ADOPTS WITH AMENDMENTS:

International Energy Conservation Code 2018 (IECC 2018)

Heads up: There are no amended sections in this chapter.
The following defaults shall apply to Chapter 4 of the Washington State Energy Code—Residential Provisions and the Washington State Energy Code—Commercial Provisions. This chapter includes tables of seasonal average heat loss coefficients for specified nominal insulation.

These coefficients were developed primarily from data and procedures from the ASHRAE Handbook of Fundamentals.

Coefficients not contained in this chapter may be computed using the procedures listed in this reference if the assumptions in the following sections are used, along with data from the sources referenced above.

Default R-values used for air films shall be as follows:

R-Value Condition
0.17 All exterior surfaces
0.61 Interior horizontal surfaces, heat flow up
0.92 Interior horizontal surfaces, heat flow down
0.68 Interior vertical surfaces

Insulation which is compressed shall be rated in accordance with Table RA101.4 or reduction in value may be calculated in accordance with the procedures in the ASHRAE Handbook of Fundamentals.

TABLE RA101.4

R-VALUE OF FIBERGLASS BATTS COMPRESSED WITHIN VARIOUS DEPTH CAVITIES
Insulation R-Values at Standard Thickness

RATED R-VALUE 82 71 60 49 38 30 22 21 19 15 13 11
Standard Thickness, Inches 26.0 22.5 19.0 15.5 12 9.5 6.5 5.5 6 3.5 3.5 3.5
Nominal
LumberSizes,
Inches
Actual Depth
of Cavity,
Inches
Insulation R-Values When Installed in a Confined Cavity
Truss 26.0 82
Truss 22.5 71
Truss 19.0 60
Truss 15.5 49
Truss 12.0 38
2x12 11.25 37
2x10 9.25 32 30
2x8 7.25 27 26 22 21 19
2x6 5.5 21 20 21 18
2x4 3.5 14 13 15 13 11
  2.5 9.8
  1.5 6.3 6.0

For SI: 1 inch = 25.4 mm.

Default R-values used for building materials shall be as shown in Table RA101.5.

TABLE RA101.5

DEFAULT R-VALUES FOR BUILDING MATERIALS

MATERIAL NOMINAL SIZE
(in.)
ACTUAL SIZE
(in.)
R-VALUE
(Heat Capacityc)
Air cavity (unventilated), between metal studs at 16 inches on centera 0.79
Air cavity (unventilated), all other depths and framing materialsa 0.91
Air film, exterior surfacesb 0.17
Air film, interior horizontal surfaces, heat flow upb 0.61
Air film, interior horizontal surfaces, heat flow downb 0.92
Air film, interior vertical surfacesb 0.68
Brick at R-0.12/in. (face brick, 75% solid/25% core area, 130 lbs/ft3) 4 3.5 0.32 (5.9)
Carpet and rubber pad 1.23
Concrete at R-0.0625/in., heavyweight (144 lbs/ft3) 2 0.13 (HC-4.8)
4 0.25 (HC-9.6)
6 0.38 (HC-14.4)
8 0.50 (HC-19.2)
10 0.63 (HC-24.0)
12 0.75 (HC-28.8)
Concrete masonry units, solid grouted, lightweight (95 lbs/ft3) 6 0.80 (HC-11.4)
Concrete masonry units, solid grouted, normal weight (135 lbs/ft3) 6 0.51 (HC-13.2)
Concrete masonry units, partly grouted, lightweight (95 lbs/ft3) 6 1.33 (HC-6.7)
Concrete masonry units, partly grouted, normal weight (135 lbs/ft3) 6 0.82 (HC-9.0)
Concrete masonry units, solid grouted, lightweight (95 lbs/ft3) 8 1.05 (HC-15.5)
Concrete masonry units, solid grouted, normal weight (135 lbs/ft3) 8 0.69 (HC-17.9)
Concrete masonry units, partly grouted, lightweight (95 lbs/ft3) 8 1.44 (HC-9.6)
Concrete masonry units, partly grouted, normal weight (135 lbs/ft3) 8 0.98 (HC-12.0)
Concrete masonry units, solid grouted, lightweight (95 lbs/ft3) 10 1.30 (HC-19.7)
Concrete masonry units, solid grouted, normal weight (135 lbs/ft3) 10 0.87 (HC-22.6)
Concrete masonry units, partly grouted, lightweight (95 lbs/ft3) 10 1.61 (HC-11.9)
Concrete masonry units, partly grouted, normal weight (135 lbs/ft3) 10 1.11 (HC-14.8)
Concrete masonry units, solid grouted, lightweight (95 lbs/ft3) 12 1.53 (HC-23.9)
Concrete masonry units, solid grouted, normal weight (135 lbs/ft3) 12 1.06 (HC-27.2)
Concrete masonry units, partly grouted, lightweight (95 lbs/ft3) 12 1.75 (HC-14.2)
Concrete masonry units, partly grouted, normal weight (135 lbs/ft3) 12 1.23 (HC-17.5)
Flooring, wood subfloor 0.75 0.94
Gypsum board 0.5 0.45
0.625 0.56
Metal deck 0
Roofing, built-up 0.375 0.33
Sheathing, vegetable fiber board, 0.78 in. 0.78 2.06
Soil at R-0.104/in. 12 1.25
Steel, mild 1 0.0031807
Stucco 0.75 0.08

For SI: 1 inch = 25.4 mm; 1 pound per cubic foot = 16.02 kg/m3.

  1. There is no credit for cavities that are open to outside air.
  2. Air films do not apply to air cavities within an assembly.
  3. For heat capacity for concrete and concrete masonry materials with densities other than the values listed in Table RA101.5, see Tables A3.1B and A3.1C in ASHRAE/IESNA Standard 90.1.

Table RA102.1 lists heat loss coefficients for the opaque portion of exterior ceilings below vented attics, vaulted ceilings and roof decks in units of Btu/h × ft2 × °F of ceiling.

They are derived from procedures listed in the ASHRAE Fundamentals Handbook. Ceiling U-factors are modified for the buffering effect of the attic, assuming an indoor temperature of 65°F (18°C) and an outdoor temperature of 45°F (7°C).


TABLE RA102.1

DEFAULT U-FACTORS FOR CEILINGS

  STANDARD
FRAME
ADVANCED
FRAME
Ceilings Below Vented Attics
Flat Baffled
R-19 0.049 0.047
R-30 0.036 0.032
R-38 0.031 0.026
R-49 0.027 0.020
R-60 0.025 0.017
Scissors Truss
R-30 (4/12 roof pitch) 0.043 0.031
R-38 (4/12 roof pitch) 0.040 0.025
R-49 (4/12 roof pitch) 0.038 0.020
R-30 (5/12 roof pitch) 0.039 0.032
R-38 (5/12 roof pitch) 0.035 0.026
R-49 (5/12 roof pitch) 0.032 0.020
Vaulted Ceilings 16" O.C. 24" O.C.
Vented
R-19 2 × 10 joist 0.049 0.048
R-30 2 × 12 joist 0.034 0.033
R-38 2 × 14 joist 0.027 0.027
Unvented
R-30 2 × 10 joist 0.034 0.033
R-38 2 × 12 joist 0.029 0.027
R-21 + R-21 2 × 12 joist 0.026 0.025
Roof Deck 4x Beams, 48" O.C.
R-12.5 2" Rigid insulation 0.064
R-21.9 3.5" Rigid insulation 0.040
R-37.5 6" Rigid insulation 0.025
R-50 8" Rigid insulation 0.019

The nominal R-values in Table RA103.3.6.2: Effective R-Values for Metal Framing and Cavity Only may be used for purposes of calculating metal-framed ceiling section U-factors in lieu of the ASHRAE zone calculation method as provided in Chapter 27 of the ASHRAE Handbook of Fundamentals.

Metal building roofs have a different construction and are addressed in Table RA102.2.5.

The four types of ceilings are characterized as shown in Sections RA102.2.1 through RA102.2.4.

Attic insulation is assumed to be blown-in, loose-fill fiberglass with a K-value of 2.6 h × ft2 × °F/Btu per inch. Full bag count for specified R-value is assumed in all cases. Ceiling dimensions for flat ceiling calculations are 45 by 30 feet (13.7 m by 9.1 m), with a gabled roof having a 4/12 pitch. The attic is assumed to vent naturally at the rate of 3 air changes per hour through soffit and ridge vents. A void fraction of 0.002 is assumed for all attics with insulation baffles. Standard-framed, unbaffled attics assume a void fraction of 0.008.

Attic framing is either standard or advanced. Standard framing assumes tapering of insulation depth around the perimeter with resultant decrease in thermal resistance. An increased R-value is assumed in the center of the ceiling due to the effect of piling leftover insulation. Advanced framing assumes full and even depth of insulation extending to the outside edge of exterior walls. Advanced framing does not change from the default value. U-factors for flat ceilings below vented attics with standard framing may be modified with the following table:

ROOF PITCH U-FACTOR FOR
R-30 R-38
4/12 0.036 0.031
5/12 0.035 0.030
6/12 0.034 0.029
7/12 0.034 0.029
8/12 0.034 0.028
9/12 0.034 0.028
10/12 0.033 0.028
11/12 0.033 0.027
12/12 0.033 0.027

Vented scissors truss attics assume a ceiling pitch of 2/12 with a roof pitch of either 4/12 or 5/12. Unbaffled standard framed scissors truss attics are assumed to have a void fraction of 0.016.

Insulation is assumed to be fiberglass batts installed in roof joist cavities. In the vented case, at least 1.5 inches (38 mm) between the top of the batts and the underside of the roof sheathing is left open for ventilation in each cavity. A ventilation rate of 3.0 air changes per hour is assumed. In the unvented or dense pack case, the ceiling cavity is assumed to be fully packed with insulation, leaving no space for ventilation.
Rigid insulation is applied to the top of roof decking with no space left for ventilation. Roofing materials are attached directly on top of the insulation. Framing members are often left exposed on the interior side.

Overall system tested values for the roof/ceiling Uo for metal-framed truss assemblies from approved laboratories shall be used, when such data are acceptable to the building official.

Alternatively, the Uo for roof/ceiling assemblies using metal truss framing may be obtained from Tables RA102.2.4(1) through RA102.2.4(5).

