Housing officials are turning to nature to beat global warming and bring fresher air to public housing tenants - while defying the law of gravity - by growing grass and herbs on walls in housing estates.
The Housing Authority has spent HK$1 million on vertical greening on Yau Lai Estate, a public rental housing development in Kwun Tong.
Deputy director Ada Fung Yin-suen said the extra greening cost would not be recovered from tenants' management fees.
A study of the 'vertical greening panels' on Yau Lai Estate Phase 4, completed this year, had demonstrated the benefits, Fung said. 'An external wall mounted with plants can be cooled by 16 degrees Celsius,' she said, adding that the temperature of the inside surface could stay at 26.5 degrees, or 1.5 to 3.5 degrees lower than those without vertical planting.
The department's senior architect, Clifford Cheng Chiu-yeung, said a 40 sq ft office could save 1.45 kilowatt-hours a day on air conditioning if its west-facing wall were screened. Fung said vertical greening panels used grass and herbs planted in a panel of rockwool, a kind of artificial mineral fibre. A few panels are then fitted into metal cladding that is hung on an external wall.
Chinese University biology professor Chu Lee-man, who participated in the Yau Lai Estate study, said the cooling effect could be better.