With the federal government requiring all federal projects to meet the energy targets of the 2030 Challenge, which aims for net zero energy to be achieved by 2030, it's no surprise that architecture firms are seeing an increased interest in net zero across all industry sectors. And, as the interest in building to net zero standards grows, there are more opportunities to showcase the benefits of using metal products.
“We are seeing an increasing number of pilot projects seeking to better understand what it takes to design to net zero energy,” says Greg Mella, FAIA, LEED AP BD+C, director of sustainable design at SmithGroupJJR, Washington, D.C. “The most basic reason is that people understand that it is possible to reach this once-lofty target. Clients who want to ‘walk the talk,’ are often clients whose mission includes a focus on sustainability. They now realize that net zero is the new LEED Platinum-the bar that should be reached to demonstrate one’s leadership in sustainability.”
The Building Envelope
Net zero energy buildings start with strong energy conservation design, rather than energy generation. James Theimer, AIA, LEED AP BD+C, principal architect at Trilogy Architecture in Redding, Calif., says energy conservation begins with designing the building envelope to interact with maximum efficiency within the climate in the area where they are building. “Since we are looking for materials that aid in the reduction of energy, that means a roof and walls that reduce heat gain in the summer, provide better insulation, and allow for a
‘breathable’ building,” he explains. “We look for materials that allow the building to work with the environment, rather than just be a barrier to it.”
“For most buildings, designers start by reducing the demand for energy by designing thermally efficient exterior envelopes, so insulation with high R-value is critical, as are window glazing systems with strong thermal properties,” Mella says. “Envelope design also typically seeks to minimize infiltration by including comprehensive air barriers. When designing active systems, we often look at overall performance efficiencies, selecting systems that balance efficiency and initial investment.”
Kevin B. Miller, AIA, principal at Salt Lake City-based GSBS Architects, says the building envelope is a really critical piece of the puzzle, since it’s where you risk losing energy. Radiant heat from the sun coming into the building can Metal products support net zero goals increase the cooling load, or for example, when you’re trying to keep up with the heating in an office building, you’re losing energy in the other direction.
Materials Matter
According to Mella, materials are about half the solution toward achieving net zero energy buildings. “Materials should have good thermal properties and high performance efficiencies,” he says. “The other half of the solution is the actual form, orientation, fenestration, and massing of the building.”
“Our principal goal is choosing materials that won’t contribute to heat gain or heat loss to better integrate them in an energy model,” says Manuel Oncina, architect at Manuel Oncina Architects Inc., La Jolla, Calif. In this case, he says metal wall and roof panels are good materials because they reflect heat and do not contribute to the heat load of the building.
Miller agrees, saying, “We’re looking for the kind of things that support driving the energy use down. We like envelopes that are incredibly tight. We like materials that do multiple things for us.”
“Every material we consider for use in our buildings is reviewed against the filter of cost versus durability, with benefit–or potential harm–to the environment at the top of our list,” Theimer explains. “Metal does tend to check all of these boxes for us. It is durable with little or no maintenance needed compared to exterior wall and roof systems with a lower initial cost, so over the life of the building, it makes sense financially.”
“Metal panels are often a good choice for sustainable buildings because metal has a high recycled content, but also can easily be disassembled and reused/recycled,” adds Mella. Metal panel systems are highly durable and are available with a high solar reflectance index (SRI), which can reduce energy loads and minimize the urban heat island impacts. “Metal does have very high thermal conduction, so it should be carefully detailed to minimize thermal bridging between the exterior and interior,” he adds.
Theimer notes that with metal roofing, energy conservation can easily be accomplished if both architect and client agree that energy considerations are as important as aesthetics when looking at roof slope and color. For metal wall panel systems, he believes they are ideal for rainscreen systems, creating better building insulation from extremes of temperature.
The benefits of using metal wall and roof panels go beyond energy considerations, Oncina says. They “include strength, durability, watertightness, ease of transport, availability of craftsmanship and relative cost-value ratios,” he adds.
Photovoltaics and Net Zero
In addition to a tight building envelope, on-site renewables, such as photovoltaics, are essential to net zero buildings. “For many net-zero buildings-especially those in dense, developed areas or those with limited solar availability-specifying the most efficient photovoltaic is necessary, recognizing these come with a premium,” Mella explains. “For projects with ample solar availability, less efficient photovoltaic panels may suffice.”
Miller likes to say, “Any building can be net zero. That isn’t the challenge. The trick is to reduce the energy use as much as possible so that the money you spend on renewables doesn’t blow your budget.”
Metal roofing is suited for these instances, since photovoltaic panels can be attached directly to the roofing seams without penetrating the roof assembly below. Metal roofing also tends to be used in sloped applications, where photovoltiacs are most efficient when oriented in a south-facing slope. As such, Mella says photovoltaics can be integrated into a metal roof seamlessly without incurring the added costs of a racking system.
A 21st Century Building Material
“We think of metal as a 21st century building material, and we think of net-zero the same way,” Theimer explains. “But it’s a contemporary design element, so it’s important to realize that many of our clients still feel more comfortable with the appearance of traditional building materials. As architects, we tend to view design with an eye toward the exciting and dramatic-while often our clients think of design it more in the nature of comfort food. Interestingly, using net zero as a reason for using metal, especially in the use of wall systems, now provides a more compelling argument than ever before to the client who may be inclined to be more traditional.”