Natural ventilation study of the National Library Building

Abstract

The National Library Building (NLB) is one of the pioneer landmark projects undertaken when the Building and Construction Authority (BCA) launched the BCA Green Mark Scheme in 2005. The NLB received many awards for its green features, which include the BCA Green Mark Platinum Award. An interesting green feature of the NLB is its design for natural ventilation, with provisions like planning and site layout, laneway sunshades and computational fluid dynamics (CFD) study. The emphasis of this study will be on the natural ventilation of the NLB, with a focus on the thermal comfort aspect. The objectives of this study include evaluating the performance of NLB’s natural ventilation through objective and subjective measurements, conducting a comparative study of natural ventilation under different conditions, making comparisons between the objective and subjective assessment, and linking the study results to possible design considerations for natural ventilation. For objective measurements, instrumentation was conducted to collect data on the indoor and outdoor environmental parameters. The indoor environmental parameters were used to compute PMV and PPD. For subjective measurements, thermal comfort survey was conducted to compute TSV, comfort votes and other variables. For different conditions, different levels of the NLB and different times of the day were selected. Three areas were chosen, namely the Open Plaza (Level 1), the Courtyard (Level 5) and Outside Open Plaza (Level 1). The Open Plaza and Courtyard are directly under NLB’s natural ventilation, while Outside Open Plaza is close to the effects. Morning, afternoon and evening sessions were conducted. The overall findings from the objective and subjective measurements show that the Courtyard and Outside Open Plaza have warmer thermal environment than the Open Plaza. The Open Plaza has a cool thermal environment and its actual overall air-speed is higher than the simulation results and BCA’s guidelines. In-depth analysis of the objective and subjective data was done, which include regression and spotting of trends and correlations. They will be discussed in more details in this study. Recommendations to further improve this study and design for natural ventilation were highlighted as well.