can be used. A variety of typical building components including LCA data can be
found in many national catalogues, such as Bauteilkatalog [9] for Switzerland,
Milieuprofiel van gebouwelementen [10] for Belgium, or Baubook [11] for Austria.
The calculation of the LCA is carried out using a parametric model [12]. The
designer can typically influence three categories of parameters of a building:
geometry, materials and HVAC systems [12]. Each category consists of a number
of parameters, such as orientation, dimensions, window area, etc. for the geometry.
The parametric LCA approach combines the calculation of the operational and
embodied environmental impact. The operational impact results from the use phase
of the building (life cycle module B6 according to EN 15978 [13]) and is based on
an energy demand calculation using monthly energy balancing [14]. The embodied
impact results from the material production, replacements and the end-of-life (life
cycle modules A1–A3, B4, C3, C4, and D). The implementation of the parametric
LCA in a design tool such as Grasshopper [15] allows for a closed workflow of
input, calculation, output without requiring any importing/exporting [16]. This is
necessary for comparing variants automatically and is the basis for computational
optimization approaches.
The parametric approach allows an advanced user to define and adjust their own
weighting factors in order to consider the individual goals of the LCA study [16].
Furthermore, it allows for employing different predefined weighting factors, such as
those from building certification systems. The DGNB system provided by the
German Sustainable Building Council employs two criteria based on LCA and
awards points for each [17]. These are weighted and combined into one indicator
called life cycle performance (LCP) [18]. This single indicator ranges from 0 to 1,
with 1 being equal to 100% of the DGNB points related LCA criteria.
3 Case Study
In the following case study, the method is applied to the early design stages of a
hypothetical residential neighbourhood providing a total gross floor area (GFA) of
2500 m
2 . Between two and four buildings are located on a rectangular site in Potsdam,
Germany. The storey height of all apartments is 3 m, and the buildings do not have
basements. The floor area ratio (FAR) is set to 0.6 and minimum and maximum
dimensions are set to ensure reasonable sizing of the building volumes. The buildings
can have two to four floors and the glazing area is constantly 30% of the exterior wall
area. It is assumed that the net floor area (NFA) equals 0.8 Â GFA. The functional
unit is 1 m
2 NFA for 1 year, and the reference study period is 50 years. Both climate
and user data are taken from DIN V 18599-10:2011 [19].
It is assumed that the design process occurs in two stages, first definition of
geometry, and second choice of materials. The HVAC systems are not modified
parametrically but fixed. The heating system is set to a gas-condensing boiler with
an efficiency of 98%, no cooling is considered and the ventilation occurs naturally.
Design-Integrated LCA Using Early BIM
271
found in many national catalogues, such as Bauteilkatalog [9] for Switzerland,
Milieuprofiel van gebouwelementen [10] for Belgium, or Baubook [11] for Austria.
The calculation of the LCA is carried out using a parametric model [12]. The
designer can typically influence three categories of parameters of a building:
geometry, materials and HVAC systems [12]. Each category consists of a number
of parameters, such as orientation, dimensions, window area, etc. for the geometry.
The parametric LCA approach combines the calculation of the operational and
embodied environmental impact. The operational impact results from the use phase
of the building (life cycle module B6 according to EN 15978 [13]) and is based on
an energy demand calculation using monthly energy balancing [14]. The embodied
impact results from the material production, replacements and the end-of-life (life
cycle modules A1–A3, B4, C3, C4, and D). The implementation of the parametric
LCA in a design tool such as Grasshopper [15] allows for a closed workflow of
input, calculation, output without requiring any importing/exporting [16]. This is
necessary for comparing variants automatically and is the basis for computational
optimization approaches.
The parametric approach allows an advanced user to define and adjust their own
weighting factors in order to consider the individual goals of the LCA study [16].
Furthermore, it allows for employing different predefined weighting factors, such as
those from building certification systems. The DGNB system provided by the
German Sustainable Building Council employs two criteria based on LCA and
awards points for each [17]. These are weighted and combined into one indicator
called life cycle performance (LCP) [18]. This single indicator ranges from 0 to 1,
with 1 being equal to 100% of the DGNB points related LCA criteria.
3 Case Study
In the following case study, the method is applied to the early design stages of a
hypothetical residential neighbourhood providing a total gross floor area (GFA) of
2500 m
2 . Between two and four buildings are located on a rectangular site in Potsdam,
Germany. The storey height of all apartments is 3 m, and the buildings do not have
basements. The floor area ratio (FAR) is set to 0.6 and minimum and maximum
dimensions are set to ensure reasonable sizing of the building volumes. The buildings
can have two to four floors and the glazing area is constantly 30% of the exterior wall
area. It is assumed that the net floor area (NFA) equals 0.8 Â GFA. The functional
unit is 1 m
2 NFA for 1 year, and the reference study period is 50 years. Both climate
and user data are taken from DIN V 18599-10:2011 [19].
It is assumed that the design process occurs in two stages, first definition of
geometry, and second choice of materials. The HVAC systems are not modified
parametrically but fixed. The heating system is set to a gas-condensing boiler with
an efficiency of 98%, no cooling is considered and the ventilation occurs naturally.
Design-Integrated LCA Using Early BIM
271