Achieving Thermal Performance in Storefronts without Losing Aesthetics

By Ellen Rogers

Finding a balance between aesthetics and performance can be a challenge in almost any architectural glazing application. Storefronts and entrances are no exception. To meet this need, manufacturers continue to advance their systems to help ensure products can be specified to achieve performance requirements, without sacrificing aesthetics.

Meeting a Need

Donnie Hunter, director, global product management, with Kawneer, based in Norcross, Ga., says storefronts have seen a number of developments over the years.

“The first aluminum storefront system was designed for ¼-inch glass, and the next generation systems were designed to accept 1-inch insulating glass units (IGU). The next game changer was to include a single thermal break in the systems for 1-inch glass; today most aluminum systems offer storefront with two or dual-thermal breaks.”

He explains that, generally, the thermal break in storefront systems is located in the glass pocket, so there is limited space for the thermal break or to increase its size.

“Most systems today are designed specifically to accept 1-inch IGUs, so the use of a triple-glazed IGU is not an option,” he says. “… [For] a typical flush-glazed system to accept thicker triple-glazed IGUs, it would require an increase to sightlines, which would require redesigning existing systems, in effect [creating a] new system.”

Mark Suehiro, the technical director, product group sales, architectural hardware for Los Angeles-based C.R. Laurence, agrees that achieving both thermal performance and aesthetics can be challenging. “Architects are trying to find something more aesthetically pleasing than just run-of-the-mill storefront doors. You can get high [performance] ratings, but it’s very cookie-cutter. So really they’re looking to go out of the box and fi nd something different.”

Suehiro says one way they have been able to meet this need is with products such as his company’s Entice series. These doors combine all-glass aesthetics with full-frame thermal performance, and feature 11/8-inch vertical stiles. The system can also support handle hardware on 1-inch IGUs using through-glass fittings.

Improving Performance

Brad Begin, CEO of Alpen High Performance Products in Louisville, Colo., says that the limited pocket size can be a challenge.

“Most aluminum storefronts and entrances manufactured in the U.S.—even the higher performance ones with multiple thermal breaks—have limited glass pocket depths of 1- to 11/8-inch. Aluminum doors used in these entrances have similarly limited 1-inch glass pockets by necessity,” he says, adding that improving overall system performance involves both frame/profile thermal improvements and glass enhancements.

“Improving frame/sash profiles, can be accomplished by engineering profiles that have multiple thermal breaks and/or integrating materials that have low thermal conductivity, such as fiberglass struts,” he says. “Improving glass can be achieved using advanced technology such as vacuum glass and krypton high performance inert gas fill, or, more economically, by changing from double-pane to triple-pane and quad-pane construction.”

He adds, though, that fitting a third lite of glass into a double-pane IGU requires the overall thickness of the IGU to be at least 1.25 times wider than a double-pane unit. “The only way to accomplish improvements in glass within aluminum storefronts and entrances is to design aluminum entrance system profiles that can accommodate 11/4-, 11/2- and wider IGUs.”

As an example, Begin says by using materials such as suspended coated film and thin glass it’s possible to overcome the narrow-glass-pocket limitation. For example, he says thin glass triples (two traditional outside glass panes and a single interior third lite of glass) can enhance performance in slightly thinner overall glass thicknesses. In addition, Begin says the use of alternative materials for high-performance framing, such as fiberglass and fiberglass-reinforced uPVC frames, is making some modest inroads.

Product Evolution

While aesthetics and energy performance will likely continue to be important, storefront and entrance products are also seeing other developments. Hunter says the modular construction trend has already begun to drive changes in product design.

“Historically, when our industry thinks of pre-glazing, we immediately think in terms of unitized curtainwalls. Today, many aluminum system providers offer pre-glazed storefront and window wall systems,” he says. “By doing more fabrication and assembly in the shop environment, quality of workmanship improves which leads to consistent product performance.”

As far as aesthetics, he adds the focus is on minimizing system sightlines and maximizing glass size. “With the trend of larger glass lites, shop glazing unitized systems is more desirable as equipment is readily available, and it is more convenient to set the glass in the framing systems in the shop. Pre-glazed unitized systems allow for the building to be enclosed faster.”

Also looking toward future developments, Begin sees a lot of opportunities for companies in the U.S. to catch up to what others are doing around the world.

“While the U.S. has many great companies building extremely good products, product innovation and the use of alternative materials in U.S. manufacturers is far less common than what we see coming in from outside the country. The U.S. has two maxims that I think are true: we are as innovative as any country on the face of the earth and we make the highest quality products found anywhere on the earth. For whatever reason, the
U.S. marketplace and, for the most part, state and federal policies don’t incentivize our mainstream manufacturers enough to encourage the development and adoption of the innovative high performance fenestration products, which we are capable of producing in the U.S.”

Suehiro says given the product evolution he’s seen when it comes to having thermally broken systems that incorporate 1-inch IG, engineers are continuing to further that development without sacrificing aesthetics. For example, making the hardware as small as possible, which could mean using a cylindrical lock instead of mortise.

He adds it’s also important for customers to understand why some of these changes are necessary.

“We need to [help them understand] and explain why these energy efficient [features] are needed and why it’s important,” he says.

It’s with this understanding, that the industry can help customers get past seeing what they “have” to do as a burden and instead something that will enhance their projects—both aesthetics and performance.

Ellen Rogers is the editor of USGlass magazine. She can be reached at

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