TABLE RA102.2.4(1)

STEEL TRUSSa FRAMED CEILING UO

Cavity
R-value
Truss Span (ft)
12 14 16 18 20 22 24 26 28 30 32 34 36
19 0.1075 0.0991 0.0928 0.0878 0.0839 0.0807 0.0780 0.0757 0.0737 0.0720 0.0706 0.0693 0.0681
30 0.0907 0.0823 0.0760 0.0710 0.0671 0.0638 0.0612 0.0589 0.0569 0.0552 0.0538 0.0525 0.0513
38 0.0844 0.0759 0.0696 0.0647 0.0607 0.0575 0.0548 0.0525 0.0506 0.0489 0.0474 0.0461 0.0449
49 0.0789 0.0704 0.0641 0.0592 0.0552 0.0520 0.0493 0.0470 0.0451 0.0434 0.0419 0.0406 0.0395

For SI: 1 inch = 25.4 mm.

  1. Assembly values based on 24-inch-on-center truss spacing; 11 Truss member connections penetrating insulation (4 at the eaves, 7 in the interior space); 1/2-inch drywall ceiling; all truss members are 2×4 "C" channels with a solid web.

TABLE RA102.2.4(2)

STEEL TRUSSa FRAMED CEILING UO WITH R-3 SHEATHINGb

Cavity
R-value
Truss Span (ft)
12 14 16 18 20 22 24 26 28 30 32 34 36
19 0.0809 0.0763 0.0728 0.0701 0.0679 0.0661 0.0647 0.0634 0.0623 0.0614 0.0606 0.0599 0.0592
30 0.0641 0.0595 0.0560 0.0533 0.0511 0.0493 0.0478 0.0466 0.0455 0.0446 0.0438 0.0431 0.0424
38 0.0577 0.0531 0.0496 0.0469 0.0447 0.0430 0.0415 0.0402 0.0392 0.0382 0.0374 0.0367 0.0361
49 0.0523 0.0476 0.0441 0.0414 0.0393 0.0375 0.0360 0.0348 0.0337 0.0328 0.0319 0.0312 0.0306

For SI: 1 inch = 25.4 mm.

  1. Assembly values based on 24-inch-on-center truss spacing; 11 Truss member connections penetrating insulation (4 at the eaves, 7 in the interior space); 1/2-inch drywall ceiling; all truss members are 2×4 "C" channels with a solid web.
  2. Ceiling sheathing installed between bottom chord and drywall.

TABLE RA102.2.4(3)

STEEL TRUSSa FRAMED CEILING UO WITH R-5 SHEATHINGb

Cavity
R-value
Truss Span (ft)
12 14 16 18 20 22 24 26 28 30 32 34 36
19 0.0732 0.0697 0.0670 0.0649 0.0633 0.0619 0.0608 0.0598 0.0590 0.0583 0.0577 0.0571 0.0567
30 0.0564 0.0529 0.0502 0.0481 0.0465 0.0451 0.0440 0.0430 0.0422 0.0415 0.0409 0.0403 0.0399
38 0.0501 0.0465 0.0438 0.0418 0.0401 0.0388 0.0376 0.0367 0.0359 0.0351 0.0345 0.0340 0.0335
49 0.0446 0.0410 0.0384 0.0363 0.0346 0.0333 0.0322 0.0312 0.0304 0.0297 0.0291 0.0285 0.0280

For SI: 1 inch = 25.4 mm.

  1. Assembly values based on 24-inch-on-center truss spacing; 11 Truss member connections penetrating insulation (4 at the eaves, 7 in the interior space); 1/2-inch drywall ceiling; all truss members are 2×4 "C" channels with a solid web.
  2. Ceiling sheathing installed between bottom chord and drywall.

TABLE RA102.2.4(4)

STEEL TRUSSa FRAMED CEILING UO WITH R-10 SHEATHINGb

Cavity
R-value
Truss Span (ft)
12 14 16 18 20 22 24 26 28 30 32 34 36
19 0.0626 0.0606 0.0590 0.0578 0.0569 0.0561 0.0555 0.0549 0.0545 0.0541 0.0537 0.0534 0.0531
30 0.0458 0.0437 0.0422 0.0410 0.0401 0.0393 0.0387 0.0381 0.0377 0.0373 0.0369 0.0366 0.0363
38 0.0394 0.0374 0.0359 0.0347 0.0337 0.0330 0.0323 0.0318 0.0313 0.0309 0.0305 0.0302 0.0299
49 0.0339 0.0319 0.0304 0.0292 0.0283 0.0275 0.0268 0.0263 0.0258 0.0254 0.0251 0.0247 0.0245

For SI: 1 inch = 25.4 mm.

  1. Assembly values based on 24-inch-on-center truss spacing; 11 Truss member connections penetrating insulation (4 at the eaves, 7 in the interior space); 1/2-inch drywall ceiling; all truss members are 2×4 "C" channels with a solid web.
  2. Ceiling sheathing installed between bottom chord and drywall.

TABLE RA102.2.4(5)

STEEL TRUSSa FRAMED CEILING UO WITH R-15 SHEATHINGb

Cavity
R-value
Truss Span (ft)
12 14 16 18 20 22 24 26 28 30 32 34 36
19 0.0561 0.0550 0.0541 0.0535 0.0530 0.0526 0.0522 0.0519 0.0517 0.0515 0.0513 0.0511 0.0509
30 0.0393 0.0382 0.0373 0.0367 0.0362 0.0358 0.0354 0.0351 0.0349 0.0347 0.0345 0.0343 0.0341
38 0.0329 0.0318 0.0310 0.0303 0.0298 0.0294 0.0291 0.0288 0.0285 0.0283 0.0281 0.0279 0.0278
49 0.0274 0.0263 0.0255 0.0249 0.0244 0.0239 0.0236 0.0233 0.0230 0.0228 0.0226 0.0225 0.0223

For SI: 1 inch = 25.4 mm.

  1. Assembly values based on 24-inch-on-center truss spacing; 11 Truss member connections penetrating insulation (4 at the eaves, 7 in the interior space); 1/2-inch drywall ceiling; all truss members are 2×4 "C" channels with a solid web.
  2. Ceiling sheathing installed between bottom chord and drywall.

Table RA102.2.5: The base assembly is a roof where the insulation is compressed when installed beneath metal roof panels attached to the steel structure (purlins). Additional assemblies include continuous insulation, uncompressed and uninterrupted by framing.

U-factors for metal building roofs shall be taken from Table RA102.2.5, provided the average purlin spacing is at least 52 inches (1321 mm) and the R-value of the thermal spacer block is greater than or equal to the thermal spacer block R-value indicated in Table RA107.2.5 for the assembly. It is not acceptable to use the U-factors in Tables RA102.2.6(1), RA102.2.6(2) or RA102.2.6(3) if additional insulated sheathing is not continuous.


TABLE RA102.2.5

DEFAULT U-FACTORS FOR METAL BUILDING ROOFS

INSULATION
SYSTEM
RATED R-VALUE
OF INSULATION
OVERALL U-FACTOR
FOR ENTIRE BASE
OVERALL U-FACTOR FOR ASSEMBLY OF BASE ROOF PLUS
CONTINUOUS INSULATION (uninterrupted by framing)
Rated R-Value of Continuous Insulation
R-6.5 R-13 R-19.5 R-26 R-32.5 R-39
Standing Seam Roofs with Thermal Spacer Blocksa,b
Single Layer None 1.280 0.137 0.073 0.049 0.037 0.030 0.025
R-10 0.115 0.066 0.046 0.035 0.029 0.024 0.021
R-11 0.107 0.063 0.045 0.035 0.028 0.024 0.021
R-13 0.101 0.061 0.044 0.034 0.028 0.024 0.020
R-16 0.096 0.059 0.043 0.033 0.027 0.023 0.020
R-19 0.082 0.053 0.040 0.031 0.026 0.022 0.020
Double Layer R-10 + R-10 0.088 0.056 0.041 0.032 0.027 0.023 0.020
R-10 + R-11 0.086 0.055 0.041 0.032 0.027 0.023 0.020
R-11 + R-11 0.085 0.055 0.040 0.032 0.026 0.023 0.020
R-10 + R-13 0.084 0.054 0.040 0.032 0.026 0.023 0.020
R-11 + R-13 0.082 0.053 0.040 0.032 0.026 0.022 0.020
R-13 + R-13 0.075 0.050 0.038 0.030 0.025 0.022 0.019
R10 + R-19 0.074 0.050 0.038 0.030 0.025 0.022 0.019
R-11 + R-19 0.072 0.049 0.037 0.030 0.025 0.022 0.019
R-13 + R-19 0.068 0.047 0.036 0.029 0.025 0.021 0.019
R-16 + R-19 0.065 0.046 0.035 0.029 0.024 0.021 0.018
R-19 + R-19 0.060 0.043 0.034 0.028 0.023 0.020 0.018
Liner System R-19 + R-11 0.035
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 0.057 0.042 0.033 0.027 0.023 0.020 0.018
Standing Seam Roofs without Thermal Spacer Blocks
Liner System R-19 + R-11 0.040
Thru-Fastened Roofs without Thermal Spacer Blocks
Single Layer R-10 0.184
R-11 0.182
R-13 0.174
R-16 0.157
R-19 0.151
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-inch (38 mm) 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.
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 (R-0.5) 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 (R-0.5) thermal spacer block between the purlins and the metal roof panels is required, unless compliance is shown by the overall assembly U-factor.
For continuous insulation (e.g., insulation boards or blankets), it is assumed that the insulation is installed below the purlins and is uninterrupted by framing members. Insulation exposed to the conditioned space or semi-heated space shall have a facing, and all insulation seams shall be continuously sealed to provide a continuous air barrier.
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 (R-0.5) 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 faced insulation installed parallel to the purlins. The second rated R-value of insulation is for unfaced insulation installed above the first layer, parallel to and between the purlins and compressed when the metal roof panels are attached. The facer of the first layer of insulation is of sufficient width to be continuously sealed to the top flange of the purlins and to accommodate the full thickness of the second layer of insulation. A supporting structure retains the bottom of the first layer at the prescribed depth required for the full thickness of the second layer of insulation being installed above it. A minimum R-5 (R-0.9) thermal spacer block between the purlins and the metal roof panels is required, unless compliance is shown by the overall assembly U-factor.

Tables RA102.2.6(1) through RA102.2.6(3): The base assembly is continuous insulation over a structural deck. These tables indicate effective U-factors for tapered roof insulation, sloped from a maximum R-value (Rmax) at the peak of the slope to a minimum R-value (Rmin) at the low point of the slope. The rows of the tables represent the rated R-value of the insulation at the minimum conditions (except at roof drains) and the columns of the table represent the rated R-value of the insulation at the maximum conditions. The slope of the tapered insulation shall be no greater than 1/4 inch per foot.

