#### 8.8.3.5 IfcMaterialLayer

| Couche de matériau
| Materialschicht

IfcMaterialLayer is a single and identifiable part of an element which is constructed of a number of layers (one or more). Each IfcMaterialLayer has a constant thickness and is located relative to the referencing IfcMaterialLayerSet along the MlsBase.

> EXAMPLE A cavity wall with brick masonry used with an air gap in between would be modeled using three IfcMaterialLayer's: [1] Brick, [2] Air gap, [3] Brick. The inner layer "Brick" would have a Name = "Brick", an individual LayerThickness, and potentially a Category indicating it as "load bearing", and a Priority that controls how this material layer interacts with other material layers in wall connections.

The IfcMaterialLayer may have a material layer name which may differ from the IfcMaterial name referenced.

> EXAMPLE The IfcMaterialLayer name of an insulation layer can be "Insulation", whereas the IfcMaterial name is "polystyrene insulating boards".

> HISTORY New entity in IFC1.5

> IFC4 CHANGE The attributes Name, Description, Category, Priority have been added at the end of attribute list. Data type of LayerThickness relaxed to IfcNonNegativeLengthMeasure.

XSD Specification:

<xs:element name="IfcMaterialLayer" type="ifc:IfcMaterialLayer" substitutionGroup="ifc:IfcMaterialDefinition" nillable="true"/>
<xs:complexType name="IfcMaterialLayer">
<xs:complexContent>
<xs:extension base="ifc:IfcMaterialDefinition">
<xs:sequence>
<xs:element name="Material" type="ifc:IfcMaterial" nillable="true" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="LayerThickness" type="ifc:IfcNonNegativeLengthMeasure" use="optional"/>
<xs:attribute name="Name" type="ifc:IfcLabel" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>

EXPRESS Specification:

ENTITY IfcMaterialLayer

| SUBTYPE OF (IfcMaterialDefinition);

Material | : | OPTIONAL IfcMaterial;
LayerThickness | : | IfcNonNegativeLengthMeasure;
IsVentilated | : | OPTIONAL IfcStrippedOptional;
Name | : | OPTIONAL IfcLabel;
Description | : | OPTIONAL IfcStrippedOptional;
Category | : | OPTIONAL IfcStrippedOptional;
Priority | : | OPTIONAL IfcStrippedOptional;

| INVERSE

ToMaterialLayerSet | : | IfcMaterialLayerSet FOR MaterialLayers;

END_ENTITY;

Attribute Definitions:

Material | : | Optional reference to the material from which the layer is constructed. Note that if this value is not given, it does not denote a layer with no material (an air gap), it only means that the material is not specified at that point.
LayerThickness | : | The thickness of the material layer. The meaning of "thickness" depends on its usage. In case of building elements elements utilizing IfcMaterialLayerSetUsage, the dimension is measured along the positive LayerSetDirection as specified in IfcMaterialLayerSetUsage. NOTE The attribute value can be 0. for material thicknesses very close to zero, such as for a membrane. Material layers with thickess 0. may not be rendered in the geometric representation. IFC4 CHANGE The attribute datatype has been changed to IfcNonNegativeLengthMeasure allowing for 0. as thickness.
IsVentilated | : | Indication of whether the material layer represents an air layer (or cavity). set to TRUE if the material layer is an air gap and provides air exchange from the layer to the outside air. set to UNKNOWN if the material layer is an air gap and does not provide air exchange (or when this information about air exchange of the air gap is not available). set to FALSE if the material layer is a solid material layer (the default).
Name | : | The name by which the material layer is known.
Description | : | Definition of the material layer in more descriptive terms than given by attributes Name or Category.
Category | : | Category of the material layer, e.g. the role it has in the layer set it belongs to (such as 'load bearing', 'thermal insulation' etc.).
Priority | : | The relative priority of the layer, expressed as ratio measure, normalised to 0..1. Controls how layers intersect in connections and corners of building elements: a layer from one element protrudes into (i.e. displaces) a layer from another element in a joint of these elements if the former element's layer has higher priority than the latter. The priority value for a material layer in an element has to be set and maintained by software applications in relation to the material layers in connected elements.
ToMaterialLayerSet | : | Reference to the IfcMaterialLayerSet in which the material layer is included.

Inheritance Graph:

ENTITY IfcMaterialLayer

| ENTITY IfcMaterialDefinition

| INVERSE

AssociatedTo | : | SET [0:?] OF IfcRelAssociatesMaterial FOR RelatingMaterial;
HasProperties | : | SET OF IfcMaterialProperties FOR Material;

| ENTITY IfcMaterialLayer

Material | : | OPTIONAL IfcMaterial;
LayerThickness | : | IfcNonNegativeLengthMeasure;
IsVentilated | : | OPTIONAL IfcStrippedOptional;
Name | : | OPTIONAL IfcLabel;
Description | : | OPTIONAL IfcStrippedOptional;
Category | : | OPTIONAL IfcStrippedOptional;
Priority | : | OPTIONAL IfcStrippedOptional;

| INVERSE

ToMaterialLayerSet | : | IfcMaterialLayerSet FOR MaterialLayers;

END_ENTITY;

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