Treating the Symptoms - A Critical Review of ... - Civic Exchange

Opposite, clockwise from top right: Wan Chai Road, between Sites A and B of The Zenith. Thereare long, unbroken podiums on either side of the road; looking up between the towers of TheZenith; The Dynasty is located along the Tsuen Wan waterfront, near the Nina Tower. Its twobroad, tightly spaced towers have been accused of creating a “wall effect”. 183VentilationThe effect of large buildings on air ventilation has become a major environmental issuein Hong Kong. Good ventilation is needed to alleviate roadside air pollution, and newdevelopments have been criticized for exacerbating the street canyon effect or blockingcoastal breezes.In 2006, the Planning Department announced guidelines for conducting air ventilationassessments for new developments. However, they are mandatory only for governmentbuilding projects, but not the private sector. The URA agreed to adopt ventilation assessmentsfor future projects, but projects planned prior to 2006 were not assessed. 182Box 7Basics of VentilationAll of the projects photographed in this report were completed or under construction beforeventilation assessments were implemented. Those that are on large or long sites have thebulkiest podiums, and some have tightly spaced towers.While the URA has made more efforts in recent years to address ventilation concerns, theextent of the improvements that can be made is restricted by financial concerns. For example,during the planning of the Kwun Tong Town Centre project in 2009, it was decided thatthe project must have a minimum GFA of 401,250m 2 in order to be financially viable. 184 Itwill feature an office tower of at least 220-280m, a very large podium and a pedestrian deckwhich will have adverse effects at street level. The URA had the flexibility to arrange thecomponents to marginally reduce the ventilation impact, but was not willing to significantlyreduce development intensity. 185 Source: Carmona et al. p.187 1811.2.3.Tall buildings do not necessarily create poor ventilation. Widthmatters more than height. Wide buildings oriented perpendicularlyto prevailing winds block ventilation the most.The street canyon effect occurs when there is an unbroken rowof bulky buildings of similar heights on either side of a street. Thisimpedes circulation and traps pollutants at street level.Varied building heights and gaps between buildings facilitate airflow and help disperse pollutants.91