Insulation Values

INSULATION VALUES

TECHNICAL BULLETIN Vol. 3, No. 1 JANUARY 2017 INSULATION VALUES

This is a thermal resistance guide for our insulated panels. This document is to serve as an explanation of code compliance and how these values were determined.

Code Compliance

In North America, the most accepted energy efficiency standard for commercial construction is the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) Standard 90.1. The current edition is 2013. This standard provides both a prescriptive and a performance path to be chosen at the designer’s discretion. The prescriptive path is most commonly used and also provides the baseline performance level that is used to determine compliance for the performance path as well, so understanding this set of requirements is critical. Within the prescriptive path, two possible methods of compliance are available to determine the minimum thermal performance of opaque areas on the building envelope. Section 5.5.3 is the pertinent passage and it reads:

5.5.3 Opaque Areas. For all opaque surfaces except doors, compliance shall be demonstrated by one of the following two methods:

a. Minimum rated R-value of insulation for the thermal resistance of the added insulation in framing cavities and continuous insulation only. Specifications listed in Normative Appendix A for each class of construction shall be used to determine compliance.

b. Maximum U-factor, C-factor, or F-factor for the entire assembly. The values for typical construction assemblies listed in Normative Appendix A shall be used to determine compliance.

Exceptions to Section 5.5.3:

1. For assemblies significantly different from those in Appendix A, calculations shall be performed in accordance with the procedures required in Appendix A.

2. For multiple assemblies within a single class of construction for a single space-conditioning category, compliance shall be shown for either (1) the most restrictive requirement or (2) an area- weighted average U-factor, C-factor, or F-factor.

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The definitions pertinent to this passage italicized above are:

Continuous insulation (c.i.): insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior or exterior or is integral to any opaque surface of the building envelope.

Rated R-value of insulation: the thermal resistance of the insulation alone as specified by the manufacturer in units of hr·ft2·°F/BTU at a mean temperature of 75°F. Rated R-value refers to the thermal resistance of the added insulation in framing cavities or insulated sheathing only and does not include the thermal resistance of other building materials or air films.

U-factor (thermal transmittance): heat transmission in unit time through unit area of a material or construction and the boundary air films, induced by unit temperature difference between the environments on each side. Units of U are BTU/hr·ft2·°F.

So in effect, there are two possible ways to comply with the prescriptive requirements for a roof or wall assembly:

A. Provide insulation with a Rated R-value that meets or exceeds the minimum R-value requirement from the prescriptive tables 5.5-1 through 5.5-8, depending on climate zone.

B. Provide an assembly with a U-factor that meets or falls below the maximum U-factor requirement from the prescriptive tables 5.5-1 through 5.5-8, depending on climate zone

Appendix A of 90.1 contains calculation and testing requirements for R-value and U-factor determination as well as a dataset of U-factors that have been predetermined in accordance with the appendix for some common assemblies. If the assembly being provided does not meet the descriptions of the common assemblies in the appendix, then a thermal test or calculation method is the only way to determine a U-factor. In fact, exception a. of 5.5.3 provides the user with a shortcut to that conclusion. Testing requirements are given in Section A9.3 and calculation requirements are given in A9.4 of Appendix A. Different levels of rigor are to be used when calculating U-factors depending on the type of assembly; however, Section A9.2 does state that two-dimensional finite element methods are always allowed.

The definitions above in conjunction with the requirements of Appendix A then dictate that if Method A is used, the R-value of the insulation must be determined by either ASTM C518 or ASTM C1363 with a mean temperature of 75 degrees Fahrenheit and cannot include air film effects. Furthermore, the assembly in question must meet the one of the descriptions in the Appendix.

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Otherwise, Method B must be used and the U-factor of the assembly is to be determined by testing per ASTM C1363 or finite element modeling. In either case, a representative sample section including panel edges, joints and thermal bridges such as fasteners is considered and the air film allowance provided in Section A.9.4.1 should be included as well.

