by Jeffrey C Kadlowec, Architect
Abstract
Rapid urbanization is creating greater demands on engineers and infrastructure while straining resource supply and natural ecosystems. Growing economies are leading to construction delays and cost overruns. Research in project life cycle explores the cost benefits of these improvements. Green building and zero-energy goals come at a higher cost, but is necessary to reduce CO2 emissions and energy consumption. Globalization requires better understanding to compare the differences in material costs and labor prices. More attention must be focused on project performance in terms of budget, schedule and quality.
Keywords: cost comparison, urban development, life cycle assessment
Cost Comparison
The rapid growth of city centers around the world is creating new challenges for engineers and infrastructures. Increased pollution, urban flooding and water scarcity have become apparent over the past decades. Low impact development (LID), best management practices (BMPs), sustainable urban drainage (SUD), and water sensitive urban design (WSUD) are emerging as the prominent strategies to control urban runoff [Zhu 2022]. Bio-retention, green roofs, grassed swales, and permeable pavement are essential measures of a Sponge City (SC) in providing and maintaining natural ecosystems.
Life cycle assessment (LCA) and life cycle costing (LCC) measure and compare the environmental impact of urban development through four steps: 1) goal and scope definition, 2) inventory analysis, 3) impact assessment, and 4) result interpolation [Zhu 2022]. By quantifying life cycle inventory (LCI), designers and developers can analyze consumption, transport and emissions along with effects, cost and benefits (see Fig 1). Results concluded that residential areas have higher impact and benefit than campuses, are more complicated with lower cost-benefit ratio than campuses, and both provide a payback time of less than thirteen years with residential areas around 12.5 years and campuses about 6 years.
Figure 1. The framework of LCA combined with LCC method [Zhu 2022]
Growing economies and urbanization require infrastructure development, further increasing the importance of construction industries. Delays and cost overruns often arise during implementation, potentially resulting in project failure, reduced profits and loss of trust [Le-Hoai 2008]. Though time and price increases can occur at any phase, the major problems usually happen during construction. Research data ranks poor site management and supervision, poor project management assistance, financial difficulties of owner or contractors, design changes, unforeseen conditions, slow payment, and inaccurate estimates as the leading causes.
Purchasing power parity (PPP) is used to convert money amounts from various countries into a common currency. This method provides a baseline measurement for construction costs [Best 2012]. Understanding these difference both in material costs and labor prices is an essential part of accurate cost estimating. The basket of construction component (BOCC) approach breaks titems down into three levels: 1) project, entire building or facility; 2) system, structural, exterior, mechanical, etc; and 3) component, combinations of material or equipment [Walsh 2006]. Spatial cost comparisons rank income production and economic activity to determine standard of living and identify poverty levels.
The construction industry contributes 30% to global CO2 emissions and consumes 40% of total energy worldwide. According to studies and comparison of the two tallest buildings in the two most polluting countries, the Shanghai Tower produces over 2.5 times the carbon emissions as One World Trade Center [Nematchoua 2017]. Though recent environmental trends recommend zero-energy buildings (ZEB) and green buildings (GB), statistical cost models show no significant differences over conventional buildings (CB) [Hu 2018]. The higher initial costs of ZEB remain a barrier to implementation.
Public projects are funded by tax dollars and must be managed efficiently due to the higher level of accountability. This typically comes at additional cost to ensure successful outcomes in terms of quality and schedules. The following equations determine overall project performance, usually as a positive value, with 0 (zero) being on budget and without delay.
A third metric for quality can be assigned using the Likert scale ranging from 1 = Very unsatisfactory through 3 = Neutral to 5 = Very satisfactory [Ling 2018]. Comparison of data collected from public projects in Beijing, Hong Kong, Singapore, and Sydney resulted in Singapore having the lowest cost overruns and Hong Kong projects the highest. Projects in Beijing had the lowest schedule overruns and those in Hong Kong again the highest. The highest quality appeared in Sydney, with the lowest in Beijing. It can be agreed upon by most team members and project managers that focus should by towards delivering projects to the highest level of quality when working in the public sector.
References
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Le-Hoai, Long; Lee, Young Dai & Lee, Jun Yong. (2008). Delay and Cost Overruns in Vietnam Large Construction Projects: A Comparison with Other Selected Countries. KSCE Journal of Civil Engineering. 12(6): 367-377. 10.1007/s12206-008-0367-7.
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Zhu, Yifei; Xu, Changqing; Yin, Dingkun; Xu, Jiaxin; Wu, Yuqi & Jia, Haifeng. (2022). Environmental and economic cost-benefit comparison of sponge city construction in different urban functional regions. Journal of Environmental Management. 10.1016/j.jenvman.2021.114230.