TABLE RA102.2.6(1)

ASSEMBLY U-FACTORS FOR ROOFS WITH TAPERED INSULATION ENTIRELY ABOVE DECK SINGLE SLOPE RECTANGULAR TO ONE-SIDEd, f, g, h, i (UNINTERRUPTED BY FRAMING)

RATED R-VALUE OF INSULATION AT MAXIMUM CONDITION (Rmaxa)
1 5 10 15 20 25 30 35 40 45 50 55 60
RATED R-VALUE OF INSULATION AT MINIMUM CONDITION (Rmina)
1 0.562 0.306 0.213 0.168 0.140 0.121 0.107 0.097 0.088 0.081 0.075 0.070 0.066
5 0.173 0.125 0.101 0.086 0.076 0.068 0.062 0.057 0.053 0.049 0.046 0.044
10 0.093 0.076 0.066 0.058 0.053 0.048 0.045 0.042 0.039 0.037 0.035
15 0.063 0.055 0.049 0.045 0.041 0.038 0.036 0.034 0.032 0.030
20 0.048 0.043 0.039 0.036 0.034 0.032 0.030 0.028 0.027
25 0.039 0.035 0.033 0.031 0.029 0.027 0.026 0.025
30 0.032 0.030 0.028 0.026 0.025 0.024 0.023
35 0.028 0.026 0.025 0.023 0.022 0.021
40 0.025 0.023 0.022 0.021 0.020
45 0.022 0.021 0.020 0.019
50 0.020 0.019 0.018
55 0.018 0.017
60 0.016

TABLE RA102.2.6(2)

ASSEMBLY U-FACTORS FOR ROOFS WITH TAPERED INSULATION ENTIRELY ABOVE DECK SLOPED TRIANGLE (ROOF WITH CENTER DRAIN)e,f,g,h,i (UNINTERRUPTED BY FRAMING)

RATED R-VALUE OF INSULATION AT MAXIMUM CONDITION (Rmaxb)
1 5 10 15 20 25 30 35 40 45 50 55 60
RATED R-VALUE OF INSULATION AT MINIMUM CONDITION (Rminb)
1 0.562 0.242 0.146 0.106 0.083 0.068 0.058 0.051 0.045 0.040 0.036 0.033 0.031
5 0.173 0.112 0.084 0.068 0.057 0.049 0.044 0.039 0.035 0.032 0.030 0.028
10 0.093 0.071 0.059 0.050 0.044 0.039 0.035 0.032 0.029 0.027 0.025
15 0.063 0.053 0.045 0.040 0.035 0.032 0.029 0.027 0.025 0.023
20 0.048 0.042 0.037 0.033 0.030 0.027 0.025 0.024 0.022
25 0.039 0.034 0.031 0.028 0.026 0.024 0.022 0.021
30 0.032 0.029 0.027 0.025 0.023 0.021 0.020
35 0.028 0.026 0.024 0.022 0.021 0.019
40 0.025 0.023 0.021 0.020 0.019
45 0.022 0.020 0.019 0.018
50 0.020 0.018 0.017
55 0.018 0.017
60 0.016

TABLE RA102.2.6(3)

ASSEMBLY U-FACTORS FOR ROOFS WITH TAPERED INSULATION ENTIRELY ABOVE DECK SLOPED TRIANGLE (ROOF WITH PERIMETER DRAINS)e,f,g,h,i (UNINTERRUPTED BY FRAMING)

RATED R-VALUE OF INSULATION AT MAXIMUM CONDITION (Rmaxc)
1 5 10 15 20 25 30 35 40 45 50 55 60
RATED R-VALUE OF INSULATION AT MINIMUM CONDITION (Rminc)
1 0.562 0.363 0.273 0.224 0.193 0.170 0.153 0.139 0.128 0.119 0.111 0.105 0.099
5 0.173 0.138 0.118 0.104 0.094 0.086 0.079 0.074 0.070 0.066 0.062 0.059
10 0.093 0.081 0.073 0.067 0.062 0.058 0.054 0.051 0.049 0.046 0.044
15 0.063 0.058 0.053 0.050 0.047 0.044 0.042 0.040 0.038 0.037
20 0.048 0.045 0.042 0.040 0.037 0.036 0.034 0.033 0.032
25 0.039 0.037 0.035 0.033 0.031 0.030 0.029 0.028
30 0.032 0.031 0.029 0.028 0.027 0.026 0.025
35 0.028 0.027 0.026 0.025 0.024 0.023
40 0.025 0.024 0.023 0.022 0.021
45 0.022 0.021 0.020 0.020
50 0.020 0.019 0.019
55 0.018 0.017
60 0.016

Footnotes to Tables RA102.2.6.1, RA102.2.6.2, and RA102.2.6.3:

  1. Rmax and Rmin are determined along the linearly tapered cross section for the respective minimum and maximum thickness values for the roof section being analyzed.
  2. For triangular roof sections Rmax refers to the insulation value along the long edge of the triangle and Rmin to the insulation at the point of the triangle which assumes that the insulation slopes to the center.
  3. For triangular roof sections Rmax refers to the insulation value at the point of the triangle and Rmin to the insulation along the long edge of the triangle which assumes that the insulation slopes to the perimeter.
  4. Effective U-factor for rectangular tapered insulation is calculated as follows:
  5. Effective U-factor for triangular tapered insulation is calculated as follows:
  6. Assembly U-factors include an exterior air film (R = 0.17) and an interior air film, horizontal with heat flow up (R = 0.61).
  7. For effective U-factors of roof assemblies with different Rmax or Rmin values not listed in the tables, interpolation is allowed.
  8. This table shall only be applied to tapered insulation that is tapered along only one axis.
  9. In areas of differing insulation slopes/configurations, individual U-values shall be calculated and an area weighted U-value calculation shall be used to determine the effective value of the roof.

The tables in this section list heat loss coefficients for the opaque portion of above-grade wood stud frame walls, metal stud frame walls and concrete masonry walls (Btu/h × ft2 × °F). They are derived from procedures listed in the ASHRAE Handbook of Fundamentals. For intermediate floor slabs which penetrate the insulated wall, use the concrete wall U-factors in Table RA103.3.7.1(1).

Insulation is assumed to uniformly fill the entire cavity and to be installed as per manufacturer's directions. All walls are assumed to be finished on the inside with 1/2-inch (12.7 mm) gypsum wallboard, and on the outside with either beveled wood siding over 1/2-inch (12.7 mm) plywood sheathing or with 5/8-inch (15.9 mm) T1-11 siding. Insulated sheathing (either interior or exterior) is assumed to cover the entire opaque wall surface, except where modified in accordance with footnote g to Table C402.1.3.

Metal building walls have a different construction and are addressed in Table RA103.3.6.3.

For wood stud frame walls, three framing types are considered and defined as shown in Sections RA103.2.1 through RA103.2.3.

Studs framed on 16-inch centers with double top plate and single bottom plate. Corners use three studs and each opening is framed using two studs. Headers consist of double 2x or single 4x material with an air space left between the header and the exterior sheathing. Interior partition wall/exterior wall intersections use two studs in the exterior wall.

Standard framing weighting factors:

Studs and plates 0.19
Insulated cavity 0.77
Headers 0.04

Studs framed on 16-inch centers with double top plate and single bottom plate. Corners use two studs or other means of fully insulating corners, and each opening is framed by two studs. Headers consist of double 2x material with R-10 insulation. Interior partition wall/exterior wall intersections are fully insulated in the exterior wall.

Intermediate framing weighting factors:

Studs and plates 0.18
Insulated cavity 0.78
Headers 0.04

Studs framed on 24-inch centers with double top plate and single bottom plate. Corners use two studs or other means of fully insulating corners, and one stud is used to support each header. Headers consist of double 2x material with R-10 insulation. Interior partition wall/exterior wall intersections are fully insulated in the exterior wall.

Advanced framing weighting factors:

Studs and plates 0.13
Insulated cavity 0.83
Headers 0.04
Default coefficients for the following types of walls are listed: Single-stud walls, strap walls, double-stud walls, log walls, stress-skin panels, metal stud walls, and metal building walls.

Tables RA103.3.1(1) through RA103.3.1(8): Assumes either 2 × 4 or 2 × 6 studs framed on 16- or 24-inch centers. Headers are solid for 2 × 4 walls and double 2x for 2 × 6 walls, with either dead-air or rigidboard insulation in the remaining space.

TABLE RA103.3.1(1)

2 × 4 Single Wood Stud: R-11 Batt

Note:

Nominal Batt R-value:

R-11 at 3.5-inch thickness

Installed Batt R-value:

R-11 in 3.5-inch cavity

SIDING MATERIAL/FRAMING TYPE
R-value of
Foam Board
Lapped Wood T1-11
STD ADV STD ADV
0 0.088 0.084 0.094 0.090
1 0.080 0.077 0.085 0.082
2 0.074 0.071 0.078 0.075
3 0.069 0.066 0.072 0.070
4 0.064 0.062 0.067 0.065
5 0.060 0.058 0.063 0.061
6 0.056 0.055 0.059 0.057
7 0.053 0.052 0.055 0.054
8 0.051 0.049 0.052 0.051
9 0.048 0.047 0.050 0.049
10 0.046 0.045 0.047 0.046
11 0.044 0.043 0.045 0.044
12 0.042 0.041 0.043 0.042

For SI: 1 inch = 25.4 mm.

TABLE RA103.3.1(2)

2 × 4 Single Wood Stud: R-13 Batt

Note:

Nominal Batt R-value:

R-13 at 3.63-inch thickness

Installed Batt R-value:

R-12.7 in 3.5-inch cavity

SIDING MATERIAL/FRAMING TYPE
R-value of
Foam Board
Lapped Wood T1-11
STD ADV STD ADV
0 0.082 0.078 0.088 0.083
1 0.075 0.072 0.080 0.076
2 0.069 0.066 0.073 0.070
3 0.065 0.062 0.068 0.065
4 0.060 0.058 0.063 0.061
5 0.057 0.055 0.059 0.057
6 0.053 0.052 0.056 0.054
7 0.051 0.049 0.052 0.051
8 0.048 0.047 0.050 0.048
9 0.046 0.045 0.047 0.046
10 0.044 0.043 0.045 0.044
11 0.042 0.041 0.043 0.042
12 0.040 0.039 0.041 0.040

For SI: 1 inch = 25.4 mm.

