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David Moss
Posted on Tuesday, May 09, 2000 - 02:45 pm:   Edit PostDelete PostPrint Post

Insulated Roof assemblies. It has always been my opinion that any area where foam insulation is used has to be thermally protected. This includees roofs. Styrofoam has the sand method, but I have always used wallboard to create a non-combustible assembly. In NYS Iheard of a school that had to replace their roof becaause this was not done. Manufacturers dodge this question everytine it is asked. Any feed back one way or the other.
Posted on Thursday, May 24, 2001 - 06:56 pm:   Edit PostDelete PostPrint Post


Are you asking if roofing can go directly over foam insulation? If so, then the practice is not recommended by NRCA and by most major roofing membrane manufacturers.

As for polystyrene insulation (of which Styrofoam is one of many), I wouldn't use it except in IRMA roof systems because it is unstable over time.
Dave Metzger
Posted on Sunday, June 03, 2001 - 11:53 am:   Edit PostDelete PostPrint Post

BOCA requires a thermal barrier for use of plastic foam in buildings, per 2603.4 in 1999 BOCA (this means anywhere in buildings, not just roofs; there are various exceptions, see BOCA 2603.4.1). The roofing membrane in an IRMA assembly (which requires extruded polystyrene above the membrane-- different from molded polystyrene) generally is applied directly to a concrete roof slab which serves as the thermal barrier.

IRMA assemblies can be used on a steel deck but then a solid deck (gypsum board, for example) must be used, not only to provide a thermal barrier but also to be solid continuous substrate for the roofing membrane.

In a traditional roofing assembly (deck, insulation, membrane), foam insulations generally require a thermal barrier between the insulation and the deck, but again, BOCA provides for exceptions in 2603.4.1.5--in my experience this is for polysiocyanurate foam insulation. However, I think it is good practice to provide the thermal barrier in any case, and if your roof assembly requires a fire rating, the test assembly may require a thermal barrier.

These are separate issues from whether roofing membranes can be applied directly over plastic insulations and I agree with Anonymous, that a barrier layer of some type is usually required between the membrane and insulation.
tony baines (Unregistered Guest)
Unregistered guest
Posted on Sunday, July 18, 2004 - 04:31 am:   Edit PostDelete PostPrint Post

i want to start to manufacture composite panel for roofing and sidewalls in the uk anybody know the setup
Richard HIrd (Unregistered Guest)
Unregistered guest
Posted on Sunday, July 18, 2004 - 11:45 am:   Edit PostDelete PostPrint Post

Although foam insulations contribute to the spread of fire, in a roof assembly this happens when the plastic insulation melts sufficiently to flow through lapped openings in the metal deck and then dropping as a burning plastic on the floor below. It is my understanding that this was discovered in the early days of testing plastic insulation, which was primarily expanded polystyrene. The gypsum deck, and other barriers, prevented this from happening and therefore were written into the code.

It has been accepted by most codes that isocyanurate insulation does not exhibit this phenomenon; melting and flowing while still burning. Therefore, the barrier is not required. I have also been told by extruded manufacturers that testing shows their product does not exhibit this phenomenon.

I would like to know if the above claims are accurate. I put my foot in my mouth often enough. I have no problem with belt and suspenders practices, but I do not like to call it good practice. It implies that to do otherwise is bad practice.
John Bunzick, CCS, CCCA
Senior Member
Username: bunzick

Post Number: 239
Registered: 03-2002
Posted on Monday, July 19, 2004 - 08:52 am:   Edit PostDelete PostPrint Post

The General Motors automobile transmission plant in Livonia, Michigan burned to the ground in a total loss in 1953, due to the combustibility of the roof. Here, a built-up roof was melted and brought to ignition by a smaller fire inside. The roof started to burn and destroyed the entire building, which was quite large. I don't believe that foam insulation was involved in that fire (who cared about thermal efficiency in 1953, especially a factory?!) but it certainly raised the awareness of this vulnerablity of roofing. Maybe someone else knows about a foam-plastic roof fire incident.

I don't know much about the manufacturing of composite materials, but I believe it is not very complex--mostly a laminating facility where the two materials are joined into one via suitable adhesive and pressure.

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