Methodologies for calculating annual energy use of buildings
are well developed and used throughout the world. Energy use
calculations have evolved from steady state heat loss and semistatic
monthly energy demand calculations to complex dynamic
energy performance simulation tools which can model annual
energy use over very short intervals (hours, minutes, even to a
fraction of a second). Simulation programs have been compared in
various papers [42,43] and detailed building energy simulation
practice is extensive not only within the research community but
also in the building industry. International standards such as EN
ISO 13790:2008 ‘Energy performance of buildings—calculation of
energy use for space heating and cooling’ [44], which include
monthly calculations methodologies, are considered of sufficient
accuracy for application in energy certification. Although ideally
every energy use should be considered in a building energy
calculation method, factors such as plug-in loads and equipment
are generally excluded in some calculation methods, particularly in
energy rating and certification methods. The methodology
presented in this paper does not restrict the calculation of annual
energy use to any particular methodology as it is suggested that
any validated building energy calculation method could be
expanded to include a ‘life cycle’ perspective as proposed. The
only pre-requisite for the application of the proposed methodology
is the conversion of the energy use results into ‘primary energy’
values. Some available software already provides results directly in
the form of primary energy using national average factors for the
different fuels used. Where the calculation tool does not directly
offer this possibility conversion factors for the different fuels used
need to be applied and implemented in accordance with national
guidelines. For countries which have no defined national primary
energy factors definitions can be found, for example, in EN
15603:2008 ‘Energy performance of buildings—overall energy use
and definition of energy ratings’ [45]. However it must be noted