3.5.3 Roofs | COMNET

Roof Name
Applicability	All roof surfaces
Definition	A unique name or code that identifies the roof and ties it to the construction documents submitted for energy code review. It is not mandatory to name roofs.
Units	Text, unique
Input Restrictions	None
Baseline Rules	None

Roof Type
Applicability	All roof surfaces
Definition	One of three classifications of roofs defined in the baseline standard. These classifications are defined in ASHRAE Standard 90.1-2001 and ASHRAE Standard 90.1-2007 along with the associated User's Manuals. The prescriptive U-factor requirements for roofs depend on the type. For green building ratings and tax credits, it is not necessary to specify this information, as the PRM fixes the type for the baseline building to “insulation entirely above the deck.” This descriptor can be derived from other building descriptors and it may not be necessary for the software user to specify it directly.
Units	List: attic and other roofs; metal building roofs; and roofs with insulation entirely above deck.
Input Restrictions	This input is optional for the purposes covered by this manual.
Baseline Rules	All roofs in the baseline building are modeled as “insulation entirely above deck.”

Roof Geometry
Applicability	All roofs, required input
Definition	Roof geometry defines the position, orientation, azimuth, tilt, and dimensions of the roof surface. The details of how the coordinate system is implemented may vary between software programs. The data structure for surfaces is described in the reference section of this chapter.
Units	Data structure: surface
Input Restrictions	There are no restrictions other than that the surfaces defined must agree with the building being modeled, as represented on the construction drawings or as-built drawings.
Baseline Rules	Roof geometry will be identical in the proposed and baseline building designs.

Roof Construction
Applicability	All roofs, required input
Definition	A reference to a construction assembly for the proposed design. See the building descriptors above for construction assemblies.
Units	Dimensionless reference
Input Restrictions	All roof surfaces must reference a construction assembly.
Baseline Rules	Roofs in the baseline building are of the type “insulation entirely above deck.” The insulation requirement is determined by climate zone and is given in [bookref id="baseline-building-r-value-and-u-factor-criteria-for-roofs"]. The baseline building roof construction shall be modeled as layers as defined in [bookref id="baseline-building -roof-construction-assemblies"]. These tables reflect a construction that is available in the standard list of constructions.

[table title="Baseline Building R-value and U-factor Criteria for Roofs" id="baseline-building-r-value-and-u-factor-criteria-for-roofs"]

Applicable Standard	Space Category	Climate Zone	Standard Design
Applicable Standard	Space Category	Climate Zone	Minimum Insulation	Maximum Assembly
90.1 – 2001	Nonresidential	1-7	R-15 c.i.	U-0.063
	Nonresidential	8	R-20 c.i.	U-0.048
	Residential	1,2,3,4,5,6,7	R-15 c.i.	U-0.063
	Residential	8	R-20 c.i.	U-0.048
	Semi-Heated	1	NR	U-1.282
		2,3,4	R-3.8 c.i.	U-0.218
		5,6,7	R-5.0 c.i.	U-0.173
		8	R-10.0 c.i.	U-0.093
90.1 – 2007 and 90.1 – 2010	Nonresidential	1	R-15 c.i.	U-0.063
	Nonresidential	2-8	R-20 c.i.	U-0.048
	Residential	1-8	R-20 c.i.	U-0.048
	Semi-Heated	1, 2	R-3.8 c.i.	U-0.218
		3, 4	R-5.0 c.i.	U-0.173
		5	R-7.6 c.i	U-0.119
		6,7	R-10.0 c.i.	U-0.093
		8	R-15.0 c.i.	U-0.063

[table title="Baseline Building Roof Construction Assemblies" id="baseline-building -roof-construction-assemblies"]

