LIFE CYCLE CARBON CALCULATIONS AND PARAMETRIC ANALYSIS OF HVAC SYSTEMS IN A NET-ZERO ENERGY BUILDING

Abstract

Labelled the enabler behind Singapore’s success, air-conditioning systems are often the centre of attention when it comes to reducing carbon emissions in Singapore. Especially so in a landscape where there has been a disproportionate focus on reducing operational carbon emissions, there is importance in promoting equal emphasis on both embodied and operational carbon emissions in HVAC systems. This research adopts a “Cradle-to-Grave” system boundary, with the scope being limited to the product and use stage. A life cycle carbon emission quantitative analysis is carried out on different types of HVAC systems, like the variable air volume (VAV) system, Dedicated Outdoor Air System (DOAS), and the Active Chilled Beam (ACB) system, and their findings are compared against each other. These following HVAC systems were simulated within a real-life net-zero energy building (ZEB) in Singapore through the use of EnergyPlus™, a building energy simulation program, before having their carbon emissions quantified via a series of meticulous methodologies proposed in this study. With the DOAS system emitting the most life cycle carbon emission, this study challenges and proves that the most energy efficient HVAC systems are not always the most carbon efficient, though it is commonly regarded as so. A parametric analysis on 2 system variables was also conducted to ascertain the significance of these variables and how they can affect the carbon emissions of the various HVAC systems, and subsequently how it alters the conclusion of this dissertation. This paper serves as a foundational study that helps propagate the importance of efforts during the inceptive period of a building’s design phase to target carbon hotspots that can be in the form of high emission materials or processes. It also contributes to the understanding of life cycle carbon calculations surrounding HVAC systems in the context of Singapore.