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Equivalent functional unit in recycled aggregate concrete 295

results assigned to a given environmental category to common units, by assuming a
cause effect relationship.
The LCIA phase also provides information for the life cycle interpretation phase
(ISO, 2006a). Therefore, a compilation of the LCIA category indicator results for
all impact categories, or LCIA profile, should be compiled after characterisation.
The LCA of construction materials or assemblies, and buildings, provides quanti-
tative data (environmental impacts) that is essential in ensuring that the designer
chooses the most environmental-friendly options. However, LCA results for alterna-
tive construction products can only be compared if these products are functionally
equivalent, which means that they have similar technical and functional perfor-
mance. This is primordial in a design project where performance requirements are
preliminary defined; thus, defining a comparative benchmark for all functionally
equivalent alternatives evaluated for a given function. The ‘functional equivalent’ is
defined as the ‘quantified functional requirements and/or technical requirements for
a building or an assembled system (part of works) for use as a basis for comparison’
(CEN, 2013).
In the end, only a fair comparison between competing alternatives similar in
functional terms will allow achieving, at the design project:

The minimisation of the consumption of materials, energy and water.
The elimination or reduction of the use of hazardous materials.
The prevention or the minimisation of the emissions and waste.

11.2.2 Definition of the concepts of declared unit and functional
unit

For the LCI stage of a LCA study, it is necessary to define the declared (or the
functional) unit, which is directly related with the reference flow—related to mass
3
or volume (e.g., flows per kg or m of product)—that characterises each type of
plant where construction materials are produced. This unit is the reference for each
unit process considered in the inventory and all quantitative input and output data
of these unit processes (that, all together, constitute the production process of a con-
struction material) will be calculated in relation to this flow. Then, the flows of all
unit processes are related to the reference flow based on the system flowchart and
on the flows between unit processes. This guarantees that all the results of the cal-
culations are referenced to the declared (or the functional) unit of the product that
is to be modelled.
The functional unit is the ‘quantified performance of a product for use as a refer-
ence unit’ (ISO, 2006a) and should be selected based on ‘the way in which the identi-
fied functions or performance characteristics of the product are quantified.. .when
integrated into a building’ and on the product’s or building’s service life (CEN, 2013).
When the exact function of the product is unknown (or if it is a raw material
instead of a construction material), the declared unit is used instead of the func-
tional unit (CEN, 2013). The declared unit provides ‘the reference for combining
material flows attributed to the construction product’ (CEN, 2013).