6.5.5 Exterior Floors

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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
Baseline Rules None
Floor Type
Applicability All exterior floor surfaces, optional
Definition One of three categories of exposed floor assemblies used to determine minimum prescriptive insulation requirements. The three floor type categories are: a) mass floor, b) steel joist floor, and c) wood and other floors. Definitions of these three exterior floor types are contained in Section 3.2, Definitions, of the baseline standard and associated User's Manuals. This building descriptor is not used for the purposes of this manual, since the type for the baseline building is fixed at “steel joist”. This building descriptor can often be derived from other information in the model and may not be required as an explicit input.
Units List: mass floor, metal joist floor, and wood and other floors
Input Restrictions This building descriptor input is optional for the purposes of this manual.
Baseline Rules The baseline building floors shall be of type “steel joist.”
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 There are no restrictions other than that the surfaces defined must agree with the building being modeled, as represented on the construction documents or as-built drawings.
Baseline Rules Baseline building floor geometry is identical to the proposed design.
Floor Construction
Applicability All floors, required input
Definition A reference to a construction assembly for the proposed design
Units Dimensionless reference
Input Restrictions All floor surfaces must reference a construction assembly that meets the mandatory measures of the baseline standards.
Baseline Rules Exterior floors in the baseline building are of type “steel joist.” The insulation requirements depend on the baseline standard and the climate zone and are given in Table 6.5.5-1. The baseline building constructions shall be modeled as layers, which are defined in Table 6.5.5-2.

Table 6.5.5-1: "Baseline Building R-value and U-factor Criteria for Exposed Floors"

Applicable Standard Space Category Climate Zone Standard Design
Minimum Insulation Maximum Assembly
90.1 - 2001 Nonresidential 1 NR U-0.350
2-5 R-19 U-0.052
6-8 R-30 U-0.038
Residential 1 NR U-0.350
2, 3 R-19 U-0.052
4- 7 R-30 U-0.038
8 R-38 U-0.032
Semi-Heated 1, 2 NR U-0.350
3- 6 R-13 U-0.069
7, 8 R-19 U-0.052
90.1 - 2007 Nonresidential 1 NR U-0.350
2,3 R-19 U-0.052
4-7 R-30 U-0.038
8 R-38 U-0.032
Residential 1 NR U-0.350
2,3 R-19 U-0.052
4,5 R-30 U-0.038
6-8 R-38 U-0.032
Semi-Heated 1 NR U-0.350
2-4 R-13 U-0.069
5-8 R-19 U-0.052

Table 6.5.5-2: "Baseline Building Exposed Floor 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)
Floor R-38 Interior air film (flow down) - - - - 0.92 -
carpet and pad - - - - 1.23 -
4" concrete 4 1.3333 140 0.2 0.25 -
R-38 insulation between joists - - - - 28 -
metal deck 0.06 26 480 0.1 0.00 -
Semi-exterior air film - - - - 0.46 -
Total for assembly         30.86 0.032
Floor R-30 Interior air film (flow down) - - - - 0.92 -
carpet and pad - - - - 1.23 -
4" concrete 4 1.3333 140 0.2 0.25 -
R-30 insulation between joists - - - - 23.5 -
metal deck 0.06 26 480 0.1 0.00 -
Semi-exterior air film - - - - 0.46 -
Total for assembly         26.36 0.038
Floor R-19 Interior air film (flow down) - - - - 0.92 -
carpet and pad - - - - 1.23 -
4" concrete 4 1.3333 140 0.2 0.25 -
R-19 insulation between joists - - - - 16.37 -
metal deck 0.06 26 480 0.1 0.00 -
Semi-exterior air film - - - - 0.46 -
Total for assembly         19.23 0.052
Floor R-13 Interior air film (flow down) - - - - 0.92 -
carpet and pad - - - - 1.23 -
4" concrete 4 1.3333 140 0.2 0.25 -
R-13 insulation between joists - - - - 11.63 -
metal deck 0.06 26 480 0.1 0.00 -
Semi-exterior air film - - - - 0.46 -
Total for assembly         14.49 0.069
Floor -no insulation Interior air film (flow down) - - - - 0.92 -
Carpet and pad - - - - 1.23 -
4" concrete 4 1.3333 140 0.2 0.25 -
Metal deck 0.06 26 480 0.1 0.00 -
Semi-exterior air film - - - - 0.46 -
Total for assembly         2.86 0.350