5.5   Building Envelope Data    

5.5.1 Materials    

Energy simulation programs commonly define construction assemblies by listing a sequence of material layers that make up the construction assembly. Appendix 5.5A has a list of standard materials that may be referenced by construction assemblies. Additional materials not 'listed in Appendix 5.5A may be defined as described below. Alternate methods may be used to define construction assemblies such as specifying the U-factor and optionally, a metric describing thermal mass such as heat capacity (HC). These alternate methods may not require identification of materials. When a material is defined, all of the properties listed below must be defined. Some materials listed in Appendix 5.5A are non-homogeneous, for instance, framing members with insulation in the cavity. Typical construction assemblies and their respective material layers are defined in Reference Appendix JA4.  Additionally, the properties of the each material layer can be found in ACM Appendix 5.5A.

Material Name

Applicability

Opaque constructions

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 in ACM Appendix 5.5A. The user may not modify entries for predefined materials.

Standard Design

Not applicable

Density

Applicability

Opaque constructions

Definition

The density (or mass per unit of volume) of the construction material as documented in Appendix 5.5A.

Units

lb/ft3

Input Restrictions

Prescribed from Appendix 5.5A

Standard Design

Not applicable

 

Specific Heat

Applicability

Opaque constructions

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

Prescribed from Appendix 5.5A

Standard Design

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

Prescribed from Appendix 5.5A

Standard Design

Not applicable

Thickness

Applicability

All non-standard materials

Definition

The thickness of a material

Units

ft or in.

Input Restrictions

Prescribed from Appendix 5.5A

Standard Design

Not applicable

 

5.5.2 Construction Assemblies    

For California Compliance and Reach, construction assemblies for the proposed design shall be created by selecting from a library of building construction layers in ACM Appendix 5.5A. The compliance software shall all specify composite layers that consist of both framing and insulation and shall use established methods defined in the ASHRAE Handbook of Fundamentals for calculating effective R-values of composite layers.

Geometry

The geometry of roofs, walls, floors, doors and fenestration 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 constructions.

Mass Walls

For mass walls, the user first chooses the mass layer from Appendix 5.5A.  After that, the user may select an insulating layer from Appendix 5.5A for outside and/or inside the mass wall.

Ballasted Roofs, Vegetated Roofs, Concrete Pavers, and Other Mass Roofs

An additional layer may be added to the roof construction assembly when thermal mass is used above the roof membrane. This exception is intended to allow ballasted roofs, concrete pavers and other massive elements to be explicitly modeled. To qualify, the weight of the stone ballast, the concrete pavers or other elements must exceed 15 lb/ft². The thickness, heat capacity, conductance and density of the additional mass layer shall be based on the measured physical properties of the material. If the surface properties of the additional mass material have been verified through the Cool Roof Rating Council (CRRC), the CRRC reported properties may be used for the proposed design; otherwise, the mass layer shall be modeled with an aged reflectance of 0.10 and an emittance of 0.85.

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.

Standard Design

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. 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

Input Restrictions

The layers method shall be used for all above-grade constructions.

Standard Design

For each construction, the proposed design specification method shall be used.

 

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. Material names must be from the standard list (Appendix E) or defined (see above) ACM Appendix 5.5A.

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 the layer descriptions.

Standard Design

See building descriptors for Roofs, Exterior Walls, Exterior Floors, Doors, Fenestration and Below Grade Walls.

5.5.3 Roofs    

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

Standard Design

None

Roof Type

Applicability

All roof surfaces

Definition

A roof classification defined in the Standards.  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 metal building, wood framed or other

Input Restrictions

Not applicable for new construction; as designed for existing buildings

Standard Design

All roofs in the baseline building are modeled as “insulation entirely above deck.” Metal building.

Standard Design, Existing Buildings

For existing buildings, the standard design roof type is the same as that for the proposed design.

 

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.

Standard Design

Roof geometry will be identical in the proposed and standard design building designs.

For alterations, roof geometry will be fixed, based on one of the building prototypes (office, retail, etc.)

Roof Solar Reflectance

Applicability

All opaque exterior surfaces exposed to ambient conditions

Definition

The solar reflectance of a material. For roofing materials, the 3-year aged reflectance value from CRRC testing should be used if available.

Units

Unitless fraction between 0 and 1

Input Restrictions

For roofs that are part of new construction, if asphalt shingles or composition shingles  are not rated by the Cool Roof Rating Council (CRRC), the default aged solar reflectance shall be equal to 0.08 for asphalt roofs and 0.10 for all other roof types .  The default value may be overridden when roof materials are used that have been tested by the (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.  If the aged CRRC reflectance is not known, the aged CRRC reflectance may be calculated from the initial CRRC reflectance using the following equation:

 

ƿaged = 0.2 + β · (ƿinit – 0.2)

Where,

ƿaged = the calculated aged reflectance

β = 0.65 for field-applied coatings, 0.7 for all other roof surfaces

ƿinit = the initial CRRC reflectance

 

Standard Design

For new construction, the standard design reflectance is defined in Table 140.3-B for nonresidential buildings, Table 140.3-C for high-rise residential buildings and hotel-motel buildings containing guestrooms, and Table 140.3-D for relocatable classroom buildings.

For alterations to more than 50% of the roof area or roof areas above 2,000 ft2 the standard design shall be modeled as the more efficient of either the existing conditions or the values required for cool roofs under Section 141.0 of the Standards. 

Roof Thermal Emittance

Applicability

All opaque exterior surfaces exposed to ambient conditions; this is prescribed for exterior walls at 0.85 and is the as-designed value entered for roofs, with some restrictions.

Definition

The thermal emittance of a material. For roofing materials, the 3-year aged emittance value from CRRC testing should be used if available.

Units

Unitless fraction between 0 and 1

Input Restrictions

For roofs, new construction:  as designed, from CRRC values.  If CRRC rating information is not available, the default thermal emittance shall be 0.75.

 

Standard Design

For roofs, new construction, the standard design thermal emittance shall be 0.85.

For alterations to more than 50% of the roof area or roof areas above 2,000 ft2 the standard design shall be modeled as the more efficient of either the existing conditions or a thermal emittance of 0.85. 

 

SPECIAL NOTE: A simplified version of the compliance software will be developed to be used for envelope tradeoffs, and for roof alterations in particular. This option will constrain almost all inputs not related to roof performance and will provide a way to determine insulation tradeoffs allowed with roof reflectance.

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, defined by a series of layers, must be equal to or more efficient than the mandatory U-factor requirements of Section 120.7 of the Standards for new construction, and Section 141.0 of the Standards for alterations.  Note that these U-Factor requirements assume an exterior air film of R-0.17 and an interior air film of R-0.61.  Each layer specified must be listed in the materials database in the ACM Appendix 5.5A. 

New Construction

Metal Building                                               U – 0.098

Wood Framed and Others                             U – 0.075

Additions and Alterations

Roof / Ceiling Insulation                                See 141.0(b)2Biii of the Standards

 

Appropriate R-values for insulation can be calculated using the formula below.

Rinsulation = (1/U-factor) – Rlayer(1) – Rlayer(2) – Rlayer(3) – Rlayer(n)

Rinsulation = Rins.continuous + Rins.framing

Ceilings that form the boundary between the modeled building of an additions and alterations project and the existing, unmodeled portion of the building may be modeled as adiabatic roofs (no heat transfer).

Standard Design

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 as defined. See Appendix 5.5B for details.

For new construction, the standard design roof type is wood framed and other, and the roof is a standing seam metal roof, with the R-value of continuous insulation adjusted to match the prescriptive Standards for wood-framed and other roofs.  The U-factor required for roof construction is defined in Table 140.3-B, C or D of the Standards.  Programs that model a U-factor shall include an exterior and interior air film resistance.  The Standard Design construction is based on JA4-10 Table 4.2.7 and assumes an exterior air film of R-0.17 and an interior air film of R-0.61.

