Exploring lifecycle energy and greenhouse gas emissions of a case study with ambitious energy compensation goals in a cooling-dominated climate

Abstract Achieving low operational energy (OE) consumption in high heating and cooling situations typically leads to well-insulated buildings. In those cases, embodied energy (EE) can exceed the operational share. Specific literature refers mostly to heating-dominated residential buildings, with a clear focus on European, Asian, and North American countries. Information on embodied impacts of buildings other regions is virtually inexistent. This paper aims at estimating lifecycle energy and greenhouse gases (GHG) emissions of selected design versions of a photovoltaic-powered Living Lab in Campinas, Brazil; and at finding the embodied-to-operational impact ratios as well as the main contributors to those overall impacts. Homer Energy software supported sizing of photovoltaic (PV) arrays for ten energy compensation scenarios to, based on simulated OE, determine the feasibility threshold for onsite generation admitted by the building design. We then modelled lifecycle energy and GHG emissions for the net zero (NZE) and threshold energy positive (E + ) versions of the case study design. The Cumulative Energy Demand (CED) and the CML 2001 v.2.05 methods supported embodied energy and global warming potential (GWP) calculations in SimaPro 7.3. The E + building compensates its OE plus non-renewable energy embodied in building products. Steel frame and partitions were the largest contributors to EEG in building products, whilst the insulated facade panels and PV array performed key energy performance roles at comparatively lower embodied impacts. Shifting from NZE towards E + status discretely increased the embodied-to-operational energy ratio (EE:OE), at similar embodied-to-operational GHG emissions (EG:OG) ratios. Pre-use share of lifecycle CED was slightly surpassed by the operational one, whilst responding for 60% of lifecycle GWP. Material replacement over the reference service life contributed significantly to operational impacts. EOL treatment had negligible effect on lifecycle impacts. EE more than tripled OE and embodied emissions exceeded OG by a factor of seven. EEG prominence confirms the crucial need for a harmonized calculation approach, as experienced for operational stage accountancy over the recent years. We acknowledge the high uncertainties involved in using simulated over measured OE consumption and in using foreign LCI databases. The former limitation can be solved by monitoring operational performance upon projects completion. This study offers practical and detailed reference for LCA practitioners in all countries facing the latter challenge, which will persist until integrated national LCI databases finally become available.

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