3.5.4 Exterior Walls

Wall Name
Applicability	All walls, optional input
Definition	A unique name or code that relates the exterior wall to the design documents. This is an optional input since there are other acceptable ways to key surfaces to the construction documents.
Units	Text, unique
Input Restrictions	None
Baseline Rules	None

Wall Type
Applicability	All wall surfaces, optional
Definition	One of four categories of above-grade wall assemblies used to determine minimum insulation requirements for walls. The four wall type categories are as follows: a) mass walls, b) metal building walls, c) metal framing walls, and d) wood framing and other walls. These wall types are defined in the baseline standards and the associated User's Manuals. The prescriptive criteria of the baseline standards depend on the wall type, but for green building ratings and tax deduction calculations, the PRM specifies that all baseline walls shall be “metal framed” so the input is not used for the purposes of this manual.
Units	List: mass walls, metal building walls, metal framing walls, and wood framing and other walls
Input Restrictions	This input is optional for the purposes covered by this manual. This input can often be derived from other inputs and may not need to be explicitly specified.
Baseline Rules	All walls in the baseline building are modeled as “metal framed.”

Wall Geometry
Applicability	All walls, required input
Definition	Wall geometry defines the position, orientation, azimuth, and tilt of the wall surface. The details of how the coordinate system is implemented may vary between simulation engines. 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	Wall geometry in the baseline building is identical to the proposed design.

Wall Construction
Applicability	All walls, 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 wall surfaces must reference a construction assembly that meets the mandatory requirements of the appropriate baseline standard.
Baseline Rules	Walls in the baseline building are all of the type “metal framed”. The insulation requirement is determined by the baseline standard and climate zone and is given in [bookref id="baseline-building-r-value-and-u-factor-criteria-for-walls"]. The baseline building construction shall be modeled as layers as defined in [bookref id="baseline-building-wall-construction-assemblies"].

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

Applicable Standard	Space Category	Climate Zone	Standard Design
Applicable Standard	Space Category	Climate Zone	Minimum Insulation	Maximum Assembly
90.1 - 2001	Nonresidential	1-4	R-13	U-0.124
		5,6	R-13 + R-3.8 c.i.	U-0.084
		7,8	R-13 + R-7.5 c.i.	U-0.064
	Residential	1,2	R-13	U-0.124
		3	R-13 + R-3.8 c.i.	U-0.084
		4- 7	R-13 + R-7.5 c.i.	U-0.064
		8	R-13 + 10.0 c.i.	U-0.055
	Semi-Heated	1- 3	NR	U-0.352
	Semi-Heated	4 - 8	R-13	U-0.124
90.1 - 2007	Nonresidential	1,2	R-13	U-0.124
		3	R-13 + R-3.8 c.i.	U-0.084
		4-8	R-13 + R-7.5 c.i.	U-0.064
	Residential	1	R-13	U-0.124
		2-6	R-13 + R-7.5 c.i.	U-0.064
		7	R-13 +15.6 c.i.	U-0.042
		8	R-13 + R-18.8 c.i.	U-0.037
	Semi-Heated	1	NR	U-0.352
		2-7	R-13	U-0.124
		8	R-13 + R-3.8 c.i.	U-0.084

[table title="Baseline Building Wall Construction Assemblies" id="baseline-building-wall-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/ ft²·°F·h)
Wall R-13 + R-18.8	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-18.8 continuous insulation	1.800	0.0200	1.8	0.29	18.8
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					26.85	0.037
Wall R-13 + R-15.6	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-15.6 continuous insulation	1.800	0.0200	1.8	0.29	15.6
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					23.65	0.042
Wall R-13 + R-10.0	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-10.0continuous insulation	1.800	0.0200	1.8	0.29	10.0
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					18.05	.055
Wall R-13 + R-7.5	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-7.5 continuous insulation	1.800	0.0200	1.8	0.29	7.50
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					15.55	0.64
Wall R-13 + R-3.8	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-3.8 continuous insulation	0.912	0.0200	1.8	0.29	3.80
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					11.85	0.84
Wall R-13	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					199.95	0.124
Wall R-13	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Cavity/steel framing					0.79
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					2.84	3.52

