Energy efficiency: The heat is on

At the Inova Schar Cancer Institute in Virginia, a shingled glass rainscreen acts as a permanent moisture shield and promotes energy efficiency by managing air infiltration and heat transfer. Photo courtesy Greg McGillivray/Halkin Mason Photography
At the Inova Schar Cancer Institute in Virginia, a shingled glass rainscreen acts as a permanent moisture shield and promotes energy efficiency by managing air infiltration and heat transfer.
Photo courtesy Greg McGillivray/Halkin Mason Photography

There are a ton of factors to consider. Building codes, costs, footprint, environment, construction teams, and many other choices have to be made. Adding demands on energy goals creates an extra challenge. Everything from roofing and façade materials to cladding has to be considered along with many of the building’s interior elements. Building owners also have their say in what they want included in the structure. Building design is like one big Rubik’s Cube, and factoring in energy demands adds another dimension to consider and solve. Like the solution to the pesky cube, every detail must align perfectly.

“The first step in designing a building is to find out what the goals are,” Overbey said. “What are we trying to accomplish with the façade? Then we have to talk about the definition of high performance. We will want to be better than the standard. But what is the standard? If we aim for a much higher percentage than the standard, what is the return on the investment?”

The envelope, please

In the quest for more energy-efficient buildings, architects usually tackle the envelope first. The primary objective is to ensure a tight envelope to keep out wind, rain, and moisture.

“The highest performance envelope is one without windows,” Overbey said. “Generally, glazing systems are the weakest links for energy efficiency, but what would a windowless building be like for users? Architects cannot overlook the human element of buildings for the sake of performance.”

In the earliest design stages, there is often debate about how much glass to include on a particular project. There is hardly a building in the world without windows. Windows are 10 times less energy-efficient than the wall area they replace, and an average home may lose 30 percent of its heat or air-conditioning energy through its windows.

“It is the tension of the two sides,” Overbey said. “You have to balance the human experience with the energy equation. The most well-insulated envelope is one that is basically a cocoon. It is important to find that sweet spot where you can specify a glass with a treatment that will also reduce the amount of heat transfer.”

Channel glass

Architects can enhance a building’s energy efficiency with channel glass. The material is preferred by some architects, as it requires minimal framing, which reduces thermal bridging. In buildings, thermal bridging occurs when conductive materials provide a bridge for energy to transfer across a thermal barrier. The bridge leads to energy loss and the potential for condensation. In colder climates, internal heat will seek to transfer to the colder side of the envelope, resulting in more energy needed to maintain room temperature. In warmer climates, exterior heat will seek to enter the envelope. Up to 33 percent of a building’s energy could be lost through thermal bridges.

Channel glass also adds insulation with its double-glaze assembly and insulation inserts that are inside the channels. It provides daylighting, thereby reducing energy demand.

At Franklin & Marshall College in Pennsylvania, Steven Holl Architects used a double layer of channel glass with translucent insulation in the school’s visual arts building. The channel glass traces the façade in vertical facets. The rest of the building envelope is either stucco or clear glass.

Translucent channel glass also provides soft illumination for art students working inside during the day and creating an ethereal aura at night.

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