Insulated panels are not an assembly type but instead are insulated sheathing that can be utilized on various kinds of assemblies. Therefore, it is not entirely clear how they apply to ASHRAE requirements. IMPs have thermally broken side joints and since the presence of fasteners alone does not violate the requirements for continuous insulation, IMPs can be interpreted to meet that definition. However, many designers do not agree with that interpretation and instead want to treat IMPs as an assembly and therefore require U-values from the manufacturer since Method A would not apply in that instance. Unfortunately, ‘thermal bridge’ is not defined in ASHRAE 90.1, so no guidance is provided by the standard itself. Because of this ambiguity, it is not clear which method from Section 5.5.3 is to be used for IMPs. Therefore, R-values determined by test and U-factors determined by calculation in accordance with ASHRAE are presented in Table 2 below and it is left to the designer’s discretion which to use.

Insulated Metal Panel R-value and U-factors

The information is provided shows the results thermal modeling using the THERM V7 which was calibrated and verified using ASTM C518 and ASTM C1363 testing. With the many different widths, profiles and thicknesses it is not possible to test every possible variable for the products offered by Metl-Span. The THERM software is widely used and was developed at Lawrence Berkeley National Laboratory (LBNL) for heat-transfer analysis of the sometimes complicated geometries of real-world building products.

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Core R-value per Nominal ASTM C518 42” Wide Panel Mean Temp Core (hr·ft2·°F/BTU) Panel (°F) Thickness Profile (in.) U-factor R-value w/o air films w/ air films (BTU/ (hr·ft2·°F/ hr·ft2·°F) BTU) 2 14.29 15.14 0.0706 14.16 2.5 17.86 18.71 0.0516 19.38 3 21.43 22.28 0.0424 23.58 75 4 28.57 29.42 0.0324 30.86 5 35.71 36.56 0.0264 37.88 CF Mesa 6 42.86 43.71 0.0224 44.64 2 15.87 16.72 0.0669 14.95 2.5 19.84 20.69 0.0491 20.37 3 23.81 24.66 0.0401 24.94 40 4 31.75 32.60 0.0305 32.79 5 39.68 40.53 0.0248 40.32 6 47.62 48.47 0.0210 47.62

Core R-value per 36" Wide Panel ASTM C518 Core (1/4" reveal) Mean Temp (hr·ft2·°F/BTU) Panel Profile Thickness (°F) U-factor R-value (in.) w/o air films w/ air films (BTU/ (hr·ft2·°F/ hr·ft2·°F) BTU) 2 14.29 15.14 0.0669 14.95 2.5 17.86 18.71 0.0500 20.00 75 3 21.43 22.28 0.0400 25.00 Architectural 4 28.57 29.42 0.0307 32.57 Flat 2 15.87 16.72 0.0637 15.70 2.5 19.84 20.69 0.0456 21.93 40 3 23.81 24.66 0.0378 26.46 4 31.75 32.60 0.0289 34.60

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Core R-value per Nominal ASTM C518 42” Wide Panel Mean Temp Core (hr·ft2·°F/BTU) Panel (°F) Thickness Profile (in.) U-factor R-value w/o air films w/ air films (BTU/ (hr·ft2·°F/ hr·ft2·°F) BTU) 2 14.29 15.14 0.0721 13.87 2.5 17.86 18.71 0.0523 19.12 3 21.43 22.28 0.0432 23.15 75 4 28.57 29.42 0.0328 30.49 5 35.71 36.56 0.0267 37.45 CF Flute 6 42.86 43.71 0.0226 44.25 2 15.87 16.72 0.0692 14.45 2.5 19.84 20.69 0.0498 20.08 3 23.81 24.66 0.0410 24.39 40 4 31.75 32.60 0.0311 32.15 5 39.68 40.53 0.0252 39.68 6 47.62 48.47 0.0214 46.73

