Where does the coating go?

Window installation has become more difficult because glaziers must ensure proper orientation of low-emissivity coatings.

While fabricators have various means of determining low-e orientation during the manufacturing of insulating glass units, glaziers’ few conventional methods for on-site verification have proven ineffective, until the advent of portable detectors. With these devices, installers no longer need to depend on their own discretion and can prevent costly errors that can cause failed inspections, or worse, financial devastation.

During the manufacturing process, fabricators verify the position of the coated surfaces by using direct-contact-style commercial coating detectors, multimeters, scanning-style meters located above work areas or brush-type detectors mounted directly on the equipment. In the past, some manufacturers relied upon visual—reflected flame—or touch methods. However, coating manufacturers warn that visual or touch methods could provide erroneous results because they require human judgment. Furthermore, handprints can corrode the low-e coating.

Once the coating has been incorporated into an insulating glass unit, determining the coated surface becomes more difficult. Using touch or multimeter methods would not be possible since the coated surface lies inside the unit. In addition, most, but not all, low-e coatings will be edge-deleted when assembled in an insulating glass unit. During edge deletion, the IG manufacturer removes the coating around the perimeter of the lite, so the sealant bonds directly to the glass surface. Sometimes, the process leaves a band of color difference, making the edge-deleted surface visually apparent. The visual method depends upon human judgment and won’t work when the low-e coating does not require edge deletion. Furthermore, edge deletion often becomes undetectable in framed units.

Innovation spawns more confusion
Manufacturers now create a multitude of self-cleaning, color-reflecting, scratch-resistant, and high visible- light-transmission style coatings that can be used in conjunction with low-e coatings. As options expand, each development underscores the ineffectiveness of conventional methods for determining orientation.

Detection devices that can determine the low-e coating from contact with any surface of glass lites assure proper installation. These simple-to-use devices can be inexpensive, fit into pockets and require no external power One such device is the D.I.G. or Detector for Insulating Glass coating detector manufactured by MLM Enterprises of Walbridge, Ohio. This pen-sized unit has two settings “present” and “contact.” When held against a pane, the device detects the side that carries the low-e coating, even if that side is not exposed. Read the device by waiting for a red light to flash and buzzer sound.

The market contains many such devices varying in size, cost and accuracy. Depending on the technology used, units cost $30 to more than $300 and use technology ranging from capacitance circuitry to high-tech optical light feedback. Users must check any instrument prior to starting an inspection to validate damage has not occurred to the unit during storage or previous use.

The advantages of this equipment outweigh numerous costly scenarios of re-installation or product replacement.

Suppliers
C. R. Laurence Co., Los Angeles,  800/421-6144, crl@crlaurence.com
Dark Field Technologies Inc., Shelton, Conn., 203/925-8581, darkfield@msn.com
LiteSentry Corp., Dundas, Minn.,  612/573-6541, mabbott@litesentry.com
MLM Enterprises, Walbridge, Ohio,  775/254-0144,   mlm@mlmenterprisesinc.com
Tool Experts, Harriman, Tenn.,  888/226-6288, info@toolexperts.com

Easy as one, two, three?
After identifying the low-emissivity surface, installation of IG units must also comply with the architect’s specifications. Usually, the low-e coating could be placed on the No. 2 or No. 3 surface when working with a standard IG unit. Surfaces are identified from the outside of the building inward. Therefore, in an IG unit that consists of only two glass lites, surface No.1 is the exterior surface and No. 4 is the surface facing the interior of the building. Even in more complex arrangements of laminated glass or triple-pane units, the glazier must know the proper orientation of the low-e coating.