TABLE RA103.3.1(3)

2 × 4 Single Wood Stud: R-15 Batt

Note:

Nominal Batt R-value:

R-15 at 3.5-inch thickness

Installed Batt R-value:

R-15 in 3.5-inch cavity

SIDING MATERIAL/FRAMING TYPE
R-value of
Foam Board
Lapped Wood T1-11
STD ADV STD ADV
0 0.076 0.071 0.081 0.075
1 0.069 0.065 0.073 0.069
2 0.064 0.061 0.068 0.069
3 0.060 0.057 0.063 0.059
4 0.056 0.053 0.059 0.056
5 0.053 0.051 0.055 0.052
6 0.050 0.048 0.052 0.050
7 0.047 0.046 0.049 0.047
8 0.045 0.044 0.047 0.045
9 0.043 0.042 0.044 0.043
10 0.041 0.040 0.042 0.041
11 0.039 0.038 0.041 0.039
12 0.038 0.037 0.039 0.038

For SI: 1 inch = 25.4 mm.

TABLE RA103.3.1(4)

2 × 6 Single Wood Stud: R-19 Batt

Note:

Nominal Batt R-value:

R-19 at 6-inch thickness

Installed Batt R-value:

R-18 in 5.5-inch cavity

SIDING MATERIAL/FRAMING TYPE
R-value of
Foam Board
Lapped Wood T1-11
STD INT ADV STD INT ADV
0 0.062 0.058 0.055 0.065 0.061 0.058
1 0.058 0.055 0.052 0.060 0.057 0.055
2 0.054 0.052 0.050 0.056 0.054 0.051
3 0.051 0.049 0.047 0.053 0.051 0.049
4 0.048 0.046 0.045 0.050 0.048 0.046
5 0.046 0.044 0.043 0.048 0.046 0.044
6 0.044 0.042 0.041 0.045 0.044 0.042
7 0.042 0.040 0.039 0.043 0.042 0.040
8 0.040 0.039 0.038 0.041 0.040 0.039
9 0.038 0.037 0.035 0.039 0.038 0.037
10 0.037 0.036 0.035 0.038 0.037 0.036
11 0.036 0.035 0.034 0.036 0.035 0.035
12 0.034 0.033 0.033 0.035 0.034 0.033

For SI: 1 inch = 25.4 mm.

TABLE RA103.3.1(5)

2 × 6 Single Wood Stud: R-21 Batt

Note:

Nominal Batt R-value:

R-21 at 5.5-inch thickness

Installed Batt R-value:

R-21 in 5.5-inch cavity

SIDING MATERIAL/FRAMING TYPE
R-value of
Foam Board
Lapped Wood T1-11
STD INT ADV STD INT ADV
0 0.057 0.054 0.051 0.060 0.056 0.053
1 0.054 0.051 0.048 0.056 0.053 0.050
2 0.050 0.048 0.045 0.052 0.050 0.047
3 0.048 0.045 0.043 0.049 0.047 0.045
4 0.045 0.043 0.041 0.047 0.045 0.043
5 0.043 0.041 0.040 0.044 0.042 0.041
6 0.041 0.039 0.038 0.042 0.041 0.039
7 0.039 0.038 0.036 0.040 0.039 0.037
8 0.038 0.036 0.035 0.039 0.037 0.036
9 0.036 0.035 0.034 0.037 0.036 0.035
10 0.035 0.034 0.033 0.036 0.035 0.033
11 0.033 0.033 0.032 0.034 0.033 0.032
12 0.032 0.031 0.031 0.033 0.032 0.031

For SI: 1 inch = 25.4 mm.

TABLE RA103.3.1(6)

2 × 6 Single Wood Stud: R-22 Batt

Note:

Nominal Batt R-value:

R-22 at 6.75-inch thickness

Installed Batt R-value:

R-20 in 5.5-inch cavity

SIDING MATERIAL/FRAMING TYPE
R-value of
Foam Board
Lapped Wood T1-11
STD INT ADV STD INT ADV
0 0.059 0.055 0.052 0.062 0.058 0.054
1 0.055 0.052 0.049 0.057 0.054 0.051
2 0.052 0.049 0.047 0.054 0.051 0.048
3 0.049 0.046 0.044 0.050 0.048 0.046
4 0.046 0.044 0.042 0.048 0.046 0.044
5 0.044 0.042 0.041 0.045 0.043 0.042
6 0.042 0.040 0.039 0.043 0.042 0.040
7 0.040 0.039 0.037 0.041 0.040 0.038
8 0.038 0.037 0.036 0.039 0.038 0.037
9 0.037 0.036 0.035 0.038 0.037 0.035
10 0.035 0.034 0.033 0.036 0.035 0.034
11 0.034 0.033 0.032 0.035 0.034 0.033
12 0.033 0.032 0.031 0.034 0.033 0.032

For SI: 1 inch = 25.4 mm.

TABLE RA103.3.1(7)

2 × 6 Single Wood Stud: Two R-11 Batts

Note:

Nominal Batt R-value:

R-22 at 7-inch thickness

Installed Batt R-value:

R-18.9 in 5.5-inch cavity

SIDING MATERIAL/FRAMING TYPE
R-value of
Foam Board
Lapped Wood T1-11
STD INT ADV STD INT ADV
0 0.060 0.057 0.054 0.063 0.059 0.056
1 0.056 0.053 0.051 0.059 0.056 0.053
2 0.053 0.050 0.048 0.055 0.052 0.050
3 0.050 0.048 0.046 0.052 0.049 0.047
4 0.047 0.045 0.044 0.049 0.047 0.045
5 0.045 0.043 0.042 0.046 0.045 0.043
6 0.043 0.041 0.040 0.044 0.043 0.041
7 0.041 0.040 0.038 0.042 0.041 0.039
8 0.039 0.038 0.037 0.040 0.039 0.038
9 0.038 0.037 0.036 0.039 0.038 0.036
10 0.036 0.035 0.034 0.037 0.036 0.035
11 0.035 0.034 0.033 0.036 0.035 0.034
12 0.034 0.033 0.032 0.034 0.034 0.033

For SI: 1 inch = 25.4 mm.

TABLE RA103.3.1(8)

2 × 8 Single Stud: R-25 Batt

Note:

Nominal Batt R-value:

R-25 at 8-inch thickness

Installed Batt R-value:

R-23.6 in 7.25-inch cavity

SIDING MATERIAL/FRAMING TYPE
R-value of
Foam Board
Lapped Wood T1-11
STD INT ADV STD INT ADV
0 0.051 0.047 0.045 0.053 0.049 0.046
1 0.048 0.045 0.043 0.049 0.046 0.044
2 0.045 0.043 0.041 0.047 0.044 0.042
3 0.043 0.041 0.039 0.044 0.042 0.040
4 0.041 0.039 0.037 0.042 0.040 0.038
5 0.039 0.037 0.036 0.040 0.038 0.037
6 0.037 0.036 0.035 0.038 0.037 0.036
7 0.036 0.035 0.033 0.037 0.035 0.034
8 0.035 0.033 0.032 0.035 0.034 0.033
9 0.033 0.032 0.031 0.034 0.033 0.032
10 0.032 0.031 0.030 0.033 0.032 0.031
11 0.031 0.030 0.029 0.032 0.031 0.030
12 0.030 0.029 0.028 0.031 0.030 0.029

For SI: 1 inch = 25.4 mm.

Table RA103.3.2: Assumes 2 × 6 studs framed on 16- or 24-inch (406 mm or 610 mm) centers. 2 × 3 or 2 × 4 strapping is run horizontally along the interior surface of the wall to provide additional space for insulation.


TABLE RA103.3.2

2 × 6: STRAP WALL

  SIDING MATERIAL/FRAME TYPE
Lapped Wood T1-11
STD ADV STD ADV
R-19 + R-11 Batts 0.036 0.035 0.038 0.036
R-19 + R-8 Batts 0.041 0.039 0.042 0.040

Tables RA103.3.3(1) and RA103.3.3(2): Assumes an exterior structural wall and a separate interior, nonstructural wall. Insulation is placed in both wall cavities and in the space between the two walls. Stud spacing is assumed to be on 24-inch (610 mm) centers for both walls.


TABLE RA103.3.3(1)

2 × 6 + 2 × 4: DOUBLE WOOD STUD

BATT CONFIGURATION SIDING MATERIAL/FRAME TYPE
Lapped Wood T1-11
Exterior Middle Interior STD ADV STD ADV
R-19 R-11 0.040 0.037 0.041 0.038
R-19 R-19 0.034 0.031 0.035 0.032
R-19 R-8 R-11 0.029 0.028 0.031 0.029
R-19 R-11 R-11 0.027 0.026 0.028 0.027
R-19 R-11 R-19 0.024 0.023 0.025 0.023
R-19 R-19 R-19 0.021 0.020 0.021 0.020


TABLE RA103.3.3(2)

2 × 4 + 2 × 4: DOUBLE WOOD STUD

BATT CONFIGURATION SIDING MATERIAL/FRAME TYPE
Lapped Wood T1-11
Exterior Middle Interior STD ADV STD ADV
R-11 R-11 0.050 0.046 0.052 0.048
R-19 R-11 0.039 0.037 0.043 0.039
R-11 R-8 R-11 0.037 0.035 0.036 0.036
R-11 R-11 R-11 0.032 0.031 0.033 0.032
R-13 R-13 R-13 0.029 0.028 0.029 0.028
R-11 R-19 R-11 0.026 0.026 0.027 0.026
U-factors for log walls shall be determined using ICC 400 Table 305.3.1.1, U-Factor of Log Wall (UW) by Log Thickness (WL) and Specific Gravity.

See Table RA103.3.5.

TABLE RA103.3.5

STRESS SKIN PANEL

NOTE:

R-value of expanded

polystyrene: R-3.85 per inch

Framing: 6%

Spline: 8%

No thermal bridging between interior and exterior splines

PANEL THICKNESS,
INCHES
U-FACTOR
3 1/2 0.071
5 1/2 0.048
7 1/4 0.037
9 1/4 0.030
11 1/4 0.025

For SI: 1 inch = 25.4 mm.

The nominal R-values in Tables RA103.3.6.1 through RA103.3.6.3 may be used for purposes of calculating metal stud wall section U-factors in lieu of the ASHRAE zone calculation method as provided in Chapter 27 of the ASHRAE Handbook of Fundamentals.

Tables RA103.3.6.1(1) and RA103.6.1(2): Assumes metal studs spaced on 16- or 24-inch (406 mm or 610 mm) centers with insulation installed to fill wall cavities. Continuous rigid board insulation is applied without creating uninsulated voids in the wall assembly.