 

The standard design construction shall include the following layers:

Layer 1         Metal Standing Seam 1/16 in.     R - 0.00

Layer 2         Continuous Insulation                R - Based on Climate Zone

Layer 3         Open Framing + No Insulation    R – 0.00

The value of the Continuous Insulation layer entirely above framing shall be set to achieve the following R-values:

Nonresidential Buildings – Continuous Ins.

Climate Zones 2, 3, 4, 9- 16   R – 24.86

Climate Zones 1, 5:               R - 19.62

Climate Zones 7, 8:               R – 14.15

Climate Zones 6:                   R – 12.55

High-Rise Residential Buildings and Hotel / Motel Guestrooms – Continuous Ins.

Climate Zones 2, 4, 8- 16       R – 34.93

Climate Zone 1                     R – 28.63

Climate Zones 3, 5, 7            R – 24.86

For mixed use buildings, the roof standard design requirements shall be determined by which space type (Nonresidential or Residential) is the majority of the floor area of the adjoining conditioned spaces.

For alterations, any approved roof type may be used.  The U-factor in the standard design shall be modeled as the more efficient of either the existing conditions or the values stated in Section 141.0 of the Standards.  Where applicable, selection shall be based on building type, assembly, and climate zone.  A construction of layers shall be defined to yield an equivalent U-factor.

 

Standard Design, Existing Buildings

For existing buildings, if the roof component is not altered, the standard design roof construction shall match the proposed design roof construction of the existing building. Also, the standard design roof that serves as the boundary between the modeled additions and alterations building and the existing, unmodeled portion of the building is modeled as an adiabatic roof, to match the proposed design.  If the roof is altered, the roof component shall meet the prescriptive requirements for new construction for the roof type of the existing building.

The roof type of the existing building is either a metal building roof or a wood-framed or other roof. The standard design roof assemblies for altered roofs are shown below for the appropriate climate zones.

The Reference Appendix JA4 reference and U-factor are provided for reference only. The U-factor does not need to exactly match the JA4 value, but the layer shall match the layer described below.

Alterations Roof Standard Design

Nonres

CZ 1,3-9

CZ 2,10-16

HRR

n/a

All Climate Zones

JA4 U-factor*

0.082

0.055

Roof Type

Wood-framed roof

Wood-framed roof

Layer 1

2x8, 24” o.c., No Insulation

JA4 4.2.2-F25

2x8, 24” o.c., No Insulation

JA4 4.2.2-H25

Layer 2

R-8 continuous insulation

R-14 continuous insulation

 

*U-factor and JA4 assembly table and cell reference is provided for reference only. The compliance software shall only require that the layers in the construction match those in this table.

For alterations, any approved roof type may be used.  The U-factor in the standard design shall be modeled as the more efficient of either the existing conditions or the values stated in Section 141.0 of the Standards.  Where applicable, selection shall be based on building type, assembly, and climate zone.  A construction of layers shall be defined to yield an equivalent U-factor.

 

5.5.4 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

Standard Design

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 five wall type categories are as follows:

a)   Mass Light,

b)   Mass Heavy

c)   Metal building,

d)   Metal framing, and

e)   Wood framing and other walls.

 

A Mass Light wall is defined as a wall with total heat capacity greater than 7 but less than 15 Btu/ft2-F. A Mass Heavy wall is defined as a wall with a total heat capacity of 15 Btu/ft2-F or greater. (Heat capacity is defined as the product of the specific heat in Btu/lb -F, the thickness in ft, and the density in lb/ft3.)

Units

List: mass light, mass heavy, metal building walls, metal framing walls, and wood framing and other walls

Input Restrictions

This input is required for existing buildings when any wall is altered. This input is not required for new construction.

Standard Design

All walls in the standard design building are modeled as “metal framed.”

 

Standard Design, Existing Buildings

The existing building standard design Wall Type shall be the same as the proposed.

 

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

As designed

Standard Design

Wall geometry in the standard design building is identical to the proposed design.

Wall Solar Reflectance

Applicability

All opaque exterior surfaces exposed to ambient conditions

Definition

The solar reflectance of a material. For roofing materials, the 3-year aged reflectance value from CRRC testing should be used if available.

Units

Unitless fraction between 0 and 1

Input Restrictions

For walls and other non-roof surfaces:  The value is prescribed to be 0.3.

 

Standard Design

For walls and other non-roof surfaces: The value is prescribed to be 0.3.

For new construction, the standard design reflectance shall meet the requirements stated in Section 140.3 of the Standards. 

For alterations to more than 50% of the roof area or roof areas above 2,000 ft2 the standard design shall be modeled as the more efficient of either the existing conditions or the values required for cool roofs under Section 141.0 of the Standards. 

Wall Thermal Emittance

Applicability

All opaque exterior surfaces exposed to ambient conditions; this is prescribed for exterior walls at 0.85 and is the as-designed value entered for roofs, with some restrictions.

Definition

The thermal emittance of a material. For roofing materials, the 3-year aged emittance value from CRRC testing should be used if available.

Units

Unitless fraction between 0 and 1

Input Restrictions

For walls and other non-roof surfaces: The value is prescribed to be 0.9.

For roofs, new construction:  as designed, from CRRC values.  If CRRC rating information is not available, the default thermal emittance shall be 0.75.

 

Standard Design

For walls and other non-roof surfaces, the thermal emittance is 0.90.

For roofs, new construction, the standard design thermal emittance shall be 0.85.

For alterations to more than 50% of the roof area or roof areas above 2,000 ft2 the standard design shall be modeled as the more efficient of either the existing conditions or a thermal emittance of 0.85. 

 

SPECIAL NOTE: A simplified version of the compliance software will be developed to be used for envelope tradeoffs, and for roof alterations in particular. This option will constrain almost all inputs not related to roof performance and will provide a way to determine insulation tradeoffs allowed with roof reflectance.

 

Wall Construction

Applicability

All walls that use the Layers method

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 wall construction type.

Units

List: Layers

Input Restrictions

The construction assembly, defined by a series of layers, must be equal to or more efficient than the mandatory U-factor requirements of Section 120.7 of the Standards for new construction.  Note that these U-Factor requirements assume an exterior air film of R-0.17 and an interior air film of R-0.68.  Each layer specified, with the exception of composite layers, must be listed in the materials database in the ACM Appendix 5.5A.

New Construction

Metal Building                                               U – 0.113

Metal Framed                                                U – 0.105

Light Mass Walls                                          U – 0.440

Heavy Mass Walls                                        U – 0.690

Wood Framed and Others                              U – 0.110

Spandrel Panels / Glass Curtain Walls            U – 0.280

Additions and Alterations

Metal Building                                               U – 0.113

Metal Framed                                               U – 0.217

Wood Framed and Others                             U – 0.110

Spandrel Panels / Glass Curtain Walls            U – 0.280

 

Appropriate R-values for insulation can be calculated using the formula below.

Rinsulation = (1/U-factor) – Rlayer(1) – Rlayer(2) – Rlayer(3) – Rlayer(n)

Rinsulation = Rins.continuous + Rins.framing

Walls that form the boundary between the modeled building of an additions and alterations project and the existing, unmodeled portion of the building may be modeled as adiabatic walls (no heat transfer).

 

Standard Design

For new construction, the standard design wall type is metal framed with continuous insulation.  The U-factor required for wall construction of the standard design building is defined in Table 140.3-B, C or D of the Standards.  Programs that model a U-factor shall use an exterior and interior air film resistance.  The Standard Design construction is based on JA4-10 Table 4.3.3 and assumes an exterior air film of R-0.17 and an interior air film of R-0.68.

