Thermal barrier for spf insulation

Archive of Older Topics Archive - Specifications Discussions #4
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Closed cell polyurethane spray foam insulation in an exterior wall must be separated from the interior by a thermal barrier under IBC 2603.4.

In cases where the spf is installed behind but not tightly applied to the gypsum board, thus resulting in a void space of 2 inches or so, does this create a concealed space with a combustible foam material in it? If so, then would IBC 717 apply: “Combustible materials shall not be permitted in concealed spaces of buildings of Type I or Type II construction.”?

I have looked all over the code and cannot find a definition of “concealed space”. Can one of you code gurus shed some light on this?

Thanks,

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PERSONALLY, THIS OLD CODE HEAD DOES NOT SEE YOUR SITUATION AS “CONCEALED SPACE”. THAT USUALLY IS SOMETHING MORE LIKE PLENUM, ABOVE-CEILING OR INTERSTITIAL SPACES. OF COURSE, ONE CAN ARGUE THAT ANYTHING NOT SEEN IS CONCEALED.

ALSO, WHY NOT FILL THE INSULATION OUT, SHAVE IT OFF AT FACE OF STUDS SO IT DOES COME VERY CLOSE TO OR MEETS THE BACK OF THE GYP BOARD?

3

The stud space would be considered a concealed space.

However, you need to follow the chain of cross references:

Section 717.5: “Combustible materials shall not be permitted in concealed spaces of buildings of Type I or II construction.” Exception 1: "Combustible materials in accordance with Section 603.

Section 603: “Combustible materials shall be permitted in buildings of Type I or II construction in the following applications and in accordance with Sections 603.1.1 through 603.1.3:
…
3. Foam plastics in accordance with Chapter 26.”

Chapter 26:

Section 2603.5: Exterior walls of buildings of Type I, II, III or IV construction of any height shall comply with Sections 2603.5.1 through 2603.5.7."

2603.5.1: Not applicable.

2603.5.2: “Any foam plastic insulation shall be separated from the building interior by a thermal barrier meeting the provisions of Section 2603.4…”

  • Section 2603.4: "…foam plastic shall be separated from the interior of a building by an approved thermal barrier of 0.5-inch (12.7 mm) gypsum wallboard or equivalent…"2603.5.3: “The potential heat of foam plastic insulation in any portion of the wall or panel shall not exceed the potential heat expressed in Btu per square feet (mJ/m2) of the foam plastic contained in the wall assembly tested in accordance with Section 2603.5.5. The potential heat of the foam plastic insulation shall be determined by tests conducted in accordance with NFPA 259…”

Section 2603.5.4: “Foam plastic insulation, exterior coatings and facings shall be tested separately in the thickness intended for use, but not to exceed 4 inches (102 mm), and shall each have a flame spread index of 25 or less and a smoke-developed index of 450 or less as determined in accordance with ASTM E 84.”

Section 2603.5.5 (This is the kicker): “The wall assembly shall be tested in accordance with and comply with the acceptance criteria of NFPA 285.”

Section 2603.5.6: This requires a label on the insulation, which is impossible for sprayed-foam insulation. I don’t know how, other than a code modification, to comply with this requirement.

Section 2603.5.7: “Exterior walls shall not exhibit sustained flaming where tested in accordance with NFPA 268.” However, if one of the five materials listed in the exception are used on the outside, then this requirement is not applicable.

It is possible to do what you want to do, but you’ll need the test data to back it up. If Section 2603.9 is applicable, then all of the other requirements I quoted from Chapter 26 are not applicable.

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As much coincidence as anything else, just last week our office had a lunch and learn presentation from our local Dow representative who introduced us to their Thermax Wall System. Theyve addressed the kicker Ron mentions by successfully testing the wall assembly with their foam insulation in accordance with NFPA 285.

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Check your local building code and bulding department. Here is the “kicker in Seattle.”

Seattle DPD will accept use of spray-applied foam insulation products only having an up-to-date ICC-ES report within wall, floor and ceiling assemblies, subject to compliance with conditions of the ICC-ES report and with provisions of the Seattle Residential Code (SRC) or the Seattle Building Code (SBC), and the Seattle Energy Code (SEC).

Other highlights are (Type V-A and V-B Construciton)
In order to validate installation, the product installer is required to provide the DPD field inspector with a letter certifying that the installation was in accordance with the manufacturers instructions and the ICC evaluation report and the DPD approved plans. The letter shall also include the date, the product name, the installers name and address, company name, and DPD address and permit number. The letter will be recorded with the EDMS file for the project.
The product shall have a maximum flame-spread index of 75 and a maximum smoke-developed index
of 450 (SBC 2603.3).
A thermal barrier, equivalent to a minimum -inch gypsum board shall separate the insulation from the interior of the building (SBC 2603.4).

Another “kicker.”
Spray-applied foam insulation is not allowed in Types I and II construction, except as specifically stated in the ICC evaluation report.

We had the same “lunch and learn” from [insert manufacturers name]. [insert manufacturers name] did not have a response for the restriction on Types I and II construction for the Seattle marketplace other then to say not every AHJ is on board. [insert manufacturers name] is investigating further. Not all AHJ’s think equally. Infact, in 2004, Seattle DPD approved the use of SPF in Types I and II construction. I specified SPF for installation in concealed spaces behind exterior precast.

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If the building official will accept only an ICC-ES report and not other documentation of code compliance then I would suggest that he is exceeding his authority. The building official has the right to see evidence, such as test reports, that the product complies with all code requirements but he cannot unreasonably require that it come from a specific source.

We are seeing a number of jurisdictions requiring similar signoff letters related to structural issues. Because there is a concern that the letters could constitute a warranty on the part of the design professional the wording of the letters may want to be checked with your E&O carrier or attorney.

7

Evaluation sheets from the code agencies back to the old “3 model codes” have been used for years as a reasonable source of information for building officials [provided they are updated and current]. They provide information not available through other sourcing short of elaborate testing etc. May be a little “fringey” to require that one be submitted, certainly they can be among those “suggested” as sources acceptable to the code offical. Usually apply to materials and material systems of a critical structural nature

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Our resident code go-to-guy states “Passing NFPA 285 oten time is not enough.”

See decision tree, Figure 2603.1 FOAM PLASITC COMPLIANCE, Page 26-4, 2006 IBC COMMENTARY.

Contact me at wayne.yancey@comcast.net for a copy our decision tree analysis of a hypothetical project provided to [insert manufacturer’s name].

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I have no problem with the responsible use of evaluation reports. The problem is that they are all too often misused.

If an evaluation report is issued to document conformance with the code, when the product or material is listed in the code, then all of the relevant testing should have been performed as part of the preparation of the evaluation report. In such cses all the evaluation report does is put a package on the information and indicate that somebody has checked to see if the product complies.

Evaluation reports cost the manufacturer to develop and maintain. In addition the firms issuing them sometimes impose requirements on the manufacturer that are not required by the building code. Besides resulting in added costs to our projects the costs and added requirements have constrained our ability to use certain products, especially when the building official requires an evaluation report.