TABLE RA103.3.6.1(1)

OVERALL ASSEMBLY U-FACTORS FOR METAL STUD WALLS WITH CONTINUOUS INSULATION

METAL
FRAMING
R-VALUE OF
CONTINUOUS FOAM
BOARD INSULATION
CAVITY INSULATION
R-0 R-11 R-13 R-15 R-19 R-21
16" o.c. R-0 (none) 0.352 0.132 0.124 0.118 0.109 0.106
R-1 0.260 0.117 0.111 0.106 0.099 0.096
R-2 0.207 0.105 0.100 0.096 0.090 0.087
R-3 0.171 0.095 0.091 0.087 0.082 0.080
R-4 0.146 0.087 0.083 0.080 0.076 0.074
R-5 0.128 0.080 0.077 0.074 0.071 0.069
R-6 0.113 0.074 0.071 0.069 0.066 0.065
R-7 0.102 0.069 0.066 0.065 0.062 0.061
R-8 0.092 0.064 0.062 0.061 0.058 0.057
R-9 0.084 0.060 0.059 0.057 0.055 0.054
R-10 0.078 0.057 0.055 0.054 0.052 0.051
R-11 0.072 0.054 0.052 0.051 0.050 0.049
R-12 0.067 0.051 0.050 0.049 0.047 0.047
R-13 0.063 0.049 0.048 0.047 0.045 0.045
R-14 0.059 0.046 0.045 0.045 0.043 0.043
R-15 0.056 0.044 0.043 0.043 0.041 0.041
R-20 0.044 0.036 0.036 0.035 0.034 0.034
24" o.c R-0 (none) 0.338 0.116 0.108 0.102 0.094 0.090
R-1 0.253 0.104 0.098 0.092 0.086 0.083
R-2 0.202 0.094 0.089 0.084 0.079 0.077
R-3 0.168 0.086 0.082 0.078 0.073 0.071
R-4 0.144 0.079 0.075 0.072 0.068 0.066
R-5 0.126 0.073 0.070 0.067 0.064 0.062
R-6 0.112 0.068 0.066 0.063 0.060 0.059
R-7 0.100 0.064 0.062 0.059 0.057 0.055
R-8 0.091 0.060 0.058 0.056 0.054 0.052
R-9 0.084 0.057 0.055 0.053 0.051 0.050
R-10 0.077 0.054 0.052 0.050 0.048 0.048
R-11 0.072 0.051 0.049 0.048 0.046 0.045
R-12 0.067 0.048 0.047 0.046 0.044 0.043
R-13 0.063 0.046 0.045 0.044 0.042 0.042
R-14 0.059 0.044 0.043 0.042 0.041 0.040
R-15 0.056 0.042 0.041 0.040 0.039 0.038
R-20 0.044 0.035 0.034 0.034 0.033 0.032

Continuous foam board insulation: Continuous insulation assumes no thermal bridging of insulation by framing or z-furring through applied foam board. Zone calculation method as provided in the ASHRAE Handbook of Fundamentals must be used for thermally bridged foam board insulation. Values for attachment of insulation with z-furring are given in Table RA103.3.6.1(2).

TABLE RA105.3.6.1(2)

OVERALL ASSEMBLY U-FACTORS FOR METAL STUD WALLS WITH INSULATION SUPPORTED BY Z-FURRING

METAL
FRAMING
R-VALUE
OF FOAM BOARD
INSULATION
Z-FURRING
ATTACHMENT
CAVITY INSULATION
R-0 R-11 R-13 R-15 R-19 R-21
16" o.c. R-0 (none) Horizontal 0.352 0.132 0.124 0.118 0.109 0.106
R-5 Horizontal 0.155 0.089 0.086 0.083 0.078 0.077
R-7.5 Horizontal 0.128 0.080 0.077 0.074 0.071 0.069
R-10 Horizontal 0.110 0.072 0.070 0.068 0.065 0.064
R-12.5 Horizontal 0.099 0.068 0.065 0.064 0.061 0.060
R-15 Horizontal 0.091 0.064 0.062 0.060 0.058 0.057
R-17.5 Horizontal 0.084 0.060 0.058 0.057 0.055 0.054
R-20 Horizontal 0.078 0.057 0.056 0.054 0.052 0.052
R-22.5 Horizontal 0.074 0.055 0.054 0.052 0.051 0.050
R-25 Horizontal 0.071 0.053 0.052 0.051 0.049 0.048
R-0 (none) Vertical 0.352 0.132 0.124 0.118 0.109 0.106
R-5 Vertical 0.165 0.093 0.089 0.086 0.081 0.079
R-7.5 Vertical 0.142 0.085 0.081 0.079 0.075 0.073
R-10 Vertical 0.126 0.079 0.076 0.074 0.070 0.069
R-12.5 Vertical 0.115 0.074 0.072 0.070 0.066 0.065
R-15 Vertical 0.107 0.071 0.069 0.067 0.064 0.063
R-17.5 Vertical 0.100 0.068 0.065 0.064 0.061 0.060
R-20 Vertical 0.094 0.065 0.063 0.061 0.059 0.058
R-22.5 Vertical 0.090 0.063 0.061 0.060 0.057 0.056
R-25 Vertical 0.086 0.061 0.059 0.058 0.056 0.055
24" o.c. R-0 (none) Horizontal 0.338 0.116 0.108 0.102 0.094 0.090
R-5 Horizontal 0.152 0.082 0.078 0.074 0.070 0.068
R-7.5 Horizontal 0.126 0.074 0.070 0.068 0.064 0.062
R-10 Horizontal 0.109 0.067 0.065 0.062 0.059 0.058
R-12.5 Horizontal 0.098 0.063 0.061 0.059 0.056 0.055
R-15 Horizontal 0.090 0.060 0.058 0.056 0.053 0.052
R-17.5 Horizontal 0.083 0.057 0.055 0.053 0.051 0.050
R-20 Horizontal 0.078 0.054 0.052 0.051 0.049 0.048
R-22.5 Horizontal 0.074 0.052 0.050 0.049 0.047 0.046
R-25 Horizontal 0.070 0.050 0.049 0.047 0.046 0.045
R-0 (none) Vertical 0.338 0.116 0.108 0.102 0.094 0.090
R-5 Vertical 0.162 0.084 0.080 0.077 0.072 0.070
R-7.5 Vertical 0.140 0.078 0.074 0.071 0.067 0.065
R-10 Vertical 0.124 0.073 0.070 0.067 0.063 0.062
R-12.5 Vertical 0.113 0.069 0.066 0.064 0.061 0.059
R-15 Vertical 0.106 0.066 0.063 0.061 0.058 0.057
R-17.5 Vertical 0.098 0.063 0.061 0.059 0.056 0.055
R-20 Vertical 0.093 0.061 0.059 0.057 0.054 0.053
R-22.5 Vertical 0.089 0.059 0.057 0.055 0.053 0.051
R-25 Vertical 0.085 0.057 0.055 0.054 0.051 0.050

Interpolation between values in Table RA105.3.6.1(2) is not allowed. The value of the foam board insulation must meet or exceed the value listed in the table in order to use the value shown.

Table RA103.3.6.2: These values may be used for the metal-framing/cavity layers in walls with metal studs spaced on 16- or 24-inch (406 mm or 610 mm) centers with insulation installed to fill wall cavities in lieu of using the zone method provided in Chapter 25 of the ASHRAE Handbook of Fundamentals.


TABLE RA103.3.6.2

EFFECTIVE R-VALUES FOR METAL FRAMING AND CAVITY ONLY

  CAVITY INSULATION
Nominal Depth, Inches Actual Depth, Inches Nominal R-Value Effective R-Value
16" O.C. 24" O.C.
Air Cavity Any Any R-0.91 (air) 0.79 0.91
Wall 4 31/2 R-11 5.5 6.6
4 31/2 R-13 6.0 7.2
4 31/2 R-15 6.4 7.8
6 51/2 R-19 7.1 8.6
6 51/2 R-21 7.4 9.0
8 71/4 R-25 7.8 9.6
Roof Insulation is
uncompressed
R-11 5.5 6.1
R-19 7.0 9.1
R-30 9.3 11.4

For SI: 1 inch = 25.4 mm.

Table RA103.3.6.3: A wall whose structure consists of metal spanning panels supported by steel structural members (does not include spandrel glass or metal panels in curtain wall systems). The first nominal R-value is for insulation compressed between metal wall panels and the steel structure. For double-layer installations, the second rated R-value of insulation is for insulation installed from the inside, covering the girts. For continuous insulation (e.g., insulation boards) it is assumed that the insulation boards are installed on the inside of the girts and uninterrupted by the framing members. Insulation exposed to the conditioned space or semi-heated space shall have a facing, and all insulation seams shall be continuously sealed to provide a continuous air barrier.


TABLE RA103.3.6.3

DEFAULT METAL BUILDING WALL U-FACTORS

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-13 R-19.5 R-26 R-32.5 R-39
Single Layer of Mineral Fiber
  None 1.180 0.136 0.072 0.049 0.037 0.030 0.025
R-10 0.186 0.084 0.054 0.040 0.032 0.026 0.023
R-11 0.185 0.084 0.054 0.040 0.032 0.026 0.023
R-13 0.162 0.079 0.052 0.039 0.031 0.026 0.022
R-16 0.155 0.077 0.051 0.039 0.031 0.026 0.022
R-19 0.147 0.075 0.050 0.038 0.030 0.025 0.022

The nominal R-values in Tables RA103.3.7.1(1) and RA103.3.7.1(2) may be used for purposes of calculating concrete masonry wall section U-factors in lieu of the ASHRAE isothermal planes calculation method as provided in Chapter 27 of the ASHRAE Handbook of Fundamentals.

