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BIM Geometry Import in the Simulation Workflow

Building performance simulation requires a model that describes both the geometry of the building and its spatial organization. The workflow depends on understanding the shape of the building, the envelope that separates indoor and outdoor conditions, and the interior volumes that later define thermal zones. Without this spatial and geometric structure, the simulation model cannot be prepared in a consistent way.

One possible approach is to create this geometry directly inside the simulation environment. This gives the user full control, but it can also require substantial manual work, particularly when the building contains many spaces, several storeys, or complex envelope geometry. When a BIM model is available, IFC import provides a way to reuse part of the information that has already been defined during design. By importing an IFC file into IDA ICE, building geometry and spatial organization can be brought into the model and used as the starting point for simulation preparation.

This can make the early stages of the workflow more efficient because the imported model already contains a representation of the building layout and its main spatial structure. At the same time, it is important to understand from the beginning that a BIM model and a simulation model are not the same thing. A BIM model is primarily created for design coordination and documentation, while a simulation model must be structured so that it can represent the physical behavior of the building. Importing an IFC file therefore does not produce a simulation-ready model, but rather a base that must still be reviewed, adjusted, and further developed inside IDA ICE.

How Buildings Are Represented in IFC

To understand how IFC models behave when imported into IDA ICE, it is useful to understand how building information is organized in the IFC data model. In contrast to simple geometric formats, IFC represents buildings as structured collections of elements that combine geometry with information describing their role in the building. Each component is represented by an entity that belongs to a specific class, such as walls, windows, doors, slabs, and spaces. Because each entity belongs to a defined class, software can recognize the type of element it is interpreting rather than treating it only as an isolated shape.

An IFC model therefore contains more than geometry. It also carries semantic information that describes what each element represents, how it relates to other elements, and which properties are associated with it.

A key part of this structure is the spatial hierarchy. In a typical IFC model, the building is organized through a sequence of spatial containers such as site, building, building storey, and space. Building elements belong to storeys, while spaces represent interior volumes such as rooms or functional areas. This hierarchy is important because it allows software to understand not only what the elements are, but also where they belong within the building.

Each element also references one or more geometric representations that define its shape and location. As a result, an IFC model always contains both objects and geometry. Objects provide the semantic structure of the building, while geometry provides the physical representation of that structure. This distinction becomes particularly important during imports, because both aspects are interpreted inside the IFC environment of IDA ICE.

What Information IDA ICE Uses from IFC

An IFC model can contain a large amount of information describing many aspects of a building, including geometry, materials, classifications, construction data, documentation properties, and administrative information. However, only part of this information is relevant when preparing a building simulation model. During import, IDA ICE focuses on the spatial and geometric information needed to reconstruct the physical structure of the building and the interior volumes that will later be used in the modelling workflow.

Spatial elements play a central role in this process. Building storeys define the vertical organization of the building and provide the reference levels to which building elements are assigned. Spaces represent interior volumes that usually correspond to rooms or functional areas in the architectural model. When these spaces are present and well defined, they provide a clear description of the building layout and often become the most important reference for defining zones in IDA ICE.

In addition to storeys and spaces, IDA ICE interprets the main building elements that define the boundaries of the building and the divisions between interior spaces. Walls, slabs, windows, and doors are particularly important in this regard. External walls define the boundary between the indoor environment and the exterior, while internal walls define the partitions between adjacent spaces. Slabs define horizontal boundaries such as floors and ceilings and help establish the vertical limits of spaces and storeys. Windows and doors define openings in those boundaries and contribute to the understanding of façade and partition geometry.

Other IFC entities may also appear after import as geometric references. These can include beams, columns, stairs, railings, façade components, and site elements. They are not normally interpreted as building simulation elements, but they can still be useful as contextual geometry, for example when reviewing the imported model visually or when preparing shading-related geometry for later analyses. IFC information such as ownership data, documentation properties, and project administration attributes is ignored during import, as it does not contribute to building geometry or spatial organization.

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