Construction	Layer	Thickness (inch)	Conductivity (Btu/h ft F)	Density (lb/ft²)	Specific Heat (Btu/lb F)	R-value (ft²·°F·h/Btu)	U-factor (Btu/h-ft²-F)
Roof R-20 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-20 continuous insulation	4.8	0.02	1.8	0.29	20.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					20.78	0.048
Roof R-15 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-15 continuous insulation	3.6	0.02	1.8	0.29	15.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					15.78	0.063
Roof R-10 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-10 continuous insulation	2.4	0.02	1.8	0.29	10.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					10.78	0.093
Roof R-7.6 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-7.6 continuous insulation	1.8	0.02	1.8	0.29	7.6
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					8.38	0.119
Roof R-5 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-5 continuous insulation	1.2	0.02	1.8	0.29	5.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					5.78	0.173
Roof R-3.8 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-3.8 continuous insulation	0.9	0.02	1.8	0.29	3.80
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					4.58	0.218
NR.	Exterior air film					0.17
	Roofing membrane					0.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					5.78	1.282

Exterior Roof Surface Properties
Applicability	All roofs
Definition	The exterior roof surface properties descriptor defines the characteristics of exterior surfaces. Exterior surface properties include emissivity, reflectivity and roughness. The first two govern radiation exchange from the surface, while the latter governs the magnitude of the exterior air film resistance.
Units	Data structure: exterior surface properties
Input Restrictions	The default value is a reflectance of 0.30 and an emittance of 0.75. The default value may be overridden when roof materials are used that have been tested by the Cool Roof Rating Council (CRRC) and are called for in the construction documents. In cases where the default value is overridden, the user is required to submit documentation identifying the test procedure that was used to establish the non-default values.
Baseline Rules	The default values (see Input Restrictions above) shall be used for roofs for the baseline building.

90.1-2007

Roof Name
Applicability	All roof surfaces
Definition	A unique name or code that identifies the roof and ties it to the construction documents submitted for energy code review. It is not mandatory to name roofs.
Units	Text, unique
Input Restrictions	None
Baseline Rules	None

Roof Type
Applicability	All roof surfaces
Definition	One of three classifications of roofs defined in the baseline standard. These classifications are defined in ASHRAE Standard 90.1-2001 and ASHRAE Standard 90.1-2007 along with the associated User's Manuals. The prescriptive U-factor requirements for roofs depend on the type. For green building ratings and tax credits, it is not necessary to specify this information, as the PRM fixes the type for the baseline building to “insulation entirely above the deck.” This descriptor can be derived from other building descriptors and it may not be necessary for the software user to specify it directly.
Units	List: attic and other roofs; metal building roofs; and roofs with insulation entirely above deck.
Input Restrictions	This input is optional for the purposes covered by this manual.
Baseline Rules	All roofs in the baseline building are modeled as “insulation entirely above deck.”

Roof Geometry
Applicability	All roofs, required input
Definition	Roof geometry defines the position, orientation, azimuth, tilt, and dimensions of the roof surface. The details of how the coordinate system is implemented may vary between software programs. The data structure for surfaces is described in the reference section of this chapter.
Units	Data structure: surface
Input Restrictions	There are no restrictions other than that the surfaces defined must agree with the building being modeled, as represented on the construction drawings or as-built drawings.
Baseline Rules	Roof geometry will be identical in the proposed and baseline building designs.

Roof Construction
Applicability	All roofs, required input
Definition	A reference to a construction assembly for the proposed design. See the building descriptors above for construction assemblies.
Units	Dimensionless reference
Input Restrictions	All roof surfaces must reference a construction assembly.
Baseline Rules	Roofs in the baseline building are of the type “insulation entirely above deck.” The insulation requirement is determined by climate zone and is given in [bookref id="baseline-building-r-value-and-u-factor-criteria-for-roofs"]. The baseline building roof construction shall be modeled as layers as defined in [bookref id="baseline-building -roof-construction-assemblies"]. These tables reflect a construction that is available in the standard list of constructions.

