SPRAYFOAM Professional - Spring 2015 - (Page 51)

ASK THE EXPERT MEASURING THERMAL BARRIER COATING THICKNESS BY SPFA'S CONSULTANT COMMITTEE, MASON KNOWLES, ROGER MORRISON, PHIL ROBARGE, JOHN HATFIELD, ROBB G. SMITH, HENRI FENNELL S PFA gets calls regularly from customers, designers, architects and others looking for straight answers to their questions on SPF. Our panel of experts recently addressed this topic: Q uestion? I've been using an intumescent thermal barrier coating for my insulation applications. The spec sheet says to use one gallon of coating per 80 square feet, but folks have told me those ratios don't always give you enough coating. Is there a way to know for sure that I am installing the right coating thickness? Most technical data sheets and Evaluation Reports recommend a specific amount of square feet per gallon or gallon per square foot, while also reporting the minimum amount of dry film thickness of coating required to qualify as a thermal barrier (or ignition barrier). Some suppliers recommend a theoretical coverage and others include a specific amount of waste factor in their recommendations. For example, your intumescent thermal barrier coating manufacture lists a theoretical coverage rate of 80 sq. ft. per gallon to achieve a wet film thickness of 20 mils and a dry film thickness of 13 mils. DRY FILM THICKNESS The more important number is the minimum dry film thickness. In the U.S., coating thickness is measured in mils. One mil equals 1/1000 of an inch. Outside of the U.S., coating thickness is measured typically in millimeters (mm). From a review of intumescenttype thermal barrier coatings, the average coating thickness over the various sprayfoam products ranges from 11 to 15 dry mils. Ignition barrier coatings typically range from 3-5 dry mils. flushing out the hoses, to overspray and uneven coating application, the waste factor can soar to more than 75%. Using our example above, if the coating manufacturer recommends 1 gallon to cover 80 square feet for a 13 mils dry film thickness, adding a 75% waste factor could increase the amount of coating required to 1.75 gallons per 80 square feet. MEASURING COATING THICKNESS The procedure for measuring coating thickness in the roofing standard can be used in building envelope applications as well. The basic procedure begins Focus the eyepiece and hold scale against sample. It makes sense therefore to measure the actual dry film thickness rather than relying on gallons per square feet. A procedure was developed decades ago by the SPF roofing industry to measure the dry film thickness of coating over sprayfoam. ASTM standard D 7119, Standard Guide for Sampling Spray Polyurethane Foam and Coating in Roofing is based on that procedure and was approved more than 10 years ago. WASTE FACTOR There is a considerable amount of waste involved in coating uneven surfaces such as sprayfoam. For example, depending on the surface profile an extra 40-50% of coating may be required to achieve the minimum dry film thickness. Add coating lost from www.sprayfoam.org | SPRAYFOAM PROFESSIONAL 51 http://www.sprayfoam.org

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

Executive Director’s Corner
President’s Post
Foam Business News
SPFA Today
Industry by Design
Legislative Update
Why I Support SPF
Safety First
Energy Codes and the Benefits of SPF
Behind the Foam
SPF Industry Prepping for Code Changes in Sweden
How to Make Money and Have Fun Doing It
What You Need to Know Before You File in 2015
Tips on Spraying Foam – Are You Doing It Right?
Choosing the Right Strategy for Complex Construction Claims
10 Ways Your Company Can Use Instagram
ABBAA News
Ask the Expert
Calendar of Events
Index of Advertisers/ Advertisers.com

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