Air ventilation in Kowloon City and its neighbouring districts will become as bad as Mong Kok and Yau Ma Tei if the government adds more flats at Kai Tak, a former government adviser fears.
Edward Ng Yan-yung, a professor of architecture at Chinese University, gave advice on the development of the site of the former airport during the early planning stages.
He reassessed the air ventilation of the area around Kai Tak in light of the latest proposal floated by supporters of Chief Executive Leung Chun-ying.
Ng said a previous assessment showed that the existing development plan with a plot ratio of five - floor space five times a site area - would already block some air coming from the harbour along the old runway.
This made air ventilation in districts behind Kai Tak such as Kowloon City, San Po Kong and Hoi Hung "marginally acceptable", he said.
But on Sunday Michael Choi Ngai-min, a member of the Long-Term Housing Strategy Steering Committee, said the number of homes on the site could be doubled to 70,000.
Ng said that under Choi's proposal, the plot ratio would rise to seven or more, with Kowloon City, San Po Kong and Hoi Hung facing even lower wind speeds and higher temperatures.
"My preliminary estimation is that air ventilation in the old districts will further deteriorate. The situation will be like Mong Kok and Yau Ma Tei, where the heat island effect is intense," he said.
Chinese University's latest studies showed the daily average temperature in Mong Kok is three to five degrees Celsius higher than in waterfront areas.
For every one degree increase above the average daily temperature in summer - usually 28 degrees - the daily mortality rate will rise by 1.8 per cent in areas like Mong Kok and Yau Ma Tei.
It will rise 4.1 per cent if the temperature is two degrees higher than the average, with the elderly more prone to heatrelated illnesses and stress.
"We may solve the housing problem but we will definitely create problems for our next generation," Ng said.
He urged the government to adopt a more visionary approach to resolve the housing issue.
Ng said the city had taken more than five years to reach the consensus that new towns should be more sustainable - a key principle in planning Kai Tak, featuring a large park, a sports complex and a housing density equivalent to Sha Tin in the 1990s.
He urged the administration not to fill every vacant site with housing developments.
The administration plans to rezone urban sites set aside for community use into residential use, but Ng criticised this strategy as "robbing the poor".
"These sites are the remaining air space in crowded districts and they are usually located next to the air paths of the city, which help increase wind circulation," he said.