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What Are Outcome-Based Codes?
July 7, 2011
Let’s start with the traditional code model. Say a building needs to comply with the ASHRAE Standard 90.1-2007. The building team will choose a prescriptive or performance-based path to compliance and the engineer will create a model based on the building’s design and systems. If the model meets the code, engineers will get it approved and voila, the building is in compliance. But there’s almost never any follow-up to see if a building actually performs even remotely close to its predicted model.
As David Hewitt, executive director of the New Buildings Institute analogizes, it's like telling a runner what shoes and shorts to wear, and approximately how fast s/he should run to meet a goal, but then never measuring the time at the end.
Outcome-based codes, however, are based on design, construction, commissioning AND operations, instead of just the first three. They force building owners to measure and monitor the ongoing performance of a building. In other words, they actually clock the time it took for the runner to run a race to see how all the other pre-race strategies worked.
Outcome-based codes, especially within the context of net-zero energy buildings, are the future of codes, according to Hewitt. California, as one example, has set a target of 100 percent of new buildings and 50 percent of existing buildings be net-zero energy by 2030. The only way to effectively regulate that is with an outcome-based code. Currently, the City of Seattle is working with the Preservation Green Lab and the New Buildings Institute on a pilot outcome-based code for existing and historic buildings.