How Thick Can Foam Be Installed Beneath a Roof Deck?

first_img GREEN PRODUCT GUIDE InsulationThe emphasis is on “was,” because Brooks had recently come across comments in a GBA blog suggesting that installers are limited by code to foam depths that vary by product but in all cases are no more than 6 in.“My question seems to be a hot potato,” Brooks writes. “I feel like the student who reminded the teacher that she forgot to assign homework.” Local code officials have the last wordReturning to the issue long after it was originally broached, John Walls is still puzzling over a fundamental issue: is allowable foam thickness related to limitations in testing equipment, or is something else behind it? “What is the science behind thinner is OK but thicker isn’t?” he asks. “Is it just a matter of volume of combustible material?”Walls is asking because he plans on using Sealection 500 foam, a brand of water-blown, open-cell foam, in an unvented attic. When he asked Demilec, the manufacturer, for information, he was directed to an ESR from early 2011 suggesting Sealection could be up to 11 1/2 in. thick under the roof and up to 9 1/2 in. on vertical surfaces. An intumescent coating or an ignition or thermal barrier would be required for both types of installation. Would this really pass muster?“There is evidence that thicker foam is more of a fire hazard than thin foam,” Holladay replies. “The code requires foam manufacturers to test their foam for fire safety. The fire safety question — and the question of which test methods are appropriate — are matters of enormous controversy and uncertainty, even among code officials and foam manufacturers.“If a foam manufacturer can’t come up with an ICC-ES evaluation report that refers to an assembly with foam thickness equal to or greater than the one you are planning to install, it’s certainly possible that a local code official can refuse to allow the installation.”Holladay suggests Walls ask his local code official whether his intended installation is consistent with the report. If the code official agrees, Walls can proceed. It’s OK to Skimp on Insulation, Icynene saysQ&A: Open-cell foam against rafters? Q&A: Spray foam strategyA statement from Icynene Our expert’s opinionOn all matters code, we turn to our GBAdvisor, Lynn Underwood, Chief Building Officer for Norfolk, VA.Lynn: Here’s the way I see it. The reference in the IRC (2009 edition) is as follows:R316.3 Surface burning characteristics. Unless otherwise allowed in Section R316.5 or R316.6, all foam plastic or foam plastic cores used as a component in manufactured assemblies used in building construction shall have a flame spread index of not more than 75 and shall have a smoke-developed index of not more than 450 when tested in the maximum thickness intended for use in accordance with ASTM E 84 or UL 723. Loose-fill type foam plastic insulation shall be tested as board stock for the flame spread index and smoke-developed index.Exception: Foam plastic insulation more than 4 inches (102 mm) thick shall have a maximum flame spread index of 75 and a smoke-developed index of 450 where tested at a minimum thickness of 4 inches (102 mm), provided the end use is approved in accordance with Section R316.6 using the thickness and density intended for use.R316.6 Specific approval. Foam plastic not meeting the requirements of Sections R316.3 through R316.5 shall be specifically approved on the basis of one of the following approved tests: NFPA 286 with the acceptance criteria of Section R302.9.4, FM4880, UL 723, UL 1040 or UL 1715, or fire tests related to actual end-use configurations. The specific approval shall be based on the actual end use configuration and shall be performed on the finished foam plastic assembly in the maximum thickness intended for use. Assemblies tested shall include seams, joints and other typical details used in the installation of the assembly and shall be tested in the manner intended for use.This provision starts out by establishing minimum flame spread and smoke developed indices (75 and 450) needed after testing at the thicknesses intended. The 4 in. limit is in the exception and leads you to Section R316.6, specific approval. That section offers extended thicknesses as permitted so as to still achieve the FS and SD ratings achieved in a tested product. An example is Spraytite by BASF achieving 12 in. thickness with a FS of 25 and SD of 450. Details are here.ASTM E84 seems to have a limit of 4 in. in thickness for the testing method. There are test methods that allow for alternate testing criteria for these thicker installations. NFPA 286 is an alternative test (called the corner room test).Lynn’s colleague, Steve Turchen from the Fairfax County, Virginia, building code office had this to add: The testing exception in R316.3 is still the confusing part for me. The language seems fairly clear that if you have a foam insulation product that is installed at thicknesses greater than 4 in., you cannot use ASTM E84 or UL 723 to do the test; select one of the other test procedures listed in R316.6. What confuses me is this: Are you still testing the “thick” sample to the 75 / 450 limits? ICC-ES seems to think so, per my read of ESR-2642, but that report is not 100% clear either.Virginia’s (VBCOA) Energy Code Committee may consider this question in an attempt to achieve consensus across the state.center_img RELATED ARTICLES Not a new issueBrooks’ original query was posted more than a year ago, but the topic continues to generate debate, confusion — and new questions.The debate isn’t over the thermal performance or air-sealing qualities of the insulation, but how spray-foam is tested for fire safety.The discussion originally touched on code-required flame-tunnel tests, which evaluate flame spread. GBA advisor Michael Chandler noted that conventional tests were limited to foam thicknesses of 5 in., and that at greater thicknesses alternative test methods were required. Fire resistant barriers, such as drywall or specialized intumescent coatings might be required.“Just to be clear,” he said, “the alternative test methods are subject to approval on a case by case basis by the inspections department.”Chandler added that while codes appeared to limit foam thickness to no more than 6 in., he routinely recommended to his clients that they use more. “I advocate spraying 11 in. and certainly never less than 8 in. here in North Carolina,” he wrote, “so technically all of my homes are in violation of code on this issue.”It appears to come down to whether the foam manufacturer can produce an Evaluation Service Report from the International Code Council that would satisfy a local building inspector on the fire safety of the installation.In the case of Icynene, a brand of open-cell foam, an ESR unearthed by GBA senior editor Martin Holladay included a number of tested assemblies with foam at thicknesses greater than 6 in.“The ESR now includes a variety of tested assemblies — tested for one-hour fire resistance, that is, not surface burning characteristics — that include Icynene that is up to 10 in. thick (R-37),” Holladay wrote. But there were a couple of caveats: builders could only depend on those test results if they used assemblies identical to those described in the report; and most of the tests included intumescent coatings, “a controversial category of products that not all fire experts trust.”In an answer to another question posed by a GBA reader, Holladay provided technical information on the controversy surrounding intumescent coatings; the information originally appeared in an article Holladay wrote for Energy Design Update. This week’s Q&A Spotlight begins with a confused architect. Like many other architects and builders, John Brooks had become accustomed to seeing spray-in polyurethane foam that completed encapsulated the rafters when sprayed on the underside of roof decks.He’d seen Building America projects that included foam at this thickness, and points to numerous projects at GreenBuildingAdvisor where the same thing had been done.“Almost every Green home tour I have visited in Texas has attic rafters covered in spray foam,” Brooks writes. “My thinking WAS that this practice is acceptable, safe and code approved.”last_img