 

For metal framed walls, the standard design construction shall include the following layers:

Layer 1         Stucco – 7/8 in.                         R - 0.18

Layer 2         Building Paper                          R – 0.06

Layer 3         Continuous Insulation                R - Based on Climate Zone

Layer 4         Closed Framing and No Ins.       R – 0.65

Layer 5         Gypsum Board – 1/2 in.             R – 0.45

 

The value of the Continuous Insulation layer entirely outside framing shall be set to achieve the following R-values:

Nonresidential Buildings – Continuous Ins.

Climate Zones 1, 6, and 7                  R – 8.01

Climate Zones 2, 4, 5, and 8 – 16       R – 13.94

Climate Zones 3                                R – 10.01

High-Rise Residential Buildings and Hotel / Motel Guestrooms – Continuous Ins.

Climate Zones 1 and 5                      R – 7.33

Climate Zones 2 – 4, and 6 – 16         R – 9.52

For mixed use buildings, that contain both nonresidential and residential spaces, walls adjacent to nonresidential spaces shall use the Nonresidential Buildings standard design construction, and walls adjacent to residential and high-rise residential spaces shall use the high-rise residential standard design construction.

 

Standard Design, Existing Buildings

For existing buildings, the standard design wall for unaltered components is the same as the proposed design.  Also, the standard design wall that serves as the boundary between the modeled additions and alterations building and the existing, unmodeled portion of the building is modeled as an adiabatic wall, to match the proposed design. For altered exterior walls, the baseline assembly shall be as follows:

Step 1. Determine the existing wall type: metal building wall, metal framed wall, mass wall, medium; mass wall, heavy; wood-framed wall. The standard design wall type for alterations in existing building shall be the same as the proposed design wall type.

Step 2. Use the tables below to determine the standard design construction assembly, (The JA4 U-factors and cell references are provided as a reference only; the assembly U-factor need not match exactly the U-factor in Reference Appendix JA4, but the assembly shall include the layers defined below.)

Metal Framed Wall – same as new construction assembly above

Mass Wall, Light (Heat Capacity > 7 Btu/ft2-F and <15 Btu/ft2-F

 

 

CZ2,10-16

CZ 1

CZ 4

CZ 3

CZ 5-9

JA4 U-factor

0.170

0.196

0.227

0.278

0.440

Layer 1

4 in MW CMU, 115 lb/sf

4.3.6-B5

4 in MW CMU, 115 lb/sf

4.3.6-B5

4 in MW CMU, 115 lb/sf

4.3.6-B5

4 in MW CMU, 115 lb/sf

4.3.6-B5

8 in NW CMU, 125 lb/ft2, partly grouted, reinforced with insulated cells

4.3.6-C10

Layer 2*

3” furring space with R-21 insulation and metal clips

4.3.14-V15

(equiv R-4.8 c.i.)

2.5” furring space with R-13 insulation and metal clips

4.3.14-R13

(equiv R-3.8 c.i.)

2” furring space with R-13 insulation and metal clips

4.3.14-N11

(equiv R-3.3 c.i.)

1.5” furring space with R-9 insulation and metal clips

4.3.14-J9

(equiv R-2.5 c.i.)

 

Layer 3

 

 

 

 

 

Layer n

 

 

 

 

 

 

Heavy Mass Wall (Heat Capacity >= 15 Btu/ft2-F):

 

 

CZ2,10-16

CZ 1

CZ 4

CZ 3

CZ 5-9

 

JA4 U-factor

0.160

0.184

0.211

0.253

0.650

0.690

Layer 1

8 in. NW CMU, 125 lb/ft2, solid grout, reinforced

4.3.5-A10

8 in. NW CMU, 125 lb/ft2, solid grout, reinforced

4.3.5-A10

8 in. NW CMU, 125 lb/ft2, solid grout, reinforced

4.3.5-A10

8 in. NW CMU, 125 lb/ft2, solid grout, reinforced

4.3.5-A10

8 in NW CMU, 125 lb/ft2, solid grout, reinforced 4.3.5-A9

8 in. NW CMU, 125 lb/ft2, solid grout, reinforced

4.3.5-A10

Layer 2*

3” furring space with R-21 insulation and metal clips

4.3.14-V15

(equiv R-4.8 c.i.)

2.5” furring space with R-13 insulation and metal clips

4.3.14-R13

(equiv R-3.8 c.i.)

2” furring space with R-13 insulation and metal clips

4.3.14-N11

(equiv R-3.3 c.i.)

1.5” furring space with R-9 insulation and metal clips

4.3.14-J9

(equiv R-2.5 c.i.)

 

 

Layer 3

 

 

 

 

 

 

Layer n

 

 

 

 

 

 

 

Metal Building Walls

JA4 U-factor

CZ15

CZ 2,4,5,8,9,10-14,16

CZ 1,3,6,7

0.057

0.061

0.113

Layer 1

R-13 batt insulation draped over purlins and compressed

 

R-13 batt insulation draped over purlins and compressed

 

R-13 batt insulation draped over purlins and compressed

Rlayer=8.85

Layer 2*

Second layer R-13 batt insulation

Second layer R-10 batt insulation

 

Layer 3

 

 

 

Layer n

 

 

 

 

Wood-Framed Walls

JA4 U-factor

CZ15

CZ 2,4,9-14,16

CZ 4

CZ 3

0.042

0.059

0.102

0.110

Layer 1

2x4, 16” o.c, with R-13 batt ins

2x4, 16” o.c., with R-11 batt ins

2x4, 16” o.c. with R-13 batt ins

2x4, 16” o.c. with R-11 batt ins

Layer 2*

R-14 continuous insulation

R-8 continuous insulation

 

 

 

5.5.5 Exterior Floors    

Floor Name

Applicability

All floor surfaces

Definition

A unique name or code that relates the exposed floor to the design documents. Exposed floors include floors exposed to the outdoors and floors over unconditioned spaces, but do not include slab-on-grade floors, below grade floors, or interior floors.

Units

Text: unique

Input Restrictions

None

Standard Design

None

Floor Type

Applicability

All exterior floor surfaces, optional

Definition

The category that defines the standard design prescriptive floor requirements.

Units

List: mass, other

Input Restrictions

Not applicable for new construction; either

Standard Design

The standard design building floors shall be of type “other” 

Standard Design, Existing Buildings

The standard design building floor type for existing buildings shall be same as proposed.

Floor Geometry

Applicability

All exterior floors, required input

Definition

Floor geometry defines the position, orientation, azimuth, and tilt of the floor 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

As designed

Standard Design

Standard design building floor geometry is identical to the proposed design.

Floor Construction

Applicability

All floors, 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 floor construction type.

Units

List: Layers

Input Restrictions

The construction assembly, defined by a series of layers, must be equal to or more efficient than the mandatory U-factor requirements of Section 120.7 of the Standards for new construction, and Section 141.0 of the Standards for alterations.  Note that these U-Factor requirements assume an exterior air film of R-0.17 and an interior air film of R-0.92.  Each layer specified must be listed in the materials database in the ACM Appendix 5.5A.

New Construction

Raised Mass Floors                                      U – 0.269

Other Floors                                                 U – 0.071

Heated Slab Floors                                       Climate Zone (see Section 120.7)

Additions and Alterations

Raised Framed Floors                                   U – 0.071

Raised Mass Floors in High-rise Res and Hotel Motel U – 0.111

Raised Mass Floors in Other Occupancies     No Requirement

 

Appropriate R-values for insulation can be calculated using the formula below.

Rinsulation = (1/U-factor) – Rlayer(1) – Rlayer(2) – Rlayer(3) – Rlayer(n)

Rinsulation = Rins.continuous + Rins.framing

Floors that form the boundary between the modeled building of an additions and alterations project and the existing, unmodeled portion of the building may be modeled as adiabatic floors (no heat transfer).

