ADOPTS WITHOUT AMENDMENTS:

ASHRAE 90.1-2016

Heads up: There are no amended sections in this chapter.

The U-factors, C-factors, F-factors, and heat capacities for typical construction assemblies are included in Sections A2 through A8. These values shall be used for all calculations unless otherwise allowed by Section A1.2. Interpolation between values in a particular table in Normative Appendix A is allowed for rated R-values of insulation, including insulated sheathing. Extrapolation beyond values in a table in Normative Appendix A is not allowed.

If the building official determines that the proposed construction assembly is not adequately represented in Sections A2 through A8, the applicant shall determine appropriate values for the assembly using the assumptions in Section A9. An assembly is deemed to be adequately represented if

  1. the interior structure, hereafter referred to as the base assembly, for the class of construction is the same as described in Sections A2 through A8 and
  2. changes in exterior or interior surface building materials added to the base assembly do not increase or decrease the R-value by more than 2 from that indicated in the descriptions in Sections A2 through A8.

Insulation, including insulated sheathing, is not considered a building material.

The buffering effect of suspended ceilings or attic spaces shall not be included in U-factor calculations.

For the purpose of Section A 1.2, the base assembly is continuous insulation over a structural deck. The U-factor includes R-0.17 for exterior air film, R-0 for metal deck, and R-0.61 for interior air film heat flow up. Added insulation is continuous and uninterrupted by framing. The framing factor is zero.

For roofs with insulation entirely above deck, the rated R-value of insulation is for continuous insulation.

Exception to A2.2.2

Interruptions for framing and pads for mechanical equipment are permitted with a combined total area not exceeding one percent of the total opaque assembly area.

U-factors for roofs with insulation entirely above deck shall be taken from Table A2.2.3. It is not acceptable to use these U-factors if the insulation is not entirely above deck or not continuous.

Table A2.2.3 Assembly U-Factors for Roofs with Insulation Entirely Above Deck

Rated R-Value of Insulation Alone Overall U-Factor for Entire Assembly
R-0 U-1.282
R-1 U-0.562
R-2 U-0.360
R-3 U-0.265
R-4 U-0.209
R-5 U-0.173
R-6 U-0.147
R-7 U-0.129
R-8 U-0.114
R-9 U-0.102
R-10 U-0.093
R-11 U-0.085
R-12 U-0.078
R-13 U-0.073
R-14 U-0.068
R-15 U-0.063
R-16 U-0.060
R-17 U-0.056
R-18 U-0.053
R-19 U-0.051
R-20 U-0.048
R-21 U-0.046
R-22 U-0.044
R-23 U-0.042
R-24 U-0.040
R-25 U-0.039
R-26 U-0.037
R-27 U-0.036
R-28 U-0.035
R-29 U-0.034
R-30 U-0.032
R-35 U-0.028
R-40 U-0.025
R-45 U-0.022
R-50 U-0.020
R-55 U-0.018
R-60 U-0.016

For the purpose of Section A1.2, the base assembly is a roof with thermal spacer blocks where the insulation is draped over the steel structure (purlins), spaced nominally 5 ft on center and compressed when the metal roof panels are attached to the steel structure (purlins).

The rated R-value of insulation is for insulation installed perpendicular to and draped over purlins and then compressed when the metal roof panels are attached. A minimum R-3 thermal spacer block between the purlins and the metal roof panels is required unless compliance is shown by the overall assembly U-factor.

The first rated R-value of insulation is for insulation installed perpendicular to and draped over purlins. The second rated R-value of insulation is for unfaced insulation installed above the first layer and parallel to the purlins and then compressed when the metal roof panels are attached. A minimum R-3 thermal spacer block between the purlins and the metal roof panels is required unless compliance is shown by the overall assembly U-factor.

For assemblies with continuous insulation the continuous insulation is installed above or below the purlins, uncompressed and uninterrupted by framing members.

A continuous membrane is installed below the purlins and uninterrupted by framing members. Uncompressed, unfaced insulation rests on top of the membrane between the purlins. For multilayer installations, the last rated R-Value of insulation is for unfaced insulation draped over purlins and then compressed when the metal roof panels are attached. A minimum R-3 thermal spacer block between the purlins and the metal roof panels is required unless compliance is shown by the overall assembly U-factor.

The first rated R-value of insulation represents faced or unfaced insulation installed between the purlins. The second rated R-value of insulation represents unfaced insulation installed above the first layer, perpendicular to the purlins and compressed when the metal roof panels are attached. A supporting structure retains the bottom of the first layer at the prescribed depth required for the full thickness of insulation. A minimum R-5 thermal spacer block between the purlins and the metal roof panels is required unless compliance is shown by the overall assembly U-factor.

U-factors for metal building roofs shall be taken from Table A2.3.3 or determined in accordance with Section A9.2, provided the average purlin spacing for systems with compressed insulation is at least 52 in. U-factors for metal building roof assemblies with average purlin spacing less than 52 in. shall be determined in accordance with Section A9.2. U-factors in Table A2.3.3 shall not be used where the insulation is substantially compressed by the bracing between the purlins.

Table A2.3.3 Assembly U-Factors for Metal Building Roofs

Insulation System Rated R-Value of Insulation Overall U-Factor for Entire Base Roof Assembly Overall U-Factor for Assembly of Base Roof
Plus Continuous Insulation (Uninterrupted by Framing)
Rated R-Value of Continuous Insulation
R-6.5 R-9.8 R-13 R-15.8 R-19 R-22.1 R-25 R-32 R-38
Standing Seam Roofs with Thermal Spacer Blocksa, b
Single Layer None 1.280 0.137 0.095 0.073 0.060 0.051 0.044 0.039 0.031 0.026
R-10 0.115 0.066 0.054 0.046 0.041 0.036 0.032 0.030 0.025 0.021
R-11 0.107 0.063 0.052 0.045 0.040 0.035 0.032 0.029 0.024 0.021
R-13 0.101 0.061 0.051 0.044 0.039 0.035 0.031 0.029 0.024 0.021
R-16 0.096 0.059 0.049 0.043 0.038 0.034 0.031 0.028 0.024 0.021
R-19 0.082 0.053 0.045 0.040 0.036 0.032 0.029 0.027 0.023 0.020
Double Layer R-10 + R-10 0.088 0.056 0.047 0.041 0.037 0.033 0.030 0.028 0.023 0.020
R-10 + R-11 0.086 0.055 0.047 0.041 0.036 0.033 0.030 0.027 0.023 0.020
R-11 + R-11 0.085 0.055 0.046 0.040 0.036 0.033 0.030 0.027 0.023 0.020
R-10 + R-13 0.084 0.054 0.046 0.040 0.036 0.032 0.029 0.027 0.023 0.020
R-11 + R-13 0.082 0.053 0.045 0.040 0.036 0.032 0.029 0.027 0.023 0.020
R-13 + R-13 0.075 0.050 0.043 0.038 0.034 0.031 0.028 0.026 0.022 0.019
R-10 + R-19 0.074 0.050 0.043 0.038 0.034 0.031 0.028 0.026 0.022 0.019
R-11 + R-19 0.072 0.049 0.042 0.037 0.034 0.030 0.028 0.026 0.022 0.019
R-13 + R-19 0.068 0.047 0.041 0.036 0.033 0.030 0.027 0.025 0.021 0.019
R-16 + R-19 0.065 0.046 0.040 0.035 0.032 0.029 0.027 0.025 0.021 0.019
R-19 + R-19 0.060 0.043 0.038 0.034 0.031 0.028 0.026 0.024 0.021 0.018
Liner System R-19 + R-11 0.037
R-25 + R-8 0.037
R-25 + R-11 0.031
R-30 + R-11 0.029
R-25 + R-11 + R-11 0.026
Filled Cavity with Thermal Spacer Blocksc
R-10+R-19 0.041 0.032 0.029 0.027 0.025 0.023 0.022 0.020 0.018 0.016
R-19+R-11 0.037
Standing Seam Roofs without Thermal Spacer Blocks
Liner System R-19+R-11 0.040
Through-Fastened Roofs without Thermal Spacer Blocks
R-10 0.184 0.084 0.066 0.054 0.047 0.041 0.036 0.033 0.027 0.023
R-11 0.182 0.083 0.065 0.054 0.047 0.041 0.036 0.033 0.027 0.023
R-13 0.174 0.082 0.064 0.053 0.046 0.040 0.036 0.033 0.026 0.023
R-16 0.157 0.078 0.062 0.052 0.045 0.039 0.035 0.032 0.026 0.023
R-19 0.151 0.076 0.061 0.051 0.045 0.039 0.035 0.032 0.026 0.022
Liner System R-19+R-11 0.044
(Multiple R-values are listed in order from inside to outside)
  1. A standing seam roof clip that provides a minimum 1.5 in. distance between the top of the purlins and the underside of the metal roof panels is required.
  2. A minimum R-3 thermal spacer block is required.
  3. A minimum R-5 thermal spacer block is required.

For the purpose of Section A1.2, the base attic roof assembly is a roof with nominal 4 in. deep wood as the lower chord of a roof truss or ceiling joist. The ceiling is attached directly to the lower chord of the truss, and the attic space above is ventilated. Insulation is located directly on top of the ceiling, first filling the cavities between the wood and later covering both the wood and cavity areas. No credit is given for roofing materials. The single-rafter roof is similar to the base attic roof with the key difference being that there is a single, deep rafter to which both the roof and the ceiling are attached. The heat flow path through the rafter is calculated to be the same depth as the insulation. Additional assemblies include continuous insulation uncompressed and uninterrupted by framing. The U-factors include R-0.46 for semiexterior air film, R-0.56 for 0.625 in. gypsum board, and R-0.61 for interior air film heat flow up. U-factors are provided for the following configurations:

  1. Attic roof standard framing: Insulation is tapered around the perimeter with a resultant decrease in thermal resistance. Weighting factors are 85% full-depth insulation, 5% half-depth insulation, and 10% joists.
  2. Attic roof advanced framing: Full and even depth of insulation extending to the outside edge of walls. Weighting factors are 90% full-depth insulation and 10% joists.
  3. Single-rafter roof. An attic roof where the roof sheathing and ceiling are attached to the same rafter. Weighting factors are 90% full-depth insulation and 10% joists.

