Civil Engineering Reference
In-Depth Information
change in the building sector (Voss et al.
2011
). Such a topic is addressed in the
EPBD recast, according to which all new buildings should be built as nearly zero
energy buildings within 2020 (Directive
2010
/31/EU). A particular focus is given
to the refurbishment of existing buildings, for which the EPBD recast prescribes
retrofit scenarios addressed to reduce operating energy.
This aspect is a key issue owing to the following topics of the building sector:
1. The turn-over rate of buildings is quite low and does not exceed more than 3 %
yearly (Eicker
2012
)
2. Buildings are the largest consumers of energy and account for about 40 % of
the total EU final energy consumption (Ardente et al.
2010
)
3. Environmental performances (climate change, resource depletion, toxicity, etc.)
are the most relevant driving forces for energy saving in buildings.
The goal of undertaking the energy and environmental assessment of building
retrofit actions is a complex matter. The energy use during the building operation
is influenced by several factors, such as climate, building envelope and other
characteristics, building occupancy and use, heating and air conditioning equip-
ment type and schedule (Cellura et al.
2010
). When a building undergoes a retrofit
project, the quantification of the related energy savings should include the fol-
lowing steps:
1. the assessment of the energy consumption of the technical equipment;
2. the assessment of the influence of significant variables (e.g. climate, building
occupancy, operation hours) on energy consumption;
3. the assessment of the energy consumption of the technical equipment after
retrofit, through post-retrofit monitoring or building energy simulations;
4. the calculation of achieved energy savings through a balance between the post-
retrofit energy uses and the pre-retrofit ones.
This approach is limited to the assessment of operation energy balances and is
not capable to deal with global energy and environmental benefits related to the
designed retrofit (Dixit et al.
2010
). The improvement of energy performances in
building operation still must be the primary goal of the design step to reduce the
operating energy demand, improving the thermal insulation of the building
envelope and the efficiency of energy devices, installing alternative energy using
systems and renewable energy technologies for heating, domestic hot water and
electricity generation (Beccali et al.
2011
; Lo Mastro and Mistretta
2004
). Nev-
ertheless, such measures could lead to an increase in embodied energy of build-
ings, which is embedded in building materials, transportation and construction
processes, and in the energy needed for demolition (disposal/recycling) (Beccali
et al.
2001
). Some studies show that 40-60 % of the life-cycle energy is used in
the production and construction phases (Ardente et al.
2008
).
The above considerations highlight the role of the life-cycle approach to per-
form a reliable and complete building energy and environmental assessment.
Designing an effective building retrofit requires an exhaustive study of all solu-
tions involving planimetric and volumetric changes and exclusion of the obsolete
