Bill Lingnell Explains Glazing Guidelines and Forensic Investigations
September 13, 2012

by Casey Neeley, cneeley@glass.com

Bill Lingnell, technical consultant for the Insulating Glass Manufacturers Alliance (IGMA), presented the "Glazing Guidelines for Commercial and Residential Insulating Glass Units" (IGUs) at IGMA's educational seminar in Las Vegas. Later in the day he also presented "Forensic Investigations of IGU Failures."

According to Lingnell, when handling an IGU, "proper cushion provides the desired support to allow the edges to be simply supported in lieu of clamped support conditions and thus minimizing the bending stresses on the unit underwind loads."

Setting blocks also are an important system of support to use when handling an IGU. "Setting blocks provide support to the bottom edge or the IGU," says Lingnell. "Two setting blocks are required and are usually placed at the quarter points along the horizontal bottom edge."

"Setting blocks should be one inch long for each ten feet of glass area with a minimum with a minimum of two inches for residential applications and four inches for commercial or larger applications greater than 25 feet," stated Lingnell in the presentation.

In his forensic presentation, Lingnell discussed the methods for investigating IG failure. One of his most important tips was to not assume that there are not any potential IG failures just because none have been reported. Lingnell suggests being proactive in the approach for examining IGUs for failure.

Additionally, Lingnell says, "do not base decisions upon a single failure rate-that is: one that covers all products and all uses lumped together."

The three analytical methods, according to Lingnell, are experience, laboratory analysis and data analysis. While logic is the most important in forensic deduction, it is important to remember that logic can sometimes be flawed. He suggested that it is important to examine the cause, effect and condition to determine the source of the IG failure.

The IGMA Educational Seminar, held at the Las Vegas Hotel and Casino in Las Vegas, concluded yesterday.