Embodied carbon workflow
The small steel model shown below will be used
to demonstrate the basic steps required to calculate, optimize and report embodied
carbon content. The model features 3 identical levels of composite slabs and rolled
I-section beams; columns are rolled I-sections and bracing is from circular hollow
sections. Wind wall panels have also been applied to each face.
Set up embodied carbon factors
Setting up and managing embodied carbon factor (ECF) values is the engineer's
responsibility. They can be set up from the Home ribbon by clicking:
Embodied Carbon FactorsThis displays the Embodied Carbon Factors dialog box. Depending on the regional code being worked to you will find sample ECF definitions will have been added for some of the categories. For example, if working to the United Kingdom (Eurocode) regional code, the following ECF definitions will have been added in the steel category.
Note: If working to the United States (ACI/AISC) regional code, it is understood that metric
units (as shown above) are more commonly required for carbon mass quantities than US
Customary units. Therefore these have been set as the default. You can however swap
carbon mass quantities back to US Customary units if you require. For details, see:
Define and modify units
Note: There is potentially considerable
variability/ uncertainty in ECFs - for example for concrete, many mix variations are
possible for every strength grade and all could be unique. Hence the sample ECFs are
included principally for guidance and are not a complete set - the engineer is
advised to review, edit and add to them as they need.
Many construction materials have ECF values that the engineer can use, and in addition manufacturers may also provide third-party verified Environmental Product Declarations (EPDs) which can be used when the engineer knows exactly which manufacturer the material will be sourced from.
To set up ECFs using the above dialog:
- You can add additional ECFs
using the Add factor button. Note: When adding factors, the values displayed in the Category filter and Entity filter on the main dialog are used as presets for the new factor. Apart from the category, each of these can then be adjusted if required within the Edit Factor dialog.
- You can remove ECFs using Remove factor.
- You can edit the description
and/or value of ECFs using Edit factor.
- Once defined, standard ECF values should be saved in global settings using Save... so that they can be applied to future models also. However there are some project specific ones (like cladding for walls and roofs) that you would not want to make available for all models.
- If you open an old model (i.e. one created before you established a global set of ECF values), initially the Embodied Carbon Factors dialog box won't contain any values, but you can click Load... in order to inherit any factors that exist as global settings.
By cycling through each category, you can quickly confirm that ECFs have been defined for all the entities in the model.
In this model, when the 'Cladding' category is reached a message is displayed in red text, as shown below.
This indicates that there are entities in the model (wind walls in this case) for which there are no defined factors in the current category. The message serves to highlight that the total embodied carbon mass of the structure may be incomplete until the factor has been added.
For this model this can be resolved by
clicking Add factor in order to define a suitable factor for the
cladding.
Clicking on OK, the factor is assigned to wind wall entities and the warning message is removed.
Related tasks
Manage how factors are applied to the model
Once the factors have been set up, the same dialog is used to manage how the ECFs in each category are applied to entities in the model.
You first select the main category you wish to view/edit at the top left e.g. 'Steel'. You can then review for this category the ECF list order, the description of each factor (which can be any variation of text and numbers etc) value, and the current number of assigned entities for each factor. This last figure is key to the management process and is circled below.
The current assignment of ECFs is a constantly active process, starting at the top of the list and working down, so the top factor has first priority and so on.
If certain factors are inappropriate for the current model they can be deactivated via the checkbox at the left of the factor to prevent them from being applied.
Once an entity in the model has a factor from the list assigned the process stops for that entity and category, hence there is no duplication of factor assignment within a category where lower (in the list) ECF definitions are also applicable.
Initially in this example 99 steel entities can be assigned to the factor at the top of the list, and the remaining 18 entities (the bracing members) can be assigned to the second factor on the list.
From here you might choose to reorder the list of factors to suit the current model by dragging factors upwards or downwards with the mouse. The assignment of factors updates automatically as edits are made - applicable factors at the top of the list always being assigned wherever possible in preference to factors occurring lower down the list.
To demonstrate, if the fourth factor in this example were dragged to the top of the list, the assignment of factors would automatically update as shown, with all 117 entities being able to be assigned to the factor newly positioned at the top of the list.
Note: There
is not a one-to-one relationship between model entities and ECFs - for example a
composite slab will have different ECFs assigned for its decking, concrete material,
and its reinforcement.
Note: Any changes to the list order, or amendments to the factors themselves will only
apply to the current model unless you choose to save them back to the global
settings set.
Related tasks
Review how factors have been applied
Probably the easiest way to review how the ECFs have been applied to the model is graphically in a Review View.
By stepping through the applicable carbon source categories you can quickly review how each of the factors have been applied.
An option is also provided here to apply overrides if required, (although preferably you should consider adding new factors instead using the Embodied Carbon Factors dialog box). Setting overrides is primarily recommended for entities that require different factors but are indistinguishable in terms of their data (and so cannot be assigned automatically) such as Roof/ Wind panels (in the “Cladding” category).
Note: There is not a one-to-one
relationship between model entities and ECFs - for example a composite slab will
have different ECFs assigned for its decking, concrete material, and its
reinforcement.
