CH-24-C002 - Existing Building Decarbonization Optimizing GHG Reduction

ABSTRACTThe built environment generates 40% of the annual global CO2 emissions. According to Architecture 2030, 2/3 of the building stock in 2040 will be buildings that already exist today. We cannot exclude this existing building stock when we tackle decarbonization globally and still further, the rate of upgrades and interventions has to be accelerated to meet some of the decarbonization targets the building industry has set for itself. To put existing buildings on a path towards decarbonization, retrofits must not only include implementation of energy conservation measures to reduce overall building load but also shifting the source of energy to fossil-fuel free solutions and adopting renewable sources of energy for generation. According to CBECS 2018, out of the 25 billion square feet of commercial building stock in the Midwest , 17 billion square feet or 66% of the buildings by area rely on natural gas as the primary space-heating energy source while only 18% relies on electricity as the primary space-heating energy source. In order to put these fossil-fuel dependent existing buildings on a path towards decarbonization, there is a need to explore a widespread approach to implementation of energy conservation that can also address electrification. In this study, several energy conservation measures to improve the performance of the envelope are analyzed to first evaluate if building loads can be reduced so that existing electrical infrastructure during an electrification retrofit can be maintained. The envelope measures are then applied to existing buildings with three types of common mechanical systems that use fossil fuels including natural gas boilers, packaged heating units and district steam. Since retrofit of buildings is dependent on resources available, the study groups intensity of retrofits and reviews the associated impact of greenhouse gas reduction over time with changes to the electric grid. This allows decision makers to evaluate different options for the mechanical plant to be upgraded either at a component level without retrofitting the associated piping and zone level equipment or a complete upgrade to the mechanical system. It also provides insights to owners and decision makers on the need and benefit for comprehensive retrofits for both envelope and HVAC upgrades while optimizing for the greatest reduction in greenhouse gas emissions.