Getting started with IFC import
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IFC in IDA ICE
IDA ICE interprets spatial and geometric information to reconstruct a representation of the building inside the application. This process does not attempt to reproduce the BIM model exactly as it appears in the authoring tool. Instead, the importer reads the available geometry, classifications, and spatial relationships, and converts them into a form that can later be used when preparing the simulation model in IDA ICE. The quality and structure of the IFC data therefore directly influence how accurately the building can be interpreted.
Units and Coordinate System
During import, units are read from the IFC file and automatically converted to the SI unit system. This ensures consistency across all imported elements and avoids ambiguity in dimensions.
The position of the model is interpreted relative to the IFC coordinate system. In many BIM workflows, models are positioned far from the origin due to survey or project coordinates. IDA ICE preserves this reference during import and provides tools that allow the model to be shifted later if needed.
If unit definitions are missing or inconsistent, scaling errors may occur in the imported geometry, affecting both the size and proportion of the building elements.
Building storeys
The overall structure of the building is derived from the IFC building and its associated storeys. IDA ICE imports the list of building storeys and the objects contained within each one, using this hierarchy to reconstruct the building level by level.
Each storey defines its elevation relative to the ground level, which is established by the IFC building and internally assumed to correspond to zero elevation. This information is used to position all elements at the correct height. If storey elevation data is missing, IDA ICE derives the vertical position from the local coordinate system of the storey.
For this interpretation to be consistent, all elements must be properly assigned to a single building storey. Walls should not extend across multiple storeys, and all elements associated with a storey must be contained within it. This organization ensures that the building can be reconstructed coherently and that elements align correctly across levels.
Building storey elevations. Source: buildingsmart.org
Spaces (IfcSpace) and Thermal Zone Preparation
Spaces, represented as IfcSpace objects, describe the interior volumes of the building and typically correspond to rooms or functional areas such as offices, corridors, or halls. IDA ICE imports these spaces primarily as intermediate elements used to generate thermal zones.
To keep the model manageable, space geometry may be simplified during import. Spaces are typically represented as prismatic volumes with a constant height, and small geometric irregularities may be removed. Holes or voids within space geometry are not interpreted and are ignored during import. As a result, spaces containing internal openings or complex shapes may be simplified into more regular volumes.
Each space must have a clearly defined name, such as “Office,” “Hall,” or “Meeting Room.”
After import, the user determines how spaces are used in the simulation model. Spaces may be converted directly into thermal zones, merged with other spaces, or used to define the overall shape of a storey.
Building Envelope Elements
Walls
Walls define the primary structure of the building envelope and play a central role in both geometry and thermal modeling. They determine the location of opaque surfaces, host windows and doors, and contribute to the definition of the building body.
During import, wall geometry is interpreted and simplified where necessary. Walls are expected to be vertical, have constant thickness, and be defined by a clear center-line axis. If these conditions are not met, IDA ICE attempts to simplify the geometry into a supported form. In cases where a clear axis is not defined, it may be derived from the wall geometry, which can introduce approximations.
Walls must be classified as internal or external, as this distinction is required for defining the building body. In addition, each wall must include a construction type, which is used to assign thermal properties in the IDA ICE simulation model. These construction types are mapped to resources in IDA ICE and using clear and consistent definitions improves both the efficiency of model setup and the reliability of simulation results.
All walls must be contained within a single building storey. This requirement ensures a consistent building structure and allows dependent elements to be interpreted correctly during the import process.
Slabs and Roof Elements
Slabs define horizontal building elements such as floors and roofs. These elements establish the vertical boundaries of spaces and contribute to the definition of the building envelope.
Each slab must include a construction type, which is used to map it to the appropriate thermal properties within IDA ICE. Roof elements are particularly important, as they must cover all storeys that are not overlapped by another level. This ensures that the upper boundary of the building is correctly defined.
Windows and Doors (Openings)
Windows and doors define openings in the building envelope and are interpreted in relation to their host walls. They must be contained within walls via properly defined openings. Standalone windows or doors are not supported and cannot be interpreted correctly by IDA ICE.
The placement of openings depends on the relationship between the opening and its host wall. The local coordinate system of the opening must correspond to that of the wall. If this relationship is not correctly defined, IDA ICE cannot determine the position of the opening, and the element is not imported.
Openings must also lie completely within the boundaries of the wall. If they extend partially or fully outside the wall, they are either partially ignored or removed entirely.
During interpretation, openings are simplified into regular geometric forms, typically rectangular volumes aligned with the base of the wall. This simplification ensures consistency and robustness in subsequent modelling steps.
Windows must include a construction type, which is used to define glazing properties within the simulation model. Similarly, doors define opening geometry and must also be associated with wall elements.
Curtain Walls and Complex Façades
Curtain walls are commonly used in BIM tools to represent glazed façade systems. However, IDA ICE does not include a dedicated curtain wall object. As a result, curtain walls must be interpreted using existing element types.
In practice, curtain walls should be exported as combinations of walls and windows. Only simple segmented curtain wall geometries are reliably supported. If curtain walls are exported as a single object without additional information, they are typically interpreted as opaque walls. Using the Simplebim IDA ICE add-on, a special Is Transparent property can be assigned so transparent plates can be imported as windows.
Building body Interpretation
Building bodies are not explicitly defined in IFC in the same way they are used in IDA ICE, so they must be derived from the available geometry and spatial relationships. The importer attempts to determine the building outline primarily from walls identified as external. However, since the classification of walls as internal or external in IFC data is often unreliable, alternative strategies may be applied, such as using all walls to establish the building envelope when necessary.
This is why the import settings described in the next section play an important role: they influence how storey boundaries, roof geometry, spaces, envelope elements, and building bodies are interpreted when the IFC model is brought into the application.
Shading and Auxiliary Geometry
IFC models may include additional elements such as surrounding buildings, trees, or external shading devices. These objects can influence simulation results by affecting solar gains and shading conditions.
While such elements can be imported as geometry, IFC does not provide detailed optical properties such as reflectance or transmittance in a way that can be directly used in IDA ICE. As a result, these objects are primarily used for geometric context rather than detailed physical simulation.
Other auxiliary elements, such as columns, beams, or furniture, may also be imported. These are typically used for visualization or shading calculations rather than for defining the thermal model.
Styles, Naming, and Property Mapping
During import, IDA ICE preserves style names, construction types, and other identifiers when they are available in the IFC model. These names play an important role in linking the imported geometry to simulation data.
For example, elements with the same style name can be mapped to a single construction or glazing system within IDA ICE. This allows the user to assign properties consistently across multiple elements.
Clear and consistent naming conventions significantly improve workflow efficiency and reduce the amount of manual work required after import. They also contribute to a more reliable and understandable simulation model.