Although the more common approach to construction deals with adhering to a specific set of details and getting them confirmed by an inspector, there could be a better way. Performance planning-based construction can give builders and architects more choices, which in turn can create a more energy-efficient final project.
"It has been our experience that the majority [of builders] go prescriptive," writes Ekotrope, a company that makes energy simulation software. The prescriptive path has always made sense for many builders: there's no need to change architectural designs or purchasing processes. Should this prescriptive process be replaced by a performance path?
The Benefit of Software Simulation Options
When a design is being created, the performance path allows the builder or architect to choose from a wide range of variables—insulation, windows, solar orientation, air sealing, mechanical systems, and more. Any combination is fine as long as the result is a home that will use less energy than the code maximum. These variables are entered into simulation software such as Ekotrope, REScheck, or REM/Design, which then estimates the home's annual energy use.
“We model everything," says Gaithersburg, Md., architect John Spears, who uses REM/Design. He says the software lets him plug in different choices, such as using a better window, and he can then compare the savings to the upgrade cost.
Increasingly Common
While the performance path's flexibility makes it popular among high-performance builders and architects like Spears, some observers see its use growing everywhere. "There's a movement toward more of a performance approach," says Jason Kantola, coordinating certification manager with JELD-WEN. "For instance, British Columbia is already performance path only, and California seems to be trending in that direction. I wouldn't be surprised if other states and provinces follow."
Some builders aren't waiting for mandates to make the switch. "We've been successful at moving every builder we work with to the performance path," says Robby Schwartz, principal at EnergyLogic, a Colorado energy consultancy. That movement started in 2009 when the code began mandating R-20 walls for the prescriptive path, which would have required builders to upgrade from 2x4 to more-expensive 2x6 walls.
"We showed them how the performance path would let them meet code with 2x4 walls," he says. The exact features used would vary by house, but options might include higher R-value spray foam or better windows. "They would save money and wouldn't have to re-engineer their structures."
Of course, that was 10 years ago, and codes have gotten stricter. Subsequent updates have made it impossible to comply using 2x4 walls. But Schwartz says that builders can still save money by using the performance path to find the most cost-effective blend of features. "We show them the most cost-effective ways to meet the code's intent and help them change their specs to get there," he says.
Installation Requirements Matters
One caution is that while software simulations will get you a building permit, the details still need to be inspected. You have to build to the approved plans.
You also have to follow the code's installation requirements. "Insulation R-values can be traded off, but how you install insulation can't," Schwartz says. There are installation requirements for batts, attic baffles, and other details. The occupancy permit will still require final testing—specifically, blower door and duct leakage tests.
By following the performance path to code compliance, builders can enjoy both design flexibility and significant financial returns. "We've seen savings of up to 4 percent in construction costs after factoring in our fees," Schwartz says.
For assistance with your projects, including code compliance, visit JELD-WEN’s professional portal.
