PSW's speech and presentation at the International Conference on Tall Buildings
International Conference on Tall Buildings
Speech by Ir LO Yiu-ching, JP
Permanent Secretary for the Environment, Transport and Works (Works)
Tuesday, 6 December 2005
Sustainable Development of Tall Buildings in Hong Kong
Professor Cheung, Prof Wang, Ladies and Gentlemen :
It gives me great pleasure to participate in the 6th International Conference on Tall Buildings and to speak to such a distinguished group of prominent professionals and academics from overseas countries, the Mainland and Hong Kong.
The topic I am going to share with you today is "the Sustainable Development of Tall Buildings in Hong Kong". I note the trend of rising concern among building professionals on sustainable development, as shown by the number of papers related to sustainability presented at this conference which is twice of that in the last conference held in Beijing. There are more than 30 papers this time.
In my presentation, I shall first introduce the reasons for the emergence of tall buildings in Hong Kong. Next, I shall highlight our Government's strategy on sustainable development and briefly go over the three pilot areas of solid waste management, use of renewable energy and urban living space within the context of building development. I shall then touch on how to sustain the movement of people "between buildings" and "within tall buildings". After going through these issues, I shall focus and talk about the more important aspects of sustainable development of tall buildings, namely the environmental considerations and energy efficiency.
Emergence of Tall Buildings
Let me start by giving some reasons for having so many tall buildings in Hong Kong. There has been great demand for office space and residential flats in Hong Kong due to our rapid population increase and economic growth over the years. To cater for this high demand, tall buildings are constructed as they are more efficient in the use of limited land in Hong Kong. On the other hand, our efficient and comprehensive infrastructural development also encourages the emergence of tall buildings. Without these advanced infrastructures, tall and dense building developments would be impossible. For individual building occupants, taller buildings can satisfy their pursuit of better view, easier access to daylight and fresh air. Tall buildings also confer prestige and enhance economic competitiveness.
Population in Hong Kong has increased steadily over the past 50 years, from about 2 million people in 1950 to nearly 7 million people in 2005. At present, we have an average population density of 6,300 people per sq km. However, in some part of our urban areas, the density is as high as 50,000 people per sq km.
During the second half of the 20th Century, buildings in Hong Kong had been taking different shapes to cope with the demand. Height of buildings grew from about 10-storeys in 1950 to well above 60-storeys in 2005.
In 1973, Government launched the New Town Development Programme to develop nine satellite towns to cope with the increase in population and to improve the living environment.
As a result, a fair proportion of the population from the over-crowded urban districts in Hong Kong Island and Kowloon was de-centralized to Shatin, Tai Po, Sheung Shui, Fanling, Tuen Mun, Tsuen Wan, Tin Shui Wai, Tseung Kwan O and Tung Chung in the New Territories. Meanwhile, re-developments in the urban areas facilitated the building of many high-rise residential blocks. Mei Foo Sun Chuen built in the mid 1960s had been widely regarded as a watershed from both property development and construction perspectives.
This successful model is a multiple intensive land-use re-development in the form of a self-contained township, which has been further developed into the nowadays residential super-high-rise towers sitting on top of a multi-storey podium with all kinds of facilities providing comfort, convenience and connectivity for thousands of people living therein.
Sustainable Development Strategy
Talking on the subject of sustainable development of tall buildings in Hong Kong, I am obliged to introduce the Government's first Sustainable Development Strategy which was promulgated by the Council for Sustainable Development in May this year. The strategy recognizes the need to balance and integrate social, economic and environmental considerations when deciding how best to accommodate our future growth.
The three pilot areas identified for further action are solid waste management, use of renewable energy and urban living space. I shall discuss each of these areas in turn on the subjects that are relevant to the building construction professionals.
Solid Waste Management
The first pilot area is solid waste management. The construction industry generates a lot of waste material known as construction and demolition waste, or C&D waste in short. Taller buildings usually generate more C&D waste in comparison with shorter ones. I must emphasis, "usually".
