A comparative sustainability assessment of standard housing blocks in Hong Kong and proposed integer concept tower alternative

This study is a comparative assessment of the relative sustainability of three Hong Kong 40-storey residential tower types: a housing authority "standard" Harmony Block (HAB), a private sector housing block (PSB), and the Integer Concept Tower (ICT) (50-year and 75-year life). The ICT is a demonstration project showing how a future residential tower of 40 stories might be designed and built for a more sustainable construction industry in Hong Kong. In this study, Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) are combined together to measure two of the three accepted environmental aspects of sustainability: economics and environment; using an internationally recognized methodology specially tailored to Hong Kong construction industry, including the South East Asia Region. According to the result study, the overall energy performance of the ICT lies between the HAB (0.22 MJ/m² CFA/annum/occupant) and the PSB (1.16 MJ/m² CFA/annum/occupant) with 0.95 MJ/m² CFA/annum/occupant over 75-year life, and when amortized over 75-year life its rate per annum is best with 563 MJ/m² CFA/annum (versus 709 for HAB and 750 for PSB). The annual rate per occupant of embodied energy is extremely efficient in the HAB. The ICT is the best performing building type for the waste indicator, over the 50 and 75-year life with respectively 19.45 and 12.51 dm³/m² CFA/annum (against 20.84 for HAB and 23.37 for PSB). The results show that the ITC is the overall best performing building with 129 and 107 CO2 kg/m² CFA/annum over 50 and 75-year life respectively, but the most striking aspect of the results is the predominance of the operational CO2 emissions. Also, the cost indicator appears to mirror the energy results. In this study, the ITC becomes the best performer over all the indicators in the 75-year life assessment, showing the importance of the following three main issues: longevity, allowing for better frame construction flexibility; energy efficiency, minimizing energy consumption and increasing the use of energy from renewable generation sources; and repair and maintenance regime efficiency, which affects the whole life cycle impacts. The Integer Concept Tower is definitely worthy of further investigation.