ReviewLife cycle energy analysis of buildings: An overview
Introduction
Buildings are constructed for residential, office and commercial purposes all over the world. They are major contributors to socio-economic development of a nation and also utilize a large proportion of energy and available natural resources. Worldwide, 30–40% of all primary energy is used for buildings and they are held responsible for 40–50% of green house gas emissions [1]. It is therefore essential for the building construction industry to achieve sustainable development in the society. Sustainable development is viewed as development with low environmental impact, and high economical and social gains. To achieve the goals of sustainability it is required to adopt a multi-disciplinary approach covering a number of features such as energy saving, improved use of materials including water, reuse and recycling of materials and emissions control. Life cycle energy analysis of buildings assumes greater significance for formulating strategies to achieve reduction in primary energy use of the buildings and control emissions.
Section snippets
Life cycle energy analysis (LCEA)
Life cycle energy analysis is an approach that accounts for all energy inputs to a building in its life cycle. The system boundaries of this analysis (Fig. 1) include the energy use of the following phases: manufacture, use, and demolition. Manufacture phase includes manufacturing and transportation of building materials and technical installations used in erection and renovation of the buildings. Operation phase encompasses all activities related to the use of the buildings, over its life
Life cycle assessment (LCA)
LCA is a process whereby the material and energy flows of a system are quantified and evaluated. Typically, upstream (extraction, production, transportation and construction), use, and downstream (deconstruction and disposal) flows of a product or service system are inventoried first. Subsequently, global and/or regional impacts (e.g. global warming, ozone depletion, eutrophication and acidification) are calculated; based on energy consumption, waste generation, etc. LCA allows for an
Literature review
Buildings consume energy directly or indirectly in all phases of their life cycle right from the cradle to the grave and there is interplay between phases of energy use (embodied and operating energy). Hence, they need to be analysed from life cycle point of view. Bekker [3] highlighted that in the building sector a life cycle approach is an appropriate method for analysis of energy and use of other natural resources as well as the impact on the environment.
Later on Adalberth [4] presented a
Methodology
A literature survey on buildings’ life cycle energy use was performed resulting in 73 case studies from 13 countries. Survey included both office and residential buildings. An attempt is made in this paper to find the normal range of life cycle energy values (energy indicative figures) for conventional office and residential buildings and to distinguish low energy buildings from conventional ones based on the life cycle energy use. Data is collected for wood, steel, concrete and other
Results and discussions
Life cycle energy, operating and embodied energy use of residential and office buildings were calculated and normalised to kWh/m2 per year to neutralize the differences in building parameters like floor area and life span and are shown in Table A.1, Table B.1 in Appendix A.
Fig. 2 depicts the relation between life cycle energy and operating energy for 73 cases. It can be seen that the relationship between operating energy and life cycle energy of the buildings is almost linear despite climatic
Conclusions
The analysis of cases found in literature showed that life cycle energy use of buildings depends on the operating (80–90%) and embodied (10–20%) energy of the buildings. Normalised life cycle energy use of conventional residential buildings falls in the range of 150–400 kWh/m2 per year (primary) and office buildings in the range of 250–550 kWh/m2 per year (primary). Building's life cycle energy demand can be reduced by reducing its operating energy significantly through use of passive and active
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