TABLE RA103.3.7.1(1)a, b, c, d, e

DEFAULT U-FACTORS FOR CONCRETE and MASONRY WALLS

8" Concrete Masonry
WALL DESCRIPTION CORE TREATMENT
Partial Grout with Ungrouted Cores Solid Grout
Empty Loose-fill insulated
Perlite Vermiculite
Exposed Block, Both Sides 0.40 0.23 0.24 0.43
R-5 Interior Insulation, Wood Furring 0.14 0.11 0.12 0.15
R-6 Interior Insulation, Wood Furring 0.14 0.11 0.11 0.14
R-10.5 Interior Insulation, Wood Furring 0.11 0.09 0.09 0.11
R-8 Interior Insulation, Metal Clips 0.11 0.09 0.09 0.11
R-6 Exterior Insulation 0.12 0.10 0.10 0.12
R-10 Exterior Insulation 0.08 0.07 0.07 0.08
R-9.5 Rigid Polystyrene Integral Insulation, Two Webbed Block 0.11 0.09 0.09 0.12
12" Concrete Masonry
WALL DESCRIPTION CORE TREATMENT
Partial Grout with Ungrouted Cores Solid Grout
Empty Loose-fill insulated
Perlite Vermiculite
Exposed Block, Both Sides 0.35 0.17 0.18 0.33
R-5 Interior Insulation, Wood Furring 0.14 0.10 0.10 0.13
R-6 Interior Insulation, Wood Furring 0.13 0.09 0.10 0.13
R-10.5 Interior Insulation, Wood Furring 0.11 0.08 0.08 0.10
R-8 Interior Insulation, Metal Clips 0.10 0.08 0.08 0.09
R-6 Exterior Insulation 0.11 0.09 0.09 0.11
R-10 Exterior Insulation 0.08 0.06 0.06 0.08
R-9.5 Rigid Polystyrene Integral Insulation, Two Webbed Block 0.11 0.08 0.09 0.12
8" Clay Brick
WALL DESCRIPTION CORE TREATMENT
Partial Grout with Ungrouted Cores Solid Grout
Empty Loose-fill insulated
Perlite Vermiculite
Exposed Block, Both Sides 0.50 0.31 0.32 0.56
R-5 Interior Insulation, Wood Furring 0.15 0.13 0.13 0.16
R-6 Interior Insulation, Wood Furring 0.15 0.12 0.12 0.15
R-10.5 Interior Insulation, Wood Furring 0.12 0.10 0.10 0.12
R-8 Interior Insulation, Metal Clips 0.11 0.10 0.10 0.11
R-6 Exterior Insulation 0.12 0.11 0.11 0.13
R-10 Exterior Insulation 0.08 0.08 0.08 0.09
6" Concrete Poured or Precast
WALL DESCRIPTION CORE TREATMENT
Partial Grout with Ungrouted Cores Solid Grout
Empty Loose-fill insulated
Perlite Vermiculite
Exposed Block, Both Sides NA NA NA 0.61
R-5 Interior Insulation, Wood Furring NA NA NA 0.16
R-6 Interior Insulation, Wood Furring NA NA NA 0.15
R-10.5 Interior Insulation, Wood Furring NA NA NA 0.12
R-8 Interior Insulation, Metal Clips NA NA NA 0.12
R-6 Exterior Insulation NA NA NA 0.13
R-10 Exterior Insulation NA NA NA 0.09

NA = Not allowed.

For SI: 1 inch = 25.4 mm.

  1. Grouted cores at 40" × 48" on center vertically and horizontally in partial grouted walls.
  2. Interior insulation values include 1/2" gypsum board on the inner surface.
  3. Furring and stud spacing is 16" on center. Insulation is assumed to fill furring space and is not compressed.
  4. Intermediate values may be interpolated using this table. Values not contained in this table may be computed using the procedures listed in the ASHRAE Handbook of Fundamentals.
  5. Concrete Masonry Unit (CMU) assembly U-values are based on local test data for Washington state CMU block material using the ASTM C236-87 steady-state thermal conductance test. Tests included an 8" × 8" × 16" CMU with all cells filled with vermiculite (1995) and 8" × 8" × 16" CMU with all cells filled with polymaster foam in-place insulation (1996). Refer to ASHRAE Standard 90.1 for additional nationally recognized data on the thermal performance of CMU block walls.

TABLE RA103.3.7.1(2)

DEFAULT U-FACTORS FOR CONCRETE AND MASONRY WALLSa,b,c,d

FRAMING TYPE
AND
DEPTH
RATED R-VALUE
OF INSULATION ALONE
ASSEMBLY U-FACTORS
FOR SOLID CONCRETE
WALLS
ASSEMBLY U-FACTORS
FOR CONCRETE
BLOCK WALLS:
SOLID GROUTED
ASSEMBLY U-FACTORS FOR
CONCRETE BLOCK WALLS:
PARTIALLY GROUTED
(CORES UNINSULATED
EXCEPT WHERE SPECIFIED)
Base Wall only
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 Wood Framing
0.75 in. R-3.0 U-0.247 U-0.226 U-0.210
1.5 in. R-6.0 U-0.160 U-0.151 U-0.143
2.0 in. R-10.0 U-0.116 U-0.111 U-0.107
3.5 in. R-11.0 U-0.094 U-0.091 U-0.088
3.5 in. R-13.0 U-0.085 U-0.083 U-0.080
3.5 in. R-15.0 U-0.079 U-0.077 U-0.075
5.5 in. R-19.0 U-0.060 U-0.059 U-0.058
5.5 in. R-21.0 U-0.057 U-0.055 U-0.054
Continuous Metal Framing at 24 in. on center horizontally
1.0 in. R-0.0 U-0.414 U-0.359 U-0.318
1.0 in. R-3.8 U-0.325 U-0.290 U-0.263
1.0 in. R-5.0 U-0.314 U-0.281 U-0.255
1.0 in. R-6.5 U-0.305 U-0.274 U-0.249
1.5 in. R-11.0 U-0.267 U-0.243 U-0.223
2.0 in. R-7.6 U-0.230 U-0.212 U-0.197
2.0 in. R-10.0 U-0.219 U-0.202 U-0.188
2.0 in. R-13.0 U-0.210 U-0.195 U-0.182
3.0 in. R-11.4 U-0.178 U-0.167 U-0.157
3.0 in. R-15.0 U-0.168 U-0.158 U-0.149
3.0 in. 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
3.5 in. R-13.0 U-0.161 U-0.152 U-0.144
3.5 in. 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
4.5 in. R-22.5 U-0.124 U-0.119 U-0.114
4.5 in. 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
5.0 in. R-25.0 U-0.115 U-0.110 U-0.106
5.0 in. R-28.0 U-0.112 U-0.107 U-0.103
5.0 in. 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
5.5 in. R-20.9 U-0.114 U-0.109 U-0.105
5.5 in. R-21.0 U-0.113 U-0.109 U-0.105
5.5 in. R-27.5 U-0.106 U-0.102 U-0.099
5.5 in. 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
6.0 in. R-30.0 U-0.099 U-0.095 U-0.092
6.0 in. 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
(also, where allowed by Section C402.1.3 of the Washington State Energy Code—Commercial Provisions,
for assemblies with a ratio of metal penetration area/mass wall area of <0.0004 or <0.04% of the mass wall area)e
1.0 in. R-3.8 U-0.210 U-0.195 U-0.182
1.0 in. R-5.0 U-0.184 U-0.172 U-0.162
1.0 in. 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
1.5 in. R-7.5 U-0.138 U-0.131 U-0.125
1.5 in. 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
2.0 in. R-10.0 U-0.110 U-0.106 U-0.102
2.0 in. 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
2.5 in. R-12.5 U-0.092 U-0.089 U-0.086
2.5 in. 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
3.0 in. R-15.0 U-0.078 U-0.076 U-0.074
3.0 in. 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
3.5 in. R-17.5 U-0.069 U-0.067 U-0.065
3.5 in. 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
4.0 in. R-20.0 U-0.061 U-0.060 U-0.058
4.0 in. 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
R-2.0 U-0.298 U-0.269 U-0.245
R-3.0 U-0.230 U-0.212 U-0.197
R-4.0 U-0.187 U-0.175 U-0.164
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
R-7.0 U-0.120 U-0.115 U-0.110
R-8.0 U-0.107 U-0.103 U-0.099
R-9.0 U-0.097 U-0.093 U-0.090
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
R-12.0 U-0.075 U-0.073 U-0.071
R-13.0 U-0.070 U-0.068 U-0.066
R-14.0 U-0.065 U-0.064 U-0.062
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
R-17.0 U-0.054 U-0.053 U-0.052
R-18.0 U-0.052 U-0.051 U-0.050
R-19.0 U-0.049 U-0.048 U-0.047
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
R-22.0 U-0.043 U-0.042 U-0.042
R-23.0 U-0.041 U-0.040 U-0.040
R-24.0 U-0.039 U-0.039 U-0.038
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
R-35.0 U-0.028 U-0.027 U-0.027
R-40.0 U-0.024 U-0.024 U-0.024
R-45.0 U-0.022 U-0.021 U-0.021
R-50.0 U-0.019 U-0.019 U-0.019
R-55.0 U-0.018 U-0.018 U-0.018
R-60.0 U-0.016 U-0.016 U-0.016
Brick cavity wall with continuous insulation
No Framing R-0.0 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-10.0 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-15.0 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-0.0 + R-19 c.i. U-0.047 U-0.046 U-0.045
1.0 in. R-3.8 + R-19 c.i. U-0.045 U-0.044 U-0.044
1.0 in. R-5.0 + R-19 c.i. U-0.045 U-0.044 U-0.043
1.0 in. R-6.5 + R-19 c.i. U-0.045 U-0.044 U-0.043
1.5 in. R-11.0 + R-19 c.i. U-0.044 U-0.043 U-0.043
2.0 in. R-7.6 + R-19 c.i. U-0.043 U-0.042 U-0.041
2.0 in. R-10.0 + R-19 c.i. U-0.042 U-0.041 U-0.041
2.0 in. R-13.0 + R-19 c.i. U-0.042 U-0.041 U-0.041
3.0 in. R-11.4 + R-19 c.i. U-0.041 U-0.040 U-0.039
3.0 in. R-15.0 + R-19 c.i. U-0.040 U-0.039 U-0.039
3.0 in. R-19.0 + R-19 c.i. U-0.040 U-0.039 U-0.038
3.5 in. R-11.0 + R-19 c.i. U-0.040 U-0.039 U-0.039
3.5 in. R-13.0 + R-19 c.i. U-0.040 U-0.039 U-0.038
5.0 in. R-19.0 + R-19 c.i. U-0.037 U-0.036 U-0.036
5.0 in. R-25.0 + R-19 c.i. U-0.036 U-0.035 U-0.035
5.0 in. R-32.5 + R-19 c.i. U-0.035 U-0.035 U-0.034
5.5 in. R-19.0 + R-19 c.i. U-0.036 U-0.036 U-0.035
5.5 in. R-21.0 + R-19 c.i. U-0.035 U-0.035 U-0.035

Notes for Default Table RA103.3.7.1(1):

For SI: 1 inch = 25.4 mm.

  1. It is acceptable to use the U-factors in Table RA103.3.7.1(2) for all concrete and masonry walls, provided that the grouting is equal to or less than that specified.