Standard Design

For new construction, the floor type for the standard design building is metal framed.  The U-factor required for floor construction is defined in Table 140.3-B, C or D of the Standards.  Programs that model a U-factor shall use an exterior and interior air film resistance.  The Standard Design construction is based on JA4-10 Table 4.4.5 and assumes an exterior air film of R-0.17 and an interior air film of R-0.92.

 

For metal framed floors, the standard design construction shall include the following layers:

Layer 1         Open Framing + No Ins.             R – 0.00

Layer 2         Continuous Insulation                R – Based on Climate Zone

Layer 3         Plywood – 5/8 in.                      R – 0.78

Layer 4         Carpet and Pad – 3/4 in.            R – 1.30

 

The value of the Continuous Insulation layer entirely above or below framing shall be set to achieve the following R-values:

Nonresidential Buildings – Continuous Ins.

Climate Zones 1                                R – 17.66

Climate Zones 2, 11, and 14 -16         R – 22.47

Climate Zones 3 – 10, 12, and 13       R – 10.91

 

High-Rise Residential Buildings and Hotel / Motel Guestrooms – Continuous Ins.

Climate Zones 1, 2, 14, and 16          R – 26.24

Climate Zones 3 – 6, 8 – 13, and 15   R – 22.47

Climate Zones 7                                R – 10.91

 

Standard Design, Existing Buildings

The standard design floor that serves as the boundary between the modeled additions and alterations building and the existing, unmodeled portion of the building is modeled as an adiabatic floor, to match the proposed design. The standard design floor construction for existing buildings depends on the floor type.

 

Raised Floors, Floor Type = Other  (framed floors)

JA4 U-factor

All Climate Zones, Nonres

0.071, JA4  4.4.2-A2

Layer 1

2x6 Wood-Framed, 16” o.c., R-11 batt

Layer 2

 

 

Raised Floors, Floor Type= Mass

JA4 U-factor

All Climate Zones, Nonres

All Climate Zones, High-Rise Res.

U=0.269

U=0.111, JA4  4.4.2-A2

Layer 1

Metal Deck, R-0

Metal Deck, R-0

Layer 2

4” Lightweight Concrete

4” Lightweight Concrete

Layer 3

 

R-6 continuous insulation

 

5.5.6 Doors    

Door Name

Applicability

All exterior doors, optional input

Definition

A unique name or code that relates the door to the design documents submitted. Doors that are more than 50% glass are treated as windows and must be determined and entered by using the Fenestration building descriptors.

Units

Text: unique

Input Restrictions

None

Standard Design

None

Door Type

Applicability

All exterior doors, required input

Definition

One of two door classifications of either: swinging or non-swinging. Non-swinging are generally roll-up doors. The prescriptive U-factor requirements depend on door type and climate.  This building descriptor may be derived from other building descriptors, in which case a specific input is not necessary.

Units

List: swinging or non-swinging

Input Restrictions

The door type shall be consistent with the type of door represented on the construction documents or as-built drawings.

Standard Design

The standard design building door type shall be the same as the proposed design.

Door Geometry

Applicability

All exterior doors

Definition

Door geometry defines the position and dimensions of the door surface relative to its parent wall surface. The azimuth and tilt (if any) of the door is inherited from the parent surface. The position of the door within the parent surface is specified through X,Y coordinates. The size is specified as a height and width (all doors are generally assumed to be rectangular in shape). The details of how the geometry of doors is specified may vary for each energy simulation program.

Units

Data structure: opening

Input Restrictions

As designed

Standard Design

Door geometry in the standard design building is identical to the proposed design.

Door Construction

Applicability

All exterior doors

Definition

The thermal transmittance of the door, including the frame.

Units

Btu/h·ft2·°F

Input Restrictions

The construction assembly must be equal to or more efficient than the mandatory U-factor requirements of Section 110.6 of the Standards for new construction.  For alterations there are no restrictions.

Standard Design

For new construction, the U-factor required for door construction is defined in Table 140.3-B, C or D of the Standards.

 

Nonresidential Buildings – U Factor

Non-Swinging Doors

Climate Zones 1, and 16                    U – 0.50

Climate Zones 2 – 15                                    U – 1.45

Swinging Doors

Climate Zones 1 – 16                                    U – 0.70

 

High-Rise Residential Buildings and Hotel / Motel Guestrooms – U Factor

Non-Swinging Doors

Climate Zones 1, and 16                    U – 0.50

Climate Zones 2 – 15                        U – 1.45

Swinging Doors

Climate Zones 1 – 16                        U – 0.70

 

For alterations, the U-factor in the standard design is either the same standard design as the new construction standard design if the door is replaced, or the equal to the existing door construction, if the door is unaltered. Where applicable, selection shall be based on building type, assembly, and climate zone.

5.5.7 Fenestration    

Note that fenestration includes windows, doors that have more than 50% glazed area, and skylights. A skylight is fenestration that has a tilt of less than 60° from horizontal.

Fenestration Name

Applicability

All fenestration, optional input

Definition

A unique name or code that relates the fenestration to the design documents and a parent surface.

Units

Text: unique

Input Restrictions

No restrictions

Standard Design

Not applicable

Fenestration Type (Vertical Fenestration)

Applicability

All vertical fenestration

Definition

This is a classification of vertical fenestration that determines the thermal performance and solar performance requirement for vertical fenestration.

Units:

List: Fixed, Operable, Curtain Wall, or Glazed Doors

Input Restrictions

As designed

Standard Design

Fixed

Fenestration Type (Skylights)

Applicability

All skylights

Definition

This is a classification of skylights that determines the thermal performance and solar performance requirement for vertical fenestration.

Units:

List: Glass, curb-mounted, Glass, deck-mounted, or Plastic

Input Restrictions

As designed.

Standard Design

Glass, curb-mounted

Default Fenestration Type

Applicability

All fenestration that uses default thermal performance factors

Definition

This is a classification of fenestration that determines the thermal performance for fenestration using defaults from Standards Section 110.6, Table 110.6-A. This is used for fenestration without NFRC ratings, or for fenestration for altered buildings that includes window films.

Units:

List: Fixed, Operable, Greenhouse/garden, doors, or Skylight

Input Restrictions

As designed

Standard Design

Not applicable

Default Glazing Type

Applicability

All fenestration that uses default thermal performance factors

Definition

This is a classification of fenestration that determines the thermal performance for fenestration using defaults from Standards Section 110.6, Table 110.6-A. This is used for fenestration without NFRC ratings, or for fenestration for altered buildings that includes window films.

Units:

List: Single Pane, Double Pane, Glass Block

Input Restrictions

As designed, Glass Block is only allowed if the Default Fenestration Type is Operable or Fixed

Standard Design

Not applicable

Default Framing Type

Applicability

All fenestration that uses default thermal performance factors and window films for altered fenestration

Definition

This is a classification of fenestration that determines the thermal performance for fenestration using defaults from Standards Section 110.6, Table 110.6-A. This is used for fenestration without NFRC ratings, or for fenestration for altered buildings that includes window films.

Units:

List: Metal, Metal with Thermal Break, Nonmetal

Input Restrictions

As designed

Standard Design

Not applicable

Fenestration Geometry

Applicability

All fenestration

Definition

Fenestration geometry defines the position and dimensions of the fenestration surface within its parent surface and the identification of the parent surface. The orientation and tilt is inherited from the parent surface. The details of how the coordinate system is implemented may vary between Compliance Software programs.

Display Perimeter.   Display perimeter is the length of an exterior wall in a B-2 occupancy that immediately abuts a public sidewalk, measured at the sidewalk level for each story that abuts a public sidewalk. The compliance software shall allow the user to specify a value for the length of display perimeter, in feet, for each floor or story of the building. The user entry for Display Perimeter shall have a default value of zero.  Note: Any non-zero input for Display Perimeter is an exceptional condition that shall be reported on the PERF-1 exceptional condition list and shall be reported on the ENV forms.  The value for Display Perimeter is used as an alternate means of establishing Maximum Wall Fenestration Area in the standard design (§140.3 of the Standards).