Core R-value per 36" Wide Panel ASTM C518 Panel Mean Temp Thickness (hr·ft2·°F/BTU) U-factor R-value Profile (°F) (in.) (BTU/ (hr·ft2·°F/ w/o air films w/ air films hr·ft2·°F) BTU) 3 Due to the deep profiling 0.0814 12.29 4 of the 7.2 Insul-Rib Panel, 0.0537 18.62 Insul-Rib 75 5 the C518 test cannot be 0.0395 25.32 used to determine thermal 6 0.0314 31.85 performance

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Nominal Core R-value per 42” Wide Panel Mean Temp Core ASTM C518 Panel Profile (°F) Thickness (hr·ft2·°F/BTU) U-factor (in.) w/o air films w/ air films (BTU/hr·ft2·°F) 3 10.83 11.68 0.0856 4 14.44 15.29 0.0654 ThermalSafe 5 18.05 18.90 0.0529 Wall 75 6 21.66 22.51 0.0444 7 25.27 26.12 0.0383 8 28.88 29.73 0.0336

Core R-value per 42” Wide Panel Core ASTM C518 Panel Mean Temp Thickness 2 U-factor R-value Profile (°F) (hr·ft ·°F/BTU) (in.) (BTU/ (hr·ft2·°F/ w/o air films w/ air films hr·ft2·°F) BTU) 2 14.29 15.07 0.0600 16.67 2.5 17.86 18.64 0.0490 20.41 3 21.43 22.21 0.0414 24.15 75 4 28.57 29.35 0.0318 31.45 5 35.71 36.49 0.0257 38.91 CFR Roof 6 42.86 43.64 0.0217 46.08 2 15.87 16.65 0.0567 17.64 2.5 19.84 20.62 0.0462 21.65 3 23.81 24.59 0.0390 25.64 40 4 31.75 32.53 0.0298 33.56 5 39.68 40.46 0.0241 41.49 6 47.62 48.40 0.0201 49.75

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Core R-value per 36" Wide Panel ASTM C518 Panel Mean Temp Thickness (hr·ft2·°F/BTU) U-factor R-value Profile (°F) (in.) 2 w/o air films w/ air films (BTU/ (hr·ft ·°F/ hr·ft2·°F) BTU) 1.5 10.71 11.56 0.0783 12.77 2 14.29 15.14 0.0602 16.61 2.5 17.86 18.71 0.0491 20.37 75 3 21.43 22.28 0.0414 24.15 4 28.57 29.42 0.0326 30.67 5 35.71 36.56 0.0268 37.31 LS-36 Wall 6 42.86 43.71 0.0227 44.05 1.5 11.90 12.75 0.0745 13.42 2 15.87 16.72 0.0569 17.57 2.5 19.84 20.69 0.0462 21.65 40 3 23.81 24.66 0.0390 25.64 4 31.75 32.60 0.0306 32.68 5 39.68 40.53 0.0250 40.00 6 47.62 48.47 0.0211 47.39

Core R-value per 36” Wide Panel ASTM C518 Panel Mean Temp Thickness 2 U-factor R-value Profile (°F) (in.) (hr·ft ·°F/BTU) (BTU/ (hr·ft2·°F/ w/o air films w/ air films hr·ft2·°F) BTU) 1.5 10.71 11.49 0.0788 12.69 2 14.29 15.07 0.0603 16.58 2.5 17.86 18.64 0.0492 20.33 75 3 21.43 22.21 0.0416 24.04 4 28.57 29.35 0.0327 30.58 5 35.71 36.49 0.0267 37.45 LS-36 6 42.86 43.64 0.0223 44.84 Roof 1.5 11.90 12.68 0.0745 13.42 2 15.87 16.65 0.0570 17.54 2.5 19.84 20.62 0.0465 21.51 40 3 23.81 24.59 0.0391 25.58 4 31.75 32.53 0.0306 32.68 5 39.68 40.46 0.0249 40.16 6 47.62 48.40 0.0210 47.62

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