In the past ten years or so, Hong Kong has seen a substantial increase in the amount of C&D waste. There were nearly 12 million and more than 20 million tonnes of C&D materials generated in 1995 and 2004 respectively. Although we have done a good job to reuse the majority of them, there are still more than 2 million tonnes a year of C&D waste ended up in landfills. With this pace of disposal, and taking into account the need to dispose of other domestic and commercial wastes, we envisage that all our existing landfills would likely be filled up within the next 6 to 10 years if we fail to introduce other effective measures.
The key to managing the disposal of C&D waste is again our old song - the 3 R's, i.e. Reduce, Reuse and Recycle. What is needed from us is just a matter of care with a simple question always born in mind "Have I done my best to reduce consumption?". Applying these 3 R's in building construction will bring huge economic benefits.
In order to provide financial incentive, our Government introduced the "user pays" principle and the Legislative Council passed the "Waste Disposal Ordinance" last year. From next year onwards, those who dispose of C&D waste at landfill sites will have to pay a levy. This measure will encourage contractors to reduce waste, sort waste and recycle them wherever possible, and hence reduce the burdens on our precious landfill areas.
The second pilot area is the use of renewable energy. Our Government is committed to promote the greater use of energy from renewable sources, and wider adoption of such practice in public works projects.
We have recently completed a study into the feasibility of using solar energy, wind, waves and landfill gas, etc. in Hong Kong. Among the various types of renewable energy sources, solar energy has in fact been used in Hong Kong for some years, in supplying hot water to a number of government facilities such as the slaughterhouse in Sheung Shui and several public swimming pools.
Photovoltaic (usually called PV in short) or BIPV (which is the abbreviation for Building Integrated Photovoltaic) panels have also been installed in a number of government and institutional buildings and parks, to convert solar energy into electricity. Earlier this year, we saw the completion of a large-scale 350kW PV panel installed on the roof of the headquarters building of the Electrical and Mechanical Services Department (EMSD). This installation alone could help reduce the generation of about 200 tonnes carbon dioxide a year.
Furthermore, waste heat from the air-conditioning system has also been utilized in conjunction with solar panels to generate hot water for office buildings, hospitals and indoor games halls. I therefore see the huge potential and enormous environmental and economic benefits on the much wider application and use of renewable energy on tall building developments.
Urban Design of Tall Buildings
The third pilot area is the urban living space. The Government has issued a set of Urban Design Guidelines in order to maintain views to ridgelines, peaks or water body and to provide breezeways by lowering building heights. High-rise nodes are allowed at selected strategic locations further inland instead of on the waterfront. These few sketches are extracted from the guidelines for illustration purpose. For instance, ridgelines should be protected as far as possible and designers should avoid the "wall" effect by creating a varying building height profile. Visual access should also be maintained to the waterfront by preserving and providing additional view corridors. Primary and secondary breezeways should be introduced to improve the micro-climate at the town centre area.
These two sketches indicate that buildings are to be designed in a stepping down manner to avoid adverse visual impact.
The Grand Millennium Plaza in Sheung Wan demonstrates how a breezeway and a visual corridor are introduced to the urban area upon redevelopment of this building site. At the same time, a nicely landscaped open space is provided to improve the micro-climate in this area.
Tall buildings and transport provision
I mentioned earlier that our efficient infrastructures have facilitated the emergence of tall buildings, of which the capability in moving people between and within buildings effectively is often a crucial factor to sustain the developments of tall buildings.
The lateral movement of people from buildings to buildings and, to a further extent, from districts to districts is called transportation. Transportation system becomes very effective, efficient and economical in Hong Kong where we have a clustering of buildings located in densely populated areas.
Railways form the backbone of our transportation system and connect up various districts. The railway system, together with the extensive highway network, provide Hong Kong with one of the best transport infrastructures in the world. As railways are massive people carriers, many high rise buildings are located conveniently and directly on top of the railway stations to maximize efficiency.
