C14 -- A Case Study in the Tradeoffs of Operational and Embodied Carbon in the Design of a Near-Zero Energy Residence

In the need to reduce the total carbon usage of buildings much attention has been given to their operational carbon with less given to the embodied carbon of the building. However, as the operational carbon gets reduced, the embodied carbon becomes a much greater portion of the total long-term carbon budget of a building. There are tradeoffs between using products that have more embodied carbon to reduce the operational carbon and using products that use less embodied carbon (and currently use more operational carbon) but anticipate lower operational carbon electricity in the future. The purpose of this paper is to present a simplified case study to illustrate the importance and potential implications of these tradeoffs in a residence. An analysis is done of the embodied and operational carbon for 38 construction options in a prototypical energy-code-minimal house design located in Climate Zone 4 in the USA. The annual carbon to produce the electrical energy (operational) and the cradle-to-gate and B1 embodied carbon were calculated for 809 combinations of construction material options. Results of these combinations and assumptions of the rate of decarbonization of the electricity supply and the amount of refrigerant leakage were investigated to illustrate the sensitivity and relationship of the embodied and operational carbon.