Exterior Wall Surface Properties
Applicability	All walls
Definition	The exterior wall surface properties descriptor describes the characteristics of exterior wall surfaces. Exterior surface properties may 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. The descriptor is a critical default structure input, applicable to all models. Critical defaults require documentation to change. Data structures are outlined in the reference data structures section of this chapter.
Units	Data structure: exterior surface properties
Input Restrictions	The default value for emittance is 0.90. The default value for reflectance is 0.30. There is no default for roughness. The default values may be overridden only in cases when the lower reflectance can be documented by manufacturers’ literature or tests.
Baseline Rules	The baseline building shall use default values for emittance and reflectance. The roughness of the baseline building walls shall be identical to the proposed design.

90.1-2007

Wall Name
Applicability	All walls, optional input
Definition	A unique name or code that relates the exterior wall to the design documents. This is an optional input since there are other acceptable ways to key surfaces to the construction documents.
Units	Text, unique
Input Restrictions	None
Baseline Rules	None

Wall Type
Applicability	All wall surfaces, optional
Definition	One of four categories of above-grade wall assemblies used to determine minimum insulation requirements for walls. The four wall type categories are as follows: a) mass walls, b) metal building walls, c) metal framing walls, and d) wood framing and other walls. These wall types are defined in the baseline standards and the associated User's Manuals. The prescriptive criteria of the baseline standards depend on the wall type, but for green building ratings and tax deduction calculations, the PRM specifies that all baseline walls shall be “metal framed” so the input is not used for the purposes of this manual.
Units	List: mass walls, metal building walls, metal framing walls, and wood framing and other walls
Input Restrictions	This input is optional for the purposes covered by this manual. This input can often be derived from other inputs and may not need to be explicitly specified.
Baseline Rules	All walls in the baseline building are modeled as “metal framed.”

Wall Geometry
Applicability	All walls, required input
Definition	Wall geometry defines the position, orientation, azimuth, and tilt of the wall surface. The details of how the coordinate system is implemented may vary between simulation engines. 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	Wall geometry in the baseline building is identical to the proposed design.

Wall Construction
Applicability	All walls, 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 wall surfaces must reference a construction assembly that meets the mandatory requirements of the appropriate baseline standard.
Baseline Rules	Walls in the baseline building are all of the type “metal framed”. The insulation requirement is determined by the baseline standard and climate zone and is given in [bookref id="baseline-building-r-value-and-u-factor-criteria-for-walls"]. The baseline building construction shall be modeled as layers as defined in [bookref id="baseline-building-wall-construction-assemblies"].

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

Applicable Standard	Space Category	Climate Zone	Standard Design
Applicable Standard	Space Category	Climate Zone	Minimum Insulation	Maximum Assembly
90.1 - 2007	Nonresidential	1,2	R-13	U-0.124
		3	R-13 + R-3.8 c.i.	U-0.084
		4-8	R-13 + R-7.5 c.i.	U-0.064
	Residential	1	R-13	U-0.124
		2-6	R-13 + R-7.5 c.i.	U-0.064
		7	R-13 +15.6 c.i.	U-0.042
		8	R-13 + R-18.8 c.i.	U-0.037
	Semi-Heated	1	NR	U-0.352
		2-7	R-13	U-0.124
		8	R-13 + R-3.8 c.i.	U-0.084

[table title="Baseline Building Wall Construction Assemblies" id="baseline-building-wall-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/ ft²·°F·h)
Wall R-13 + R-18.8	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-18.8 continuous insulation	1.800	0.0200	1.8	0.29	18.8
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					26.85	0.037
Wall R-13 + R-15.6	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-15.6 continuous insulation	1.800	0.0200	1.8	0.29	15.6
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					23.65	0.042
Wall R-13 + R-10.0	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-10.0continuous insulation	1.800	0.0200	1.8	0.29	10.0
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					18.05	.055
Wall R-13 + R-7.5	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-7.5 continuous insulation	1.800	0.0200	1.8	0.29	7.50
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					15.55	0.64
Wall R-13 + R-3.8	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-3.8 continuous insulation	0.912	0.0200	1.8	0.29	3.80
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					11.85	0.84
Wall R-13	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					199.95	0.124
Wall R-13	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Cavity/steel framing					0.79
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					2.84	3.52