    • For ungrouted walls, use the partially grouted column.
    • For metal studs and z-furring, use the continuous-metal-framing category.
    • For discontinuous metal clips 1 inch square or smaller, use the metal-clip category.
    • For insulation that is attached without any framing members (e.g., glued), use the continuous-insulation uninterrupted-by-framing category. Continuous insulation may be installed on the interior or exterior of masonry walls, or between stand-alone walls in multilayer masonry walls, or on the interior or exterior of the concrete.
  2. For Table RA103.3.7.1(2), the U-factor includes 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. 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/ft and solid grouted cores.
    3. Partially grouted concrete block wall: 8-in. medium weight ASTM C90 concrete block with a density of 115 lb/ft 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.
  3. For walls with insulation contained in a framing layer, the U-factors in Table RA103.3.7.1(4) assume contact (and thermal bridging) between the mass wall and other framing. For wall assemblies with multiple layers where the wood or metal framing layer does not contact the concrete or masonry layer (i.e., walls with an airspace between the stud wall layer and the mass wall layer), it is acceptable to use the appropriate wood or metal frame wall default U-factors in Tables RA103.3.1 or RA103.3.6.1. Note: It is acceptable to use this approach where the insulation extends beyond the framing and is in contact with the mass wall layer (e.g., a nominal 4-inch metal stud containing insulation that is nominally 6 inches thick and therefore extends 2 inches beyond the back of the metal stud).
  4. Except for wall assemblies qualifying for note c, if not taken from Table RA103.3.7.1(2), mass wall U-factors shall be determined in accordance with ASHRAE 90.1, Appendix RA, Section A3.1 and Tables RA3.1A to RA3.1D, or Section A9.4.
  5. See ASHRAE Handbook of Fundamentals for determination of U-factors for assemblies that include metal other than screws and nails.

See Table RA103.3.7.2.

TABLE RA103.3.7.2

DEFAULT U-FACTORS FOR PERIPHERAL EDGES OF INTERMEDIATE CONCRETE FLOORSa, b, c

SLAB EDGE TREATMENT AVERAGE THICKNESS OF WALL ABOVE AND BELOW
6 inches 8 inches 10 inches 12 inches
Exposed Concrete 0.816 0.741 0.678 0.625
R-5 Exterior Insulation 0.161 0.157 0.154 0.152
R-6 Exterior Insulation 0.138 0.136 0.134 0.132
R-7 Exterior Insulation 0.122 0.120 0.118 0.116
R-8 Exterior Insulation 0.108 0.107 0.106 0.104
R-9 Exterior Insulation 0.098 0.097 0.095 0.094
R-10 Exterior Insulation 0.089 0.088 0.087 0.086
R-11 Exterior Insulation 0.082 0.081 0.080 0.079
R-12 Exterior Insulation 0.076 0.075 0.074 0.074
R-13 Exterior Insulation 0.070 0.070 0.069 0.068
R-14 Exterior Insulation 0.066 0.065 0.065 0.064
R-15 Exterior Insulation 0.062 0.061 0.061 0.060

For SI: 1 inch = 25.4 mm.

  1. Exterior insulation values listed above are continuous R-values on the exterior side of the concrete floor.
  2. For conditions with an exterior wall above the peripheral edge of intermediate concrete floor but with no wall below the intermediate concrete floor, this table may be used as long as the code minimum insulation is applied to the floor slab below the concrete floor.
  3. Typical conditions where conditioned space building envelope wall thermal insulation values are broken concrete floors include, but are not limited to, the following examples:

    1. Elevator hoistway shafts that serve the conditioned building and pass through unconditioned floors such as parking garage levels;
    2. Stairwell enclosures that serve the conditioned building and pass through unconditioned floors such as parking garage levels;
    3. Walls between interior and exterior building envelope that separate the interior conditioned space from an exterior courtyard or roofdeck;
    4. Walls between interior and exterior building envelope that separate the interior conditioned space from an exterior unconditioned space on parking garage levels.

Table RA104.1 lists heat loss coefficients for below-grade walls and floors.

Coefficients for below-grade walls are given as U-factors (Btu/h × ft2 × °F of wall area). Coefficients for below-grade slabs are listed as F-factors (Btu/h × ft × °F per lineal foot of slab perimeter).

Below-grade wall U-factors are only valid when used with the accompanying below-grade slab F-factor, and vice versa.


TABLE RA104.1

DEFAULT WALL U-FACTORS AND SLAB F-FACTORS FOR BASEMENTS

  BELOW GRADE
WALL U-FACTOR
BELOW GRADE
SLAB F-FACTOR
2-Foot Depth Below Grade
Uninsulated 0.331 0.58
R-11 Interior 0.063 0.67
R-11 Interior w/TB 0.065 0.59
R-19 Interior 0.042 0.68
R-19 Interior w/TB 0.045 0.59
R-21 Interior 0.040 0.68
R-21 Interior w/TB 0.042 0.59
R-21 + R-5 Interior 0.031 0.68
R-21 + R-5 Interior w/TB 0.032 0.59
R-21 + R-7 Interior 0.029 0.68
R-21 + R-7 Interior w/TB 0.030 0.59
R-10 Exterior 0.089 0.56
R-12 Exterior 0.061 0.60
3.5-Foot Depth Below Grade
Uninsulated 0.271 0.51
R-11 Interior 0.058 0.61
R-11 Interior w/TB 0.061 0.55
R-19 Interior 0.041 0.62
R-19 Interior w/TB 0.042 0.55
R-21 Interior 0.038 0.63
R-21 Interior w/TB 0.040 0.56
R-21 + R-5 Interior 0.030 0.63
R-21 + R-5 Interior w/TB 0.031 0.56
R-21 + R-7 Interior 0.027 0.63
R-21 + R-7 Interior w/TB 0.029 0.56
R-10 Exterior 0.075 0.52
R-12 Exterior 0.057 0.57
7 Foot Depth Below Grade
Uninsulated 0.185 0.43
R-11 Interior 0.051 0.54
R-11 Interior w/TB 0.053 0.49
R-19 Interior 0.036 0.54
R-19 Interior w/TB 0.037 0.50
R-21 Interior 0.035 0.56
R-21 Interior w/TB 0.035 0.50
R-21 + R-5 Interior 0.027 0.56
R-21 + R-5 Interior w/TB 0.028 0.51
R-21 + R-7 Interior 0.025 0.57
R-21 + R-7 Interior w/TB 0.026 0.51
R-10 Exterior 0.058 0.47
R-12 Exterior 0.050 0.42

TB = Thermal Break

For SI: 1 inch = 25.4 mm; 1 foot = 304.8 mm.

All below-grade walls are assumed to be 8-inch (203 mm) concrete. The wall is assumed to extend from the slab upward to the top of the mud sill for the distance specified in Table RA104.1, with 6 inches (152 mm) of concrete wall extending above grade.

Interior insulation is assumed to be fiberglass batts placed in the cavity formed by 2 × 4 framing on 24-inch (610 mm) centers with 1/2-inch (12.7 mm) gypsum board as the interior finish material. Exterior insulation is assumed to be applied directly to the exterior of the below-grade wall from the top of the wall to the footing. The exterior case does not assume any interior framing or sheetrock.

In all cases, the entire wall surface is assumed to be insulated to the indicated nominal level with the appropriate framing and insulation application. Coefficients are listed for wall depths of 2 feet (51 mm), 31/2 feet (89 mm) and 7 feet (178 mm) below grade. Basements shallower than 2 feet (51 mm) should use on-grade slab coefficients.

Heat-loss calculations for wall areas above-grade should use above-grade wall U-factors, beginning at the mudsill.

Coefficients are listed for the following four configurations:

  1. Uninsulated: No insulation or interior finish.
  2. Interior insulation: Interior 2 × 4 insulated wall without a thermal break between concrete wall and slab.
  3. Interior insulation with thermal break: Interior 2 × 4 insulated wall with R-5 rigid board providing a thermal break between the concrete wall and the slab.
  4. Exterior insulation: Insulation applied directly to the exterior surface of the concrete wall.

Tables RA105.1(1), RA105.1(2) and RA105.1(3) list heat loss coefficients for floors over unconditioned spaces in units of Btu/h × ft2 × °F.

They are derived from procedures listed in the ASHRAE Handbook of Fundamentals, assuming an average outdoor temperature of 45°F (7°C), an average indoor temperature of 65°F (18°C) and a crawlspace area of 1350 ft2 (125 m2) and 100 feet (30 480 mm) of perimeter. The crawlspace is assumed to be 2.5 feet (762 mm) high, with 24 inches (610 mm) below grade and 6 inches (152 mm) above grade.

TABLE RA105.1(1)

DEFAULT U-FACTORS FOR WOOD-FRAMED FLOORS OVER VENTED CRAWLSPACE OR UNHEATED BASEMENT

NOMINAL R-VALUE U-FACTOR
Floor Perimeter Post & Beam Joists
0 0 0.112 0.134
11 0.100 0.116
19 0.098 0.114
30 0.093 0.107
11 0 0.052 0.056
11 0.048 0.052
19 0 0.038 0.041
11 0.036 0.038
22 0 0.034 0.037
11 0.033 0.035
25 0 0.032 0.034
11 0.031 0.033
30 0 0.028 0.029
11 0.027 0.028
38 0 0.024 0.025
11 0.024 0.024

TABLE RA105.1(2)

DEFAULT U-FACTORS FOR WOOD-FRAMED FLOORS OVER HEATED PLENUM CRAWLSPACES

NOMINAL R-VALUE PERIMETER U-FACTOR
11 0.085
19 0.075
30 0.069

Note: Crawlspaces used as heated plenums have an approximately 30% higher heat-loss rate than unvented crawlspaces with the same assumed ACH. Default U-factors in Table RA105.1(2) reflect this higher rate of heat loss.

TABLE RA105.1(3)

DEFAULT U-FACTORS FOR EXPOSED FLOORS

U-FACTOR
Nominal R-Value Concrete Wood Joist Metal Joist
R-11 0.077 0.088 0.14
R-15 0.059 0.076 0.12
R-19 0.048 0.062 0.11
R-21 0.043 0.057 0.11
R-25 0.037 0.051 0.10
R-30 0.031 0.040 0.09
R-38 0.025 0.034 0.08
Four configurations are considered: naturally ventilated crawlspace, mechanically vented crawlspace, heated plenum crawlspace and exposed floor.
Assumed to have 3.0 air changes per hour, with at least 1.0 ft2 (0.09 m2) of net-free ventilation in the foundation for every 300 ft2 (28 m2) of crawlspace floor area. The crawlspace is not actively heated. Floors over unheated areas, such as garages, may only use those values which have R-0 perimeter insulation.
Assumed to have 1.5 air changes per hour, with less than 1.0 ft2 (0.09 m2) of net-free ventilation in the foundation for every 300 ft2 (28 m2) of crawlspace floor area. The crawlspace is not actively heated. Floors over unheated basements may only use those values which have R-0 perimeter insulation.
Assumed to have 0.25 air changes per hour, with no foundation vents. Heated supply air from central furnace is blown into a crawlspace and allowed to enter the living space unducted via holes cut into the floor.
Assumes no buffer space, and a covering of 1/2-inch (12.7 mm) T1-11 on the exterior of the cavity exposed to the outside air or rigid insulation below a concrete floor, such as over parking garages.