Table A2.4.2 Single-Rafter Roofs

Climate Zone Minimum Insulation R-Value or Maximum Assembly U-Factor
Wood Rafter Depth, d (Actual)
d ≤ 8 in. 8 < d ≤ 10 in. 10 < d ≤ 12 in.
0 to 7 R-19/U-0.055 R-30/U-0.036 R-38/U-0.028
8 R-21/U-0.052 R-30/U-0.036 R-38/U-0.028

For attics and other roofs, the rated R-value of insulation is for insulation installed both inside and outside the roof or entirely inside the roof cavity.

Occasional interruption by framing members is allowed but requires that the framing members be covered with insulation when the depth of the insulation exceeds the depth of the framing cavity.

Insulation in such roofs shall be permitted to be tapered at the eaves where the building structure does not allow full depth.

For single-rafter roofs, the requirement is the lesser of the values for attics and other roofs and those listed in Table A2.4.2.

U-factors for attic roofs with wood joists shall be taken from Table A2.4.3. It is not acceptable to use these U-factors if the framing is not wood. For attic roofs with steel joists, see Section A2.5.

Table A2.4.3 Assembly U-Factors for Attic Roofs with Wood Joists

Rated R-Value of Insulation Alone Overall U-Factor for Entire Assembly
Wood-Framed Attic, Standard Framing
None U-0.613      
R-11 U-0.091      
R-13 U-0.081      
R-19 U-0.053      
R-30 U-0.034      
R-38 U-0.027      
R-49 U-0.021      
R-60 U-0.017      
R-71 U-0.015      
R-82 U-0.013      
R-93 U-0.011      
R-104 U-0.010      
R-115 U-0.009      
R-126 U-0.008      
Wood-Framed Attic, Advanced Framing
None U-0.613      
R-11 U-0.088      
R-13 U-0.078      
R-19 U-0.051      
R-30 U-0.032      
R-38 U-0.026      
R-49 U-0.020      
R-60 U-0.016      
R-71 U-0.014      
R-82 U-0.012      
R-93 U-0.011      
R-104 U-0.010      
R-115 U-0.009      
R-126 U-0.008      
Wood Joists, Single-rafter Roof
Cavity Insulation R-Value Overall U-Factor for Assembly of Base Roof Plus Continuous Insulation
(Uninterrupted by Framing)
Rated R-Value of Continuous Insulation
None R-5 R-10 R-15
None U-0.417 U-0.135 U-0.081 U-0.057
R-11 U-0.088 U-0.061 U-0.047 U-0.038
R-13 U-0.078 U-0.056 U-0.044 U-0.036
R-15 U-0.071 U-0.052 U-0.041 U-0.034
R-19 U-0.055 U-0.043 U-0.035 U-0.030
R-21 U-0.052 U-0.041 U-0.034 U-0.029
R-25 U-0.042 U-0.035 U-0.030 U-0.026
R-30 U-0.036 U-0.030 U-0.026 U-0.023
R-38 U-0.029 U-0.025 U-0.022 U-0.020

For the purpose of Section A1.2, the base assembly is a roof supported by steel joists with insulation between the joists. The assembly represents a roof in many ways similar to a roof with insulation entirely above deck and a metal building roof. It is distinguished from the metal building roof category in that there is no metal exposed to the exterior. It is distinguished from the roof with insulation entirely above deck in that the insulation is located below the deck and is interrupted by metal trusses that provide thermal bypasses to the insulation. The U-factors include R-0.17 for exterior air film, R-0 for metal deck, and R-0.61 for interior air film heat flow up. The performance of the insulation/framing layer is calculated using the values in Table A9.2-1.

U-factors for attic roofs with steel joists shall be taken from Table A2.5.2. It is acceptable to use these U-factors for any attic roof with steel joists.

Table A2.5.2 Assembly U-Factors for Attic Roofs with Steel Joists (4.0 ft on Center)

Rated R-Value of Insulation Alone Overall U-Factor for Entire Assembly
R-0 U-1.282
R-4 U-0.215
R-5 U-0.179
R-8 U-0.120
R-10 U-0.100
R-11 U-0.093
R-12 U-0.086
R-13 U-0.080
R-15 U-0.072
R-16 U-0.068
R-19 U-0.058
R-20 U-0.056
R-21 U-0.054
R-24 U-0.049
R-25 U-0.048
R-30 U-0.041
R-35 U-0.037
R-38 U-0.035
R-40 U-0.033
R-45 U-0.031
R-50 U-0.028
R-55 U-0.027

Table A3.1-1 Assembly U-Factors for Above-Grade Concrete Walls and Masonry Walls

Framing Type and Depth Rated R-Value of Insulation Alone Assembly U-Factors for 8 in. Normal Weight 145 lb/ft3 Solid Concrete Walls Assembly U-Factors for 8 in. Medium Weight 115 lb/ft3 Concrete Block Walls: Solid Grouted Assembly U-Factors for 8 in. Medium Weight 115 lb/ft3 Concrete Block Walls: Partially Grouted (Cores Uninsulated Except Where specified)
No Framing R-0 U-0.740 U-0.580 U-0.480
Ungrouted Cores Filled with Loose-Fill Insulation NA NA U-0.350
Continuous Metal Framing at 24 in. on Center Horizontally
1.0 in. R-0 U-0.414 U-0.359 U-0.318
R-3.8 U-0.325 U-0.290 U-0.263
R-5 U-0.314 U-0.281 U-0.255
R-6.5 U-0.305 U-0.274 U-0.249
1.5 in. R-11 U-0.267 U-0.243 U-0.223
2.0 in. R-7.6 U-0.230 U-0.212 U-0.197
R-10 U-0.219 U-0.202 U-0.188
R-13 U-0.210 U-0.195 U-0.182
3.0 in. R-11.4 U-0.178 U-0.167 U-0.157
R-15 U-0.168 U-0.158 U-0.149
R-19.0 U-0.161 U-0.152 U-0.144
3.5 in. R-11.0 U-0.168 U-0.158 U-0.149
R-13.0 U-0.161 U-0.152 U-0.144
R-15.0 U-0.155 U-0.147 U-0.140
4.5 in. R-17.1 U-0.133 U-0.126 U-0.121
R-22.5 U-0.124 U-0.119 U-0.114
R-25.2 U-0.122 U-0.116 U-0.112
5.0 in. R-19.0 U-0.122 U-0.117 U-0.112
R-25.0 U-0.115 U-0.110 U-0.106
R-28.0 U-0.112 U-0.107 U-0.103
R-32.0 U-0.109 U-0.105 U-0.101
5.5 in. R-19.0 U-0.118 U-0.113 U-0.109
R-20.9 U-0.114 U-0.109 U-0.105
R-21.0 U-0.113 U-0.109 U-0.105
R-27.5 U-0.106 U-0.102 U-0.099
R-30.8 U-0.104 U-0.100 U-0.096
6.0 in. R-22.8 U-0.106 U-0.102 U-0.098
R-30.0 U-0.099 U-0.095 U-0.092
R-33.6 U-0.096 U-0.093 U-0.090
6.5 in. R-24.7 U-0.099 U-0.096 U-0.092
7.0 in. R-26.6 U-0.093 U-0.090 U-0.087
7.5 in. R-28.5 U-0.088 U-0.085 U-0.083
8.0 in. R-30.4 U-0.083 U-0.081 U-0.079
1 in. Metal Clips at 24 in. on Center Horizontally and 16 in. Vertically
1.0 in. R-3.8 U-0.210 U-0.195 U-0.182
R-5.0 U-0.184 U-0.172 U-0.162
R-5.6 U-0.174 U-0.163 U-0.154
1.5 in. R-5.7 U-0.160 U-0.151 U-0.143
R-7.5 U-0.138 U-0.131 U-0.125
R-8.4 U-0.129 U-0.123 U-0.118
2.0 in. R-7.6 U-0.129 U-0.123 U-0.118
R-10.0 U-0.110 U-0.106 U-0.102
R-11.2 U-0.103 U-0.099 U-0.096
2.5 in. R-9.5 U-0.109 U-0.104 U-0.101
R-12.5 U-0.092 U-0.089 U-0.086
R-14.0 U-0.086 U-0.083 U-0.080
3.0 in. R-11.4 U-0.094 U-0.090 U-0.088
R-15.0 U-0.078 U-0.076 U-0.074
R-16.8 U-0.073 U-0.071 U-0.069
3.5 in. R-13.3 U-0.082 U-0.080 U-0.077
R-17.5 U-0.069 U-0.067 U-0.065
R-19.6 U-0.064 U-0.062 U-0.061
4.0 in. R-15.2 U-0.073 U-0.071 U-0.070
R-20.0 U-0.061 U-0.060 U-0.058
R-22.4 U-0.057 U-0.056 U-0.054
5.0 in. R-28.0 U-0.046 U-0.046 U-0.045
6.0 in. R-33.6 U-0.039 U-0.039 U-0.038
7.0 in. R-39.2 U-0.034 U-0.034 U-0.033
8.0 in. R-44.8 U-0.030 U-0.030 U-0.029
9.0 in. R-50.4 U-0.027 U-0.027 U-0.026
10.0 in. R-56.0 U-0.024 U-0.024 U-0.024
11.0 in. R-61.6 U-0.022 U-0.022 U-0.022
Continuous Insulation Uninterrupted by Framing
No Framing R-1.0 U-0.425 U-0.367 U-0.324
No Framing R-2.0 U-0.298 U-0.269 U-0.245
No Framing R-3.0 U-0.230 U-0.212 U-0.197
No Framing R-4.0 U-0.187 U-0.175 U-0.164
No Framing R-5.0 U-0.157 U-0.149 U-0.141
No Framing R-6.0 U-0.136 U-0.129 U-0.124
No Framing R-7.0 U-0.120 U-0.115 U-0.110
No Framing R-8.0 U-0.107 U-0.103 U-0.099
No Framing R-9.0 U-0.097 U-0.093 U-0.090
No Framing R-10.0 U-0.088 U-0.085 U-0.083
No Framing R-11.0 U-0.081 U-0.079 U-0.076
No Framing R-12.0 U-0.075 U-0.073 U-0.071
No Framing R-13.0 U-0.070 U-0.068 U-0.066
No Framing R-14.0 U-0.065 U-0.064 U-0.062
No Framing R-15.0 U-0.061 U-0.060 U-0.059
No Framing R-16.0 U-0.058 U-0.056 U-0.055
No Framing R-17.0 U-0.054 U-0.053 U-0.052
No Framing R-18.0 U-0.052 U-0.051 U-0.050
No Framing R-19.0 U-0.049 U-0.048 U-0.047
No Framing R-20.0 U-0.047 U-0.046 U-0.045
No Framing R-21.0 U-0.045 U-0.044 U-0.043
No Framing R-22.0 U-0.043 U-0.042 U-0.042
No Framing R-23.0 U-0.041 U-0.040 U-0.040
No Framing R-24.0 U-0.039 U-0.039 U-0.038
No Framing R-25.0 U-0.038 U-0.037 U-0.037
No Framing R-30.0 U-0.032 U-0.032 U-0.031
No Framing R-35.0 U-0.028 U-0.027 U-0.027
No Framing R-40.0 U-0.024 U-0.024 U-0.024
No Framing R-45.0 U-0.022 U-0.021 U-0.021
No Framing R-50.0 U-0.019 U-0.019 U-0.019
No Framing R-55.0 U-0.018 U-0.018 U-0.018
No Framing R-60.0 U-0.016 U-0.016 U-0.016
Brick Cavity Wall with Continuous Insulation
No Framing R-0 U-0.337 U-0.299 U-0.270
No Framing R-3.8 U-0.148 U-0.140 U-0.133
No Framing R-5.0 U-0.125 U-0.120 U-0.115
No Framing R-6.5 U-0.106 U-0.102 U-0.098
No Framing R-7.6 U-0.095 U-0.091 U-0.088
No Framing R-10 U-0.077 U-0.075 U-0.073
No Framing R-10.5 U-0.079 U-0.077 U-0.075
No Framing R-11.4 U-0.070 U-0.068 U-0.066
No Framing R-15 U-0.056 U-0.055 U-0.053
No Framing R-16.5 U-0.054 U-0.053 U-0.052
No Framing R-19.0 U-0.046 U-0.045 U-0.044
No Framing R-22.5 U-0.041 U-0.040 U-0.039
No Framing R-28.5 U-0.033 U-0.032 U-0.032
Continuous Insulation Uninterrupted by Framing with Stucco and Continuous Metal Framing at 24 in. on Center Horizontally
1.0 in. R-0+R-19.0 c.i. U-0.047 U-0.046 U-0.045
R-3.8+R-19.0 c.i. U-0.045 U-0.044 U-0.044
R-5+R-19.0 c.i. U-0.045 U-0.044 U-0.043
R-6.5+R-19.0 c.i. U-0.045 U-0.044 U-0.043
1.5 in. R-11+R-19.0 c.i. U-0.044 U-0.043 U-0.043
2.0 in. R-7.6+R-19.0 c.i. U-0.043 U-0.042 U-0.041
R-10+R-19.0 c.i. U-0.042 U-0.041 U-0.041
R-13+R-19.0 c.i. U-0.042 U-0.041 U-0.041
3.0 in. R-11.4+R-19.0 c.i. U-0.041 U-0.040 U-0.039
R-15+R-19.0 c.i. U-0.040 U-0.039 U-0.039
R-19.5+R-19.0 c.i. U-0.040 U-0.039 U-0.038
3.5 in. R-11.0+R-19.0 c.i. U-0.040 U-0.039 U-0.039
R-13.0+R-19.0 c.i. U-0.040 U-0.039 U-0.038
5.0 in. R-19.0+R-19.0 c.i. U-0.037 U-0.036 U-0.036
R-25+R-19.0 c.i. U-0.036 U-0.035 U-0.035
R-32.5+R-19.0 c.i. U-0.035 U-0.035 U-0.034
5.5 in. R-19.0+R-19.0 c.i. U-0.036 U-0.036 U-0.035
R-21.0+R-19.0 c.i. U-0.035 U-0.035 U-0.035