Exterior Wall Surface Properties
Applicability	All walls
Definition	The exterior wall surface properties descriptor describes the characteristics of exterior wall surfaces. Exterior surface properties may 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. The descriptor is a critical default structure input, applicable to all models. Critical defaults require documentation to change. Data structures are outlined in the reference data structures section of this chapter.
Units	Data structure: exterior surface properties
Input Restrictions	The default value for emittance is 0.90. The default value for reflectance is 0.30. There is no default for roughness. The default values may be overridden only in cases when the lower reflectance can be documented by manufacturers’ literature or tests.
Baseline Rules	The baseline building shall use default values for emittance and reflectance. The roughness of the baseline building walls shall be identical to the proposed design.

Wall Name
Applicability	All walls, optional input
Definition	A unique name or code that relates the exterior wall to the design documents. This is an optional input since there are other acceptable ways to key surfaces to the construction documents.
Units	Text, unique
Input Restrictions	None
Baseline Rules	None

Wall Type
Applicability	All wall surfaces, optional
Definition	One of four categories of above-grade wall assemblies used to determine minimum insulation requirements for walls. The four wall type categories are as follows: a) mass walls, b) metal building walls, c) metal framing walls, and d) wood framing and other walls. These wall types are defined in the baseline standards and the associated User's Manuals. The prescriptive criteria of the baseline standards depend on the wall type, but for green building ratings and tax deduction calculations, the PRM specifies that all baseline walls shall be “metal framed” so the input is not used for the purposes of this manual.
Units	List: mass walls, metal building walls, metal framing walls, and wood framing and other walls
Input Restrictions	This input is optional for the purposes covered by this manual. This input can often be derived from other inputs and may not need to be explicitly specified.
Baseline Rules	All walls in the baseline building are modeled as “metal framed.”

Wall Geometry
Applicability	All walls, required input
Definition	Wall geometry defines the position, orientation, azimuth, and tilt of the wall surface. The details of how the coordinate system is implemented may vary between simulation engines. 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	Wall geometry in the baseline building is identical to the proposed design.

Wall Construction
Applicability	All walls, 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 wall surfaces must reference a construction assembly that meets the mandatory requirements of the appropriate baseline standard.
Baseline Rules	Walls in the baseline building are all of the type “metal framed”. The insulation requirement is determined by the baseline standard and climate zone and is given in Table 6.5.4-1. The baseline building construction shall be modeled as layers as defined in Table 6.5.4-2.

Table 6.5.4-1: Baseline Building R-value and U-factor Criteria for Walls

Applicable Standard	Space Category	Climate Zone	Standard Design
Applicable Standard	Space Category	Climate Zone	Minimum Insulation	Maximum Assembly
90.1 - 2007	Nonresidential	1,2	R-13	U-0.124
		3	R-13 + R-3.8 c.i.	U-0.084
		4-8	R-13 + R-7.5 c.i.	U-0.064
	Residential	1	R-13	U-0.124
		2-6	R-13 + R-7.5 c.i.	U-0.064
		7	R-13 +15.6 c.i.	U-0.042
		8	R-13 + R-18.8 c.i.	U-0.037
	Semi-Heated	1	NR	U-0.352
		2-7	R-13	U-0.124
		8	R-13 + R-3.8 c.i.	U-0.084

Table 6.5.4-2: Baseline Building Wall 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/ ft²·°F·h)
Wall R-13 + R-18.8	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-18.8 continuous insulation	1.800	0.0200	1.8	0.29	18.8
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					26.85	0.037
Wall R-13 + R-15.6	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-15.6 continuous insulation	1.800	0.0200	1.8	0.29	15.6
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					23.65	0.042
Wall R-13 + R-10.0	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-10.0continuous insulation	1.800	0.0200	1.8	0.29	10.0
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					18.05	.055
Wall R-13 + R-7.5	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-7.5 continuous insulation	1.800	0.0200	1.8	0.29	7.50
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					15.55	0.64
Wall R-13 + R-3.8	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-3.8 continuous insulation	0.912	0.0200	1.8	0.29	3.80
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					11.85	0.84
Wall R-13	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					199.95	0.124
Wall R-13	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Cavity/steel framing					0.79
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					2.84	3.52

