Life cycle cost-based design of energy-efficient office buildings for sustainable urban transition in tropical cities

Office buildings are an expanding and prominent component of urban infrastructure. In rapidly urbanizing cities, they contribute significantly to energy consumption within the commercial sector. Despite their potential to support urban sustainability goals, the integration of energy-efficient design features is often hindered by misconceptions about high initial investment costs and perceived long payback periods. This study attempted to explore possible energy-efficient strategies and evaluate their economic performance throughout the building's life cycle to address this issue. Focusing on ten (10) low-rise office buildings in Colombo, Sri Lanka’s commercial capital, the research compares conventional building practices with energy-efficient features across four (04) design stages. The preliminary survey identified high initial cost and payback period as the two main hurdles for office building owners to move towards energy-efficient buildings. Results revealed that a conventional office building has an LCC of 700-1,000 USD/m 2 and an Energy Use Intensity (EUI) of around 250kWh/m 2 /annum. While energy-efficient buildings entail a 20–30% increase in initial construction costs and a 30-40% rise in maintenance costs, they also achieve a 20-25% reduction in overall life cycle costs with payback periods of just 3-4 years. The study identifies the Stage 4 platinum-level design as the most cost-effective and sustainable option. By demonstrating the long-term economic and environmental benefits of energy-efficient design, this research provides practical insights for urban planners, policymakers, and building industry stakeholders seeking to promote liveable, low-carbon cities.