Table A3.1-2 Assembly U-Factors, C-Factors, Ru, Rc, and HC for Concrete

Density, lb/ft3 Properties Thickness, in.
3 4 5 6 7 8 9 10 11 12
20 U-factor 0.22 0.17 0.14 0.12 0.10 0.09 0.08 0.07 0.07 0.06
C-factor 0.27 0.20 0.16 0.13 0.11 0.10 0.09 0.08 0.07 0.07
Ru 4.60 5.85 7.10 8.35 9.60 10.85 12.10 13.35 14.60 15.85
Rc 3.75 5.00 6.25 7.50 8.75 10.00 11.25 12.50 13.75 15.00
HC 1.0 1.3 1.7 2.0 2.3 2.7 3.0 3.3 3.7 4.0
30 U-factor 0.28 0.22 0.19 0.16 0.14 0.12 0.11 0.10 0.09 0.09
C-factor 0.37 0.28 0.22 0.18 0.16 0.14 0.12 0.11 0.10 0.09
Ru 3.58 4.49 5.40 6.30 7.21 8.12 9.03 9.94 10.85 11.76
Rc 2.73 3.64 4.55 5.45 6.36 7.27 8.18 9.09 10.00 10.91
HC 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
40 U-factor 0.33 0.27 0.23 0.19 0.17 0.15 0.14 0.13 0.11 0.11
C-factor 0.47 0.35 0.28 0.23 0.20 0.18 0.16 0.14 0.13 0.12
Ru 2.99 3.71 4.42 5.14 5.85 6.56 7.28 7.99 8.71 9.42
Rc 2.14 2.86 3.57 4.29 5.00 5.71 6.43 7.14 7.86 8.57
HC 2.0 2.7 3.3 4.0 4.7 5.3 6.0 6.7 7.3 8.0
50 U-factor 0.38 0.31 0.26 0.23 0.20 0.18 0.16 0.15 0.14 0.13
C-factor 0.57 0.43 0.34 0.28 0.24 0.21 0.19 0.17 0.15 0.14
Ru 2.61 3.20 3.79 4.38 4.97 5.56 6.14 6.73 7.32 7.91
Rc 1.76 2.35 2.94 3.53 4.12 4.71 5.29 5.88 6.47 7.06
HC 2.5 3.3 4.2 5.0 5.8 6.7 7.5 8.3 9.2 10.0
85 U-factor 0.65 0.56 0.50 0.44 0.40 0.37 0.34 0.31 0.29 0.27
C-factor 1.43 1.08 0.86 0.71 0.61 0.54 0.48 0.43 0.39 0.36
Ru 1.55 1.78 2.01 2.25 2.48 2.71 2.94 3.18 3.41 3.64
Rc 0.70 0.93 1.16 1.40 1.63 1.86 2.09 2.33 2.56 2.79
HC 4.3 5.7 7.1 8.5 9.9 11.3 12.8 14.2 15.6 17.0
95 U-factor 0.72 0.64 0.57 0.52 0.48 0.44 0.41 0.38 0.36 0.33
C-factor 1.85 1.41 1.12 0.93 0.80 0.70 0.62 0.56 0.51 0.47
Ru 1.39 1.56 1.74 1.92 2.10 2.28 2.46 2.64 2.81 2.99
Rc 0.54 0.71 0.89 1.07 1.25 1.43 1.61 1.79 1.96 2.14
HC 4.8 6.3 7.9 9.5 11.1 12.7 14.3 15.8 17.4 19.0
105 U-factor 0.79 0.71 0.65 0.59 0.54 0.51 0.47 0.44 0.42 0.39
C-factor 2.38 1.79 1.43 1.18 1.01 0.88 0.79 0.71 0.65 0.59
Ru 1.27 1.41 1.56 1.70 1.84 1.98 2.12 2.26 2.40 2.54
Rc 0.42 0.56 0.70 0.85 0.99 1.13 1.27 1.41 1.55 1.69
HC 5.3 7.0 8.8 10.5 12.3 14.0 15.8 17.5 19.3 21.0
115 U-factor 0.84 0.77 0.70 0.65 0.61 0.57 0.53 0.50 0.48 0.45
C-factor 2.94 2.22 1.75 1.47 1.25 1.10 0.98 0.88 0.80 0.74
Ru 1.19 1.30 1.42 1.53 1.65 1.76 1.87 1.99 2.10 2.21
Rc 0.34 0.45 0.57 0.68 0.80 0.91 1.02 1.14 1.25 1.36
HC 5.8 7.7 9.6 11.5 13.4 15.3 17.3 19.2 21.1 23.0
125 U-factor 0.88 0.82 0.76 0.71 0.67 0.63 0.60 0.56 0.53 0.51
C-factor 3.57 2.70 2.17 1.79 1.54 1.35 1.20 1.03 0.98 0.90
Ru 1.13 1.22 1.31 1.41 1.50 1.59 1.68 1.78 1.87 1.96
Rc 0.28 0.37 0.46 0.56 0.65 0.74 0.83 0.93 1.02 1.11
HC 6.3 8.3 10.4 12.5 14.6 16.7 18.8 20.8 22.9 25.0
135 U-factor 0.93 0.87 0.82 0.77 0.73 0.69 0.66 0.63 0.60 0.57
C-factor 4.55 3.33 2.70 2.22 1.92 1.67 1.49 1.33 1.22 1.11
Ru 1.07 1.15 1.22 1.30 1.37 1.45 1.52 1.60 1.67 1.75
Rc 0.22 0.30 0.37 0.45 0.52 0.60 0.67 0.75 0.82 0.90
HC 6.8 9.0 11.3 13.5 15.8 18.0 20.3 22.5 24.8 27.0
144 U-factor 0.96 0.91 0.86 0.81 0.78 0.74 0.71 0.68 0.65 0.63
C-factor 5.26 4.00 3.23 2.63 2.27 2.00 1.79 1.59 1.45 1.33
Ru 1.04 1.10 1.16 1.23 1.29 1.35 1.41 1.48 1.54 1.60
Rc 0.19 0.25 0.31 0.38 0.44 0.50 0.56 0.63 0.69 0.75
HC 7.2 9.6 12.0 14.4 16.8 19.2 21.6 24.0 26.4 28.8

The U-factors and Ru include standard air film resistances.

The C-factors and Rc are for the same assembly without air film resistances.

Note that the following assemblies do not qualify as a mass wall or mass floor: 3 in. thick concrete with densities of 85, 95, 125, and 135 lb/ft3.