Related task
Examine embodied carbon overview
At an early stage you might choose to display the embodied carbon overview in a tabular data view. This is very useful because it rapidly provides a grand total of the embodied carbon mass for the entire structure.
The overview can grouped in a variety of ways as shown below.
-
Group by Construction Type
The total embodied carbon mass for each construction type is listed.
-
By Level - Summary
The total embodied carbon mass between one level and the next is listed.
i.e. - level 1 includes everything above foundation level up to and including items in level 1, level 2 includes everything above level 1 up to and including items in level 2, etc.
A total floored area is determined for each level and hence the embodied carbon per unit area can be reported for each story height of the building.
-
Group by Material
The embodied carbon mass is reported as a single total for each material. In the below example, Steel appears twice because there are two types of steel with different EPDs (i.e. they are considered to be different materials) - the same would apply to different concrete or timber grades.
-
Group by Plane
The embodied carbon mass is reported for each plane, items that not referenced to a specific plane being referenced as 'Other'. The total floored area and embodied carbon per unit area are reported for each plane.
-
Group by Level & Construction Type
This works in a similar way to By Level - Summary, but is broken down into the individual construction types that exist between one level and the next.
A total floored area is determined for each level, allowing the embodied carbon per unit area to be reported for each construction type for each story height of the building.
- Because the 3 floor levels in this model are identical, as expected items that exist in the identical level planes have identical carbon masses (e.g. the composite slabs).
- Items which exist between the planes are also assigned to a level:
- e.g. steel column stacks, braces and wind walls.
- These can be different at each level.
- Items that exist between reporting levels are assigned to the
level above:
- e.g. Braces and top stacks of columns assigned to level 3.
- Spans/stacks are not split - they are assigned to one level based on their highest point. (If a beam started below level 2 and finished above then it would be assigned to level 3.)
-
Wind walls do get split and are shared between levels as appropriate.
-
Group by Construction Type & Material
This works in a similar way to Group by Construction Type, but with the totals further broken down into individual materials, (so for example the steel total is separated for beams, composite beams, columns, braces, etc.)
Use of Level Properties 'Reporting Level' when grouping by level
In Level Properties there is a Reporting Level checkbox. Unselecting this affects how the overview is presented when using the Group by Level & Construction Type or By Level - Summary' options.
This is demonstrated in the below example showing the overview by level summary before and after switching off the Reporting Level checkbox at levels 1 and 3:
- Everything that was in St.1 and St.2 is now combined in the St.2 totals
- St.2 becomes the highest designated reporting level, everything above that level must be assigned to something so a “Top” level is used for that.
- Note that the overall totals are unaffected.
Reporting for specific construction types only
Clicking Toggle Selection in the ribbon switches between all construction types being selected and being unselected.
After unselecting, you can then choose specific construction types to be considered by choosing the required Material Types, Characteristics, Constructions and Fabrications.
This is demonstrated below - the overview is being grouped by plane, but is reporting the masses for steel beams only.
Related task
Display the overview data as a chart
The embodied carbon overview data can also be displayed in charts, with three types being available. Various settings are available to configure the appearance of each chart.
-
Embodied Carbon by Level
The total embodied carbon mass between one level and the next is displayed in a bar chart. One of the settings provided is to group by construction type if required (as shown below).
-
Embodied Carbon by Construction Type
The total embodied carbon mass for each construction type is displayed in a pie chart.
-
Embodied Carbon by Material
The total embodied carbon mass is displayed by material in a pie chart. In this chart materials with the same name but different carbon factors are combined.
Note: For this chart the "Merge segments contributing less than" setting defaults to 1.5%. Segments smaller than this value are displayed as "Other Materials".
Related tasks
Examine embodied carbon details
If you want to investigate where the values in the overview data table and charts have come from, you also have the option to display the embodied carbon detail for individual construction types in a tabular data view.
This can be displayed-
as a summary...
-
or, broken down to shown the separate components that contribute to the total for each entity...
Note: For steel members with pinned or fixed connections, the carbon mass of the connections at each end is determined as a percentage of that of the member. This percentage can be adjusted via Embodied carbon settings
Related tasks
Review utilization and embodied carbon
Once the model has been designed you can investigate the potential for optimizing utilization and embodied carbon in a Review View.
This view shows the embodied carbon usage for all, or selected entity types. It also has filters that can be configured to locate any parts of the model where high carbon usage coincides with low utilization.
Note: There is not a one-to-one
relationship between model entities and ECFs - for example a composite slab will
have different ECFs assigned for its decking, concrete material, and its
reinforcement.
Having rapidly identified inefficiency in this way, you can then consider the potential for optimizing your design in some way.
Related tasks
Create reports
Embodied carbon mass is automatically included in the Material Listing report.
Additionally, a separate Embodied Carbon report can be created which by default summarizes the embodied carbon in the model by level and by construction type.
Note: You can also include a table of
Embodied Carbon Factors in the same report if required, or group the summary by
plane, or by level & construction type.
Related tasks