The concept of a zero energy building is a significant sustainable strategy to reduce greenhouse gas emissions. The challenges of zero energy building (ZEB) achievement in Thailand are that the design approach to reach ZEB in office buildings is unclear and inconsistent. In addition, its implementation requires a relatively high investment cost. This study proposes a guideline for cost-optimal design to achieve the ZEB for three representative six-story office buildings in hot and humid Thailand. The energy simulations of envelope designs incorporating high-efficiency systems are carried out using eQuest and daylighting simulation using DIALux evo. The final energy consumptions meet the national ZEB target but are higher than the rooftop PV generation. To reduce such an energy gap, the ratios of building height to width are proposed. The cost-benefit of investment in ZEB projects provides IRRs ranging from 10.73 to 13.85%, with payback periods of 7.2 to 8.5 years. The energy savings from the proposed designs account for 79.2 to 81.6% of the on-site energy use. The investment of high-performance glazed-windows in the small office buildings is unprofitable (NPVs = −14.77–−46.01). These research results could help architects and engineers identify the influential parameters and significant considerations for the ZEB design. Strategies and technical support to improve energy performance in large and mid-rise buildings towards ZEB goals associated with the high investment cost need future investigations.
BIM-BEM support tools for early stages of zero-energy building design