Table A3.1-3 Assembly U-Factors, C-Factors, Ru, Rc, and HC for Concrete Block Walls

Product Size, in. Density, lb/ft3 Properties Concrete Block Grouting and Cell Treatment
Solid Grouted Partly Grouted, Cells Empty Partly Grouted, Cells Insulated Unreinforced, Cells Empty Unreinforced, Cells Insulated
6 in. block 85 U-factor 0.57 0.46 0.34 0.40 0.20
C-factor 1.11 0.75 0.47 0.60 0.23
Ru 1.75 2.18 2.97 2.52 5.13
Rc 0.90 1.33 2.12 1.67 4.28
HC 10.9 6.7 7.0 4.2 4.6
6 in. block 95 U-factor 0.61 0.49 0.36 0.42 0.22
C-factor 1.25 0.83 0.53 0.65 0.27
Ru 1.65 2.06 2.75 2.38 4.61
Rc 0.80 1.21 1.90 1.53 3.76
HC 11.4 7.2 7.5 4.7 5.1
6 in. block 105 U-factor 0.64 0.51 0.39 0.44 0.24
C-factor 1.38 0.91 0.58 0.71 0.30
Ru 1.57 1.95 2.56 2.26 4.17
Rc 0.72 1.10 1.71 1.41 3.32
HC 11.9 7.7 7.9 5.1 5.6
6 in. block 115 U-factor 0.66 0.54 0.41 0.46 0.26
C-factor 1.52 0.98 0.64 0.76 0.34
Ru 1.51 1.87 2.41 2.16 3.79
Rc 0.66 1.02 1.56 1.31 2.94
HC 12.3 8.1 8.4 5.6 6.0
6 in. block 125 U-factor 0.70 0.56 0.45 0.49 0.30
C-factor 1.70 1.08 0.73 0.84 0.40
Ru 1.44 1.78 2.23 2.04 3.38
Rc 0.59 0.93 1.38 1.19 2.53
HC 12.8 8.6 8.8 6.0 6.5
6 in. block 135 U-factor 0.73 0.60 0.49 0.53 0.35
C-factor 1.94 1.23 0.85 0.95 0.49
Ru 1.36 1.67 2.02 1.90 2.89
Rc 0.51 0.82 1.17 1.05 2.04
HC 13.2 9.0 9.3 6.5 6.9
8 in. block 85 U-factor 0.49 0.41 0.28 0.37 0.15
C-factor 0.85 0.63 0.37 0.53 0.17
Ru 2.03 2.43 3.55 2.72 6.62
Rc 1.18 1.58 2.70 1.87 5.77
HC 15.0 9.0 9.4 5.4 6.0
8 in. block 95 U-factor 0.53 0.44 0.31 0.39 0.17
C-factor 0.95 0.70 0.41 0.58 0.20
Ru 1.90 2.29 3.27 2.57 5.92
Rc 1.05 1.44 2.42 1.72 5.07
HC 15.5 9.6 10.0 6.0 6.6
8 in. block 105 U-factor 0.55 0.46 0.33 0.41 0.19
C-factor 1.05 0.76 0.46 0.63 0.22
Ru 1.81 2.17 3.04 2.44 5.32
Rc 0.96 1.32 2.19 1.59 4.47
HC 16.1 10.2 10.6 6.6 7.2
8 in. block 115 U-factor 0.58 0.48 0.35 0.43 0.21
C-factor 1.14 0.82 0.50 0.68 0.25
Ru 1.72 2.07 2.84 2.33 4.78
Rc 0.87 1.22 1.99 1.48 3.93
HC 16.7 10.8 11.2 7.2 7.8
8 in. block 125 U-factor 0.61 0.51 0.38 0.45 0.24
C-factor 1.27 0.90 0.57 0.74 0.30
Ru 1.64 1.96 2.62 2.20 4.20
Rc 0.79 1.11 1.77 1.35 3.35
HC 17.3 11.4 11.8 7.8 8.4
8 in. block 135 U-factor 0.65 0.55 0.42 0.49 0.28
C-factor 1.44 1.02 0.67 0.83 0.37
Ru 1.54 1.83 2.35 2.05 3.55
Rc 0.69 0.98 1.50 1.20 2.70
HC 17.9 12.0 12.4 8.4 9.0
10 in. block 85 U-factor 0.44 0.38 0.25 0.35 0.13
C-factor 0.70 0.57 0.31 0.50 0.14
Ru 2.29 2.61 4.05 2.84 7.87
Rc 1.44 1.76 3.20 1.99 7.02
HC 19.0 11.2 11.7 6.5 7.3
10 in. block 95 U-factor 0.47 0.41 0.27 0.37 0.14
C-factor 0.77 0.62 0.35 0.55 0.16
Ru 2.15 2.46 3.73 2.67 6.94
Rc 1.30 1.61 2.88 1.82 6.09
HC 19.7 11.9 12.4 7.3 8.1
10 in. block 105 U-factor 0.49 0.43 0.29 0.39 0.16
C-factor 0.85 0.68 0.39 0.59 0.19
Ru 2.03 2.33 3.45 2.54 6.17
Rc 1.18 1.48 2.60 1.69 5.32
HC 20.4 12.6 13.1 8.0 8.8
10 in. block 115 U-factor 0.52 0.45 0.31 0.41 0.18
C-factor 0.92 0.73 0.42 0.64 0.21
Ru 1.94 2.22 3.21 2.42 5.52
Rc 1.09 1.37 2.36 1.57 4.67
HC 21.1 13.4 13.9 8.7 9.5
10 in. block 125 U-factor 0.54 0.48 0.34 0.44 0.21
C-factor 1.01 0.80 0.48 0.70 0.25
Ru 1.84 2.10 2.95 2.28 4.81
Rc 0.99 1.25 2.10 1.43 3.96
HC 21.8 14.1 14.6 9.4 10.2
10 in. block 135 U-factor 0.58 0.51 0.38 0.47 0.25
C-factor 1.14 0.90 0.56 0.79 0.32
Ru 1.72 1.96 2.64 2.12 4.00
Rc 0.87 1.11 1.79 1.27 3.15
HC 22.6 14.8 15.3 10.2 11.0
12 in. block 85 U-factor 0.40 0.36 0.22 0.34 0.11
C-factor 0.59 0.52 0.27 0.48 0.12
Ru 2.53 2.77 4.59 2.93 9.43
Rc 1.68 1.92 3.74 2.08 8.58
HC 23.1 13.3 14.0 7.5 8.5
12 in. block 95 U-factor 0.42 0.38 0.24 0.36 0.12
C-factor 0.66 0.57 0.30 0.52 0.13
Ru 2.30 2.60 4.22 2.76 8.33
Rc 1.53 1.75 3.37 1.91 7.48
HC 23.9 14.2 14.8 8.3 9.3
12 in. block 105 U-factor 0.44 0.41 0.26 0.38 0.14
C-factor 0.71 0.62 0.33 0.57 0.15
Ru 2.25 2.47 3.90 2.62 7.35
Rc 1.40 1.62 3.05 1.77 6.50
HC 24.7 15.0 15.6 9.1 10.2
12 in. block 115 U-factor 0.47 0.42 0.28 0.40 0.15
C-factor 0.77 0.66 0.36 0.61 0.18
Ru 2.15 2.36 3.63 2.49 6.54
Rc 1.30 1.51 2.78 1.64 5.69
HC 25.6 15.8 16.4 10.0 11.0
12 in. block 125 U-factor 0.49 0.45 0.30 0.42 0.18
C-factor 0.84 0.72 0.40 0.66 0.21
Ru 2.04 2.23 3.34 2.36 5.68
Rc 1.19 1.38 2.49 1.51 4.83
HC 26.4 16.6 17.3 10.8 11.8
12 in. block 135 U-factor 0.52 0.48 0.34 0.46 0.21
C-factor 0.94 0.81 0.47 0.74 0.26
Ru 1.91 2.08 2.98 2.19 4.67
Rc 1.06 1.23 2.13 1.34 3.82
HC 27.2 17.5 18.1 11.6 12.6

Table A3.1-4 Effective R-Values for Insulation/Framing Layers Added to Above-Grade Mass Walls and Below-Grade Walls

Depth, in. Framing Type Rated R-Value of Insulation
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Effective R-value if Continuous Insulation Uninterrupted by Framing (Includes Gypsum Board)
  None 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 25.5
Effective R-value if Insulation is Installed in Cavity between Framing (Includes Gypsum Board)
0.5 Wood 1.3 1.3 1.9 2.4 2.7 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
Metal 0.9 0.9 1.1 1.1 1.2 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
0.75 Wood 1.4 1.4 2.1 2.7 3.1 3.5 3.8 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
Metal 1.0 1.0 1.3 1.4 1.5 1.5 1.6 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
1.0 Wood 1.3 1.5 2.2 2.9 3.4 3.9 4.3 4.6 4.9 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
Metal 1.0 1.1 1.4 1.6 1.7 1.8 1.8 1.9 1.9 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
1.5 Wood 1.3 1.5 2.4 3.1 3.8 4.4 4.9 5.4 5.8 6.2 6.5 6.8 7.1 NA NA NA NA NA NA NA NA NA NA NA NA NA
Metal 1.1 1.2 1.6 1.9 2.1 2.2 2.3 2.4 2.5 2.5 2.6 2.6 2.7 NA NA NA NA NA NA NA NA NA NA NA NA NA
2.0 Wood 1.4 1.5 2.5 3.3 4.0 4.7 5.3 5.9 6.4 6.9 7.3 7.7 8.1 8.4 8.7 9.0 9.3 NA NA NA NA NA NA NA NA NA
Metal 1.1 1.2 1.7 2.1 2.3 2.5 2.7 2.8 2.9 3.0 3.1 3.2 3.2 3.3 3.3 3.4 3.4 NA NA NA NA NA NA NA NA NA
2.5 Wood 1.4 1.5 2.5 3.4 4.2 4.9 5.6 6.3 6.8 7.4 7.9 8.4 8.8 9.2 9.6 10.0 10.3 10.6 10.9 11.2 11.5 NA NA NA NA NA
Metal 1.2 1.3 1.8 2.3 2.6 2.8 3.0 3.2 3.3 3.5 3.6 3.6 3.7 3.8 3.9 3.9 4.0 4.0 4.1 4.1 4.1 NA NA NA NA NA
3.0 Wood 1.4 1.5 2.5 3.5 4.3 5.1 5.8 6.5 7.2 7.8 8.3 8.9 9.4 9.9 10.3 10.7 11.1 11.5 11.9 12.2 12.5 12.9 NA NA NA NA
Metal 1.2 1.3 1.9 2.4 2.8 3.1 3.3 3.5 3.7 3.8 4.0 4.1 4.2 4.3 4.4 4.4 4.5 4.6 4.6 4.7 4.7 4.8 NA NA NA NA
3.5 Wood 1.4 1.5 2.6 3.5 4.4 5.2 6.0 6.7 7.4 8.1 8.7 9.3 9.8 10.4 10.9 11.3 11.8 12.2 12.6 13.0 13.4 13.8 14.1 14.5 14.8 15.1
Metal 1.2 1.3 2.0 2.5 2.9 3.2 3.5 3.8 4.0 4.2 4.3 4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.1 5.2 5.2 5.3 5.4 5.4 5.4 5.5
4.0 Wood 1.4 1.6 2.6 3.6 4.5 5.3 6.1 6.9 7.6 8.3 9.0 9.6 10.2 10.8 11.3 11.9 12.4 12.8 13.3 13.7 14.2 14.6 14.9 15.3 15.7 16.0
Metal 1.2 1.3 2.0 2.6 3.0 3.4 3.7 4.0 4.2 4.5 4.6 4.8 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.8 5.9 5.9 6.0 6.0
4.5 Wood 1.4 1.6 2.6 3.6 4.5 5.4 6.2 7.1 7.8 8.5 9.2 9.9 10.5 11.2 11.7 12.3 12.8 13.3 13.8 14.3 14.8 15.2 15.7 16.1 16.5 16.9
Metal 1.2 1.3 2.1 2.6 3.1 3.5 3.9 4.2 4.5 4.7 4.9 5.1 5.3 5.4 5.6 5.7 5.8 5.9 6.0 6.1 6.2 6.3 6.4 6.4 6.5 6.6
5.0 Wood 1.4 1.6 2.6 3.6 4.6 5.5 6.3 7.2 8.0 8.7 9.4 10.1 10.8 11.5 12.1 12.7 13.2 13.8 14.3 14.8 15.3 15.8 16.3 16.7 17.2 17.6
Metal 1.2 1.4 2.1 2.7 3.2 3.7 4.1 4.4 4.7 5.0 5.2 5.4 5.6 5.8 5.9 6.1 6.2 6.3 6.5 6.6 6.7 6.8 6.8 6.9 7.0 7.1
5.5 Wood 1.4 1.6 2.6 3.6 4.6 5.5 6.4 7.3 8.1 8.9 9.6 10.3 11.0 11.7 12.4 13.0 13.6 14.2 14.7 15.3 15.8 16.3 16.8 17.3 17.8 18.2
Metal 1.3 1.4 2.1 2.8 3.3 3.8 4.2 4.6 4.9 5.2 5.4 5.7 5.9 6.1 6.3 6.4 6.6 6.7 6.8 7.0 7.1 7.2 7.3 7.4 7.5 7.6

