Volume 2 Issue 3 Fall 2001
s t r a t i o n f o
c u s
by Werner Lichtenberger, P.E.
As in North America, the process to harmonize insulating glass (IG) standards has been underway for the last few years. With the recent approval of CEN 1279, Europe has moved forward with harmonizing IG manufacturing standards and certification. Approved by the European Committee for Standardization (CEN), the new standard is scheduled to go into effect in either 2002 or 2003.
CEN 1279, although daunting at 180 pages, is unique since all aspects of system testing, production control and certification are presented together in one document. The document is broken into six sections, which are only summarized here due to limited space. The six sections include:
1. Generalities, dimensional tolerances and rules for the system description;
2. Long-term test method and requirements for moisture penetration;
3. Long-term test method and requirements for gas leakage rates and for gas concentration tolerances;
4. Methods of tests for the physical attributes of edge seals;
5. Evaluation of conformity; and
6. Factory production control and periodic tests.
|ďCENís consolidation of all relevant IG standards into
one standard is a good approach. Many have already
begun to voice support for such a unified worldwide standard.Ē
Section one of the new European IG standard focuses on the three essential factors associated with insulating glass: energy savings, health and safety. Insulating glass is defined not only as an assembly of various components, but also by the durability of its characteristics as determined by extensive testing. In other words, any product not meeting the standard requirements cannot be referred to as insulating glass.
This section reviews the procedure for measuring desiccant depletion caused by temperature and humidity cycling (referred to as climate testing). Moisture vapor transmission resistance of the IG seal system and desiccant loading are the key factors that determine the potential longevity or life expectancy of IG units. It also sets out a minimum requirement that no more than 20 percent of the desiccant may be consumed in the test. The concept is simple: measure the initial and final moisture content of the desiccant. Then, establish by test or tabular data, the standard (total) desiccant moisture adsorption capacity. These values are then used to calculate the amount of depletion.
Part three of the standard focuses on the testing of gas leakage rates. Using a special apparatus, the leakage rate of gas is measured after climate cycling. Samples are subjected to climate testing for a shorter period of time (28 temperature cycles and four weeks at 58 C high humidity) than used in moisture vapor transmission testing. The IG unit or just the edge of the IG unit is kept in a gas-tight container from which all ambient gas has been purged and replaced with high-purity helium. With time, gas leaks from the IG unit gap into the helium. This mixture of gases is collected by passing it through a liquid nitrogen-cooling trap. Gas chromatography is then used to analyze the gas mixture. The measured value is used to calculate an annual leakage rate. The requirement is that annual leakage rate must be less than 1 percent.
This part of the standard covers the evaluation of edge-seal strength and partial evaluation of moisture and gas permeation through sealant. To test the strength of an edge seal, the IG unit is tested in three exposures: heat (60 C for 168 hours), water immersion (distilled water at 23 C for 168 hours) and ultraviolet rays (96 hours UVA range at 40W/m2). However, these exposures are not combined. Testing moisture and gas permentation is required primarily for substitution of sealants, to prevent the use of materials with lesser properties.
The fifth section of the standard focuses on evaluating the conformity of IG units. It identifies the characteristics for both the initial type testing and the factory production control. It also identifies the responsibilities of tasks of the manufacturer and the notified body for CE marking.
The final and most important section of the document includes documented quality-control procedures and monitoring based on production volume, unlike the North American approach. In North America, responsibilities for physical IG test methods and quality-control procedures have been separated. The American Society for Testing Materials and Canadian General Standards Board handle testing, while certification agencies assume responsibility for quality control.
CEN 1279 requires audits and regular inspections of IG unitsí construction for conformity with the declared specification. The draft includes a table with a recommended random sample inspection plan where the volume of 12 daysí production determines how many units are to be inspected. The results are recorded for auditing purposes.
CENís consolidation of all relevant IG standards into one standard is a good approach. Many have already begun to voice support for such a unified worldwide standard. Recently, the CEN harmonization proposal was presented to the World International Standards Organization for consideration as a model for the development of a global IG standard. As the standards are applied in Europe, we will watch carefully to see the standards, as they may eventually serve as the foundation for the first unified IG standard.
Werner Lichtenberger, P.E., serves as special projects manager for TruSeal Technologies, based in Beachwood, Ohio.
© Copyright 2001 Key Communications Inc. All rights reserved. No reproduction of any type without expressed written permission.