SPRAYFOAM Professional - Winter 2015 - (Page 35)

abaa nEWs ExcEssivE sHrinkagE oF cELLuLar PLastic Foam insuLation By LaVErnE DaLGLEIsH, prInCIpaL, BuILDInG profEssIonaLs T here have been quite a few articles in various publications pointing out problem of shrinkage of cellular plastic foam insulation. This is a real concern of the design and construction community, especially if the cellular plastic insulation will be used to provide the plane of airtightness. If there is excessive shrinkage in the product, this will result in the joints opening up and the plane of airtightness compromised. With spray polyurethane foam, there can be shrinkage; however, there does not have to be. The shrinkage can be severe to the point of twisting wood framing members or denting metal. Normally, the foam will give way within itself and crack open - this is referred to as thermal cracking. To fully understand this statement, you need to understand both the material and also how the material is tested. Whether the material will shrink (or expand) after being installed, starts with the chemist for the material. The chemist blends together many chemicals to produce a resin which, when combined with isocyanate, produces a material with very specific performance and specific physical properties. That chemist can make the material do almost anything (the key word is "almost"). This means that there can be a "bad" material, either by improper chemistry or something happening during the blending process. When you look at the specification sheet for a spray polyurethane foam material, you will normally see results for dimensional stability testing. Typically, the specification sheet will list 3 atmospheres: 1. Cold (-20°C) 2. Hot (80°C) 3. Hot/humid (70°C and 97% relative humidity) This will cover most of the conditions, whether you are installing the material in cold climates, desert climates, and hot and humid climates. Typically, in cold climates, you are concerned about shrinkage and in hot and humid climates you are concerned Sprayfoam that was not dimensionally stable was installed on a mockup. about expansion. In any case, you will want to know how the material performs in all environments. This will tell you a lot about the material. Do not modify the material on site by adding chemicals to the resin. What is blended and what you get is what you have to deal with. The first step is to determine if the material meets a specific material specification standard. The material specification standard that has been around the longest for an air barrier application is the CaN/ ulC S705.1 Standard for Thermal Insulation - Spray Applied Rigid Polyurethane Foam, Medium Density, Material - Specification. If the material you are considering to use does not meet a standard, then it is your responsibility to determine what you need and how the material will work in a specific application, under certain conditions. As a consumer, builder, or designer, making these decisions is beyond the normal decision making process. The dimensional stability test method used for cellular plastic is aStM D2126 Standard Test Method for Response of Rigid Cellular Plastics to Thermal and Humid Aging. When conducting this test, specimens are www.sprayfoam.org Thermal cracking. Sprayfoam releasing from the substrate. | sprayfoam Professional 35 http://www.sprayfoam.org

Table of Contents for the Digital Edition of SPRAYFOAM Professional - Winter 2015

EXECUTIVE DIRECTOR’S CORNER
PRESIDENT’S POST
FOAM BUSINESS NEWS
SPFA TODAY
LEGISLATIVE UPDATE
SAFETY FIRST
Sprayfoam 2016 Convention & Expo – February 8-11, 2016
SPFA’s History Proves Our Perseverance
ABAA NEWS
SPF Research on Air Quality – PART 1
2015 SPFA CONTRACTOR AWARDS
MAKING MONEY: Paint Your Own Picture of Success
ASK THE EXPERT
UPCOMING EVENTS
INDEX OF ADVERTISERS

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