For the purpose of Section A1.2, the base assembly is a masonry or concrete wall. Continuous insulation is installed on the interior or exterior or within the masonry units, or it is installed on the interior or exterior of the concrete. The brick cavity wall has continuous insulation between the brick and the concrete or masonry. The U-factors include R-0.17 for exterior air film and R-0.68 for interior air film, vertical surfaces. For insulated walls, the U-factor also includes R-0.45 for 0.5 in. gypsum board. For the cavity wall, the U-factor includes R-0.74 for brick. U-factors are provided for the following configurations:

  1. Concrete wall: 8 in. normal weight concrete wall with a density of 145 lb/ft3.
  2. Solid grouted concrete block wall: 8 in. medium weight ASTM C90 concrete block with a density of 115 lb/ft3 and solid grouted cores.
  3. Partially grouted concrete block wall: 8 in. medium weight ASTM C90 concrete block with a density of 115 lb/ft3 having reinforcing steel every 32 in. vertically and every 48 in. horizontally, with cores grouted in those areas only. Other cores are filled with insulating material only if there is no other insulation.

Mass wall HC shall be determined from Table A3.1-2 or A3.1-3.

The rated R-value of insulation is for continuous insulation uninterrupted by framing other than 20 gage 1 in. metal clips spaced no closer than 24 in. on center horizontally and 16 in. on center vertically.

Where other framing, including metal and wood studs, is used, compliance shall be based on the maximum assembly U-factor.

Where rated R-value of insulation is used for concrete sandwich panels, the insulation shall be continuous throughout the entire panel.

U-factors for mass walls shall be taken from Table A3.1-1 or determined by the procedure in this subsection. It is acceptable to use the U-factors in Table A3.1-1 for all mass walls, provided that the grouting is equal to or less than that specified. HC for mass walls shall be taken from Table A3.1-2 or A3.1-3.

If not taken from Table A3.1-1, mass wall U-factors shall be determined from Tables A3.1-2, A3.1-3, or A3.1-4 using the following procedure:

  1. If the mass wall is uninsulated or only the cells are insulated:
    1. For concrete walls, determine the U-factor from Table A3.1-2 based on the concrete density and wall thickness.
    2. For concrete block walls, determine the U-factor from Table A3.1-3 based on the block size, concrete density, degree of grouting in the cells, and whether the cells are insulated.
  2. If the mass wall has additional insulation:
    1. For concrete walls, determine the Rc from Table A3.1-2 based on the concrete density and wall thickness. Next, determine the effective R-value for the insulation/framing layer from Table A3.1-4 based on the rated R-value of insulation installed, the thickness of the insulation, and whether it is installed between wood or metal framing or with no framing. Then, determine the U-factor by adding the Ru and the effective R-value together and taking the inverse of the total.
    2. For concrete block walls, determine the Ru from Table A3.1-3 based on the block size, concrete density, degree of grouting in the cells, and whether the cells are insulated. Next, determine the effective R-value for the insulation/framing layer from Table A3.1-4 based on the rated R-value of insulation installed, the thickness of the insulation, and whether it is installed between wood or metal framing or with no framing. Then, determine the U-factor by adding the Ru and the effective R-value together and taking the inverse of the total.

For the purpose of Section A1.2, the base assembly is a wall with metal wall panels and a metal structure. Insulation is installed in accordance with this section. Insulation exposed to a conditioned space or semiheated space shall have a facing with seams overlapped or sealed.

The first rated R-value of insulation is for insulation compressed between metal wall panels and the steel structure.

For assemblies with continuous insulation, the continuous insulation is installed on the outside or inside of the girts, uncompressed and uninterrupted by the framing members.

The insulation is installed in the cavity between the girts, not compressed by the framing. A membrane or facing, installed separately or adhered to the insulation, is installed inside of the girts to form a continuous layer. A thermal spacer block or thermal break strip between the girts and metal wall panels is required when specified in Table A3.2.3.

The first rated R-value of insulation is for insulation installed in the cavity between the girts, not compressed by the framing. The second rated R-value of insulation is for insulation compressed between metal wall panels and the steel structure. A membrane or facing, installed separately or adhered to the insulation, is installed inside of the girts to form a continuous layer. A thermal spacer block or thermal break strip between the girts and metal wall panels is required when specified in Table A3.2.3.

U-factors for metal building walls shall be taken from Table A3.2.3 or determined in accordance with Section A9.2. provided the average girt spacing is at least 52 in. U-factors for metal building wall assemblies with average girt spacing less than 52 in. shall be determined in accordance with Section A9.2.

Table A3.2.3 Assembly U-Factors for Metal Building Walls

Insulation System Rated R-Value of Insulation Overall U-Factor for Entire Base Wall Assembly Overall U-Factor for Assembly of Base Wall
Plus Continuous Insulation (Uninterrupted by Framing)
R-6.5 R-9.8 R-13 R-15.8 R-19 R-22.1 R-25 R-32 R-38
Continuous insulation only None 1.180 0.136 0.094 0.072 0.060 0.050 0.044 0.039 0.030 0.026
Single compressed layer R-10 0.186 0.084 0.066 0.054 0.047 0.041 0.036 0.033 0.027 0.023
R-11 0.185 0.084 0.066 0.054 0.047 0.041 0.036 0.033 0.027 0.023
R-13 0.162 0.079 0.063 0.052 0.046 0.040 0.035 0.032 0.026 0.023
R-16 0.155 0.077 0.062 0.051 0.045 0.039 0.035 0.032 0.026 0.022
R-19 0.147 0.075 0.060 0.050 0.044 0.039 0.035 0.031 0.026 0.022
Single layer in cavity R-25a 0.059 0.044 0.039 0.035 0.032 0.029 0.027 0.025 0.021 0.019
R-30b 0.052 0.042 0.037 0.033 0.031 0.028 0.026 0.024 0.021 0.019
Double layer R-25 + R-10 0.047
R-25 + R-16 0.042
R-25 + R-10c 0.039
R-30 + R-16 0.039

(Multiple R-values are listed in order from inside to outside.)

  1. A minimum R-0.375 thermal spacer block or thermal break strip is required when installed without continuous insulation.
  2. A minimum R-0.75 thermal spacer block or thermal break strip is required when installed without continuous insulation.
  3. A minimum R-3 thermal spacer block is required.

For the purpose of Section A1.2, the base assembly is a wall where the insulation is installed within the cavity of the steel stud framing but where there is not a metal exterior surface-spanning member. The steel stud framing is a minimum uncoated thickness of 0.043 in. for 18 gage or 0.054 in. for 16 gage. The U-factors include R-0.17 for exterior air film, R-0.08 for stucco, R-0.56 for 0.625 in. gypsum board on the exterior, R-0.56 for 0.625 in. gypsum board on the interior, and R-0.68 for interior vertical surfaces air film. The performance of the insulation/framing layer is calculated using the values in Table A9.2-2. Additional assemblies include continuous insulation uncompressed and uninterrupted by framing. U-factors are provided for the following configurations:

  1. Standard framing: Steel stud framing at 16 in. on center with cavities filled with 16 in. wide insulation for both 3.5 in. deep and 6.0 in. deep wall cavities.
  2. Advanced framing: Steel stud framing at 24 in. on center with cavities filled with 24 in. wide insulation for both 3.5 in.deep and 6.0 in. deep wall cavities.

The first rated R-value of insulation is for uncompressed insulation installed in the cavity between steel studs. It is acceptable for this insulation to also be continuous insulation uninterrupted by framing.

If there are two values, the second rated R-value of insulation is for continuous insulation uninterrupted by framing, etc., to be installed in addition to the first insulation.

Opaque mullions in spandrel glass shall be covered with insulation complying with the steel-framed wall requirements.

U-factors for steel-framed walls shall be taken from Table A3.3.3.1.