Exterior Wall Surface Properties
Applicability	All walls
Definition	The exterior wall surface properties descriptor describes the characteristics of exterior wall surfaces. Exterior surface properties may 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. The descriptor is a critical default structure input, applicable to all models. Critical defaults require documentation to change. Data structures are outlined in the reference data structures section of this chapter.
Units	Data structure: exterior surface properties
Input Restrictions	The default value for emittance is 0.90. The default value for reflectance is 0.30. There is no default for roughness. The default values may be overridden only in cases when the lower reflectance can be documented by manufacturers’ literature or tests.
Baseline Rules	The baseline building shall use default values for emittance and reflectance. The roughness of the baseline building walls shall be identical to the proposed design.

Wall Name
Applicability	All walls, optional input
Definition	A unique name or code that relates the exterior wall to the design documents. This is an optional input since there are other acceptable ways to key surfaces to the construction documents.
Units	Text, unique
Input Restrictions	None
Baseline Rules	None

Wall Type
Applicability	All wall surfaces, optional
Definition	One of four categories of above-grade wall assemblies: a) mass walls, b) metal building walls, c) metal framing walls, and d) wood framing and other walls. These wall types are defined in Standard 90.1-2013 and the associated User's Manuals. The prescriptive criteria of the baseline standards depend on the wall type, but for performance calculations, the PRM specifies that all baseline walls shall be “metal framed”.
Units	List: mass walls, metal building walls, metal framing walls, and wood framing and other walls
Input Restrictions	This input is optional for the purposes covered by this manual. This input can often be derived from other inputs and may not need to be explicitly specified.
Baseline Rules	All walls in the baseline building are modeled as “metal framed.”

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

Wall Construction
Applicability	All walls, 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 wall surfaces must reference a construction assembly that meets the mandatory requirements of Standard 90.1-2013.
Baseline Rules	Walls in the baseline building are all of the type “metal framed”. The insulation requirement is determined by the baseline standard and climate zone and is given in Table 3.5.4-1. The baseline building construction shall be modeled as layers as defined in Table 3.5.4-2.

Table 3.5.4-1: Baseline Building R-value and U-factor Criteria for Walls

Climate Zone	Nonresidential		Residential		Semi-Heated
	Name	U-factor	Name	U-factor	Name	U-factor
1	R-13	0.124	R-13	0.124	NR	0.352
2
3			R-13+R-7.5 ci	0.064	R-13	0.124
4	R-13+R-3.8 ci	0.084
5
6
7	R-13+R-7.5 ci	0.064
8			R-13+R-10 ci	0.055

Table 3.5.4-2: Baseline Building Wall 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/ ft²·°F·h)
R-13 + R-10.0	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-10.0 continuous insulation	1.800	0.0200	1.8	0.29	10.0
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					18.05	.055
R-13 + R-7.5	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-7.5 continuous insulation	1.800	0.0200	1.8	0.29	7.50
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					15.55	0.64
R-13 + R-3.8	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-3.8 continuous insulation	0.912	0.0200	1.8	0.29	3.80
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					11.85	0.84
R-13	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					199.95	0.124
NR	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Cavity/steel framing					0.79
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					2.84	3.52

Exterior Wall Surface Properties
Applicability	All walls
Definition	The exterior wall surface properties descriptor describes the characteristics of exterior wall surfaces. Exterior surface properties may 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. Data structures are outlined in the reference data structures section of this chapter.
Units	Data structure: exterior surface properties
Input Restrictions	The default value for emittance is 0.90. The default value for reflectance is 0.30. There is no default for roughness. The default values may be overridden only in cases when the lower reflectance can be documented by manufacturers’ literature or tests.
Baseline Rules	The baseline building shall use default values for emittance and reflectance. The roughness of the baseline building walls shall be identical to the proposed design.

3.5.4 Roofs

Geometry

The geometry of roofs, walls, floors, doors, and fenestration should match the construction documents or as-built drawings as accurately as possible. Curved surfaces such as a dome or semi-circular wall may be approximated by a series of flat constructions with orientation or tilt differences of no more than 45 degrees from the actual surface.

