Portfolio retrofit evaluation: A methodology for optimizing a large number of building retrofits to achieve triple-bottom-line objectives

Abstract Buildings account for approximately 40% of the total energy consumption and associated GHG emissions globally. As buildings age and energy codes become more stringent, significant investment is required to bring their performance in line with market expectations and competition for newer, more sustainable buildings. In large portfolios, the challenge is not only to identify the optimal building retrofits, but also which buildings have the most improvement potential. This paper presents a methodology to overcome this challenge. First, the building portfolio is screened using available data; potential energy improvement potential and commercial improvement potential are ranked to identify priority buildings. Second, a series of retrofit bundles (combinations of energy conservation measures and other improvements) is tested on the priority buildings to calculate estimated energy savings, undertake financial analysis and property/portfolio value impact, evaluate risks, and evaluate qualitative indicators affecting occupant comfort to inform a development appraisal or renovation business case. These estimates are refined using an energy model for the most promising retrofit bundle. Non-priority buildings are improved using portfolio-wide strategies to take advantage of low/no-cost interventions. Four global case studies using this framework are presented: two at the portfolio scale and two at the building scale. In each case, the modelling approach and data used in this decision-making are described and resulting project recommendations are presented. Although developed primarily for commercial buildings, this approach is applicable to all building types and recommendations are offed for its adaptation across sectors.