Architects’ Guide to Glass

Unlocking the Energy Key
Architects Discuss the Role Glass Can Play When Designing a Sustainable Structure
by Charles Cumpston

Energy usage and efficiency are pillars of the economic recovery plan. How architects design structures is at the core of effective energy usage and efficiency. How does the architectural community see the role of glass in this equation?

The Right Fit
According to Richard King, senior associate and a technical design leader at architectural firm RMJM’s Princeton, N.J., office, there are varying degrees of performance for glass systems that can provide very good energy efficiency. 

“Early on in a project, our primary effort in determining energy savings is more a question of how much glass and where, rather than what kind. We generally keep our glazing at a maximum of 40 to 50 percent of the building exterior skin to maximize the aesthetic impact of the glass, while balancing that against potential savings on energy and construction costs,” he explains. 

“With some clients we are able to discuss more advanced systems such as high-performance climate wall technology,” he adds. “We have developed this for our Okhta Center project in St. Petersburg, Russia, among others, where the concept is an all-glass, crystalline form with exceptional energy performance. The design achieves energy efficiency with more than 50 percent savings when compared to a typical Russian building, which has only a small area of window. High-performance glazing systems offer excellent opportunities for energy savings, coupled with interesting aesthetic potential for the design.” 

Going a step further, he explains, “We have also investigated interesting alternatives for this project, including heated glass systems and glazing systems, which include phase change materials to provide insulation only at certain times of the year, when it is needed most.”

Questions Answered
Denise Beneke, an architect with MarmonMok Architecture in San Antonio, says, “When we design a building such as the library project I just finished, which has lots of glass—in this case floor-to-ceiling glass—the first questions we typically get from clients are ‘Isn’t it going to get hot in there?’ and ‘Is that going to be expensive to air condition?’”

Another question that she says seems to come up a lot is whether operable windows are efficient.

“There are mixed opinions in San Antonio from both architects and engineers as to whether they really provide any energy savings since our climate is so hot and opening the windows and turning off the air conditioning isn’t an option for most of the year,” she explains. 

Architects say that there are a number of ways that they can respond to these questions and any concerns when it comes to architectural glass and energy efficiency.

According to Beneke, “Our response to the first question about too much glass getting hot and being expensive to condition is that, first, we will typically provide adequate shading of the glass on the south and west and even the east sides of the building; second, because north facing windows are the best, we like to have lots of that glass to let light in and provide views of the outside, while still not having the solar gain that the other facades of the building have; and third, with better options for glass available [such as some of the high-performance glass products now on the market], which we typically use on most commercial projects, that is also helping.”

She continues, “The pros of glass usage, such as the views and daylighting it can provide, are so great that if the cons of the heat gain can be mitigated through the use of glass or a shading element, I think architects shouldn’t be afraid to use it. It does have to be done correctly, though. I’m speaking from personal experience; I work in an all glass high-rise that has no shading devices, which results in an office that is always hot on the south side and cold on the north side.”

King says the fact that glass products have evolved over the years and become more energy efficient has made the material much more attractive for use in architectural projects.

“Glass today is much more energy efficient than years ago and we have successfully managed to reduce mechanical equipment sizes because of these advances,” says King. “Metal and ceramic coatings are now offering us even greater design latitude where sun control is more critical. We are also using more laminated glass systems, because they offer excellent flexibility for translucent glass as well as improved safety and structural capacity.”

King continues, “Advanced computer modeling to compare the various wall and glazing options is essential, especially when trying to maximize energy savings from daylighting. We are working on rainscreen wall systems that integrate glass panels in more of a spandrel application, so that we can achieve the appearance of glass with the energy savings of a solid wall.”

“Metal and ceramic coatings are now offering us even greater design latitude where sun control is more critical. We are also using more laminated glass systems, because they offer excellent flexibility for translucent glass as well as improved safety and structural capacity.”
– Richard King, RMJM

The LEED Role
With energy efficiency becoming a pillar of architectural design, glass is one material that plays a prominent role in helping create a high-performance structure. And today, with more and more architects designing and submitting projects with the goal of attaining Leadership in Energy and Environmental Design (LEED) certification, architectural glazing materials can also fill a significant part in reaching that criteria. 

“LEED requirements,” explains King, “are no longer a significant issue for us as the requirements are now such an integral part of our design process. We have become more precise in how and where we use glass systems as a result. We use glass and metal systems together to control daylighting and glare, especially in controlling strong southern exposures. We often take advantage of how well-integrated glass framing systems are with various sunscreen systems to achieve these savings.”

Beneke points out, “One of the biggest parts of LEED and where you can get the most points is energy efficiency. That is where some start to worry about using too much glass and requiring too much conditioning of the space. However, energy doesn’t just come from the HVAC systems. These energy savings can come from using more efficient lights and fewer of them, which can be done by using more daylight. Other ways to save on energy efficiency is by using better HVAC systems. If you’re looking just at energy efficiency alone, then yes, glass will make it a little more difficult; but, when you look at LEED as a whole, you can see that by having windows you are also eligible for points because you are providing views and daylight.”

As glass and glazing materials continue to evolve and as the importance of creating energy-efficient, sustainable structures continues, so, too, will the architectural community’s use of these products.

Charles Cumpston is a contributing editor for the Architects’ Guide to Glass & Metal.

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