Floors are assumed to be either joisted floors framed on 16-inch (406 mm) centers, or post and beam on 4-foot by 8-foot (1219 mm by 2438 mm) squares. Insulation is assumed to be installed under the sub-flooring between the joists or beams with no space between the insulation and the subfloor. Insulation is assumed to be uncompressed. Exposed floors also include concrete with continuous rigid insulation assumed.

Perimeter insulation is assumed to extend from the top of the rim joist to the crawlspace floor and then inward along the ground (on top of the ground cover) for at least 24 inches (610 mm).

Floor coverings are assumed to be light carpet with rubber pad.

Table RA106.1 lists heat loss coefficients for heated on-grade slab floors, in units of
Btu/h x °F per lineal foot of perimeter.

TABLE RA106.1

DEFAULT F-FACTORS FOR ON-GRADE SLABS

INSULATION TYPE R-0 R-5 R-10 R-15
Unheated Slab
Uninsulated slab 0.73
2 ft Horizontal (No thermal break) 0.70 0.70 0.69
4 ft Horizontal (No thermal break) 0.67 0.64 0.63
2 ft Vertical 0.58 0.54 0.52
4 ft Vertical 0.54 0.48 0.45
Fully insulated slab 0.36
Heated Slab
Uninsulated slab 0.84
Fully insulated slab 0.74 0.55 0.44
R-5 Center (With perimeter insulation) 0.66 0.62
R-10 Center (With perimeter insulation) 0.51
3 ft Vertical 0.78

For SI: 1 foot = 304.8 mm.

All on-grade slab floors are assumed to be 6-inch (610 mm) concrete poured directly onto the earth. The bottom of the slab is assumed to be at grade line. Monolithic and floating slabs are not differentiated.

Soil is assumed to have a conductivity of 0.75 Btu/h × ft2 × °F. Slabs 2 feet (610 mm) or more below grade should use basement coefficients.

Coefficients are provided for the following three configurations:

  1. Two-foot (or four-foot) vertical: Insulation is applied directly to the slab exterior, extending downward from the top of the slab to a depth of 2 feet (610 mm) [or 4 feet (1219 mm)] below grade.
  2. Two-foot (or four-foot) horizontal: Insulation is applied directly to the underside of the slab, and runs horizontally from the perimeter inward for 2 feet (610 mm) [or 4 feet (1219 mm)]. The slab edge is exposed in this configuration.

    Note: A horizontal installation with a thermal break of at least R-5 at the slab edge should use the vertical-case F-factors.

  3. Fully insulated slab: Insulation extends from the top of the slab, along the entire perimeter, and completely covers the area under the slab. Thicker perimeter insulation covers the slab edge and extends 2 feet (610 mm) under the slab.

Doors that do not have NFRC certification shall be assigned the appropriate U-factor from Tables RA107.1(1) through RA107.1(4).

TABLE RA107.1(1)

DEFAULT U-FACTORS FOR DOORSc

DOOR TYPE NO GLAZED SINGLE
GLAZING
DOUBLE
GLAZING WITH
1/4 IN. AIRSPACE
DOUBLE
GLAZING WITH
1/2 IN. AIRSPACE
DOUBLE
GLAZING WITH
e=0.10,
1/2 IN. ARGON
SWINGING DOORS (Rough opening — 38 in. × 82 in.)
Slab Doors
Wood slab in wood frame a 0.46
6% glazed fenestration (22 in. × 8 in. lite) 0.48 0.47 0.46 0.44
25% glazed fenestration (22 in. × 36 in. lite) 0.58 0.48 0.46 0.42
45% glazed fenestration (22 in. × 64 in. lite) 0.69 0.49 0.46 0.39
More than 50% glazed fenestration Use Table R303.1.3(1) as appropriate
Insulated steel slab with wood edge in wood framea 0.16
6% glazed fenestration (22 in. × 8 in. lite) 0.21 0.20 0.19 0.18
25% glazed fenestration (22 in. × 36 in. lite) 0.39 0.28 0.26 0.23
45% glazed fenestration (22 in. × 64 in. lite) 0.58 0.38 0.35 0.26
More than 50% glazed fenestration Use Table R303.1.3(1) as appropriate
Foam insulated steel slab with metal edge in steel frameb 0.37
6% glazed fenestration (22 in. × 8 in. lite) 0.44 0.42 0.41 0.39
25% glazed fenestration (22 in. × 36 in. lite) 0.55 0.50 0.48 0.44
45% glazed fenestration (22 in. × 64 in. lite) 0.71 0.59 0.56 0.48
More than 50% glazed fenestration Use Table R303.1.3(1) as appropriate
Cardboard honeycomb slab with metal edge in steel frameb 0.61
Style and Rail Doors
Sliding glass doors/French doors Use Table R303.1.3(1) as appropriate
Site-Assembled Style and Rail Doors
Aluminum in aluminum frame 1.32 0.99 0.93 0.79
Aluminum in aluminum frame with thermal break 1.13 0.80 0.74 0.63

For SI: 1 inch = 25.4 mm.

  1. Thermally broken sill (add 0.03 for nonthermally broken sill).
  2. Nonthermally broken sill.
  3. Nominal U-factors are through the center of the insulated panel before consideration of thermal bridges around the edges of the door section and due to the frame.

TABLE RA107.1(2)

DEFAULT U-FACTORS FOR REVOLVING DOORS

REVOLVING DOORS
Size (W x H) U-Factor
3-wing
8 ft x 7 ft 0.79
10 ft x 8 ft 0.80
4-wing
7 ft x 6.5 ft 0.63
7 ft x 7.5 ft 0.64
Open
82 in x 84 in 1.32

For SI: 1 inch = 25.4 mm; 1 foot = 304.8 mm.

TABLE RA107.1(3)

DEFAULT U-FACTORS FOR STEEL EMERGENCY DOORS

DOUBLE-SKIN STEEL EMERGENCY EXIT DOORS
Core Insulation 3 ft x 6 ft 8 in 6 ft x 6 ft 8 in
13/8 in. thickness
Honeycomb kraft paper
Mineral wool, steel ribs
Polyurethane foam
0.57
0.44
0.34
0.52
0.36
0.28
13/4 in. thickness
Honeycomb kraft paper
Mineral wool, steel ribs
Polyurethane foam
0.57
0.41
0.31
0.54
0.33
0.26
13/8 in. thickness
Honeycomb kraft paper
Mineral wool, steel ribs
Polyurethane foam
0.60
0.47
0.37
0.55
0.39
0.31
13/4 in. thickness
Honeycomb kraft paper
Mineral wool, steel ribs
Polyurethane foam
0.60
0.44
0.34
0.57
0.37
0.30

For SI: 1 inch = 25.4 mm; 1 foot = 304.8 mm.

TABLE RA107.1(4)

DEFAULT U-FACTORS FOR STEEL GARAGE AND HANGAR DOORS

DOUBLE-SKIN STEEL GARAGE AND AIRCRAFT HANGAR DOORS
Insulatione One-piece tilt-upa Sectional tilt-upb Aircraft hangar
8 ft. x 7 ft. 16 ft. x 7 ft. 9 ft. x 7 ft. 72 ft. x 12 ft.c 240 ft. x 50 ft.d
13/8 in. thickness
EPS, steel ribs
XPS, steel ribs
0.36
0.33
0.33
0.31
0.34 — 0.39
0.31 — 0.36
2 in. thickness
EPS, steel ribs
XPS, steel ribs
0.31
0.29
0.28
0.26
0.29 — 0.33
0.27 — 0.31
3 in. thickness
EPS, steel ribs
XPS, steel ribs
0.26
0.24
0.23
0.21
0.25 — 0.28
0.24 — 0.27
4 in. thickness
EPS, steel ribs
XPS, steel ribs
0.23
0.21
0.20
0.19
0.23 — 0.25
0.21 — 0.24
6 in. thickness
EPS, steel ribs
XPS, steel ribs
0.20
0.19
0.16
0.15
0.20 — 0.21
0.19 — 0.21
4 in. thickness
Noninsulated
Expanded polystyrene
Mineral wool, steel ribs
Extruded polystyrene
1.10
0.25
0.25
0.23
1.23
0.16
0.16
0.15
6 in. thickness
Noninsulated
Expanded polystyrene
Mineral wool, steel ribs
Extruded polystyrene
1.10
0.21
0.23
0.20
1.23
0.13
0.13
0.12
Uninsulated
All products
1.15
  1. Values are for thermally broken or thermally unbroken doors.
  2. Lower values are for thermally broken doors; upper values are for doors with no thermal break.
  3. Typical size for a small private airplane (single-engine or twin).
  4. Typical hangar door for a midsize commercial jet airliner.
  5. EPS is extruded polystyrene, XPS is expanded polystyrene.

Tables RA108.1(1) and RA108.1(2) list effective air change rates and heat capacities for heat loss due to infiltration for Single-Family Residential.

The estimated seasonal average infiltration rate in air changes per hour (ACH) is given for standard air-leakage control (see Section R402.4 for air leakage requirements for Single-Family Residential). The effective air change rate shall be used in calculations for compliance under either the Component Performance or Systems Analysis approaches.

Heat loss due to infiltration shall be computed using the following equation:

Qinfil = ACHeff × HCP

where:

Qinfil = Heat loss due to air infiltration.

ACHeff= The effective air infiltration rate in Table RA108.1(1).

HCP = The Heat Capacity Density Product for the appropriate elevation or climate zone as given in Table RA108.1(2).


TABLE RA108.1(1)

ASSUMED EFFECTIVE AIR CHANGES PER HOUR

AIR-LEAKAGE
CONTROL PACKAGE
AIR CHANGES PER HOUR
Natural Effective
Standard 0.35 0.35


TABLE RA108.1(2)

DEFAULT HEAT CAPACITY/DENSITY PRODUCT FOR AIR

ZONE AVERAGE
ELEVATION
HEAT CAPACITY/
DENSITY
1 Mean Sea Level 0.0180 Btu/h • °F
2 2000 0.0168 Btu/h • °F
3 3000 0.0162 Btu/h • °F