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 Building	None

Roof Type
Applicability	All roof surfaces
Definition	One of three classifications of roofs defined in Standard 90.1-2019, i.e., insulation entirely above deck, metal building, and attic and other. The prescriptive U-factor requirements for roofs depend on the type. The PRM fixes the type for the baseline building to “insulation entirely above deck.”
Units	List: Attic and Other Roofs; Metal Building Roofs; and Roofs with Insulation Entirely Above Deck
Input Restrictions	As designed
Baseline Building	The baseline building roof type is of the type “insulation entirely above deck.” Refer to descriptor ‘Roof Construction’ for more details.

Roof Geometry
Applicability	All roofs, required input
Definition	Roof geometry defines the position, orientation, azimuth, tilt, and dimensions of the roof surface. The geometry of roofs should match the construction documents or as-built drawings as accurately as possible. Unusual curved surfaces such as a dome or semi-circular wall may be approximated by a series of flat constructions with orientation or tilt differences of no more than 45 degrees from the actual surface. The details of how the coordinate system is implemented may vary among software programs. The data structure for surfaces is described in Section 3.11.3 of this manual.
Units	Data structure: surface
Input Restrictions	The only restriction is that the surfaces defined must agree with the building being modeled, as represented on the construction drawings or as-built drawings
Baseline Building	Roof geometry will be identical in the proposed and baseline building designs

Roof Construction
Applicability	All roofs, required input
Definition	A specification containing a series of layers that result in a construction assembly for the proposed design. The first layer in the series represents the outside (or exterior) layer and the last layer represents the inside (or interior) layer. See the building descriptors above for roof construction type.
Units	List: layers
Input Restrictions	The construction assembly, as designed, defined by a series of layers. Each layer specified must consist of materials as described in Section 3.5.2. NOTE: Table A₉.2A in Standard 90.1-2019 Appendix A specifies the effective insulation/framing layer R-values for roof and floor insulation installed between metal framing 4’ OC. These values are intended to be used for all other framing, 16”, 2’ and 3’.
Baseline Building	Roofs in the baseline building are of the type “insulation entirely above deck.” The insulation requirement is determined by climate zone and baseline standard. The baseline building roof construction shall be modeled as layers. For new construction, the baseline building roof type is insulation above deck. The U-factor required for baseline roof construction is defined in Table 21. The layer by layer construction corresponding to each U-factor shall be modeled as shown in Table 22. For existing buildings, the baseline roof shall follow the same rules as new buildings.

Table 21. Standard 90.1-2019 Requirements for Baseline Roof Insulation for each Space Conditioning Category

	U-Factor (Btu/ ft²·°F·h/)
	Nonresidential	Residential	Semiheated
Climate Zone 0 and 1	0.063	0.063	1.282
Climate Zone 2	0.063	0.063	0.218
Climate Zone 3	0.063	0.063	0.218
Climate Zone 4	0.063	0.063	0.218
Climate Zone 5	0.063	0.063	0.173
Climate Zone 6	0.063	0.063	0.173
Climate Zone 7	0.063	0.063	0.173
Climate Zone 8	0.048	0.048	0.093

Table 22. Standard 90.1-2019 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
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-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									116.18			1.28

Roof Solar Reflectance and Thermal Emittance
Applicability	All opaque exterior roof surfaces exposed to ambient conditions
Definition	The solar reflectance of a material. For roofing materials, the 3-year-aged reflectance value from a laboratory accredited by a nationally recognized accreditation organization such as the Cool Roof Rating Council (CRRC) testing should be used.
Units	Unitless fraction between 0 and 1
Input Restrictions	For roof surfaces: The default value is prescribed to be 0.3 for solar reflectance and 0.9 for emittance. For roofs these defaults may be overridden when 3-year-aged data for reflectance and emittance is determined according to CCR-1 Standard.
Baseline Building	Roofs in the baseline building shall be modeled with a solar reflectance shall be 0.30 and thermal emittance of 0.90

Wall Name
Applicability	All walls, optional input
Definition	A unique name or code that relates the exterior wall to the design documents. This is an optional input since there are other acceptable ways to key surfaces to the construction documents.
Units	Text, unique
Input Restrictions	None

Wall Geometry
Applicability	All walls, required input
Definition	Wall geometry defines the position, orientation, azimuth, and tilt of the wall surface. The details of how the coordinate system is implemented may vary between simulation engines. 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.