Vertical Transportation in Tall Buildings
As regards vertical movement of people within buildings, various types and combinations of lifts are used to cater for the needs of building occupants. To enhance efficiency, lifts of higher speed are often used in taller buildings. However acceleration and deceleration of the lift car will have to be carefully designed in order to ensure passenger comfort. For very tall buildings, splitting the building into several different service levels will be the answer. There are also suggestions to use double-deck lifts for tall buildings in recent devleopments. Apart from saving space, the number of stops per ride could be cut to half. As an illustration, passengers will enter the lift cars at ground floor and first floor podium at the same time and the lift will serve the odd and even floors above respectivley.
Fire Safety Engineering
Although lifts do not normally play a role in the evacuation of building occupants, we do have fire lifts as a statutory requirement for tall buildings to be used by firemen. Recently, there are studies carried out on the use of lifts in case of fire, especially for those occupants with limited mobility. I am also aware that there are new developments in the international arena where lift designers adopt a risk assessment approach to quantify the threat and develop suitable mitigation measures, phased or total evacuation of building occupants.
Having gone through some general issues, I shall now focus on the environmental aspect and energy efficiency of tall buildings. The environmental features of buildings are often called the green features; and the buildings called green buildings or sustainable buildings.
Our Government has been advocating construction of green buildings and issued two Joint Practice Notes to encourage the adoption of green features in buildings, such as balconies, sky gardens, prefabricated external wall panels, etc. in new private building development since 2001.
For rooms with tall ceiling height such as hall, provision of openings could fairly often remove the stack effect of hot air and improve ventilation. Sun shade louvres can often be used to reduce direct sunlight and avoid glare. Cross ventilation through a building will be effective if windows are provided on both sides.
Provision of sunshade louvres at the Public Health Laboratory Centre at Nam Cheong Street has been proved to be very effective.
In tall buildings, the wind pressure can be very high on the upper floors creating air tightness on the facade. As you all know, single skin facade with non-openable windows will in general have poorer thermal insulation. Double skin facades will be better than the single skin, where the space between the two skins is ventilated through natural uprising air currents thereby, the amount of heat transferred into the buildings could be reduced. The double skin facades could also offer the additional advantages of noise reduction.
The environmental performance of a building is dependent on the thermal insulation of its external walls, thickness of floor slabs and window panels, type of facade and the roofing system. The Architectural Services Department has commissioned studies and come up with a Facade Rating Scheme and a Sustainability Rating System for metal roofs in terms of sustainable environmental performance. From these studies, several checklists of mandatory and selective criteria as well as spreadsheet tools are developed. This slide shows the construction details of a metal roof on the left and a green roof on the right. After inputting the parameters into the rating system, it can be seen that the green roof is more sustainable due to its lower life cycle cost and overall environmental benefits.
We should also pay attention to the indoor air quality (IAQ in short). People living in the city spend a lot of their time indoors nowadays, and the quality of indoor environment becomes increasingly important. To improve IAQ and promote public awareness of its importance, we have launched a voluntary IAQ Certification Scheme for Offices and Public Places since 2003. I am glad to say that many government premises, in particular tall buildings, and a significant number of private developments have actively participated in this scheme.
We have also issued guidance notes and publications to promote IAQ. These guidance notes outline innovative design to segregate contaminated area from clean area; selection of low emission building materials; provision of adequate outdoor air and ventilation for dilution; and elimination of contaminants such as bacteria; fungi, particulates, etc.
My final topic today is energy efficiency which is another important aspect for achieving sustainable development of tall buildings.
Electricity generation emits, among others, the bulk of the greenhouse gases produced locally. Reducing the consumption of electricity can directly improve the local air quality and help combat the problem of global warming. Air-conditioning accounts for roughly one-third of the total power consumption in Hong Kong and costs more than $10 billion every year. The Government has introduced a pilot scheme at designated areas to promote the wider use of fresh water in evaporative cooling towers for energy-efficient air-conditioning systems since 2000. This scheme would be suitable for new installations and those using the air cooled type air conditioning system. As at the end of October 2005, the cooling capacities and the gross floor areas for buildings completed under the pilot scheme have reached 217,000 kW and 1,284,000 m2 respectively. These cooling capacities would yield an annual energy saving of 20 million kWh, which is approximately equivalent to $18M. The greenhouse gas emission would also be reduced by 14,000 tonnes. It is estimated that an annual saving of 68 million kWh of electricity, which is equivalent to about $60M can be achieved upon completion of all those water-cooled air conditioning systems currently registered under the pilot scheme.