Table A3.3.3.1 Assembly U-Factors for Steel-Frame Walls

Framing
Type and
Spacing
Width
(Actual
Depth)
Cavity
Insulation
R-Value:
Rated
(Effective
Installed [see
Table A9.2.2])
Overall
U-Factor
for Entire
Base Wall
Assembly
Overall U-Factor for Assembly of Base Wall Plus Continuous Insulation (Uninterrupted by Framing)
Rated R-Value of Continuous Insulation
R-1.00 R-2.00 R-3.00 R-4.00 R-5.00 R-6.00 R-7.00 R-8.00 R-9.00 R-10.00 R-11.00 R-12.00 R-13.00 R-14.00 R-15.00 R-20.00 R-25.00 R-30.00 R-35.00 R-40.00
Steel Framing at 16 in. on Center
3.5 in. depth None (0.0) 0.352 0.260 0.207 0.171 0.146 0.128 0.113 0.102 0.092 0.084 0.078 0.072 0.067 0.063 0.059 0.056 0.044 0.036 0.030 0.026 0.023
R-11 (5.5) 0.132 0.117 0.105 0.095 0.087 0.080 0.074 0.069 0.064 0.060 0.057 0.054 0.051 0.049 0.046 0.044 0.036 0.031 0.027 0.024 0.021
R-13 (6.0) 0.124 0.111 0.100 0.091 0.083 0.077 0.071 0.066 0.062 0.059 0.055 0.052 0.050 0.048 0.045 0.043 0.036 0.030 0.026 0.023 0.021
R-15 (6.4) 0.118 0.106 0.096 0.087 0.080 0.074 0.069 0.065 0.061 0.057 0.054 0.051 0.049 0.047 0.045 0.043 0.035 0.030 0.026 0.023 0.021
6.0 in. depth R-19 (7.1) 0.109 0.099 0.090 0.082 0.076 0.071 0.066 0.062 0.058 0.055 0.052 0.050 0.047 0.045 0.043 0.041 0.034 0.029 0.026 0.023 0.020
R-21 (7.4) 0.106 0.096 0.087 0.080 0.074 0.069 0.065 0.061 0.057 0.054 0.051 0.049 0.047 0.045 0.043 0.041 0.034 0.029 0.025 0.022 0.020
Steel Framing at 24 in. on Center
3.5 in. depth None (0.0) 0.338 0.253 0.202 0.168 0.144 0.126 0.112 0.100 0.091 0.084 0.077 0.072 0.067 0.063 0.059 0.056 0.044 0.036 0.030 0.026 0.023
R-11 (6.6) 0.116 0.104 0.094 0.086 0.079 0.073 0.068 0.064 0.060 0.057 0.054 0.051 0.048 0.046 0.044 0.042 0.035 0.030 0.026 0.023 0.021
R-13 (7.2) 0.108 0.098 0.089 0.082 0.075 0.070 0.066 0.062 0.058 0.055 0.052 0.049 0.047 0.045 0.043 0.041 0.034 0.029 0.025 0.023 0.020
R-15 (7.8) 0.102 0.092 0.084 0.078 0.072 0.067 0.063 0.059 0.056 0.053 0.050 0.048 0.046 0.044 0.042 0.040 0.034 0.029 0.025 0.022 0.020
6.0 in. depth R-19 (8.6) 0.094 0.086 0.079 0.073 0.068 0.064 0.060 0.057 0.054 0.051 0.048 0.046 0.044 0.042 0.041 0.039 0.033 0.028 0.025 0.022 0.020
R-21 (9.0) 0.090 0.083 0.077 0.071 0.066 0.062 0.059 0.055 0.052 0.050 0.048 0.045 0.043 0.042 0.040 0.038 0.032 0.028 0.024 0.022 0.020

For steel-framed walls with framing at less than 24 in. on center, use the standard framing values as described in Section A3.3.1(a).

For steel-framed walls with framing from 24 to 32 in. on center, use the advanced framing values as described in Section A3.3.1(b).

For steel-framed walls with framing greater than 32 in. on center, use the metal building wall values in Table A3.2.3.

For the purpose of Section A1.2, the base assembly is a wall where the insulation is installed between 2 in. nominal wood framing. Cavity insulation is full depth, but values are taken from Table A9.4.3 for R-19 insulation, which is compressed when installed in a 5.5 in. cavity. Headers are double 2 in. nominal wood framing. The U-factors include R-0.17 for exterior air film, R-0.08 for stucco, R-0.56 for 0.625 in. gypsum board on the exterior, R-0.56 for 0.625 in. gypsum board on the interior, and R-0.68 for interior air film, vertical surfaces. Additional assemblies include continuous insulation uncompressed and uninterrupted by framing. U-factors are provided for the following configurations:

  1. Standard framing: Wood framing at 16 in. on center with cavities filled with 14.5 in. wide insulation for both 3.5 in. deep and 5.5 in. deep wall cavities. Double headers leave no cavity. Weighting factors are 75% insulated cavity, 21% studs, plates, and sills, and 4% headers.
  2. Advanced framing: Wood framing at 24 in. on center with cavities filled with 22.5 in. wide insulation for both 3.5 in. deep and 5.5 in. deep wall cavities. Double headers leave uninsulated cavities. Weighting factors are 78% insulated cavity, 18% studs, plates, and sills, and 4% headers.
  3. Advanced framing with insulated headers: Wood framing at 24 in. on center with cavities filled with 22.5 in. wide insulation for both 3.5 in. deep and 5.5 in. deep wall cavities. Double header cavities are insulated. Weighting factors are 78% insulated cavity, 18% studs, plates, and sills, and 4% headers.

The first rated R-value of insulation is for uncompressed insulation installed in the cavity between wood studs. It is acceptable for this insulation to also be continuous insulation uninterrupted by framing.

If there are two values, the second rated R-value of insulation is for continuous insulation uninterrupted by framing, etc., to be installed in addition to the first insulation.

U-factors for wood-framed walls shall be taken from Table A3.4.3.1.

Table A3.4.3.1 Assembly U-Factors for Wood-Frame Walls 

Framing
Type and
Spacing
Width
(Actual
Depth)
Cavity
Insulation
R-Value:
Rated
(Effective
Installed [see
Table A9.4.3])
Overall
U-Factor
for Entire
Base Wall
Assembly
Overall U-Factor for Assembly of Base Wall Plus Continuous Insulation (Uninterrupted by Framing)
Rated R-Value of Continuous Insulation
R-1.00 R-2.00 R-3.00 R-4.00 R-5.00 R-6.00 R-7.00 R-8.00 R-9.00 R-10.00 R-11.00 R-12.00 R-13.00 R-14.00 R-15.00 R-20.00 R-25.00 R-30.00 R-35.00 R-40.00
Wood Studs at 16 in. on Center
3.5 in. depth None (0.0) 0.292 0.223 0.181 0.152 0.132 0.116 0.104 0.094 0.086 0.079 0.073 0.068 0.064 0.060 0.056 0.053 0.042 0.035 0.030 0.026 0.023
R-11 (11.0) 0.096 0.087 0.079 0.073 0.068 0.063 0.059 0.056 0.053 0.050 0.048 0.046 0.044 0.042 0.040 0.038 0.032 0.028 0.024 0.022 0.020
R-13 (13.0) 0.089 0.080 0.074 0.068 0.063 0.059 0.056 0.053 0.050 0.047 0.045 0.043 0.041 0.040 0.038 0.037 0.031 0.027 0.024 0.021 0.019
R-15 (15.0) 0.083 0.075 0.069 0.064 0.060 0.056 0.053 0.050 0.047 0.045 0.043 0.041 0.039 0.038 0.036 0.035 0.030 0.026 0.023 0.020 0.019
5.5 in. depth R-19 (18.0) 0.067 0.062 0.058 0.054 0.051 0.048 0.046 0.044 0.042 0.040 0.038 0.037 0.036 0.034 0.033 0.032 0.027 0.024 0.021 0.019 0.018
R-21 (21.0) 0.063 0.058 0.054 0.051 0.048 0.045 0.043 0.041 0.039 0.038 0.036 0.035 0.034 0.032 0.031 0.030 0.026 0.023 0.021 0.019 0.017
+ R-10 headers R-19 (18.0) 0.063 0.059 0.055 0.052 0.049 0.047 0.045 0.043 0.041 0.039 0.038 0.036 0.035 0.034 0.033 0.031 0.027 0.024 0.021 0.019 0.017
R-21 (21.0) 0.059 0.055 0.051 0.049 0.046 0.044 0.042 0.040 0.038 0.037 0.035 0.034 0.033 0.032 0.031 0.030 0.026 0.023 0.020 0.018 0.017
Wood Studs at 24 in. on Center
3.5 in. depth None (0.0) 0.298 0.227 0.183 0.154 0.133 0.117 0.105 0.095 0.086 0.079 0.074 0.068 0.064 0.060 0.057 0.054 0.042 0.035 0.030 0.026 0.023
R-11 (11.0) 0.094 0.085 0.078 0.072 0.067 0.062 0.059 0.055 0.052 0.050 0.047 0.045 0.043 0.041 0.040 0.038 0.032 0.027 0.024 0.022 0.019
R-13 (13.0) 0.086 0.078 0.072 0.067 0.062 0.058 0.055 0.052 0.049 0.047 0.045 0.043 0.041 0.039 0.038 0.036 0.031 0.026 0.023 0.021 0.019
R-15 (15.0) 0.080 0.073 0.067 0.062 0.058 0.055 0.052 0.049 0.046 0.044 0.042 0.040 0.039 0.037 0.036 0.035 0.029 0.026 0.023 0.020 0.018
5.5 in. depth R-19 (18.0) 0.065 0.060 0.056 0.053 0.050 0.047 0.045 0.043 0.041 0.039 0.038 0.036 0.035 0.034 0.033 0.032 0.027 0.024 0.021 0.019 0.018
R-21 (21.0) 0.060 0.056 0.052 0.049 0.046 0.044 0.042 0.040 0.038 0.037 0.036 0.034 0.033 0.032 0.031 0.030 0.026 0.023 0.020 0.018 0.017
+ R-10 headers R-19 (18.0) 0.062 0.058 0.054 0.051 0.048 0.046 0.044 0.042 0.040 0.039 0.037 0.036 0.034 0.033 0.032 0.031 0.027 0.024 0.021 0.019 0.017
R-21 (21.0) 0.057 0.053 0.050 0.047 0.045 0.043 0.041 0.039 0.037 0.036 0.035 0.033 0.032 0.031 0.030 0.029 0.025 0.023 0.020 0.018 0.017

For wood-framed walls with framing at less than 24 in. on center, use the standard framing values as described in Section A3.4.1(a).

For wood-framed walls with framing from 24 to 32 in. on center, use the advanced framing values as described in Section A3.4.1(b) if the headers are uninsulated, or the advanced framing with insulated header values as described in Section A3.4.1(c) if the headers are insulated.

