6.7 Building Materials and Construction

Only materials approved by the CEC may be used in defining constructions. Additional materials may be added to the compliance manager at the CEC’s discretion.

Table 18: Materials List shows a partial list of the materials available for construction assemblies. Additional material information can be found in Reference Appendix Joint Appendix 4.

Some materials, such as three-coat stucco, are defined with a specific thickness (not editable by the compliance user). The thickness of other materials, such as softwood used for framing, is selected by the compliance user based on the construction of the building.

The conductivity of the material is the steady-state heat flow per square foot, per foot of thickness, or per degree Fahrenheit temperature difference. It is used in simulating the heat flow in the construction.

Material Name	Thickness (in.)	Conductivity (Btu/h-°F-ft)	Coefficient for Temperature Adjustment of Conductivity (°F(-1))	Specific Heat (Btu/lb-°F)	Density (lb/ft³)	R-Value per Inch (°F-ft²-h/ Btu-in)
Gypsum Board	0.5	0.09167	0.00122	0.27	40	0.9091
Wood Layer	Varies	0.06127	0.0012	0.45	41	1.36
Synthetic Stucco	0.375	0.2		0.2	58	0.2
3 Coat Stucco	0.875	0.4167		0.2	116	0.2
All other siding						0.21
Carpet	0.5	0.02		0.34	12.3	4.1667
Light Roof	0.2	1		0.2	120	0.0833
5 PSF Roof	0.5	1		0.2	120	0.0833
10 PSF Roof	1	1		0.2	120	0.0833
15 PSF Roof	1.5	1		0.2	120	0.0833
25 PSF Roof	2.5	1		0.2	120	0.0833
TileGap	0.75	0.07353		0.24	0.075	1.1333
SlabOnGrade	3.5	1		0.2	144	0.0833
Earth		1		0.2	115	0.0833
SoftWood		0.08167	0.0012	0.39	35	1.0204
Concrete		1		0.2	144	0.0833
Foam Sheathing	Varies	varies	0.00175	0.35	1.5	varies
Ceiling Insulation	Varies	varies	0.00418	0.2	1.5	Varies
Cavity Insulation	varies	varies	0.00325	0.2	1.5	Varies
Vertical Wall Cavity	3.5	0.314	0.00397	0.24	0.075
GHR Tile	1.21	0.026	0.00175	0.2	38
ENSOPRO	0.66	0.03	0.00175	0.35	2
ENSOPRO Plus	1.36	0.025	0.00175	0.35	2
Door						5

The conductivity of insulation materials varies with temperature according to the coefficient listed. Other materials have a coefficient of zero (0), and the conductivity does not vary with temperature.

The specific heat is the amount of heat in British thermal units (Btu) it takes to raise the temperature of 1 pound of the material 1 degree Fahrenheit (Btu/lb-°F).

The density of the material is the weight of the material in pounds per cubic foot (lb/ft³).

6.7.2 Construction Assemblies

“Constructions” are defined by the compliance user for use in defining the building. The user assembles a construction from one or more layers of materials, as shown in Figure 16. For framed constructions, there is a framing layer that has parallel paths for the framing and the cavity between the framing members. The layers that are allowed depend on the surface type. The compliance manager calculates a winter design U-factor that is compared to a construction that meets the prescriptive standard. The U-factor is displayed as an aid to the user. The calculations used in the energy simulation are based on each layer and framing rather than the U-factor.

Ceiling below attic (the roof structure is not defined here, but is part of the attic), wood-framed. In a residence with a truss roof, the ceiling is where the insulation is located, while the structure above the ceiling is encompassed by the term “attic” or “roof.” The attic or roof consists of (moving from inside to outside) the radiant barrier, below-deck insulation, framing, above-deck insulation, and the roofing product, such as asphalt or tile roofing. See more in Chapter 6.10.2 Ceiling Below Attic.

Ø Cathedral ceiling (with the roof defined as part of the assembly), wood-framed. Since there is no attic, the roof structure is connected to the insulated assembly at this point.

Ø Party surfaces separate conditioned space included in the analysis from conditioned space that may or may not be included in the analysis. Party surfaces for spaces that are modeled include surfaces between multifamily dwelling units. Party surfaces for spaces not included in the analysis include spaces joining an addition alone to the existing dwelling. Interior walls, ceilings, or floors can be party surfaces.

Spray-foam insulation R-values are calculated based on the nominal thickness of the insulation multiplied by the default thermal resistivity per inch, or the total R-value may be calculated based on the thickness of the insulation multiplied by the tested R-value per inch as certified by the Department of Consumer Affairs, Bureau of Household Goods and Services (see details Chapter 6.7.3 Spray-Foam Insulation and Reference Appendices, Residential Appendix RA3.5).

