen Mun Town Plaza in Hong Kong incorporates a swimming pool, tennis courts, landscaped areas, skateboard track, and more, demonstrating the effectiveness of the waterproof concrete system. On this complex structure with many diverse rooftop uses, the architect saved eight weeks in design time by not having to detail any membranes. Construction was considerably faster as well, since the design was a simple structural concrete slab with the waterproofing built right in.

What are the benefits of greening in HK?

Protecting the structure of the building The green plants act as a protective layer to the building Helping to reduce the maintenance cost

Energy-saving It helps to reduce the room temperature by 1 to 2 ºC Reduce the use of air conditioners Reduce the energy consumption Energy efficiency is high

Improve drainage It helps to reduce the risk of urban flooding It reduces rainwater runoff water loss by evaporation  less discharge  flooding is prevented

Noise barrier Green rooftop acts as sound absorber Improving quality of living

Educational purpose Greening the rooftop in schools, offices, homes A chance for education

Difficulties encountered

References http://www.hku.hk/bse/greensiteoffice/greenroof.htm http://www.arch.hku.hk/research/BEER/sustain-weblinks.htm