3.5.2 Construction Assemblies

Assembly Name
Applicability	All projects
Definition	The name of a construction assembly that describes a roof, wall, or floor assembly. The name generally needs to be unique so it can be referenced precisely by surfaces.
Units	Text, unique
Input Restrictions	Construction name is a required input.
Baseline Rules	Not applicable

Specification Method
Applicability	All projects
Definition	The method of describing a construction assembly. The more simple method is to describe the U-factor of the construction assembly which can account for thermal bridging and other factors. However with this method, the time delay of heat transfer through the construction assembly is not accounted for. Generally, with the U-factor method, heat transfer is assumed to occur instantly. The more complex method is to describe the construction assembly as a series of layers, each layer representing a material. With this method, heat transfer is delayed in accord with the thermal mass and other properties of the assembly.
Units	List: choices are U-factor or Layers
Input Restrictions	The layers method shall be used for all constructions except for metal building or similar constructions with negligible thermal mass.
Baseline Rules	For each construction, the proposed design specification method shall be used.

U-factor
Applicability	All construction assemblies that are specified by a U-factor
Definition	The steady state rate of heat transfer through a construction assembly
Units	Btu/h-ft²-°F
Input Restrictions	U-factors should be consistent with values in Appendix A of ASHRAE Standard 90.1-2013.
Baseline Rules	Not applicable

Layers
Applicability	All construction assemblies that use the layers method of specification
Definition	A structured list of pairs of material names that describe a construction assembly, beginning with exterior finish and progressing through to the interior finish. Material names must be from the standard list (Appendix D) or defined (see above).
Units	Data structure: construction assembly
Input Restrictions	The user is required to describe all layers in the actual roof assembly and the proposed design will be modeled as input by the user.
Baseline Rules	See building descriptors for roofs, walls, and floors.

3.5.2 Materials

Energy simulation programs commonly define construction assemblies by listing a sequence of material layers that make up the construction assembly. Typical construction assemblies and their respective material layers are defined in Normative Appendix A of Standard 90.1-2019.

Material Name
Applicability	When construction assemblies reference materials that are not standard
Definition	The name of a construction material used in the exterior envelope of the building
Units	Text, unique
Input Restrictions	Material name is a required input for materials not available from the standard list. The user may not modify entries for predefined materials.
Baseline Building	Not applicable

Density
Applicability	All non-standard materials
Definition	The density (or mass per unit of volume) of the construction material
Units	lb/ft³
Input Restrictions	Density is a required input when non-standard materials are specified as documented in an ASHRAE handbook, a comparably reliable reference, or manufacturers’ literature
Baseline Building	Not applicable

Specific Heat
Applicability	All non-standard materials
Definition	The specific heat capacity of a material is numerically equal to the quantity of heat that must be supplied to a unit mass of the material to increase its temperature by 1°F
Units	Btu/lb·°F
Input Restrictions	Specific heat is a required input when non-standard materials are specified. The specific heat capacity of the construction material as documented in an ASHRAE handbook, a comparably reliable reference, or manufacturers’ literature.
Baseline Building	Not applicable

Thermal Conductivity
Applicability	All non-standard materials
Definition	The thermal conductivity of a material of unit thickness is numerically equal to the quantity of heat that will flow through a unit area of the material when the temperature difference through the material is 1 °F.
Units	Btu/h·ft·°F
Input Restrictions	Thermal conductivity is a required input for non-standard materials as documented in an ASHRAE handbook, a comparably reliable reference, or manufacturers’ literature.
Baseline Building	Not applicable

Thickness
Applicability	All non-standard materials
Definition	The thickness of a material
Units	ft or in.
Input Restrictions	Thickness is a required input for non-standard materials
Baseline Building	Not applicable