[table title="Baseline Building R-value and U-factor Criteria for Roofs" id="baseline-building-r-value-and-u-factor-criteria-for-roofs"]

Applicable Standard	Space Category	Climate Zone	Standard Design
Applicable Standard	Space Category	Climate Zone	Minimum Insulation	Maximum Assembly
90.1 – 2007 and 90.1 – 2010	Nonresidential	1	R-15 c.i.	U-0.063
	Nonresidential	2-8	R-20 c.i.	U-0.048
	Residential	1-8	R-20 c.i.	U-0.048
	Semi-Heated	1, 2	R-3.8 c.i.	U-0.218
		3, 4	R-5.0 c.i.	U-0.173
		5	R-7.6 c.i	U-0.119
		6,7	R-10.0 c.i.	U-0.093
		8	R-15.0 c.i.	U-0.063

[table title="Baseline Building Roof Construction Assemblies" id="baseline-building -roof-construction-assemblies"]

Construction	Layer	Thickness (inch)	Conductivity (Btu/h ft F)	Density (lb/ft²)	Specific Heat (Btu/lb F)	R-value (ft²·°F·h/Btu)	U-factor (Btu/h-ft²-F)
Roof R-20 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-20 continuous insulation	4.8	0.02	1.8	0.29	20.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					20.78	0.048
Roof R-15 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-15 continuous insulation	3.6	0.02	1.8	0.29	15.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					15.78	0.063
Roof R-10 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-10 continuous insulation	2.4	0.02	1.8	0.29	10.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					10.78	0.093
Roof R-7.6 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-7.6 continuous insulation	1.8	0.02	1.8	0.29	7.6
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					8.38	0.119
Roof R-5 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-5 continuous insulation	1.2	0.02	1.8	0.29	5.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					5.78	0.173
Roof R-3.8 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-3.8 continuous insulation	0.9	0.02	1.8	0.29	3.80
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					4.58	0.218
NR.	Exterior air film					0.17
	Roofing membrane					0.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					5.78	1.282

Exterior Roof Surface Properties
Applicability	All roofs
Definition	The exterior roof surface properties descriptor defines the characteristics of exterior surfaces. Exterior surface properties include emissivity, reflectivity and roughness. The first two govern radiation exchange from the surface, while the latter governs the magnitude of the exterior air film resistance.
Units	Data structure: exterior surface properties
Input Restrictions	The default value is a reflectance of 0.30 and an emittance of 0.75. The default value may be overridden when roof materials are used that have been tested by the Cool Roof Rating Council (CRRC) and are called for in the construction documents. In cases where the default value is overridden, the user is required to submit documentation identifying the test procedure that was used to establish the non-default values.
Baseline Rules	The default values (see Input Restrictions above) shall be used for roofs for the baseline building.

Roof Name
Applicability	All roof surfaces
Definition	A unique name or code that identifies the roof and ties it to the construction documents submitted for energy code review. It is not mandatory to name roofs.
Units	Text, unique
Input Restrictions	None
Baseline Rules	None

Roof Type
Applicability	All roof surfaces
Definition	One of three classifications of roofs defined in the baseline standard. These classifications are defined in ASHRAE Standard 90.1-2001 and ASHRAE Standard 90.1-2007 along with the associated User's Manuals. The prescriptive U-factor requirements for roofs depend on the type. For green building ratings and tax credits, it is not necessary to specify this information, as the PRM fixes the type for the baseline building to “insulation entirely above the deck.” This descriptor can be derived from other building descriptors and it may not be necessary for the software user to specify it directly.
Units	List: attic and other roofs; metal building roofs; and roofs with insulation entirely above deck.
Input Restrictions	This input is optional for the purposes covered by this manual.
Baseline Rules	All roofs in the baseline building are modeled as “insulation entirely above deck.”

Roof Geometry
Applicability	All roofs, required input
Definition	Roof geometry defines the position, orientation, azimuth, tilt, and dimensions of the roof surface. The details of how the coordinate system is implemented may vary between software programs. The data structure for surfaces is described in the reference section of this chapter.
Units	Data structure: surface
Input Restrictions	There are no restrictions other than that the surfaces defined must agree with the building being modeled, as represented on the construction drawings or as-built drawings.
Baseline Rules	Roof geometry will be identical in the proposed and baseline building designs.

