Embodied Carbon of Heating, Ventilation, Air Conditioning and Refrigerants (HVAC+R) Systems

Abstract

This dissertation expands on preliminary studies of embodied carbon in building systems in commercial office buildings and aims to advance the understanding of the role that heating, ventilation, air conditioning, and refrigeration (HVAC+R) systems play in whole building life carbon. Previous studies on embodied carbon in buildings using Whole Building Life Cycle Assessment (WBLCA) have developed the understanding of this topic over the last years. However, these studies have focused primarily on estimating the embodied carbon of manufacturing (life cycle stage A), rarely including maintenance, energy use, or end-of-life impacts. In addition, most of these studies have focused solely on estimating carbon embodied in the structural system of the building, seldom considering mechanical, electrical, and plumbing (MEP) systems, tenant improvements, or site development impacts. Thus, this dissertation aims to fill in the gap regarding the estimation the HVAC+R component of MEP across the whole building life cycle. This dissertation seeks to answer the following research question: What is the contribution of individual equipment and distribution material types in typical HVAC+R systems for commercial office buildings of the Pacific Northwest (PNW) relative to total embodied carbon and in relation to the impact of the use phase (replacement and maintenance). In order to answer this question, an observational study design using a mixed methods triangulation approach was completed. The first study involved the development of a systematic framework to assess embodied carbon in HVAC+R. This exploratory qualitative research stage included a systematic literature review of existing WBLCA methods and participation of an advisory committee to assess the embodied carbon of HVAC+R systems in 16 hypothetically representative office buildings and 20 existing high-performance buildings registered under LEED v3 2009 in Washington State. Finally, a third study assessed the embodied carbon of HVAC+R in one “in depth” case study using an alternative method to assess material quantities . Three contributions of this dissertation to the literature of the field are: a) development of a systematic framework to estimate embodied carbon of HVAC+R systems in buildings, b) a database of embodied carbon of HVAC+R systems and their equipment, c) and a typical range of embodied carbon of HVAC+R systems, including refrigerants, in commercial office buildings in the PNW