The window is a building element that is predominately used to provide natural light and fresh air. It includes vertical opening but also horizontal opening such as skylights or light domes. It includes constructions with swinging, pivoting, sliding, or revolving panels and fixed panels. A window consists of a lining and one or several panels.

NOTE  Definition according to ISO 6707-1
Construction for closing a vertical or near vertical opening in a wall or pitched roof that will admit light and may admit fresh air.

The IfcWindow defines a particular occurrence of a window inserted in the spatial context of a project. A window can:

• be inserted into an IfcOpeningElement using the IfcRelFillsElement relationship, then the IfcWindow has an inverse attribute FillsVoids provided,
• be part of an element assembly, often an IfcCurtainWall, using the IfcRelAggregates relationship, then the inverse attribute Decomposes is provided.
• or be a "free standing" window, then the IfcWindow has no inverse attributes FillsVoids or Decomposes provided.

NOTE  View definitions or implementer agreements may restrict the relationship to only include one window (or door) into one opening.

There are two entities for window occurrences:

• IfcWindowStandardCase used for all occurrences of windows, that have a 'Profile' shape representation defined to which a set of shape parameters for lining and framing properties apply. Additionally it requires the provision of an IfcWindowType that references one IfcWindowLiningProperties and on to many IfcWindowPanelProperties.
• IfcWindow used for all other occurrences of windows, particularly for windows having only 'Brep', or 'SurfaceModel' geometry without applying shape parameters.

The actual parameter of the window and/or its shape is defined at the IfcWindow as the occurrence definition (or project instance), or by the IfcWindowType as the specific definition (or project type). The following parameters are given:

• at the IfcWindow or IfcWindowStandardCase for occurrence specific parameters. The IfcWindow specifies:
• • the window width and height
  • the window opening direction (by the y-axis of the ObjectPlacement)
• at the IfcWindowType to which the IfcWindow is related by the inverse relationship IsDefinedBy pointing to IfcRelDefinesByType, for type parameters common to all occurrences of the same type.
• • the partitioning type (single panel, double panel, tripel panel, more panels)
  • the operation type (swing, tilt and turn, pivot revolve, fixed case ment, etc.)
  • the window panel hinge side (by using two different styles for right and left opening windows)
  • the construction material type
  • the particular attributes for the lining by the IfcWindowLiningProperties
  • the particular attributes for the panels by the  IfcWindowPanelProperties

HISTORY  New entity in IFC1.0.

IFC4 CHANGE  The attributes PredefinedType and OperationType are added, the applicable type object has been changed to IfcDoorType.

Parameteric Representation using parameters at IfcWindowType

The parameters, which define the shape of the IfcWindow, are given at the IfcWindowType and the property sets, which are included in the IfcWindowType. The IfcWindow only defines the local placement. The overall size of the IfcWindow to be used to apply the lining or panel parameter provided by the IfcWindowType is determined by the IfcShapeRepresentation with the RepresentationIdentifier = 'Profile'. Only in case of an IfcWindow inserted into an IfcOpeningElement using the IfcRelFillsElement relatioship, having a horizontal extrusion (along the y-axis of the IfcDoor), the overall size is determined by the extrusion profile of the IfcOpeningElement.

Figure 261 illustrates the insertion of a window into the IfcOpeningElement by creating an instance of IfcWindow with PartitioningType = DoublePanelHorizontal. The parameters OverallHeight and OverallWidth show the extent of the window in the positive Z and X axis of the local placement of the window. The lining and the transom are created by the given parameters.

Figure 261 — Window placement

Figure 262 illustrates the final window (DoublePanelHorizontal) with first panel having PanelPosition = TOP, OperationType = BOTTOMHUNG and second panel having PanelPosition = BOTTOM and OperationType = TILTANDTURNLEFTHAND.

