Civil Engineering Reference
In-Depth Information
(EU) is the Directive
2002
/91/EC on the energy performance of buildings (EPBD),
which promotes the required measures to increase the energy performance of the
buildings for all the EU member states and introduces environmental performances
as the most relevant driving force for energy saving in buildings (climate change,
resource depletion, toxicity, etc.). Moreover, the EU Directive
2006
/32/EC
encourages energy efficiency by means of the development of the energy service
market and the delivery of energy efficiency strategies and measures addressed to
end users.
The Directive
2010
/31/EC (known as the EPBD recast) strengthens the energy
performance requirements promoted in the Directive
2002
/91/EC and clarifies
some of its provisions and goals to reduce the large differences among the member
states' practices.
According to the EPBD recast, all new buildings should be built as nearly zero
energy buildings within 2020. Furthermore, a particular highlight is addressed to
the retrofit of existing buildings. In fact, the EPBD recast prescribes that suitable
measures should be taken by the EU member states to decrease the energy demand
of the existing buildings through retrofit actions addressed toward the target of
nearly zero energy buildings. With this regard, the directive defines ''nearly net
zero energy'' a building that has a very high energy performance and whose
amount of energy required should be covered to a very significant extent by on-site
or nearby renewable sources. Since no minimum or maximum harmonized
requirements are given, as well as details of energy performance calculation
framework, it will be up to the member states to define what for them exactly
constitutes a ''very high energy performance.'' However, until now, the Net ZEB
concept has not been implemented yet in national building codes and international
standards, owing to the lack of a consistent definition and a commonly agreed
energy calculation methodology (Cellura et al.
2011
; Salom et al.
2011
).
The idea of a Net ZEB arises from the development of design criteria and
construction methods, addressed to curb the operating energy, increasing the
energy efficiency of building equipment and appliances, and of the thermal insu-
lation of envelope components, and enhancing the on-site energy generation, by
means of renewable sources, to cover the annual building energy loads.
Until recently, only operating energy has been considered in many literature
studies, owing to its significant share in the total life cycle energy consumption
of a standard building (70-90 %) (Napolitano et al.
2012
; Chen et al.
2001
).
Conversely, embodied energy of building materials and components has been
traditionally neglected when performing building energy analysis, as in standard
buildings, it amounted to a small fraction of the life cycle energy consumption
(10-20 %). This made most building regulations and directives overlook this issue
(Hernandez and Kenny
2010
).
However, from a life cycle perspective, when shifting from standard houses
toward low-energy buildings, the relative share of operating energy decreases,
while the relative share of embodied energy increases (Dixit et al.
2010
;
Gustavsson and Joelsson
2010
; Ardente et al.
2008, 2011
). Therefore, the lower
the operating energy, the more important it is to adopt a life cycle approach to