For wood-framed walls with framing greater than 32 in. on center, U-factors shall be determined in accordance with Section A9.

For the purpose of Section A1.2, the base assembly is 8 in. medium-weight concrete block with a density of 115 lb/ft3 and solid grouted cores. Continuous insulation is installed on the interior or exterior. In contrast to the U-factor for above-grade walls, the C-factor for below-grade walls does not include R-values for exterior or interior air films or for soil. For insulated walls, the C-factor does include R-0.45 for 0.5 in. gypsum board.

C-factors for below-grade walls shall be taken from Table A4.2.1 or determined by the procedure described in this subsection.

Table A4.2.1 Assembly C-Factors for Below-Grade Walls

Framing Type and Depth Rated R-Value of Insulation Alone Specified C-Factors
(Wall Only, without Soil and Air Films)
No Framing R-0 C-1.140
Exterior Insulation, Continuous and Uninterrupted by Framing
No Framing R-5.0 C-0.170
No Framing R-7.5 C-0.119
No Framing R-10.0 C-0.092
No Framing R-12.5 C-0.075
No Framing R-15.0 C-0.063
No Framing R-17.5 C-0.054
No Framing R-20.0 C-0.048
No Framing R-25.0 C-0.039
No Framing R-30.0 C-0.032
No Framing R-35.0 C-0.028
No Framing R-40.0 C-0.025
No Framing R-45.0 C-0.022
No Framing R-50.0 C-0.020
Continuous Metal Framing at 24 in. on Center Horizontally
3.5 in. R-11.0 C-0.182
3.5 in. R-13.0 C-0.174
3.5 in. R-15.0 C-0.168
5.5 in. R-19.0 C-0.125
5.5 in. R-21.0 C-0.120
1 in. Metal Clips at 24 in. on Center Horizontally and 16 in. Vertically
1.0 in. R-3.8 C-0.233
1.0 in. R-5.0 C-0.201
1.0 in. R-5.6 C-0.189
1.5 in. R-5.7 C-0.173
1.5 in. R-7.5 C-0.147
1.5 in. R-8.4 C-0.138
2.0 in. R-7.6 C-0.138
2.0 in. R-10.0 C-0.116
2.0 in. R-11.2 C-0.108
2.5 in. R-9.5 C-0.114
2.5 in. R-12.5 C-0.096
2.5 in. R-14.0 C-0.089
3.0 in. R-11.4 C-0.098
3.0 in. R-15.0 C-0.082
3.0 in. R-16.8 C-0.076
3.5 in. R-13.3 C-0.085
3.5 in. R-17.5 C-0.071
3.5 in. R-19.6 C-0.066
4.0 in. R-15.2 C-0.076
4.0 in. R-20.0 C-0.063
4.0 in. R-22.4 C-0.058

It is acceptable to use the C-factors in Table A4.2.1 for all below-grade walls.

If not taken from Table A4.2.1, below-grade wall C-factors shall be determined from Tables A3.1-2, A3.1-3, or A3.1-4 using the following procedure:

  1. If the below-grade wall is uninsulated or only the cells are insulated:
    1. For concrete walls, determine the C-factor from Table A3.1-2 based on the concrete density and wall thickness.
    2. For concrete block walls, determine the C-factor from Table A3.1-3 based on the block size, concrete density, degree of grouting in the cells, and whether the cells are insulated.
  2. If the mass wall has additional insulation:
    1. For concrete walls, determine the Rc from Table A3.1-2 based on the concrete density and wall thickness. Next, determine the effective R-value for the insulation/framing layer from Table A3.1-4 based on the rated R-value of insulation installed, the thickness of the insulation, and whether it is installed between wood or metal framing or with no framing. Then determine the C-factor by adding the Rc and the effective R-value together and taking the inverse of the total.
    2. For concrete block walls, determine the Rc from Table A3.1-3 based on the block size, concrete density, degree of grouting in the cells, and whether the cells are insulated. Next, determine the effective R-value for the insulation/framing layer from Table A3.1-4 based on the rated R-value of insulation installed, the thickness of the insulation, and whether it is installed between wood or metal framing or with no framing. Then determine the C-factor by adding the Rc and the effective R-value together and taking the inverse of the total.

The buffering effect of crawlspaces or parking garages shall not be included in U-factor calculations. See Section A6 for slab-on-grade floors.

For the purpose of Section A1.2, the base assembly is continuous insulation over or under a solid concrete floor. The U-factors include R-0.92 for interior air film, heat flow down; R-l .23 for carpet and rubber pad; R-0.50 for 8 in. concrete; and R-0.46 for semiexterior air film. Added insulation is continuous and uninterrupted by framing. Framing factor is zero.

The rated R-value of insulation is for continuous insulation uninterrupted by framing.

Where framing, including metal and wood joists, is used, compliance shall be based on the maximum assembly U-factor rather than the minimum rated R-value of insulation.

For waffle-slab floors, the floor shall be insulated either on the interior above the slab or on all exposed surfaces of the waffle.

For floors with beams that extend below the floor slab, the floor shall be insulated either on the interior above the slab or on the exposed floor and all exposed surfaces of the beams that extend 24 in. and less below the exposed floor.

The U-factors for mass walls shall be taken from Table A5.2.3.1.

Table A5.2.3.1 Assembly U-Factors for Mass Floors

Framing Type and Spacing Width (Actual Depth) Cavity Insulation R-Value: Rated (Effective Installed) Overall U-Factor for Entire Base Floor Assembly Overall U-Factor for Assembly of Base Floor Plus Continuous Insulation (Uninterrupted by Framing)
Rated R-Value of Continuous Insulation
R-1.00 R-2.00 R-3.00 R-4.00 R-5.00 R-6.00 R-7.00 R-8.00 R-9.00 R-10.00 R-11.00 R-12.00 R-13.00 R-14.00 R-15.00 R-20.00 R-25.00 R-30.00 R-35.00 R-40.00
Concrete Floor with Rigid Foam
  None (0.0) 0.322 0.243 0.196 0.164 0.141 0.123 0.110 0.099 0.090 0.083 0.076 0.071 0.066 0.062 0.058 0.055 0.043 0.036 0.030 0.026 0.023
Concrete Floor with Pinned Boards
  R-4.2 (4.2) 0.137 0.121 0.108 0.097 0.089 0.081 0.075 0.070 0.065 0.061 0.058 0.055 0.052 0.049 0.047 0.045 0.037 0.031 0.027 0.024 0.021
  R-6.3 (6.3) 0.107 0.096 0.088 0.081 0.075 0.070 0.065 0.061 0.058 0.054 0.052 0.049 0.047 0.045 0.043 0.041 0.034 0.029 0.025 0.023 0.020
  R-8.3 (8.3) 0.087 0.080 0.074 0.069 0.065 0.061 0.057 0.054 0.051 0.049 0.047 0.045 0.043 0.041 0.039 0.038 0.032 0.027 0.024 0.022 0.019
  R-10.4 (10.4) 0.074 0.069 0.064 0.060 0.057 0.054 0.051 0.049 0.046 0.044 0.042 0.041 0.039 0.038 0.036 0.035 0.030 0.026 0.023 0.021 0.019
  R-12.5 (12.5) 0.064 0.060 0.057 0.054 0.051 0.048 0.046 0.044 0.042 0.041 0.039 0.038 0.036 0.035 0.034 0.033 0.028 0.025 0.022 0.020 0.018
  R-14.6 (14.6) 0.056 0.053 0.051 0.048 0.046 0.044 0.042 0.040 0.039 0.037 0.036 0.035 0.034 0.033 0.032 0.031 0.027 0.023 0.021 0.019 0.017
  R-16.7 (16.7) 0.051 0.048 0.046 0.044 0.042 0.040 0.039 0.037 0.036 0.035 0.034 0.032 0.031 0.030 0.030 0.029 0.025 0.022 0.020 0.018 0.017
Concrete Floor with Spray-On Insulation
1 in. R-4 (4.0) 0.141 0.123 0.110 0.099 0.090 0.083 0.076 0.071 0.066 0.062 0.058 0.055 0.052 0.050 0.047 0.045 0.037 0.031 0.027 0.024 0.021
2 in. R-8 (8.0) 0.090 0.083 0.076 0.071 0.066 0.062 0.058 0.055 0.052 0.050 0.047 0.045 0.043 0.041 0.040 0.038 0.032 0.028 0.024 0.022 0.020
3 in. R-12 (12.0) 0.066 0.062 0.058 0.055 0.052 0.050 0.047 0.045 0.043 0.041 0.040 0.038 0.037 0.036 0.034 0.033 0.028 0.025 0.022 0.020 0.018
4 in. R-16 (16.0) 0.052 0.050 0.047 0.045 0.043 0.041 0.040 0.038 0.037 0.036 0.034 0.033 0.032 0.031 0.030 0.029 0.026 0.023 0.020 0.018 0.017
5 in. R-20 (20.0) 0.043 0.041 0.040 0.038 0.037 0.036 0.034 0.033 0.032 0.031 0.030 0.029 0.028 0.028 0.027 0.026 0.023 0.021 0.019 0.017 0.016
6 in. R-24 (24.0) 0.037 0.036 0.034 0.033 0.032 0.031 0.030 0.029 0.028 0.028 0.027 0.026 0.026 0.025 0.024 0.024 0.021 0.019 0.018 0.016 0.015

It is not acceptable to use the U-factors in Table A5.2.3.1 if the insulation is not continuous.

For the purpose of Section A1.2, the base assembly is a floor where the insulation is either placed between the steel joists or is sprayed on the underside of the floor and the joists. In both cases, the steel provides a thermal bypass to the insulation. The U-factors include R-0.92 for interior air film, heat flow down; R-1.23 for carpet and pad; R-0.25 for 4 in. concrete; R-0 for metal deck; and R-0.46 for semiexterior air film. The performance of the insulation/framing layer is calculated using the values in Table A9.2-1.

The first rated R-value of insulation is for uncompressed insulation installed in the cavity between steel joists or for spray-on insulation.

It is acceptable for this insulation to also be continuous insulation uninterrupted by framing. All continuous insulation shall be installed either on the interior above the floor structure or below a framing cavity completely filled with insulation.

The U-factors for steel-joist floors shall be taken from Table A5.3.3.1.

