188
cast-in- place concrete. The wood structural system consists of glulam columns and
beams. The floor system consists of CLT planks topped with a thin, reinforced layer
of cast-in-place concrete.
The benefit of an LCA study is the holistic look at environmental impacts across
a building’s life span in several different categories. This approach ensures that no
one category will suffer greatly at the expense of another (Athena 2019). However,
this can also be somewhat of a drawback when it comes to acting on the results of
the study. While one impact category may indicate that one option is the better
choice, a separate impact category may show the opposite. Factors including who is
carrying out a study and why may influence which impact categories priority is
given to. If this study was only concerned with GWP, then a wood structural system
would be the clear choice to use as it has the lowest impact using both Tally and One
Click LCA (Fig. 9.10). However, when taking a broader look at the project across
impact categories, it gets more challenging to figure out what the best decision to
make is.
When looking at the results from One Click LCA, a wood structural system is the
least impactful choice in all categories barring eutrophication where it was very
close to the values of concrete. In Tally, wood is only the least impactful choice in
GWP but is close to the other values in all impact categories except for eutrophication, which stands out significantly on the graph. It is worth noting that the numerical values do not even differ by one order of magnitude. Tally shows 1402 kg Neq
and 1247 kg Neq for steel and concrete, respectively, and 8277 kg O 3 for wood.
While this difference seems extreme on the graph, looking at the values themselves
tells a different story. Eutrophication does set wood apart from the other materials
in Tally, but not enough to outweigh the benefits in the other categories.
It can be very hard to negotiate the tradeoffs between environmental impact categories and reach a final conclusion. Several practitioners and tools, including
BEES and BIRDS, have recognized the challenge in negotiating the incompatible
impact categories, and many attempts have been made to combine the results of all
of the different impact categories into one overall score indicative of the total environmental impacts of the design (Kneifel and O’Rear 2018). Further discussion on
the benefits and drawbacks of this can be found in Sect. 8.6.2.
Overall, this study tested the assumption made that a steel structural system
would be the best choice because it could reuse the existing columns. However, the
majority of the steel was new, and this option ended up being more impactful than
switching to a concrete or wood structural system. The benefit of an LCA study can
be seen here, both in terms of quantifying (and disproving) assumptions as well as
taking a holistic look at the impacts of the building’s structure across several impact
categories.
9 Case Studies
cast-in- place concrete. The wood structural system consists of glulam columns and
beams. The floor system consists of CLT planks topped with a thin, reinforced layer
of cast-in-place concrete.
The benefit of an LCA study is the holistic look at environmental impacts across
a building’s life span in several different categories. This approach ensures that no
one category will suffer greatly at the expense of another (Athena 2019). However,
this can also be somewhat of a drawback when it comes to acting on the results of
the study. While one impact category may indicate that one option is the better
choice, a separate impact category may show the opposite. Factors including who is
carrying out a study and why may influence which impact categories priority is
given to. If this study was only concerned with GWP, then a wood structural system
would be the clear choice to use as it has the lowest impact using both Tally and One
Click LCA (Fig. 9.10). However, when taking a broader look at the project across
impact categories, it gets more challenging to figure out what the best decision to
make is.
When looking at the results from One Click LCA, a wood structural system is the
least impactful choice in all categories barring eutrophication where it was very
close to the values of concrete. In Tally, wood is only the least impactful choice in
GWP but is close to the other values in all impact categories except for eutrophication, which stands out significantly on the graph. It is worth noting that the numerical values do not even differ by one order of magnitude. Tally shows 1402 kg Neq
and 1247 kg Neq for steel and concrete, respectively, and 8277 kg O 3 for wood.
While this difference seems extreme on the graph, looking at the values themselves
tells a different story. Eutrophication does set wood apart from the other materials
in Tally, but not enough to outweigh the benefits in the other categories.
It can be very hard to negotiate the tradeoffs between environmental impact categories and reach a final conclusion. Several practitioners and tools, including
BEES and BIRDS, have recognized the challenge in negotiating the incompatible
impact categories, and many attempts have been made to combine the results of all
of the different impact categories into one overall score indicative of the total environmental impacts of the design (Kneifel and O’Rear 2018). Further discussion on
the benefits and drawbacks of this can be found in Sect. 8.6.2.
Overall, this study tested the assumption made that a steel structural system
would be the best choice because it could reuse the existing columns. However, the
majority of the steel was new, and this option ended up being more impactful than
switching to a concrete or wood structural system. The benefit of an LCA study can
be seen here, both in terms of quantifying (and disproving) assumptions as well as
taking a holistic look at the impacts of the building’s structure across several impact
categories.
9 Case Studies