The Display Perimeter shall be calculated separately for West facing fenestration, and for non-West facing fenestration.

Floor Number.  The compliance software shall also allow the user to specify the Display Perimeter associated with each floor (story) of the building.

Units

Data structure: opening

Geometry is defined relative to the parent surface and can include setbacks.

Inputs include:

Geometry of opening (window or skylight), parent surface, display perimeter (optional), percent of roof area exempt from skylight requirements §140.3 of the Standards.

Input Restrictions

As designed.

Specification of the fenestration position within its parent surface is required for the following conditions:

1) Exterior shading is modeled from buildings, vegetation, other objects; or

2) If daylighting is modeled within the adjacent space.

Standard Design

The standard design calculates the window wall ratio (WWR) for each orientation and the overall window wall ratio for the building.  The window wall ratio is the total fenestration area (including framing) divided by the gross exterior wall area.

The standard design vertical fenestration area and horizontal fenestration area for data center buildings shall be zero (0).

For all other buildings, the geometry of the fenestration in the standard design shall be identical to the proposed design with the following exceptions:

Exception 1. Either the whole building window wall ratio or west window wall ratio exceeds 40%.

Exception 2. If display perimeter is entered, the fenestration area exceeds the greater of 40% of the gross wall area (excluding adiabatic walls) and six times the display perimeter.

Exception 1.  The fenestration is adjusted based on the following conditions:

        Case 1.  WWRo > 0.40, WWRw <=0.40

In this case, the fenestration area of all windows is reduced by multiplying the fenestration area by the ratio 0.40/WWRo.  The dimensions of each window is reduced by multiplying the proposed window dimension by (0.40/WWRo)1/2, so that the same window aspect ratio is maintained.

        Case 2:  WWRo < 0.40. WWRw > 0.40

In this case, the fenestration area of all windows on the west orientation is reduced by multiplying the fenestration area by the ratio 0.40/WWRo.  The dimensions of each window is reduced by multiplying the proposed window dimension by (0.40/WWRo)1/2, so that the same window aspect ratio is maintained.

      Case 3: WWRo > 0.40. WWRw > 0.40

If both the west window wall ratio and the overall window wall ratio exceed the prescriptive limit of 0.40, the fenestration areas must be reduced by:

1)   Adjust the West window area multiplying the west window area by the ratio 0.4/WWRw.

2)   Calculate the WWR of the north, east and south facades:

WWRnes = Window Area nes / Gross Wall Area nes

3)   Adjust the window area of the windows on the north, east and south facades by the following ratio:

WindowAreaN,std = WindowAreaN,prop x 0.4 / WWRnes

WindowAreaE,std = WindowAreaE,prop x 0.4 / WWRnes

WindowAreaS,std = WindowAreaS,prop x 0.4 / WWRnes

4)   Adjust each window geometry for the west façade by multiplying each dimension by (0.4/WWRw)1/2

5)   Adjust each window geometry for the north, east and south façade by multiplying each dimension by (0.4/WWRnes)1/2

Exception 2.  If the display perimeter is entered and the window area exceeds the prescriptive limit, the window area for the standard design is calculated by multiplying the proposed window area by the following ratio:

        WindowAreastd = 6 x DisplayPerimeter

The geometry of each window is modified by the following:

        WindowHeightstd = WindowHeightprop x (WindowAreastd/WindowAreaprop)1/2

        WindowWidthstd = WindowWidthprop x (WindowAreastd/WindowAreaprop)1/2

 

The following rules apply for calculating geometry of skylights. For the calculation of the standard design skylight area, the gross roof area is defined as the total roof area, including skylights, that is directly over conditioned space.

1)   The skylight area of the standard design is set to:

2)   For buildings without atria or with atria having a height less than 55 feet over conditioned space, the smaller of the proposed skylight area and 5% of the gross roof area that is over conditioned space

3)   For buildings with atria at a height of 55ft or greater over conditioned spaces, the smaller of the proposed skylight area and 10% of the gross roof area that is over conditioned space

For buildings with atria or other roof area directly over unconditioned spaces, the smaller of the proposed skylight area or 5% of the roof area excluding the atria area and excluding any adiabatic walls, if present in the modeled building. The skylight area of the atria or roof area directly over unconditioned space is not included in the skylight area limit in this case.

The skylight area for atria over unconditioned space is not included in determining the skylight to roof ratio (SRR) for the building.

Depending on the following condition, adjustments to the SRR as described below shall be made.

i.    For open spaces other than auditoriums, churches, movie theaters, museums and refrigerated warehouses, for buildings in climate zones 2 through 15, and when spaces have ceiling heights greater than 15 ft and floor areas greater than 5000 ft2, - building Floor area x 0.75 = Total primary daylit area+ Total skylit daylit area. See 5.4.5|topic=5.4.5 Daylighting Control for detail description on Primary Daylit area and Skylit Daylit area.

ii.    If the above condition is met and SRR ≤ 0.05, no adjustments are needed.

iii.   If the condition is met and SRR > 0.05, skylight dimensions = Existing Dimension x [1- √ (0.05/SRR of Proposed Building)]

iv.   If the condition is not met triggering the need for additional skylights, the baseline case shall be modeled with new skylights irrespective of the skylight location of the proposed case. The new skylights shall be distributed uniformly such that there is no overlapping of primary daylit areas from skylights or sidelights. The dimension of the new skylights shall be the same as the proposed design if calculated new SRR ≤ 0.05. If SRR > 0.05, skylight dimensions = Existing Dimension x [1- √ (0.05/SRR of Proposed Building)].

Note that the adjustments to SRR is done after adjustments to WWR, if any is completed.

Standard Design, Existing Buildings, Additions and Alterations

For alterations of existing vertical fenestration or skylights, where no fenestration area is added, the Fenestration Geometry of the standard design shall be the same as the proposed for the existing building.

For additions of vertical fenestration or skylights, where the additional fenestration causes the fenestration area to exceed the limit of 40% window to wall ratio (WWR) for the building, 40% WWR for the west orientation of the building, 5% skylight to roof ratio (SRR) for existing buildings without atria 55 feet or higher, or 10% SRR for existing buildings with atria 55 feet or higher, the fenestration geometry for the standard design shall be adjusted from the proposed design according to the rules set forth under the Standard Design rules.

For additions of vertical fenestration and/or skylights that do not cause the fenestration area to exceed any of these limits, the fenestration geometry of the standard design shall be the same as the proposed design.

Skylight Requirement Exception Fraction

Applicability

All buildings with interior ceiling heights greater than 15 feet

Definition

This is the fraction of floor area that is exempt from the minimum skylight area requirement for spaces with high ceilings.

Identifying areas subject to §140.3 of the Standards

When a proposed space has ceiling heights greater than 15 feet, with exterior surfaces having a tilt angle less than 60 degrees (roofs) and no more than 3 stories above grade, the user shall enter the fraction of the modeled space that is exempt from requirements of §140.3 of the Standards. If the proposed design has skylights, the user shall also indicate the area of the proposed design daylight area under skylights in this space. When the user enters a value greater than 0 %for the fraction of the space area exempt to §140.3 of the Standards, the compliance software shall require that the user indicate at least one of the following exceptions:

1.   The building is not located in climate zone 1 or climate zone 16.

2.   Designed general lighting is less than 0.5 W/ft2

3.   Existing walls on plans result in enclosed spaces less than 5,000 ft2

4.   Future walls or ceilings on plans result in enclosed spaces less than 5,000 ft2 or ceiling heights less than 15 feet.

