Glass

Helping navigate complexity and opportunity

We often spend more time talking with clients about glass than we do windows and doors. That might sound odd at first but there are four good reasons why:

1. For homeowners, 90% of their direct experience with fenestration is with the glass rather than the frames or sash. We respect that and we give it careful attention.
2. In the past five years, glass technology has advanced exponentially. That means great benefits, but it also means more complexity in glass compositions with more pros and cons than ever before. We take the time to explain the options.
3. As code compliance tightens in all regions, getting the glass specifications right is critical, without losing sight of aesthetics and other benefits and values. This is especially true for modern homes with large percentages of glass in the building envelope.
4. As glass becomes a more significant architectural material, the quality of the glass and ASTM standards are under greater scrutiny. Glass is never perfect, so being aware and informed of this reality is critical to managing client expectations and costs.

Glass and glazing can be a mind-bending topic. We’re here to help you. In the meantime, here are a few pointers that may inform your exploration

• Single, dual and triple glazing options are available, depending on the specific needs and desires of each project and the fenestration involved. Maximum sizes, weight, sight lines, thermal performance and warranty should be considered. Code compliance in most regions means that single glazing is restricted to interior applications.
• Low Emissivity Coatings (LoE) are available in several coatings, depending on performance values, glass sizes, tints, and code compliance. It is best to explore this option early so that, when schematic design moves to the permitting set, the challenges have been overcome and design development can proceed uninterrupted. Higher thermal performance can be achieved with dual coat LoEs within a sealed unit. For example, a soft-coat LoE can be applied on surface #2 and a hard-coat LoE on surface #4. Visual light transmittance is diminished but the trade-off on higher U values and SHGCs can be worth it and can make code compliance more achievable, especially with metal fenestration.
• Standard glass sizes help constrain costs, with maximum sheet sizes typically being 96” x 144” in North America. Sealed unit sizes will be slightly less due to edge deletion. Check that NFRC certification exists on the IGU composition you are considering. This will make it much easier to get along with the permitting authorities and building inspectors.
• Oversized glass is available up to 130” x 300”. However, weight, cost, quality, warranty and logistics should be discussed in detail before you commit. The spacer bar sight lines are typically greater on oversized glass, so glazing stops should be adjusted accordingly and close attention paid to daylight alignments as a result. The weight of the glass may require specific engineering of the sill jamb of the window.
• Laminated glass boosts UV filtration to mitigate fading, as well as provides sound abatement and security. Urban dwellings like penthouses and townhouses that are affected by road and air traffic are good examples where laminated glass can improve the quality of the owner’s daily life by significantly reducing sound transmission. The additional UV filtration helps protect furnishings, artwork, book collections, draperies and hardwood floors.
• Hurricane Impact Glass with Sentry .090 interlayer. This is specifically designed to resist air-borne debris (disconcertingly referred to as “missiles”) for projects in hurricane code zones.
• Low Iron ultra-clear glass for maximum clarity. Low Iron glass has greater clarity and transparency than regular float glass, achieved by reducing the amount of iron in the molten glass itself. It has a higher price point than float glass but may be worth the investment for particularly demanding clients with multi-million dollar views.
• Switch Lite Glass turns from clear to obscure with the flick of a switch. Switch Lite can be used in exterior and interior applications. Maximum sizes are in the range of 48” x 110”. Window and door frames can be machined for concealed wire pass-through.
• Low reflectivity glass is very desirable for its ability to dramatically improve views. Sizes, thermal performance and costs should be explored in early design to ensure the specifications meet all the necessary criteria. Some regional codes require low reflectivity glass to reduce glare, such as with waterfront homes in Lake Tahoe.
• Restoration glass is available for historical and traditional projects. Restoration glass can be handmade or machine drawn. Maximum sizes vary, as do the grades of glass distortion. Restoration glass is best used in one pane only of an Insulated Glass Unit (IGU) otherwise the combined distortion can become too obtrusive.
• Ballistic glazing is available for high security applications. In addition to several sources, the sizes and thicknesses vary depending on the caliber of munitions the glass is intended to resist. The thickness of ballistic glazing often requires a deeper and wider glazing cavity in the fenestration.
• Warm edge spacer bars are used as a default to maximize thermal performance and IGU life expectancy. Some applications may require stainless steel or aluminum hard bars
• Factory glazing is recommended whenever possible. This allows us to control the glazing under factory conditions, to ensure precise sight lines are maintained, and to provide the highest standard of workmanship.

Resources

Lessons Learned Working with Architectural Oversized Glass

Sound Transmission Class & the Architectural Pursuit of Serenity

What’s the Deal with Distortion in Architectural Glass?

Laminated Glass Keeps Tigers Out of Your Bedroom

When is a Defect Not a Defect? ASTM Glass Standards for General Contractors

Managing Code Compliance with Modern Architectural Home Designs