For a city with very little industry, Hong Kong emits a disproportionate amount of carbon dioxide.
“Hong Kong’s average carbon footprint is higher than what we call the fair share,” says Secretary for the Environment Wong Kam Sing. “So we need to reduce it. In Hong Kong, 90 per cent of our electricity is consumed in buildings, and they account for nearly two-thirds of greenhouse gas emissions. So buildings are our problem, but at the same time they can be probably our solution.”
Part of that solution is Hong Kong’s first Zero Carbon Building (ZCB), a project by the Construction Industry Council and the government’s Development Bureau. Nestled in Kowloon Bay, the HK$240 million project is a model for sustainable development and a showcase for dozens of cutting-edge green technology projects.
In fact, ZCB, which opens to the public next month, aspires to go beyond being carbon neutral, and to be “energy positive.” It will generate more energy than it consumes – in addition to the “embodied energy” of its major material used during its construction, including the transportation of materials – and will export surplus electricity back to the local supplier, CLP Power.
“We target a higher goal,” explains MK Leung, Director of Sustainable Design at Hong Kong architectural firm Ronald Lu & Partners. “We want to produce and save more energy in order to have a surplus.”
Solar Panels and Bio-Fuel
Electricity is produced from photovoltaic (PV) cells covering most of ZCB’s sloping, south-facing roof, and by an onsite generator from clean-burning bio-fuel refined locally from waste cooking oil collected from Hong Kong restaurants.
Mr Leung calculates that about 70 per cent of the building’s power needs will be provided by solar energy and 110 per cent by the biofuel. “So we calculate that we’re producing 70 to 80 per cent surplus every year in order to be energy positive.”
The other side of the renewable-energy coin is using less energy in daily living, and in Hong Kong, that begins with reducing dependence on air-conditioning. “For energy-demand control, there are a lot of practical lessons to be learned,” he says. “We use passive design strategies to reduce 20 per cent of the energy consumption and high-energy-efficient active systems to reduce another 25 per cent.”
Passive or climate-responsive design includes the orientation of the building to take advantage of wind direction, placement of windows and other openings to enhance natural ventilation, external shading and high-performance glazing.
Among the active systems is an efficient air-conditioning system. “We use an underfloor displacement system, in which the air comes from below,” says Mr Leung. “The building has high headroom space, and we only cool the occupants’ zone, the two metres above the floor. The cold air stays low. As it picks up heat from humans, it slowly rises by natural convection. So we are not cooling the whole space.”
The air circulation strategies make use of natural ventilation to capture the wind, aided by big ceiling fans. “Because this is a public building, when the temperature gets above 28 degrees, we switch on the air-conditioning.” That’s about two-thirds of the time in the summer, although natural ventilation can suffice in the early morning.
The building’s open-sided lobby is cross-ventilated and requires no air-conditioning. “The wisdom is not new,” he remarks. “There are a number of traditional Chinese buildings that make use of cross-ventilated space.”
ZCB is monitored by a building management system (BMS), featuring sensors that collect environmental data and, based on preset protocols, control the building. When the BMS finds that the outdoor environment is comfortable, it will open the windows, said Mr Leung, adding that a “cool biz dress code” discourages visitors and staff from wearing jackets and ties in summer.
Landscaping helps make the 14,700-square-metre site climate positive. “We formed the site in such a way that in the perimeter it is a little bit high, and we planted 320 trees to have a sheltered space in the middle.” He said having the trees and making use of cool material such as permeable paver blocks would reduce the temperature by one to two degrees. “The paver blocks can absorb water, so they cool down the environment by evaporation,” he said. A constructed wetland helps filter stormwater and grey water, which is used for irrigation. Toilet water, meanwhile, is treated and recycled onsite.
The three-storey building also features a demonstration flat to showcase how to be green at home.
Environment Secretary Wong, an architect by profession who was ZCB’s project director before joining the new government administration, calls the new building a trendsetter. “It’s very important to set a world-class example in Hong Kong for low-carbon, highly energy-efficient buildings. Behaviour is a very critical factor when we talk about energy efficiency,” he says. “This CIC project not only demonstrates the best technology and design, it also enlightens people about how to live a low-carbon lifestyle.”
Mr Wong notes that the “milestone” legislation, the Buildings Energy Efficiency Ordinance, comes into full effect this week, requiring all new buildings and those undergoing major renovation, to meet the minimum energy efficiency standards stipulated for air-conditioning, electrical, lighting, lifts and escalator installations.
For the past three years, the Buildings Energy Efficiency Funding Schemes provided matching subsidies totalling more than HK$390 million for owners of more than 6,000 buildings to upgrade the energy performance of their common areas. “But with the launch of the Buildings Energy Efficiency Ordinance, we move from the incentive mode to a regulatory mode. In short, we have the carrot and stick approach to address the issue.”
Another government initiative was launched in April 2011, promoting the BEAM Plus green-building certification. All new private buildings need to register for BEAM Plus certification, in order to gain gross-floor area concessions for green and amenity features. This summer, the Environment Bureau also launched the Energy Saving Charter, inviting developers and property management companies to pledge to maintain indoor temperature of their shopping malls to between 24 and 26 degrees in the summer months. More than 100 shopping malls to date have signed up to this charter.
Source: Hong Kong Trader