Spray Foam Professional - Fall 2012 - (Page 35)
ASK THE EXPERT
PFA gets calls regularly from customers, designers, architects and others looking for straight answers to their questions on SPF. Here are two of the questions received recently that our panel of experts addressed:
I have read that closed-cell sprayfoam can be sprayed too thick causing problems. What problems are we talking about and how do I know how thick to install the foam?
Since polyurethane foam is an excellent insulator this exothermic heat is retained in the foam mass and, therefore, the more insulation there is the more heat is retained. This exothermic heat is necessary for the foam to form and obtain the physical properties needed for its performance. This temperature within the curing foam product can get to be excessive if the foam is sprayed too thick in one pass (typically greater than 2 inches) or if multiple passes are applied without sufﬁcient cooling between each pass. Spray polyurethane foam manufacturers usually indicate the range of pass thickness for their products and these limits should be followed. The foam can deteriorate exhibiting blowholes, ﬁssures, voids, gaps, discoloration and may produce odors if applied too thick. In extreme excessive lift or pass thicknesses where the temperature becomes very high, the closed-cell foam can auto-ignite if the core is exposed to air. (A lift is a layer of sprayfoam installed in a speciﬁc area using multiple passes at one time. Multiple lifts are typically installed in an insulation application.) The best way to avoid problems due to excessive heat is to review the manufacturer’s guidelines and then test the
Scorched foam shows this foam came close to auto-ignition.
Spray polyurethane closed cell foam is applied in the ﬁeld through proportioning spray equipment combining A and B components under pressure to create a rigid polyurethane foam insulation. The chemical reaction that occurs in seconds gives off heat (observed as exothermic temperature increase) as a result of this chemical reaction. The more foam mass (e.g., greater foam density and/or greater pass thickness) there is, the more heat is given off.
This column is the product of the new SPFA Consultant Committee members: Roger Morrison, Deer Ridge Consulting Inc. Phil Robarge, AMEC E&I, Inc. John Hatﬁeld, Penta Rooﬁ ng Consultants, Inc. Mason Knowles, Mason Knowles Consulting, LLC The article was also reviewed by the Technical Committee.
Numerous blowholes and the darker color in the center of the samples indicate excessive exothermic heat developed within the foam. This sample also exhibited strong odors.
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Table of Contents for the Digital Edition of Spray Foam Professional - Fall 2012
EXECUTIVE DIRECTOR’S CORNER
FOAM BUSINESS NEWS
BEHIND THE FOAM
2012 SPFA CONTRACTOR AWARDS
GETTING SUSTAINABLE ROOFING RIGHT
MILITARY STANDARDS AND SPRAY POLYURETHANE FOAM INSULATION – PART 2
IRAQ – U.S. MILITARY IN IRAQ BENEFITS FROM PERFORMANCE OF SPF
ASK THE EXPERT
INDEX OF ADVERTISERS/ADVERTISERS.COM
Spray Foam Professional - Fall 2012