5.     Plans or documents show that space is an auditorium, religious building of worship, movie theater, museum, or refrigerated warehouses.

 

Units:

Data Structure:

Unitless fraction between 0 and 1

List: Four exceptions 'listed above (specified if fraction > 0)

Input Restrictions

No restrictions, other than that the vertical fenestration type must agree with the type specified on the construction documents or the as-built drawings.

Standard Design

Same as the proposed design

Standard Design, Existing Buildings

Not applicable

 

Fenestration Construction

Applicability

All fenestration

Definition

A collection of values that together describe the performance of a fenestration system. The values that are used to specify the criteria are U-factor, SHGC and VT. U-factor and SHGC inputs are whole-window values.

Units

Data structure: shall include at a minimum the following properties as specified by NFRC ratings:

U-factor: whole window U-factor

SHGC: whole window solar heat gain coefficient

VT: visible transmittance

 

Input Restrictions

For new construction, performance information for fenestration shall be obtained from NFRC test results or shall be developed from procedures outlined in section 110.6 of the Standards, as specified below. Values entered shall be consistent with the specifications and the construction documents.

For manufactured products:

      U-factor, SHGC and VT shall be equivalent to NFRC rated values.

      For products not rated by NFRC, U-factor, SHGC and VT shall be determined from CEC default tables (110.6-A and B).

For site built products:

      U-factor, SHGC and VT shall be equivalent to NFRC rated values.

      For products not rated by NFRC, U-factor, SHGC and VT shall:

      be determined from CEC default tables (110.6 A and B) when total site built fenestration > 1000 ft2

      be determined from methods outlined in NA-6 Procedure to Calculate Thermal Performance when total site built fenestration <=1000 ft2

For field fabricated products:

      U-factor, SHGC and VT shall be determined from CEC default tables (110.6 A and B)

For buildings with fenestration area that meets requirements for use of center-of-glass U-factor and SHGC, the fenestration overall U-factor, SHGC and VT shall be determined by the following equations from the Reference Appendix NA6:

UT = C1 + (C2 · Uc)

SHGCT = 0.08 + (0.86 · SHGCc)

VTT = VTF · VTC

Where,

UT = U-factor Is the Total Performance of the fenestration including glass and frame

C1 = Coefficient selected from Table NA6-5 in Reference Appendix NA6

C2 = Coefficient selected from Table NA6-5 in Reference Appendix NA6

UC = Center of glass U-factor calculated in accordance with NFRC 100 Section 4.5.3.1

SHGCT = SHGC Is

SHGCC = Center of glass SHGC calculated in accordance with NFRC 200 Section 4.5.1.1

VTT = Is the Total Performance of the fenestration including glass and frame

VTF = 0.53 for projecting windows, such as casement and awning windows

VTF = 0.67 for operable or sliding windows

VTF = 0.77 for fixed or non-operable windows

VTF = 0.88 for curtain wall/storefront, Site-built and manufactured non-curb mounted skylights

VTF = 1.0 for Curb Mounted manufactured Skylights

VTC = Center of glass VT is calculated in accordance with NFRC 200 Section 4.5.1.1 or NFRC 202 for Translucent Products or NFRC 203 for Tubular Daylighting Devices and Hybrid Tubular Daylighting Devices or ASTM E972

For skylights, the default values shall be the alternate default U-factor and SHGC using default calculations specified above and in Reference Appendix NA6 or the U-factor and SHGC listed in Table 110.6-A and Table 110.6-B in the Standards.

 

For alterations of existing fenestration using window films, the thermal performance for solar heat gain coefficient shall be calculated from two user inputs:

1)   Default Glazing Reference: unique identifier for the glazing without film, that determines the CEC default value (column 3 in table below) and the SHGC ratio multiplier (column 4), and

2)   NFRC window film SHGC: the solar heat gain coefficient multiplier for the window film, from NFRC ratings.

The adjusted SHGC for the glazing with the window film is:

SHGCadj = DefaultSHGCValue x SHGCRatio x NFRCfilm

Where

DefaultSHGCValue = the CEC default value from 110.6, given in column 3 in the table below

SHGCRatio = multiplier based on the default glazing reference, given in column 4 in the table below

NFRCfilm – the NFRC SHGC rating of the window film

1

2

3

 

4

 

5

 

6

Operator Type

Default Glazing Reference

CEC

 Default

SHGC Value

Table 110.6-B

X

 

SHGC Ratio

Xy

 

NFRC Window Film SHGC1,2,3  

Z

 

New Adjusted Total Value

T

Residential or Commercial

Fixed

3 mm (1/8in.) clear

(Single Pane)

0.83

x

1.1528

x

 

=

 

Fixed

3 mm (1/8in.) clear

3 mm (1/8in.) clear

(Double Pane - Clear)

0.73

x

1.1406

x

 

=

 

 

1

2

3

 

4

 

5

 

6

 

Operator Type

Default Glazing Reference

CEC

 Default

SHGC Value

Table 110.6-B

X

 

SHGC Ratio

Xy

 

NFRC Window Film SHGC1,2,3  

Z

 

New Adjusted Total Value

T

 

Residential or Commercial

 

Fixed

3 mm (1/8in.) clear

(Single Pane)

0.83

x

1.1528

x

 

=

 

 

Fixed

3 mm (1/8in.) clear

3 mm (1/8in.) clear

(Double Pane - Clear)

0.73

x

1.1406

x

 

=

 

 

 

 

Standard Design

For new construction, the requirements for vertical fenestration U factor, Solar Heat Gain Coefficient, and Visible light transmission by window type and framing type are specified in Table 140.3-B, C or D of the Standards.

 

Standard Design, Existing Buildings

The U-factor, SHGC and VT in the standard design shall be modeled as design if unchanged, as the values stated in Table 141.0-A of the Standards when the existing window area is unchanged (different than the new construction performance requirement), or Table 140.3-B, C or D of the Standards for all other cases.

The standard design does not include window films.

 

External Shading Devices

Applicability

All fenestration

Definition

Devices or building features that are documented in the construction documents and shade the glazing, such as overhangs, fins, shading screens, and setbacks of windows from the exterior face of the wall. Objects that shade the building but are not part of the building and parts of the building that cause the building to shade itself are also modeled, but are not a part of this building descriptor. See Shading of the Building Site. The Title 24 compliance software shall be capable of modeling vertical fins and overhangs. Recessed windows may also be modeled with side fins and overhangs.

Units

Data structure: opening shade

Input Restrictions

No restrictions other than that the inputs must match the construction documents

Standard Design

The standard design building is modeled without external shading devices.

Internal Shading Devices

Applicability

All fenestration

Definition

Curtains, blinds, louvers, or other devices that are applied on the room side of the glazing material. Glazing systems that use blinds between the glazing layers are also considered internal shading devices. Glass coatings, components or treatments of the glazing materials are addressed through the Fenestration Construction building descriptor.

Units

Data structure: Indicates the type of control, or blind schedule if applicable

Input Restrictions

Internal shading shall not be modeled in the proposed design, unless it is automatically controlled, based on input from an astronomical timeclock, an exterior pyronometer, or other sensors. The control algorithm shall be documented on the construction documents. Interior shades without automatic controls shall not be modeled Interior shades shall only be modeled when automatic controls are present.

Standard Design

The baseline building shall be modeled without interior shades. None (not applicable)

SHGC Dim Fraction

Applicability

Fenestration with switchable glazing

Definition

For switchable glazing, this is the fraction of the solar heat gain coefficient when darkened to the solar heat gain coefficient during normal operation.  This can be applied when the solar heat gain exceeds a specified threshold, or controlled by an electrical signal.