Table A5.3.3.1 Assembly U-Factors for Steel-Joist Floors

Framing Type and Spacing Width (Actual Depth) Cavity Insulation R-Value: Rated (Effective Installed [See Table A9.2-1]) Overall U-Factor for Entire Base Floor Assembly Overall U-Factor for Assembly of Base Floor Plus Continuous Insulation (Uninterrupted by Framing)
Rated R-Value of Continuous Insulation
R-1.00 R-2.00 R-3.00 R-4.00 R-5.00 R-6.00 R-7.00 R-8.00 R-9.00 R-10.00 R-11.00 R-12.00 R-13.00 R-14.00 R-15.00 R-20.00 R-25.00 R-30.00 R-35.00 R-40.00
Steel Joist Floor with Rigid Foam
  None (0.0) 0.350 0.259 0.206 0.171 0.146 0.127 0.113 0.101 0.092 0.084 0.078 0.072 0.067 0.063 0.059 0.056 0.044 0.036 0.030 0.026 0.023
Steel Joist Floor with Spray-on Insulation
1 in. R-4 (3.88) 0.148 0.129 0.114 0.103 0.093 0.085 0.078 0.073 0.068 0.064 0.060 0.056 0.053 0.051 0.048 0.046 0.037 0.032 0.027 0.024 0.021
2 in. R-8 (7.52) 0.096 0.088 0.081 0.075 0.070 0.065 0.061 0.058 0.054 0.052 0.049 0.047 0.045 0.043 0.041 0.039 0.033 0.028 0.025 0.022 0.020
3 in. R-12 (10.80) 0.073 0.068 0.064 0.060 0.057 0.054 0.051 0.048 0.046 0.044 0.042 0.041 0.039 0.038 0.036 0.035 0.030 0.026 0.023 0.021 0.019
4 in. R-16 (13.92) 0.060 0.056 0.053 0.051 0.048 0.046 0.044 0.042 0.040 0.039 0.037 0.036 0.035 0.034 0.032 0.031 0.027 0.024 0.021 0.019 0.018
5 in. R-20 (17.00) 0.050 0.048 0.046 0.044 0.042 0.040 0.039 0.037 0.036 0.035 0.033 0.032 0.031 0.030 0.030 0.029 0.025 0.022 0.020 0.018 0.017
6 in. R-24 (19.68) 0.044 0.042 0.041 0.039 0.038 0.036 0.035 0.034 0.033 0.032 0.031 0.030 0.029 0.028 0.027 0.027 0.024 0.021 0.019 0.017 0.016
Steel Joist Floor with Batt Insulation
  None (0.0) 0.350 0.259 0.206 0.171 0.146 0.127 0.113 0.101 0.092 0.084 0.078 0.072 0.067 0.063 0.059 0.056 0.044 0.036 0.030 0.026 0.023
  R-11 (10.01) 0.078 0.072 0.067 0.063 0.059 0.056 0.053 0.050 0.048 0.046 0.044 0.042 0.040 0.039 0.037 0.036 0.030 0.026 0.023 0.021 0.019
  R-13 (11.70) 0.069 0.064 0.060 0.057 0.054 0.051 0.049 0.046 0.044 0.042 0.041 0.039 0.038 0.036 0.035 0.034 0.029 0.025 0.022 0.020 0.018
  R-15 (13.20) 0.062 0.059 0.055 0.052 0.050 0.047 0.045 0.043 0.042 0.040 0.038 0.037 0.036 0.034 0.033 0.032 0.028 0.024 0.022 0.020 0.018
  R-19 (16.34) 0.052 0.050 0.047 0.045 0.043 0.041 0.040 0.038 0.037 0.035 0.034 0.033 0.032 0.031 0.030 0.029 0.026 0.023 0.020 0.018 0.017
  R-21 (17.64) 0.049 0.047 0.044 0.043 0.041 0.039 0.038 0.036 0.035 0.034 0.033 0.032 0.031 0.030 0.029 0.028 0.025 0.022 0.020 0.018 0.017
  R-25 (20.25) 0.043 0.041 0.040 0.038 0.037 0.036 0.034 0.033 0.032 0.031 0.030 0.029 0.028 0.028 0.027 0.026 0.023 0.021 0.019 0.017 0.016
  R-30C (23.70) 0.038 0.036 0.035 0.034 0.033 0.032 0.031 0.030 0.029 0.028 0.027 0.027 0.026 0.025 0.025 0.024 0.021 0.019 0.018 0.016 0.015
  R-30 (23.70) 0.038 0.036 0.035 0.034 0.033 0.032 0.031 0.030 0.029 0.028 0.027 0.027 0.026 0.025 0.025 0.024 0.021 0.019 0.018 0.016 0.015
  R-38C (28.12) 0.032 0.031 0.030 0.029 0.029 0.028 0.027 0.026 0.026 0.025 0.024 0.024 0.023 0.023 0.022 0.022 0.020 0.018 0.016 0.015 0.014
  R-38 (28.12) 0.032 0.031 0.030 0.029 0.029 0.028 0.027 0.026 0.026 0.025 0.024 0.024 0.023 0.023 0.022 0.022 0.020 0.018 0.016 0.015 0.014

It is acceptable to use these U-factors for any steel-joist floor.

For the purpose of Section A1.2, the base assembly is a floor attached directly to the top of the wood joist with insulation located directly below the floor and ventilated air space below the insulation. The heat flow path through the joist is calculated to be the same depth as the insulation. The U-factors include R-0.92 for interior air film, heat flow down; R-1.23 for carpet and pad; R-0.94 for 0.75 in. wood subfloor; and R-0.46 for semiexterior air film. The weighting factors are 91% insulated cavity and 9% framing.

The first rated R-value of insulation is for uncompressed insulation installed in the cavity between wood joists.

It is acceptable for this insulation to also be continuous insulation uninterrupted by framing. All continuous insulation shall be installed either on the interior above the floor structure or below a framing cavity completely filled with insulation.

The U-factors for wood-framed floors shall be taken from Table A5.4.3.1.

Table A5.4.3.1 Assembly U-Factors for Wood-Joist Floors

Framing Type and Spacing Width (Actual Depth) Cavity Insulation R-Value: Rated (Effective Installed [See Table A9.2-1]) Overall U-Factor for Entire Base Floor Assembly Overall U-Factor for Assembly of Base Floor Plus Continuous Insulation (Uninterrupted by Framing)
Rated R-Value of Continuous Insulation
R-1.00 R-2.00 R-3.00 R-4.00 R-5.00 R-6.00 R-7.00 R-8.00 R-9.00 R-10.00 R-11.00 R-12.00 R-13.00 R-14.00 R-15.00 R-20.00 R-25.00 R-30.00 R-35.00 R-40.00
Wood Joists
5.5 in. None (0.0) 0.282 0.220 0.180 0.153 0.132 0.117 0.105 0.095 0.087 0.080 0.074 0.069 0.064 0.060 0.057 0.054 0.042 0.035 0.030 0.026 0.023
R-11 (11.0) 0.074 0.069 0.064 0.060 0.057 0.054 0.051 0.048 0.046 0.044 0.042 0.040 0.039 0.037 0.036 0.035 0.030 0.026 0.023 0.020 0.019
R-13 (13.0) 0.066 0.062 0.058 0.055 0.052 0.049 0.047 0.045 0.043 0.041 0.039 0.038 0.036 0.035 0.034 0.033 0.028 0.025 0.022 0.020 0.018
R-15 (15.0) 0.060 0.057 0.053 0.050 0.048 0.046 0.044 0.042 0.040 0.038 0.037 0.036 0.034 0.033 0.032 0.031 0.027 0.024 0.021 0.019 0.017
R-19 (18.0) 0.051 0.048 0.046 0.044 0.042 0.040 0.038 0.037 0.036 0.034 0.033 0.032 0.031 0.030 0.029 0.028 0.025 0.022 0.020 0.018 0.017
R-21 (21.0) 0.046 0.043 0.042 0.040 0.038 0.037 0.035 0.034 0.033 0.032 0.031 0.030 0.029 0.028 0.027 0.027 0.023 0.021 0.019 0.017 0.016
7.25 in. R-25 (25.0) 0.039 0.037 0.036 0.035 0.033 0.032 0.031 0.030 0.029 0.028 0.028 0.027 0.026 0.025 0.025 0.024 0.022 0.019 0.018 0.016 0.015
R-30C (30.0) 0.034 0.033 0.032 0.031 0.030 0.029 0.028 0.027 0.026 0.026 0.025 0.024 0.024 0.023 0.023 0.022 0.020 0.018 0.016 0.015 0.014
9.25 in. R-30 (30.0) 0.033 0.032 0.031 0.030 0.029 0.028 0.027 0.027 0.026 0.025 0.024 0.024 0.023 0.023 0.022 0.022 0.020 0.018 0.016 0.015 0.014
11.25 in. R-38C (38.0) 0.027 0.026 0.025 0.025 0.024 0.024 0.023 0.022 0.022 0.021 0.021 0.020 0.020 0.020 0.019 0.019 0.017 0.016 0.015 0.014 0.013
13.25 in. R-38 (38.0) 0.026 0.026 0.025 0.024 0.024 0.023 0.023 0.022 0.022 0.021 0.021 0.020 0.020 0.019 0.019 0.019 0.017 0.016 0.015 0.014 0.013

It is not acceptable to use these U-factors if the framing is not wood.

For the purpose of Section A1.2, the base assembly is a slab floor of 6 in. concrete poured directly on to the earth, the bottom of the slab is at grade line, and soil conductivity is 0.75 Btu/h-ft-°F. In contrast to the U-factor for floors, the F-factor for slab-on-grade floors is expressed per linear foot of building perimeter. F-factors are provided for unheated slabs and for heated slabs. Unheated slab-on-grade floors do not have heating elements, and heated slab-on-grade floors do have heating elements within or beneath the slab. F-factors are provided for three insulation configurations:

  1. Horizontal Insulation: Continuous insulation is applied directly to the underside of the slab and extends inward horizontally from the perimeter for the distance specified, or continuous insulation is applied downward from the top of the slab and then extends horizontally to the interior or the exterior from the perimeter for the distance specified.
  2. Vertical Insulation: Continuous insulation is applied directly to the slab exterior, extending downward from the top of the slab for the distance specified.
  3. Fully Insulated Slab: Continuous insulation extends downward from the top of the slab and along the entire perimeter and completely covers the entire area under the slab.

The rated R-value of insulation shall be installed around the perimeter of the slab-on-grade floor to the distance specified.

Exception to A6.2.1

For a monolithic slab-on-grade floor, the insulation shall extend from the top of the slab-on-grade to the bottom of the footing.

Insulation installed inside the foundation wall shall extend downward from the top of the slab a minimum of the distance specified or to the top of the footing, whichever is less.