The Wall Layer subnode is available from the context menu (right-click the Wall Heat Transfer parent node) or from the Physics toolbar, Attributes menu. Use it to define the thermal conductivity and wall thickness. You can add more layers.

Select an option from the Thermal conductivity list k (SI unit: W/(m·K)) — Not set (the default) or User defined to enter a different value or expression. The default is 0 W/(m·K).

Select an option from the Wall thickness list Δw (SI unit: m) — Not set (the default) or User defined. For User defined enter a value or expression. The default is 0 m.