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| Environmental, Health and Safety Report 2003 / 04
Our Vision for Sustainable Housing | Message from the Chairman | Message from the Director | Summary | Feedback Form About this Report | Business Overview & EHS Management Structure | Significant EHS Aspects | 2003 / 04 Highlights | Performance Review | Targets and Initiatives for 2004 / 05 and Beyond | Verification Statement | Annexes |
Life Cycle Assessment and Life Cycle Costing In recognition of our environmental responsibilities to the community and the need for cost effectiveness, in 2003 / 04 we started research into Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) of building materials and components used in our domestic blocks. In LCA, a "cradle-to-grave" approach is adopted in which all environmental impacts arising from the manufacture, use and disposal of a product are quantified. These impacts include all extractions (i.e. resources) from, and all emissions (i.e. discharges) to the environment throughout the whole life cycle. The LCA process allows designers to compare options and make choices of building materials by taking life cycle environmental impacts into consideration. Taking a similar approach, LCC takes into account the expenditure on the building material during its maintenance and demolition stages on top of the initial capital cost. Our research will develop a decision-supporting tool that integrates environmental and economic considerations. By doing so we can select building materials that provide best value solutions from a long-term perspective, and thus contribute to achieving more sustainable building designs. Timber [Photo: Precast facade.] [Photo: Wooden plank produced by 'butt-jointing'.] One of our common good practices over the past decade has been the use of metal formwork, metal hoardings and semi-precast slabs and staircases in our projects - thereby reducing our timber requirements. Overall, in 2003 / 04 the use of metal formwork and precast concrete elements, such as precast external kitchen wall façades, enabled us to save over 28 500 tonnes of timber during the production of some 20 000 flats. This is equivalent to a timber saving per flat of approximately 1.4 tonnes and is consistent with our achievement in the year 2002 / 03. Moreover, we continue to investigate the potential to adopt alternative materials and technologies for substituting wooden materials to further reduce timber consumption. One example of a new technology for which we have conducted a small-scale trial in our housing blocks is "butt-joining" shortened pieces of wood to produce wooden planks. This reduces wood waste while the planks have also been proven to be both durable and fire resistant. We also require our contractors to use readily renewable softwoods in construction works in place of tropical hardwood. Pulverized Fuel Ash For many years we have required our contractors to use pulverized fuel ash (PFA) in concreting works wherever possible to reduce the volume of cement and to provide a suitable disposal option for the PFA residue from power stations. For example, in our foundation works we require contractors to replace the use of cement by 35% PFA. In cases where construction time is not critical, we also encourage the use of up to 25% PFA in some massive superstructure elements such as transfer plates, transfer beams, retaining wall, etc. We continue to use PFA in our construction works, although our cement saving in 2003 / 04 was lower than that in 2002 / 03 due to reduced construction activity.
Recycled Aggregates We insist on using recycled aggregates (RA) in our construction works to reduce the consumption of new aggregates and reduce our waste disposal requirements. In 2003 / 04, we increased our use of RA in construction sites year-on-year by 20%. We used around 700 tonnes for pipe surrounds, 90 tonnes for drainage and 2 260 tonnes for rock-fill in sub-base works. In April 2003, we extended our efforts in this area by specifying that all new contracts must adopt at least 20% RA in drainage and road works. We allow 20% RA in concrete for external walls, and are now monitoring the effectiveness of this initiative on our new construction sites. We also conducted a trial scheme in 2003 / 04 to adopt 20% RA in substructure works.
Precast Construction Materials [Photo: Precast materials.] We have been using prefabricated building elements in our construction projects for more than 10 years. Prefabricated materials adopted include staircase and slabs, façades, panel walls and door-sets. Trials adopting the use of volumetric precasting, which has the benefit of enhanced material and waste savings, started in 2003 and are presently being monitored. We will report on this initiative in next year's report. top |
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