Figure 262 — Window planes

Window opening operation by window type

The parameters that defines the shape of the IfcWindow, are given at the IfcWindowType and the property sets, which are included in the IfcWindowType. The IfcWindow only defines the local placement which determines the opening direction of the window. The overall layout of the IfcWindow is determined by its IfcWindowType.PartitioningType. Each window panel has its own operation type, provided by IfcWindowPanelProperties.OperationType. All window panels are assumed to open into the same direction (if relevant for the particular window panel operation. The hindge side (whether a window opens to the left or to the right) is determined by the IfcWindowPanelProperties.OperationType.

NOTE   There are different conventions in different countries on how to show the symbolic presentation of the window panel operation (the "triangles"). Either as seen from the exterior, or from the interior side. The following figures show the symbolics from the exterior side (the convention as used predominately in Europe).

Figure 263 illustrates window operation types.

The window panel (for side hung windows) opens always into the direction of the positive Y axis of the local placement. The determination of whether the window opens to the left or to the right is done at IfcWindowPanelProperties.OperationType. Here it is a left side opening window given by OperationType = SideHungLeftHand. If the window should open to the other side, then the local placement has to be changed. It is still a left hung window, given by IfcWindowPanelProperties.OperationType = SideHungLeftHand. If the window panel (for side hung windows) opens to the right, a separate window panel style needs to be used (here IfcWindowPanelProperties.OperationType = SideHungRightHand) and it always opens into the direction of the positive Y axis of the local placement.  If the window should open to the other side, then the local placement has to be changed. It is still a right hung window, given by IfcWindowPanelProperties.OperationType = SideHungRightHand. .

Figure 263 — Window operations

The Door Attributes concept applies to this entity.

The Property Sets for Objects concept template applies to this entity as shown in Table 209.

The Object Typing concept template applies to this entity as shown in Table 210.

The Quantity Sets concept template applies to this entity as shown in Table 211.

The Material Constituent Set concept template applies to this entity as shown in Table 212.

The material of the IfcWindow is defined by the IfcMaterialConstituentSet or as fall back by IfcMaterial and attached by the IfcRelAssociatesMaterial.RelatingMaterial. It is accessible by the inverse HasAssociations relationship.

If the fall back single IfcMaterial is referenced, it applies to the lining and framing of the window.

The Spatial Containment concept template applies to this entity as shown in Table 213.

The IfcWindow, as any subtype of IfcBuildingElement, may participate alternatively in one of the two different containment relationships:

• the Spatial Containment (defined here), or
• the Element Composition.

The IfcWindow may also be connected to the IfcOpeningElement in which it is placed as a filler. In this case, the spatial containment relationship shall be provided, see Figure 264.

	NOTE  The containment shall be defined independently of the filling relationship, that is, even if the IfcWindow is a filling of an opening established by IfcRelFillsElement, it is also contained in the spatial structure by an IfcRelContainedInSpatialStructure.
Figure 264 — Window spatial containment

The Product Local Placement concept template applies to this entity as shown in Table 214.

The following restriction is imposed:

1. The PlacementRelTo relationship of IfcLocalPlacement shall point to the local placement of the same element (if given), in which the IfcWindow is used as a filling (normally an IfcOpeningElement), as provided by the IfcRelFillsElement relationship.
2. If the IfcWindow is not inserted into an IfcOpeningElement, then the PlacementRelTo relationship of IfcLocalPlacement shall point (if given) to the local placement of the same IfcSpatialStructureElement that is used in the ContainedInStructure inverse attribute or to a referenced spatial structure element at a higher level.
3. If the relative placement is not used, the absolute placement is defined within the world coordinate system.

NOTE  The product placement is used to determine the opening direction of the window.

The Profile 3D Geometry concept applies to this entity.

The window profile is represented by a three-dimensional closed curve within a particular shape representation. The profile is used to apply the parameter of the parametric window representation. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

• RepresentationIdentifier : 'Profile'
• RepresentationType : 'Curve3D', only a single closed curve shall be contained in the set of IfcShapeRepresentation.Items.

A 'Profile' representation has to be provided if:

• a parametric representation shall be applied to the window AND
• • the window is 'free standing', or
  • the opening into which the window is inserted is not extruded horizontally (i.e. where the opening profile does not match the window profile)