Units

Unitless

Input Restrictions

Between 0 and 1Internal shading shall not be modeled in the proposed design, unless it is automatically controlled, based on input from an astronomical timeclock, an exterior pyronometer, or other sensors. The control algorithm shall be documented on the construction documents. Interior shades without automatic controls shall not be modeled

Standard Design

Not applicable

 

VT Dim Fraction

Applicability

Fenestration with switchable glazing

Definition

For switchable glazing, this is the fraction of the visible transmittance when darkened to the visible transmittance during normal operation.  This can be applied when the solar heat gain exceeds a specified threshold, or controlled by an electrical signal.

Units

Unitless

Input Restrictions

Between 0 and 1Internal shading shall not be modeled in the proposed design, unless it is automatically controlled, based on input from an astronomical timeclock, an exterior pyronometer, or other sensors. The control algorithm shall be documented on the construction documents. Interior shades without automatic controls shall not be modeled

Standard Design

Not applicable

 

Switchable Solar Heat Gain Threshold

Applicability

Fenestration with automatically controlled switchable glazing.

Definition

For switchable glazing, this is the solar heat gain threshold above which the dynamic glazing is active (darkened). When the solar heat gain drops below this threshold, the glazing is switched back to being inactive (clearest setting).  Indoor and outdoor air temperatures are the setpoints required for controlling the Switchable Solar Heat Gain Threshold. A flag may be used to indicate that this control is not used. During both occupied and unoccupied hours, the recommendation for the control of solar heat gain coefficient (SHGC) is to have the switchable glazing set to inactive (clearest setting) when the outdoor air temperature is below the heating setpoint, and active (darkened) when the outdoor air temperature is equal to or above the heating setpoint.  The heating setpoint value shall be based on building type from ACM Appendix 5.4B.

Units

Incident solar threshold (Btu/h-ft2)

Input Restrictions

As designed. During both occupied and unoccupied hours, the recommendation for the control of solar heat gain coefficient (SHGC) is to have the switchable glazing set to inactive (clearest setting) when the outdoor air temperature is below the heating setpoint, and active (darkened) when the outdoor air temperature is equal to or above the heating setpoint.  The heating setpoint value shall be based on building type from ACM Appendix 5.4B.

Standard Design

Not applicable

Switchable Space Temperature Threshold

Applicability

Fenestration with automatically controlled switchable glazing.

Definition

For switchable glazing, this is the space temperature above which the dynamic glazing is active (darkened). When the solar heat gain drops below this threshold, the glazing is switched back to being inactive (clearest setting).  Indoor and outdoor air temperatures are the setpoints required for controlling the Switchable Solar Heat Gain Threshold. This may be used in combination with the solar heat gain and illuminance thresholds for control. A flag may be used to indicate that this control is not used. During both occupied and unoccupied hours, the recommendation for the control of solar heat gain coefficient (SHGC) is to have the switchable glazing set to inactive (clearest setting) when the outdoor air temperature is below the heating setpoint, and active (darkened) when the outdoor air temperature is equal to or above the heating setpoint.  The heating setpoint value shall be based on building type from ACM Appendix 5.4B.

Units

°F

Input Restrictions

The space heating and cooling setpoints are prescribed from Appendix 5.4B.  A flag may be used to indicate that this control is not used. During both occupied and unoccupied hours, the recommendation for the control of solar heat gain coefficient (SHGC) is to have the switchable glazing set to inactive (clearest setting) when the outdoor air temperature is below the heating setpoint, and active (darkened) when the outdoor air temperature is equal to or above the heating setpoint.  The heating setpoint value shall be based on building type from ACM Appendix 5.4B.

Standard Design

Not applicable

 

Switchable Illuminance Threshold

Applicability

Fenestration with automatically controlled switchable glazing.

Definition

For switchable glazing, this is the illuminance threshold above which the dynamic glazing is regulated between active (darkened) and inactive (clearest setting).  With a single illuminance setpoint the switchable glazing will adjust between the clearest and darkest setting to allow the desired illuminance level. A flag may be used to indicate that this control is not used. During both occupied and unoccupied hours, the recommendation for the control of solar heat gain coefficient (SHGC) is to have the switchable glazing set to inactive (clearest setting) when the outdoor air temperature is below the heating setpoint, and active (darkened) when the outdoor air temperature is equal to or above the heating setpoint.  The heating setpoint value shall be based on building type from ACM Appendix 5.4B.

 

Units

Lux

Input Restrictions

As designed

During occupied hours, the recommendation for the illuminance threshold setpoint is to match a point within the recommended illumination levels, based on space type, from Appendix 5.4A.  Values below this recommended range may require special documentation.

During unoccupied hours, the recommendation is to have the Switchable Solar Heat Gain Threshold descriptor in control of the switchable glass. If this descriptor is used in conjunction with the Switchable Solar Heat Gain Threshold descriptor, glare will need to be an additional parameter to control which threshold is used during occupied hours.

Standard Design

Not Applicable

 

Switchable Glazing Schedule

Applicability

Fenestration with switchable glazing controlled by an electrical signal

Definition

For switchable glazing, this is an hourly schedule for the when the switchable glazing is darkened, when controlled by an electrical signal.

Units

Boolean: 1 if switchable glazing is active (darkened); 0 if not active

Input Restrictions

0 or 1 for schedule values

Standard Design

Not applicable

 

5.5.8 Below Grade Walls    

Below Grade Wall Name

Applicability

All projects, optional input

Definition

A unique name that keys the below grade wall to the construction documents

Units:

Text: unique

Input Restrictions

None

Standard Design

Not applicable

Below Grade Wall Geometry

Applicability

All projects

Definition

A geometric construct that describes the dimensions and placement of walls located below grade. Below grade walls have soil or crushed rock on one side and interior space on the other side. Some simulation models take the depth below grade into account when estimating heat transfer, so the geometry may include height and width.

Units

Data structure: below grade wall geometry

Input Restrictions

As designed

Standard Design

The geometry of below grade walls in the standard design building is identical to the below grade walls in the proposed design.

Below Grade Wall Construction

Applicability

All projects, 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 below grade wall construction type.

Units

Data structure: construction assembly

The construction can be described as a C-factor which is similar to a U-factor, except that the outside air film is excluded, or the construction can be represented as a series of layers, like exterior constructions.

Input Restrictions

The construction assembly, defined by a series of layers, must be equal to or more efficient than the mandatory R-value and C-factor requirements of Section 120.7 of the Standards for new construction, and Section 141.0 of the Standards for alterations.  Note that these requirements only apply when the slab floor connected to the below grade wall is heated.

For new construction, the inputs shall be in agreement with the construction documents. Values for the C-factor shall be taken from Table 4.3.5, 4.3.6 or 4.3.7 of Reference Appendix JA4.

For alterations there are no restrictions.

Standard Design

For new construction, See Table 13. The standard design building shall use default values for C-factor. The height shall be the same as specified in the proposed design.

For below grade walls, the standard design construction shall include the following layers:

Layer 1         CMU Solid Grout 115lb/ft3 – 8 in.            R – 0.87            C – 1.14

Table 13 – Standard Design Building Below-Grade 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)

C-factor (Btu/ft²·°F·h)

NR

115 lb/ft3 CMU, solid grout

8

0.45

115

0.20

0.87

1.140

R-7.5 c.i.

115 lb/ft3 CMU, solid grout

8

0.45

115

0.20

0.87

 

 

R-10 continuous insulation

1.8

0.02

1.8

0.29

7.50

 

 

Total assembly

 

 

 

 

8.37

0.119

R-10 c.i.

115 lb/ft3 CMU, solid grout

8

0.45

115

0.20

0.87

 

 

R-10 continuous insulation

2.4

0.02

1.8

0.29

10.00

 

 

Total assembly

 

 

 

 

10.87

0.092

R-12.5 c.i.

