A Plant Tour: Single-Source Glass Fabrication
Applying the coating on the #3 glass surface instead of the #2 glass surface can significantly impact solar management and thermal performance. (According to experts, the #2 surface is optimal for commercial and institutional buildings.) Keeping the supply chain short can help to manage the process and avoid costly mistakes.
Specifications should consider the possible interactions between IGU components, and other fenestration and enclosure systems. Single-source fabricators tend to be helpful in this regard as they can offer architectural and technical services that help architectural teams select the right products for their buildings.
Understanding the Limits of Fabrication
A number of challenges face the architect in designing buildings with enclosure glazing systems. Some are endemic to the manufacturing choices specified or implied by the design team.
One important concern is roller-wave distortion, the imperfections and waviness caused by some process variables such as heat, temperature, speed through the fabricator's oven, and quenching, or cooling of the outer surface of the glass. Roller-wave distortion will occur in tempered glass. These flaws can create highly visible distortions in the reflections on glazing units. This is not avoidable.
Fabricators and installers of glass units should be able to reveal their tolerances for distortion and localized warp. A typical rule of thumb for ¼-in. rectangular glass is a warp tolerance of 1/32 of an inch (about 0.8mm) over any 12-inch span (305mm).6 This is a good visual specification, and it is about half of what is called out in ASTM C 1048, Standard Specification for Heat-Treated Flat Glass. This minimum manufacturing standard is met with a tolerance of 1/16 inch over any 12-inch span.
Notice
