Reducing Life Cycle Embodied Energy of Residential Buildings: Importance of Building and Material Service Life

Abstract

Energy use in the building sector is considered among major contributors of greenhouse gas emissions and related environmental impacts. While striving to reduce the energy consumption from this sector, it is important to avoid burden shifting from one building life cycle stage to another; thus, this requires a good understanding of the energy consumption across the building life cycle. The literature shows greater emphasis on operational energy reduction but less on embodied energy, although both have a clear impact on the building’s footprint and associated environmental impact. In previous studies the importance these energy aspects have been presented; however, the critical role of embodied energy linked to the replacement of materials over a building’s life is not well documented. Therefore, there is a knowledge gap in the available the literature about the ways to reduce the embodied energy requirements of buildings over their useful life. Service life of buildings and their constituent materials may play an important role in this regard. However, their potential role in this respect have not been explored in the previous research. This study critically addresses the above-mentioned gaps in the literature by investigating the combined effect of building and material service life on life cycle embodied energy requirements of residential buildings. Life cycle embodied energy of a case study house for an assessment period of 150 years was calculated based on minimum, average and maximum material service life values for the building service life of 50, 100 and 150 years. A comprehensive input–output hybrid analysis based on the bill of quantities was used for the embodied energy assessment of the initial and recurrent embodied energy calculation for each scenario. The combined effect of building and material service life variations was shown to result in a reduction in the life cycle embodied energy demand in the order of up to 61%. This provides quantifiable and verifiable data that shows the importance of building and material service life considerations in designing, constructing, and managing the buildings in efforts to reduce energy consumption by buildings. A secondary contribution of this paper is a detailed sensitivity analysis which was carried out by varying the material service life values of each building material and the embodied energies for each new scenario was recalculated for two assessment periods. The findings show that, for each material service life variation, the LCEE increases as BSL increases for a 50-year assessment period, but the LCEE decreases for a 150-year assessment period.