Recently, in order to echo the World Environment Day, my Bureau has urged the public to adjust their air-conditioning system so that the room temperature is maintained at 25.5oC in the summer months with a view to reduce the emission of carbon dioxide and to lessen the effect of global warming. Our Government has set an example in strictly implementing this energy-saving strategy among government offices. Colleagues are encouraged to dress light. The results are encouraging as positive feedback from the public on the scheme has been obtained.
The footprint for taller buildings can be reduced for the same aggregate floor area to allow the opportunity of maximizing the use of daylight. For perimeter zones of the building with daylight penetration, daylighting can be integrated with electric lighting to reduce energy consumption.
We have been advocating ongoing initiatives on environmentally responsible development by enhancing the use of energy efficient devices in building services installations and promoting wider adoption of renewable energy in public works projects.
We have also adopted an Overall Energy Approach in the design of new government buildings. There are guidelines issued on the maximum overall thermal transfer values for these buildings. All these control measures are designed to cut down the heat gain at building envelope and to reduce cooling load of the building. Our Government has also published four prescriptive and one performance-based building energy codes for building services installations in order to promote energy efficiency in buildings in Hong Kong.
We firmly believe that by changing the habits of use and improving the methods of design, construction, operation and maintenance of buildings, energy use per unit building floor area can be significantly reduced.
Building Environmental Assessment Methods
Much has been talked on the green features and environmental considerations of buildings. However, how can the greenness of a building be measured or assessed? Building Environmental Assessment Methods (called BEAMs in short) have emerged since the early 1990s and are now adopted in United Kingdom, United State and Hong Kong, with different national adaptations. The most common aspects used by BEAMs in measuring the sustainability of a building are energy, material, water, indoor environmental quality and land. These methods allocate points or credits under various assessment aspects and, depending on the score, different award levels or grades are given to the building under assessment. I am pleased to let you know that nine government buildings have been assessed to be excellent which is the top rating under HK-BEAM. These assessment methods are now extended to cover the concept of embodied energy which is an inventory of the materials used in the construction of a building.
With known energy for producing a unit volume of a particular material, we can then calculate the total energy used in the whole building, including the energy consumed in the construction process. With this embodied energy concept, we can then make a life cycle assessment of the energy consumption of a building.
Besides HK-BEAM, our Government has taken further steps to study the life cycle assessment and costing in a Comprehensive Environmental Performance Assessment Scheme (known as the CEPAS). CEPAS has now gained much wider attention of the industry. My Bureau has also commissioned EMSD, with the support of other relevant departments, to carry out study on the Life Cycle Energy Analysis of building works in order to promote the concept of sustainable construction. Developers and construction professionals can use the new software to assess the life cycle energy consumption of their buildings so as to minimize negative environmental impact.
To conclude, the adoption of energy efficient designs and the incorporation of renewable energy sources into new buildings and infrastructure projects have become a global trend in striving for a sustainable future. Designers of tall buildings should put more emphasis on green features, sustainability, and the economic benefits in terms of cost savings in materials and energy use during construction and operation.
I am aware that concurrent to this Conference, there is a Mini Symposium on Sustainable Cities with sub-themes on sustainable planning and design as well as energy efficiency and assessment methods. No doubt this Conference and the Mini Symposium will provide all of us with very good opportunities to learn more about what is happening in other countries and to draw upon the experiences of the speakers and participants in their specialties.
At the end of this Conference, I trust all of us will be able to gain further valuable insights on the latest trends and development on sustainability in the context of tall buildings.
Thank you for your attention.
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