Abstract
We analyze 100 case studies, which were conducted in 23 countries, and contrast their data on embodied and operational energy in residential and commercial buildings. The case studies include conventional, retrofit, low-energy, passive, and net-zero energy buildings. The buildings have different lifetimes varying from 25 to 100 years. We calculate the estimated total Life Cycle Energy (LCE) as the sum of Embodied Energy (EE) and Operational Energy (OE). The LCE in the 100 case studies ranges from 50.8 to 1840 MJ/m2 per year. Our results show that operational energy significantly dominates the life cycle energy of the buildings by an average of 419 MJ/m2 per year and an average share of 72%. The share of embodied energy increases with decreasing operational energy. However, the overall LCE decreases significantly when the operational energy decreases. Naturally, the assumptions on the lifetime of the buildings have a great impact on the LCE. We conclude that operational energy should be primarily reduced in order to decrease greenhouse gas emissions from the existing building stock because most of the buildings are already built and changes in the embodied energy are often obtained only through new construction or deep retrofit strategies. Depending on the strategy to decrease OE, the share of EE was found to show wide fluctuations within the case studies, ranging from 4% up to 100%. In addition, most of the operational energy consumption has been reported by using energy simulation tools. Only about 14% of the case studies had metered operational energy data. In order to create more accurate data, metering of buildings should be considered in future case studies.
Highlights
Buildings are considered a major source of greenhouse gas (GHG) emissions stemming from energy consumption during construction, operation, and demolition
The average EE and Operational Energy (OE) show that the EE of the retrofit buildings increased by 22%, but overall its Life Cycle Energy (LCE) decreased by 32%
The overall LCE decreases with decreasing OE for discussed 100 case studies
Summary
Buildings are considered a major source of greenhouse gas (GHG) emissions stemming from energy consumption during construction, operation, and demolition. 40% of energy-related Carbon dioxide (CO2) is emitted by buildings either directly via their operational energy (OE) or indirectly via the embodied energy (EE) [1]. OE refers to the energy consumed during the lifetime of a building after the building is occupied, while EE denotes the energy consumed in order to produce and transport building materials and install them in buildings. EE incorporates the energy consumed for renovation and demolition. As GHG contributes to climate change, emissions from the building stock have to be dramatically reduced to meet climate mitigation goals.
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