Roof Construction
Applicability	All roofs, required input
Definition	A reference to a construction assembly for the proposed design. See the building descriptors above for construction assemblies.
Units	Dimensionless reference
Input Restrictions	All roof surfaces must reference a construction assembly.
Baseline Rules	Roofs in the baseline building are of the type “insulation entirely above deck.” The insulation requirement is determined by climate zone and is given in Table 6.5.3-1. The baseline building roof construction shall be modeled as layers as defined in Table 6.5.3-2. These tables reflect a construction that is available in the standard list of constructions.

Table 6.5.3-1: Baseline Building R-value and U-factor Criteria for Roofs

Applicable Standard	Space Category	Climate Zone	Standard Design
Applicable Standard	Space Category	Climate Zone	Minimum Insulation	Maximum Assembly
90.1 – 2007 and 90.1 – 2010	Nonresidential	1	R-15 c.i.	U-0.063
	Nonresidential	2-8	R-20 c.i.	U-0.048
	Residential	1-8	R-20 c.i.	U-0.048
	Semi-Heated	1, 2	R-3.8 c.i.	U-0.218
		3, 4	R-5.0 c.i.	U-0.173
		5	R-7.6 c.i	U-0.119
		6,7	R-10.0 c.i.	U-0.093
		8	R-15.0 c.i.	U-0.063

Table 6.5.3-2: Baseline Building Roof Construction Assemblies

Construction	Layer	Thickness (inch)	Conductivity (Btu/h ft F)	Density (lb/ft²)	Specific Heat (Btu/lb F)	R-value (ft²·°F·h/Btu)	U-factor (Btu/h-ft²-F)
Roof R-20 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-20 continuous insulation	4.8	0.02	1.8	0.29	20.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					20.78	0.048
Roof R-15 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-15 continuous insulation	3.6	0.02	1.8	0.29	15.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					15.78	0.063
Roof R-10 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-10 continuous insulation	2.4	0.02	1.8	0.29	10.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					10.78	0.093
Roof R-7.6 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-7.6 continuous insulation	1.8	0.02	1.8	0.29	7.6
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					8.38	0.119
Roof R-5 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-5 continuous insulation	1.2	0.02	1.8	0.29	5.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					5.78	0.173
Roof R-3.8 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-3.8 continuous insulation	0.9	0.02	1.8	0.29	3.80
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					4.58	0.218
NR.	Exterior air film					0.17
	Roofing membrane					0.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					5.78	1.282

Exterior Roof Surface Properties
Applicability	All roofs
Definition	The exterior roof surface properties descriptor defines the characteristics of exterior surfaces. Exterior surface properties include emissivity, reflectivity and roughness. The first two govern radiation exchange from the surface, while the latter governs the magnitude of the exterior air film resistance.
Units	Data structure: exterior surface properties
Input Restrictions	The default value is a reflectance of 0.30 and an emittance of 0.75. The default value may be overridden when roof materials are used that have been tested by the Cool Roof Rating Council (CRRC) and are called for in the construction documents. In cases where the default value is overridden, the user is required to submit documentation identifying the test procedure that was used to establish the non-default values.
Baseline Rules	In climate zones 1-3, the solar reflectance shall be 0.55 and thermal emittance shall be 0.75. For all other climate zones the default values (see Input Restrictions above) shall be used.

Roof Name
Applicability	All roof surfaces
Definition	A unique name or code that identifies the roof and ties it to the construction documents submitted for energy code review. It is not mandatory to name roofs.
Units	Text, unique
Input Restrictions	None
Baseline Rules	None

Roof Type
Applicability	All roof surfaces
Definition	One of three classifications of roofs defined in Standard 90.1-2013 This building descriptor can be derived from other building descriptors and it may not be necessary for the software user to specify it directly.
Units	List: attic and other roofs; metal building roofs; and roofs with insulation entirely above deck.
Input Restrictions	This input is optional for the purposes covered by this manual.
Baseline Rules	All roofs in the baseline building are modeled as Insulation Entirely above Deck and other properties are specified as described below.

