On July 9, the CEC (California Energy Commission) held its High-Performance Windows Forum workshop at the Sacramento Municipal Utilities District building. With regional and national builders and window manufacturers in attendance, the purpose of the meeting was to introduce the concept of “Skinny Triples” (also referred to as “Thin Triple”) and to present an economic case for the adoption of this new form of insulating glass (IG) in California to meet the latest iteration of California Title 24, Part 6, that is scheduled to go into effect Jan. 1, 2020.

The proposed 2019 Title 24 updates for residential buildings will require that all new buildings achieve Net Zero Energy (NZE) levels by 2020 for residences and by 2030 for commercial buildings. That means updates to current standards that include:

  • The maximum U-factor for windows will be 0.30 (previously 0.32);
  • The maximum SHGC in cooler climates will be 0.23 (previously 0.25);
  • The maximum U-factor for doors with less than 25% glazing will be 0.20; and
  • Skylight requirements remain unchanged.

Additionally, the California residential building code is making photovoltaic (PV) panels mandatory as part of its de-carbonization strategy. In 2016, PV panels were optional but could be used as a performance tradeoff against other building envelope performance requirements, such as high-performance attics and two-by-six framing and insulation.

Are Skinny Triples the Answer?

Conventional triple-pane glazing has been around for many years, but has a very small share of the IG market (estimated at between 2%–6%) in the U.S. In Europe, however, triple-pane is the dominant configuration for residential windows. Adoption has been slower here because the weight of a conventional triple can add labor to the installation cost as well as potential re-engineering of framing and reinforcement.

On the other hand, Skinny Triples are thought to be a more viable option to meet building code requirements because they are more economical for manufacturers with fewer design changes required. For builders, they are much lighter and can be more easily dropped into existing applications.

Skinny Triples use a very thin glass for the center lite and krypton gas filling in a triple pane IGU, which has been made possible at a reasonable cost because of the volume of thin glass being produced for flat panel TVs and the much lower cost of krypton gas. In terms of cost savings, the CEC compared the cost of alternative building envelope improvements and came up with a potential savings between $5.50 and $6.60 per square foot of window area.

Why We Should All Take Notice

With all the benefits, there’s really only one thing standing in the way of wider-spread adoption: availability.

At this point, there is only one manufacturer building windows with Skinny Triples, so increased adoption by window manufacturers is critical, as well as the time to implement them since builders will have to have compliance options in place by January 2020. It was made clear at the meeting that conventional triples could satisfy the performance requirements albeit with the previously mentioned limitations for weight and structural requirements.

The View from Here is that for anyone building homes in California or selling windows into that market (around 10% of national production), Skinny Triples could be a game changer in that state and beyond. As more states adopt tougher building code requirements, high-performance windows are a meaningful alternative to some more expensive building envelope choices.

As I have always said, when economics favor higher performance choices, wider-spread adoption will certainly follow.

What’s your View? Email me directly at eric.jackson@quanex.com.

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