Civil Engineering Reference
In-Depth Information
3.2.1 Building's Life Cycle Energy Analysis
Buildings demand energy in their life cycle right from its construction to demolition.
Studies on the total energy use during the life cycle are desirable to identify phases of
largest energy use and to develop strategies for its reduction. Ramesh et al. (
2010
)
presented a critical review of the life cycle energy analyses of buildings resulting
from 73 cases across 13 countries. The study includes both residential and office
buildings. Results show that operating (80-90 %) and embodied (10-20 %) phases
of energy use are significant contributors to building's life cycle energy demand. Life
cycle energy (primary) requirement of conventional residential buildings falls in the
range of 150-400 kWh/m
2
/year and that of office buildings in the range of
250-550 kWh/m2/year. Building's life cycle energy demand can be reduced by
reducing its operating energy significantly through use of passive and active
technologies even if it leads to a slight increase in embodied energy. However, an
excessive use of passive and active features in a building may be counterproductive.
It is observed that low-energy buildings perform better than self-sufficient (zero
operating energy) buildings in the life cycle context. Worldwide, 30-40 % of all
primary energy is used for buildings, and they are held responsible for 40-50 % of
green house gas emissions. It is therefore essential for the building built environment
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 signifi-
cance for formulating strategies to achieve reduction in primary energy use of the
buildings and control emissions (Ramesh et al.
2010
).
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) include the
energy use of the following phases: manufacture, use and demolition. Manufacture
phase includes manufacturing and transportation of building materials and tech-
nical installations used in erection and renovation of the buildings. Operation
phase encompasses all activities related to the use of the buildings, over its life-
span. These activities include maintaining comfort condition inside the buildings,
water use and powering appliances. Finally, demolition phase includes destruction
of the building and transportation of dismantled materials to landfill sites and/or
recycling plants (Ramesh et al.
2010
).
A large variety of materials are being used in building construction. Some of
them may have a life-span less than that of the building. As a result, they are
replaced to rehabilitate the building. In addition to this, buildings require some
regular annual maintenance. The energy incurred for such repair and replacement
(rehabilitation) needs to be accounted during the entire life of the buildings. It is
the energy required for maintaining comfort conditions and day-to-day mainte-
nance of the buildings. It is the energy for heating, ventilation and air conditioning
(HVAC), domestic hot water, lighting and for running appliances. Operational