115 lb/ft3 CMU, solid grout

8

0.45

115

0.20

0.87

 

 

R-10 continuous insulation

3.0

0.02

1.8

0.29

12.50

 

 

Total assembly

 

 

 

 

13.37

0.075

 

For alterations, the C-factor in the standard design shall be modeled as the more efficient of either the existing conditions, or the values stated above for new construction standard design.

For below grade walls, the alteration standard design assembly shall include the appropriate existing layers.

5.5.9 Slab Floors in Contact with Ground    

These building descriptors apply to slab-on-grade or below-grade floors that are in direct contact with the ground.

Slab Floor Name

Applicability

All slab floors, optional

Definition

A unique name or code that relates the exposed floor to the construction documents.

Units

Text: unique

Input Restrictions

None

Standard Design

Not applicable

Slab Floor Type

Applicability

All slab floors, required

Definition

One of two classes for floors in contact with ground. The classes are:

1) Heated slab-on-grade floors,

2) Unheated slab-on-grade floors

3) Heated below-grade floors

4) Unheated below-grade floors.

Heated slab-on-grade floors include all floors that are heated directly in order to provide heating to the space. Unheated slab-on-grade floors are all other floors in contact with ground.

Units

List: restricted to the four selections 'listed above

Input Restrictions

None

Standard Design

The slab for type is unheated (either unheated slab-on-grade for slab-on-grade floors or unheated below-grade for below grade floors.

Slab Floor Geometry

Applicability

All slab floors, required

Definition

A geometric construct representing a slab floor in contact with the earth. The geometric representation can vary depending on how the energy simulation software models slabs-on-grade. Some models require that only the perimeter of the slab be entered. Other models divide the slab into a perimeter band within 2 ft of the edge and the interior portion or core area, such that the perimeter area and the core area sum to the total area of the slab.

Units:

Data structure: as appropriate for the simulation tool

This may include: Area, Perimeter Exposed

Input Restrictions

No restrictions

Standard Design

The geometry of the slab floor in the standard design building is identical to the slab floor in the proposed design.

Slab Floor Construction

Applicability

All slab floors, 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 slab floor construction type.

A description of how the slab is insulated (or not). How the construction is described will depend on the energy simulation model. The construction can be represented by an F-factor that represents the entire construction (floor and insulation).

Simple models may include just an F-factor, representing an instantaneous heat loss/gain to outside air. The F-factor could be related to the configuration of insulation in the proposed design. Other slab loss models may require that the surface area of the slab floor be divided between the perimeter and the interior. The insulation conditions then define heat transfer between both outside air and ground temperature.

The insulation condition for slabs includes the R-value of the insulation and the distance it extends into the earth at the slab edge and how far it extends underneath the slab.

Units

List

F-factor from Reference Appendix JA4|topic=Appendix JA4 – U-factor\, C-factor\, and Thermal Mass Data; this is one selection from list 1 and one selection from list 2.  Note that some combinations from list 1 and list3 are not allowed – see Reference Appendix JA4 Table 4.4.8 and Table 4.4.7 for details.

List 1:  None, 12 in horizontal, 24 in horizontal, 36 in horizontal, 48 in horizontal, 12 in vertical, 24 in vertical, 36 in vertical, 48 in vertical, Fully insulated slab

List 2: R-0, R-5, R-7.5, R-10, R-15, R-20, R-25, R-30, R-35, R-40, R-45, R-50, R-55

Input Restrictions

The construction assembly, defined by an F-factor, must be equal to or more efficient than the mandatory F-factor requirements of Section 120.7 of the Standards for new construction, and Section 141.0 of the Standards for alterations.

For new construction, F-factors shall be taken from Table 4.4.8 of Reference Appendix JA4 for heated slab floors and Table 4.4.7 for unheated slab floors. For all methods, inputs shall be consistent with the construction documents. For heated slab floors, the F-factor shall be determined by the mandatory R-value and installation requirements in Section 110.8 of the Standards, and then that information is used in Table 4.4.8 of Reference Appendix JA4 to determine the required F-factor.  For alterations the same requirements apply.

Standard Design

Slab loss shall be modeled with the simple method (F-factor).

The standard design construction shall include the following layers:

Layer 1         Concrete 140lb/ft3 – 6 in.           R - 0.44

The Standard Design shall include No insulation, equivalent to an F-factor of 0.73.

For alterations, the F-factor in the standard design shall be modeled as the more efficient of either the existing conditions, or the values stated above for new construction standard design.

5.5.10    Heat Transfer between Thermal zones    

Partition Name

Applicability

All partitions, optional

Definition

A unique name or code that relates the partition to the construction documents.

Units

Text: unique

Input Restrictions

The text should provide a key to the construction documents.

Standard Design

Not applicable

Partition Geometry

Applicability

All partitions

Definition

A geometric construct that defines the position and size of partitions that separate one thermal zone from another. The construct shall identify the thermal zones on each side of the partition. Since solar gains are not generally significant for interior partitions, the geometry of partitions is sometimes specified as just an area along with identification of the thermal zones on each side.

Units

Data structure: surface with additional information identifying the two thermal zones that the partition separates.

Input Restrictions

No restrictions other than agreement with the construction documents

Standard Design

The geometry of partitions in the standard design building shall be identical to the proposed design.

Partition Construction

Applicability

All partitions

Definition

A description of the construction assembly for the partition

Units

Data structure: construction assembly

Input Restrictions

As designed

Standard Design

Partitions in the baseline building shall be steel framed walls with 5/8 in. gypsum board on each side. For walls, partitions in the standard design building shall be steel framed walls with 5/8 in. gypsum board on each side. For interior floors and ceilings, baseline construction shall be 5/8 in. gypsum board, an air space of 4” or more, and 5/8” gypsum board.

Demising Partition Construction

Applicability

All demising walls and demising partitions (ceilings, floors) that separate conditioned spaces from unconditioned spaces

Definition

A description of the construction assembly for the partition

Units

Data structure: construction assembly

Input Restrictions

As designed

Standard Design

Partitions in the baseline building shall be steel framed walls with 5/8 in. gypsum board on each side. For walls, partitions in the standard design building shall be steel framed walls with 5/8 in. gypsum board on each side and R-13 fiberglass batt insulation between the studs

Demising ceiling partitions, separating conditioned space from unconditioned space and attics, shall be insulated to the same levels as exterior roofs in section 5.5.3. Demising floor partitions shall be insulated to the same levels as exterior floors in section 5.5.5.

5.5.11    Simplified Geometry Simulation Option    

The compliance software may have an option to model a building with simplified (two-dimensional geometry).  This is an optional capability as an alternative to modeling the three-dimensional geometry of a building.  If the compliance software only provides a two-dimensional building model, the following features cannot be modeled:

      Daylighting controls and dimming

      Exterior shading or self-shading

All mandatory and prescriptive daylight controls must be present when submitting a compliance project using software that only models a building with two-dimensional geometry.

The compliance software must pass all reference method tests corresponding to two-dimensional geometry to meet certification requirements as compliance software.  Consult Appendix 3B of the ACM Reference Manual for additional information. The software must pass the ruleset implementation tests, and for the sensitivity tests that verify simulation accuracy, there are 2D tests specified for building envelope, but for other building components (lighting, HVAC), the software is compared against the results of the reference method, which uses a three-dimensional geometry model.

The compliance software must have sufficient information to specify each exterior surface when modeling a building with two-dimensional geometry. At a minimum, building surface azimuth, elevation, area are required and the tilt, azimuth and area is specified for roof components. The model must use only vertical walls for the analysis. The model follows all other ACM requirements for space and zone definitions, lighting and HVAC specifications, and follows the same rules for the standard design and proposed design constraints.

The model also requires the following explicit inputs from the user:

      Total Building Story Count – the total number of stories

      Total Above Grade Stories – the total number of stories above grade, used in determination of high-rise residential classification