As assemblies are completed, the screen displays whether the construction meets the prescriptive requirement for that component.

The user defines a construction for each surface type included in the proposed design. Any variation in insulation R-value, framing size or spacing, interior or exterior sheathing, or interior or exterior finish requires the user to define a different construction. Insulation R-values are based on manufacturer-rated properties rounded to the nearest whole R-value. Layers such as sheetrock, wood sheathing, stucco, and carpet whose properties are not compliance variables are included as generic layers with standard thickness and properties.

Walls separating the house from an attached unconditioned attic or garage are modeled as interior walls with unconditioned space as the adjacent zone, which the compliance manager recognizes as a “demising wall.” Floors over a garage are modeled as an interior or demising floor. The exterior walls, floor, and ceiling/roof of the garage are modeled as part of the unconditioned garage zone.

The compliance software assembles a construction that meets the prescriptive standards for each user-defined construction or assembly. For ceiling/roof the standard design is based on Table 170.2-A Option C. Wall designs are based on Table 170.2-A and vary based on the type of wall and climate zone.

All proposed constructions, including insulation, frame type, frame size, and exterior finish or exterior condition, are listed on the LMCC or NRCC. Nonstandard framing (e.g., 24” on center wall framing, advanced wall framing) is reported as a special feature.

6.7.3 Spray-Foam Insulation

The R-values for spray-applied polyurethane foam (SPF) insulation differ depending on whether the product is open cell or closed cell.

Additional documentation and verification requirements for a value other than the default values shown in Table 19: Required Thickness Spray Foam Insulation (in inches) are required. (See RA3.5.6.) For continuous insulation refer to Section 5.5.4 Exterior Walls.

Required R-values for SPF insulation	R-11	R-13	R-15	R-19	R-21	R-22	R-25	R-30	R-38
Required thickness closed cell @ R5.8/inch	2.00	2.25	2.75	3.50	3.75	4.00	4.50	5.25	6.75
Required thickness open cell @ R3.6/inch	3.0	3.5	4.2	5.3	5.8	6.1	6.9	8.3	10.6

The default R-value for spray-foam insulation with a closed cellular structure is R-5.8 per inch, based on the installed nominal thickness of insulation. Closed-cell insulation has an installed nominal density of 1.5 to 2.5 pounds per cubic foot (pcf).

The default R-value for spray-foam insulation with an open cellular structure is calculated as R-3.6 per inch, based on the nominal required thickness of insulation. Open-cell insulation has an installed nominal density of 0.4 to 1.5 pounds per cubic foot (pcf).

The user will select either typical values for open-cell or closed-cell spray-foam insulation or higher-than-typical values and enter the total R-value (rounded to the nearest whole value).

The compliance software assembles a construction that meets the prescriptive standards for each assembly type (ceiling/roof, wall, and floor).

When the user elects to use higher-than-typical R-values for open-cell or closed-cell spray-foam insulation, a special features note is included on the LMCC requiring documentation requirements specified in Reference Appendices, Joint Appendix JA4.1.7. Furthermore, a HERS verification requirement for the installation of spray-foam insulation using higher-than-default values is included on the LMCC.

6.7.4 Quality Insulation Installation For Building Up To Three Habitable Stories

The compliance software user may specify quality insulation installation (QII) for the proposed design as “yes” or “no.” The effective R-value of cavity insulation is reduced, as shown in Table 16 in buildings with no QII. When set to “no,” framed walls, ceilings, and floors are modeled with added winter heat flow between the conditioned zone and attic to represent construction cavities open to the attic. QII does not affect the performance of continuous sheathing in any construction.

The compliance software user may specify compliance with QII. The default is “no” for QII. This results in a 30% derating applied to the cavity insulation.

The standard design is modeled with “yes” for verified QII for newly constructed multifamily buildings and additions greater than 700 square feet in Climate Zones 1-6 and 8-16 (Climate Zone 7 has no QII for multifamily buildings). This results in the removal of the 30% derating to the cavity insulation.

The presence of QII is reported in the HERS required verification listings on the LMCC. Verified QII is certified by the installer and field verified to comply with RA3.5. Credit for verified QII applies to ceilings/attics, knee walls, exterior walls, and exterior floors.

For alterations to existing pre-1978 construction, if the existing wall construction is assumed to have no insulation, no wall degradation is assumed for the existing wall.