Roof Geometry
Applicability	All roofs, required input
Definition	Roof geometry defines the position, orientation, azimuth, tilt, and dimensions of the roof surface. The details of how the coordinate system is implemented may vary between software programs. The data structure for surfaces is described in the reference section of this chapter.
Units	Data structure: surface
Input Restrictions	The geometry of roofs should match the construction documents or as-built drawings as accurately as possible. Unusual curved surfaces such as a dome may be approximated by a series of flat constructions.
Baseline Rules	Roof geometry in the baseline building shall be identical to the proposed design.

Roof Construction
Applicability	All roofs, required input
Definition	A reference to a construction assembly for the proposed design. See the building descriptors above for construction assemblies.
Units	Dimensionless reference
Input Restrictions	All roof surfaces must reference a construction assembly.
Baseline Rules	Roofs in the baseline building are of the type “insulation entirely above deck.” The insulation requirement is determined by climate zone and thermal block occupancy type and given in Table 3.5.3-1. The baseline building roof construction shall be modeled as layers as defined in Table 3.5.3-2. These tables reflect a construction that is available in the standard list of constructions.

Table 3.5.3-1: Baseline Building R-value and U-factor Criteria for Roofs

Climate Zone	Nonresidential		Residential		Semi-Heated
	Name	U-factor	Name	U-factor	Name	U-factor
1	R-15 ci	U-0.063	R-15 ci	U-0.063	NR	U-1.282
2					R-3.8 ci	U-0.218
3
4
5					R-5 ci	U-0.173
6
7
8	R-20 ci	U-0.048	R-20 ci	U-0.048	R-15 ci	U-0.063

Table 3.5.3-2: Baseline Building Roof Construction Assemblies

Name	Layer	Thickness (inch)	Conductivity (Btu/h ft F)	Density (lb/ft²)	Specific Heat (Btu/lb F)	R-value (ft²·°F·h/Btu)	U-factor (Btu/h-ft²-F)
R-20 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-20 continuous insulation	4.8	0.02	1.8	0.29	20.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					20.78	0.048
R-15 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-15 continuous insulation	3.6	0.02	1.8	0.29	15.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					15.78	0.063
R-10 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-10 continuous insulation	2.4	0.02	1.8	0.29	10.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					10.78	0.093
R-7.6 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-7.6 continuous insulation	1.8	0.02	1.8	0.29	7.6
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					8.38	0.119
R-5 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-5 continuous insulation	1.2	0.02	1.8	0.29	5.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					5.78	0.173
R-3.8 c.i.	Exterior air film					0.17
	Roofing membrane					0.00
	R-3.8 continuous insulation	0.9	0.02	1.8	0.29	3.80
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					4.58	0.218
NR.	Exterior air film					0.17
	Roofing membrane					0.00
	Steel deck	0.06	26	480	0.10	0.00
	Interior air film					0.61
	Total for assembly					5.78	1.282

Exterior Roof Surface Properties
Applicability	All roofs
Definition	The exterior roof surface properties descriptor defines the characteristics of exterior surfaces. Exterior surface properties include emissivity, reflectivity and roughness. The first two govern radiation exchange from the surface, while the latter governs the magnitude of the exterior air film resistance.
Units	Data structure: exterior surface properties
Input Restrictions	The default value is a reflectance of 0.30 and an emittance of 0.90. The default value may be overridden when roof materials are used that have been tested by the Cool Roof Rating Council (CRRC) and are called for in the construction documents.
Baseline Rules	Roofs in the baseline building shall be modeled with a solar reflectance shall be 0.30 and thermal emittance of 0.90.

3.5.3 Construction Assemblies

For use with Standard 90.1-2019, construction assemblies for the proposed design shall be created by selecting from a library of building construction layers in Standard 90.1-2019, Appendix A. The software shall specify all composite layers that consist of both framing and insulation and shall use established methods defined in the Standard 90.1- 2019 Appendix A or the ASHRAE Handbook of Fundamentals for calculating effective R-values of composite layers.

