4. Supplementing BIM data from external sources

4.1. Sources for supplementary data

BIM data is typically supplemented using external sources when BIM information is unavailable. Typical sources for supplementing information are:

Structural design documents with information on e.g.:
- Design of steel rebars e.g., 8-150 rebar net.
- Material details, e.g., Ready-mix concrete C30/37.
Architectural design documents with information on e.g.:
- Surface/room descriptions
  - Surface materials
- Paved and green areas and site constructions according to ground plan/site layout.
- Brick and mortar mass, calculated separately depending on the size and type of bricks.
- Mass of steel profiles in internal walls
- Box units (Assessment is challenging due to lack of available EPDs for box units)
- The number of elevators and escalators, building height does not currently impact the quantity of equipment (e.g. a 3-floor and a 10-floor elevator produce the same calculation outcome)
Building services design documents (when not included in the nationally predefined values):
- Masses of the building service components
- Large-size technical equipment, such as hospital equipment, is supplemented from other design documents.

Building services are included in the Finnish assessment methodology; Sweden and Norway leave out all technical equipment, and Denmark leaves most plumbing-related parts out from the calculations.

Energy reports and design documents, depending on the building's heating/cooling source (geothermal) and electricity source (e.g., solar panels).
- Area of solar panels
- Design specification of geothermal systems such as:
  - Length of geothermal probes
  - Effect of heat pumps

The area used in life cycle assessment varies by country and assessment method. Finland and Estonia use the heated net area from energy reports. Sweden and Norway use the gross floor area from building descriptions. Denmark uses the reference area for embodied emissions and the heated gross floor area for operational emissions. The used area should be included in the BIM model.

4.2. Material assumptions

When calculations require making assumptions about materials, the employed assumptions should be documented. Assumptions should be based on the best available knowledge and expertise, such as benchmark data or generic manufacturer estimates. LCA tools provide usable generic material assumptions that may be used in calculations when detailed information is unavailable.

4.3. LCA documentation

LCA reporting is done according to the national LCA reporting requirements or another applicable standard. The reporting requirement also applies to disclosing employed source data, scope, assumptions, and environmental product declarations (EPDs). The main assumptions should also be documented and provided transparently to the client with the LCA results.

It is recommended that the LCA expert keeps track of the employed data sources and supplements information in a manner that enables straightforward calculation revision. For example, if LCA calculations are first performed in an early design stage and the models are updated, the analyst can revise the sources of previous data and compare differences.