necessary to deliver products and services, can effectively serve as
a form of ‘net energy’ analysis when compared to the energy used
by the building in operation over the life cycle. Probably the first
studies using this approach were those by Hannon et al. [25] in
which they used embodied energy values extracted from an inputoutput
model of energy flows through the US economy and
compared them with the typical energy use of family residences.
Most of the more recent studies use existing detailed LCA tools
such as SIMAPRO [26] or ATHENA[27], which offer the possibility
of analyzing, in detail, a wide range of environmental aspects of
materials including embodied energy, gathered in most cases
through life cycle inventory analysis such as described in ISO
14040 and relative standards [28]. A review of 60 case studies
where this type of analysis had been performed was carried out by
Sartori and Hestnes [29], highlighting the increasing importance
and relevance of this type of analysis as we move towards ‘lowenergy’
buildings. In buildings with a ‘zero energy’ balance in use
(energy delivered to a grid is equal to energy in use) the life cycle
energy is solely due to the process of delivering and maintaining
the building and its components. At this stage it is important to
clarify the definition of ‘zero energy building’, and ‘net-zero energy
building’.