Wall Construction
Applicability	All walls, 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 wall surfaces must reference a construction assembly that meets the mandatory requirements of the appropriate baseline standard.

[table title="Baseline Building Wall Construction Assemblies" id="baseline-building-wall-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/ ft²·°F·h)
Wall R-13 + R-18.8	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-18.8 continuous insulation	1.800	0.0200	1.8	0.29	18.8
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					26.85	0.037
Wall R-13 + R-15.6	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-15.6 continuous insulation	1.800	0.0200	1.8	0.29	15.6
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					23.65	0.042
Wall R-13 + R-10.0	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-10.0continuous insulation	1.800	0.0200	1.8	0.29	10.0
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					18.05	.055
Wall R-13 + R-7.5	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-7.5 continuous insulation	1.800	0.0200	1.8	0.29	7.50
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					15.55	0.64
Wall R-13 + R-3.8	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-3.8 continuous insulation	0.912	0.0200	1.8	0.29	3.80
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					11.85	0.84
Wall R-13	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					199.95	0.124
Wall R-13	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Cavity/steel framing					0.79
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					2.84	3.52

Exterior Wall Surface Properties
Applicability	All walls
Definition	The exterior wall surface properties descriptor describes the characteristics of exterior wall surfaces. Exterior surface properties may 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. The descriptor is a critical default structure input, applicable to all models. Critical defaults require documentation to change. Data structures are outlined in the reference data structures section of this chapter.
Units	Data structure: exterior surface properties
Input Restrictions	The default value for emittance is 0.90. The default value for reflectance is 0.30. There is no default for roughness. The default values may be overridden only in cases when the lower reflectance can be documented by manufacturers’ literature or tests.

Wall Name
Applicability	All walls, optional input
Definition	A unique name or code that relates the exterior wall to the design documents. This is an optional input since there are other acceptable ways to key surfaces to the construction documents.
Units	Text, unique
Input Restrictions	None

Wall Geometry
Applicability	All walls, required input
Definition	Wall geometry defines the position, orientation, azimuth, and tilt of the wall surface. The details of how the coordinate system is implemented may vary between simulation engines. 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.

Wall Construction
Applicability	All walls, 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 wall surfaces must reference a construction assembly that meets the mandatory requirements of the appropriate baseline standard.

[table title="Baseline Building Wall Construction Assemblies" id="baseline-building-wall-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/ ft²·°F·h)
Wall R-13 + R-18.8	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-18.8 continuous insulation	1.800	0.0200	1.8	0.29	18.8
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					26.85	0.037
Wall R-13 + R-15.6	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-15.6 continuous insulation	1.800	0.0200	1.8	0.29	15.6
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					23.65	0.042
Wall R-13 + R-10.0	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-10.0continuous insulation	1.800	0.0200	1.8	0.29	10.0
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					18.05	.055
Wall R-13 + R-7.5	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-7.5 continuous insulation	1.800	0.0200	1.8	0.29	7.50
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					15.55	0.64
Wall R-13 + R-3.8	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	R-3.8 continuous insulation	0.912	0.0200	1.8	0.29	3.80
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					11.85	0.84
Wall R-13	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	Gypsum board	0.625	0.0930	50	0.2	0.56
	R-13 insulation/steel framing					6.00
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					199.95	0.124
Wall R-13	Air film					0.17
	Stucco	0.400	0.4167	116	0.2	0.08
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Cavity/steel framing					0.79
	Gypsum board	0.625	0.0930	50	0.2	0.56
	Interior air film					0.68
	Total for assembly					2.84	3.52

Exterior Wall Surface Properties
Applicability	All walls
Definition	The exterior wall surface properties descriptor describes the characteristics of exterior wall surfaces. Exterior surface properties may 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. The descriptor is a critical default structure input, applicable to all models. Critical defaults require documentation to change. Data structures are outlined in the reference data structures section of this chapter.
Units	Data structure: exterior surface properties
Input Restrictions	The default value for emittance is 0.90. The default value for reflectance is 0.30. There is no default for roughness. The default values may be overridden only in cases when the lower reflectance can be documented by manufacturers’ literature or tests.