The Enable composite layers menu option on the main dialog allows you to be able to create composite layers in a construction layer, where a single layer is composed of 2 or 3 separate materials in given proportions. Therefore this should be enabled if you need to create constructions with composite layers.
The Composite button in the Project construction dialogs is only available if you have already enabled composite layers (see above). It converts a non-composite layer to a composite layer with two sub-layers. If it is already a composite layer with two sub-layers it adds another sub-layer, i.e. converts it to a composite layer with three sub-layers. There is a maximum of three sub-layers. Sub-layers initially use “in-line” data instead of real materials, but they can be “promoted” to using real materials.
NB Previously only one composite layer was allowed per construction. This restriction is now lifted because some constructions using BRE materials may need several composite layers.
Composite layers are generated in certain ASHRAE wizard-generated constructions. However these do not normally require subsequent editing.
Composite layers are also used in the cost planning and life cycle software where sub-layers using real materials can be used to increase the accuracy of material usage. This software imposes certain rules on allowed combinations of BRE materials in a composite layer; after any such edit any rule violations will be checked and if necessary a validation window will display showing the rule violations and inviting you to fix them or enter a justification for the edit. See BRE materials for details.
