Each building type in Carbon Designer 3D comes with its own assumptions: window and balcony areas, building and roof shapes, the number of stairs and elevators, and above all the spacing of internal walls and columns. This article explains how to model buildings that do not fit neatly into one building type, such as mixed-use buildings, parking structures, buildings with floors of different sizes, and reference designs built from a proposed design.
Choose your approach
There are two ways to model a complex building. Start with the first whenever you can.
Approach | When to use it | Why |
One design, adjusted | The building parts share a similar structural grid and building parameters | All information stays in one calculation, so there is less risk of counting elements twice |
Split and merge | Parts of the building differ a lot, for example industrial floors below residential floors | Each part gets the building type that fits it |
One design, adjusted
Select the building type that best represents the whole building. Then adjust individual parameters where the building differs, such as window area or internal wall area.
Split and merge
Model each part of the building as its own design, with the building type that fits it.
Create a new design for the whole building.
Copy the data from each part into it: on the project page, go to Input data and select Copy data from another design.
Remove anything counted twice. The scenarios below explain what to check for each case.
Alternative: when you save a part from Carbon Designer 3D, choose Merge with existing project design to combine it with a design already in your project. The same double-counting checks apply.
Every design needs at least one above-ground floor. You cannot model an underground garage on its own as one part.
Mixed-use buildings
Different uses on different floors
Recommended: use one design with the most representative building type, and adjust parameters for the floors that differ.
If the floors differ a lot: model the upper and lower floors as separate designs and merge them into a third.
Watch out for:
In the design for the upper floors, remove the foundations and ground slab.
In the design for the lower floors, remove the roof slab and add the same area as floor slab.
Different uses on the same floor
Recommended: use one design with the most representative building type, and adjust parameters where needed.
If the parts differ a lot: model each part as its own design and merge them into a third.
Watch out for:
The wall that separates the two parts is not an external wall. Do not count it as one in either design.
Columns and beams along the dividing line belong in one design only.
Check that the total number of stairs and elevators is right.
Floors of different sizes and shared floors
Floors of different sizes
Recommended: model the whole building in one design.
If you prefer separate designs: model the floors separately and merge them into a new design. Check foundations, ground slab and roof slab as described under Different uses on different floors.
Mezzanine floors: if a mezzanine covers only part of a floor, leave it out of the floor count and floor height. Instead, add its quantities manually, for example as extra slab area and column and beam lengths under Building structures. Match the extra slab area to a suitable construction.
A floor shared by several buildings
Recommended: split the shared floor’s area between the buildings.
Watch out for:
The sides of the shared floor where buildings meet are not external walls.
Spread the elements on those sides evenly between the buildings, and count each one only once.
Parking and underground structures
Underground parking larger or smaller than the floors above
Recommended: use the dimensions of the above-ground part of the building. Then adjust, as a minimum:
The underground wall areas and ground slab, to match the underground floor.
The foundations area, to cover the building’s full footprint.
Parking as a separate building
There is no parking building type. Choose another building type and adjust its dimensions and building part areas. The industrial building type is often the closest fit, because it assumes large open spaces and no balconies.
Watch out for:
Reduce doors and windows to what the structure actually has.
Adjust the flooring and ceiling types.
Check that the default structure meets your requirements.
Calculate ramps separately and add them to the design, then reduce the slab area by the same amount.
Fully underground structures
Every design needs at least one above-ground floor. To model a structure with no floors above ground, include one above-ground floor and then remove what that floor adds. For example, remove its cladding and floor slab, reduce flooring, ceiling finishes, columns and beams by that floor’s share, and add the roof construction over the underground structure.
Parts not covered by Carbon Designer 3D
Some parts of a project, such as open-air parking or building equipment like heating devices, are not generated by Carbon Designer 3D.
Recommended: add them directly in the design before your final calculation, and lock them so that later changes to the design do not overwrite them.
For parts you use often: create a standard construction once, for example outdoor parking per square metre. Next time, you only need to enter the area.
Reference designs
Some assessments compare a proposed or as-built design against a reference building. Instead of using a reference building from Carbon Designer 3D, you can build the reference from your own design so both share the same geometry.
Build a reference from your proposed design
Import or model your proposed or as-built design in Carbon Designer 3D.
Copy the design.
In the copy, replace the materials with generic, typical materials for the region, for example a standard concrete class instead of a specific product. This copy is your reference.
Document comparability
To show that the reference and the proposed or as-built design are comparable:
Export the material lists to show that both have comparable frame types and main elements.
Report key characteristics for both, such as gross floor area and number of floors.
Use the same LCA parameters for both designs. This is automatic when both designs are in the same project.
Record every assumption you made when modifying the reference.
Frequently asked questions
Should I use one design or several?
One design whenever the building parts share a similar structural grid. Split into several designs only when parts differ a lot, and check for double counting when you merge them.
How do I merge designs?
Create a new design, then on the project page go to Input data and select Copy data from another design for each part.
Alternatively, when you save a design from Carbon Designer 3D, choose Merge with existing project design.
Can I model an underground garage on its own?
No. Every design needs at least one above-ground floor. See Fully underground structures above.
Is there a parking building type?
No. Use another building type, often industrial, and adjust it. See Parking as a separate building above.
Related articles
Article | Read it when |
You are new to Carbon Designer 3D or want the full workflow | |
You want operational energy and carbon alongside embodied carbon | |
You already have an IFC model of the building | |
You want to know how regional baselines are built and which data they use |