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 Building	Not applicable

Specification Method
Applicability	All projects
Definition	The method of describing a construction assembly. The simpler method is to describe the U-factor of the construction assembly, which can account for thermal bridging and other factors. However, this method does not account for the time delay of heat transfer through the construction assembly. 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. For below-grade constructions, a C-factor can be specified; for slab-on-grade constructions, an F-factor is specified.
Units	List: layers, U-factor, C-factor, F-factor, R-value
Input Restrictions	The layers method shall be used for all constructions except for metal building or similar constructions with negligible thermal mass may use the U-factor method
Baseline Building	Construction assembly for the baseline building will be defined in layers

Layers
Applicability	All construction assemblies that use the layers method of specification
Definition	A structured list of material names that describe a construction assembly, beginning with the exterior finish and progressing through the assembly to the interior finish. Materials are described in Section 3.5.2
Units	List: layers of construction assembly
Input Restrictions	The user is required to describe all layers in the actual assembly and model the proposed design based on the layer descriptions
Baseline Building	See building descriptors for roofs, exterior walls, exterior floors, doors, fenestration, and below-grade walls

Roof Name
Applicability	All roof surfaces
Definition	A unique name or code that identifies the roof and ties it to the construction documents submitted for energy code review. It is not mandatory to name roofs.
Units	Text, unique
Input Restrictions	None

Roof Geometry
Applicability	All roofs, required input
Definition	Roof geometry defines the position, orientation, azimuth, tilt, and dimensions of the roof surface. The details of how the coordinate system is implemented may vary between software programs. The data structure for surfaces is described in the reference section of this chapter.
Units	Data structure: surface
Input Restrictions	There are no restrictions other than that the surfaces defined must agree with the building being modeled, as represented on the construction drawings or as-built drawings.

Roof Construction
Applicability	All roofs, required input
Definition	A reference to a construction assembly for the proposed design. See the building descriptors above for construction assemblies
Units	Dimensionless reference
Input Restrictions	All roof surfaces must reference a construction assembly.

Exterior Roof Surface Properties
Applicability	All roofs
Definition	The exterior roof surface properties descriptor defines the characteristics of exterior surfaces. Exterior surface properties include emissivity, reflectivity and roughness. The first two govern radiation exchange from the surface, while the latter governs the magnitude of the exterior air film resistance.
Units	Data structure: exterior surface properties
Input Restrictions	The default value is a reflectance of 0.30 and an emittance of 0.75. The default value may be overridden when roof materials are used that have been tested by the Cool Roof Rating Council (CRRC) and are called for in the construction documents. In cases where the default value is overridden, the user is required to submit documentation identifying the test procedure that was used to establish the non-default values.

Roof Name
Applicability	All roof surfaces
Definition	A unique name or code that identifies the roof and ties it to the construction documents submitted for energy code review. It is not mandatory to name roofs.
Units	Text, unique
Input Restrictions	None

Roof Geometry
Applicability	All roofs, required input
Definition	Roof geometry defines the position, orientation, azimuth, tilt, and dimensions of the roof surface. The details of how the coordinate system is implemented may vary between software programs. The data structure for surfaces is described in the reference section of this chapter.
Units	Data structure: surface
Input Restrictions	There are no restrictions other than that the surfaces defined must agree with the building being modeled, as represented on the construction drawings or as-built drawings.

Roof Construction
Applicability	All roofs, required input
Definition	A reference to a construction assembly for the proposed design. See the building descriptors above for construction assemblies
Units	Dimensionless reference
Input Restrictions	All roof surfaces must reference a construction assembly.

Exterior Roof Surface Properties
Applicability	All roofs
Definition	The exterior roof surface properties descriptor defines the characteristics of exterior surfaces. Exterior surface properties include emissivity, reflectivity and roughness. The first two govern radiation exchange from the surface, while the latter governs the magnitude of the exterior air film resistance.
Units	Data structure: exterior surface properties
Input Restrictions	The default value is a reflectance of 0.30 and an emittance of 0.75. The default value may be overridden when roof materials are used that have been tested by the Cool Roof Rating Council (CRRC) and are called for in the construction documents. In cases where the default value is overridden, the user is required to submit documentation identifying the test procedure that was used to establish the non-default values.