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The Push and Pull of Building Performance

Alan Scott

Energy codes are often thought of as bringing up the rear, preventing the worst from happening, but not as drivers of innovation. Randy Croxton, FAIA is famously quoted for his astute observation, “Building to code means that if the building were designed any worse it would be against the law.” Most energy codes include two compliance options; a prescriptive path and a performance-based approach. The prescriptive path sets minimum performance requirements for building components (windows, insulation, HVAC equipment, etc.) and assumes that if each is met, the building will save energy. The performance-based approach uses energy modeling to compare a baseline that meets prescriptive standards to a proposed design that offsets some lower performing components with others that exceed prescriptive minimums. 

Architects find the prescriptive path too limiting, and often opt for performance-based energy code compliance that allows, for example, specifying higher efficiency HVAC equipment as a tradeoff for more glass on the facade. Both compliance options have their limitations in terms of design, and in achieving desired energy reduction results. New, more stringent energy code requirements implemented in some states and cities have presented design teams and owners with new challenges that cannot be solved with business as usual.


Higher Standards

California has been one of the leaders in pushing energy efficiency and greenhouse gas (GHG) emission reduction through codes. The State’s current code, Title 24 2016 (T24), increased prescriptive component efficiencies, and introduced a new tool (CBECC-COM) for performance modeling that integrates T24 requirements with Energy Plus via Open Studio, adding more rigor to compliance efforts compared to previous codes with performance modeling using DOE-2 simulation. The 2016 codes also added mandatory envelop commissioning requirements to help ensure that enclosure components are installed correctly and working together to achieve the excepted efficiency. Some new construction must also be solar ready, with a dedicated, unobstructed solar zone equal to 15 percent of the total roof area (minus skylights), structure designed to support a solar array, and conduit pathways leading from the roof to the electrical room.

California was also the first state in the U.S. to adopt a mandatory green building code (CALGreen). It mandates measures that reduce the negative environmental and health impacts of buildings, mostly related to site design, water efficiency, material selection, and construction practices. Some California cities have set sustainability standards exceeding CALGreen requirements. For example, the San Francisco Green Building Code now requires all new buildings greater than 250,000 square feet to use available rainwater, graywater, and foundation drainage for toilet and urinal flushing and irrigation.

Perhaps the most interesting thing in California is not the current code, but what is coming. The California Energy Efficiency Strategic Plan includes a rule requiring all new residential construction to be zero net energy starting in 2020, followed by new commercial development in 2030, which is an aggressive goal that will require innovation and creativity in technology and design.

Similarly, New York City is adopting aggressive codes aimed at energy and GHG reduction. The City is introducing a voluntary “stretch energy code” setting low energy use intensity targets for buildings, leading to a possible code compliance requirement in 2025 based on predicted energy use targets. Starting in 2020, every large commercial and residential building in the city must post a letter grade (A to F) based on its Energy Star score on a sign near the building entrance, which will prompt both retrofits of existing buildings and a greater focus on efficiency in new construction.

Washington State and the City of Seattle now have some of the most stringent energy codes in the country. The 2015 code makes it difficult to design a building with more than 40 percent glazing, because the required HVAC system type (Dedicated Outdoor Air System) and increased HVAC efficiency makes it hard to wring more energy savings out of equipment to offset a lower performing envelope. Additionally, in Seattle, if the window-to-wall ratio exceeds 45 percent, higher glazing performance requirements (U-value and SHGC) and additional efficiency requirements kick-in. The Seattle code is also pushing a move away from fossil fuels in prescriptive compliance requirements, giving projects the option to use heat pumps for space heating, or to specify triple-pane glazing. The latter can be cost prohibitive, making heat pumps the de facto system choice.

While sustainability frameworks like LEED helped drive market transformation toward healthier and higher-performance building over the past two decades, we have not seen the universal adoption needed to fully address the broad environmental and climate impacts of buildings.

New Approaches

Typical energy codes address only a few of the many design factors that affect energy use in buildings, and ignore the operation and maintenance practices that influence actual energy consumption, resulting in buildings that pass based on components, but fail as a system, ultimately not achieving desired results. One of the most interesting remedies for this, championed by New Buildings Institute (NBI), is outcome-based code compliance. This compliance pathway was included in the 2015 International Green Construction Code (IgCC) and is gaining traction.

The concept is simple—energy use targets are set based on climate zone and building type, and compliance is determined based on actual performance for a 12-month period within 24 months of occupancy. Project teams benefit because it eliminates the focus on individual components, and supports increased flexibility and creativity in design and operational strategies to save energy. It also improves the chances of meeting a jurisdiction’s goals for energy use and GHG emission reduction. This approach still requires an energy model to demonstrate that the design can meeting the target, but compliance is based on actual performance. Outcome-based compliance does create a new set of challenges for enforcement. By the time the code jurisdiction knows if the building meets code, it is built and occupied for at least a year. New enforcement mechanisms such as “fee-bates” or performance bonds are needed, along with reasonable remedies to bring the building into compliance.

Seattle recently adopted an outcome-based code (Target Performance Path), that is gaining popularity because it allows greater freedom in envelope design and systems selection, in exchange for a pledge by the owner to achieve a prescribed Energy Use Index (EUI) target based on the building type. For example, an office building must achieve an EUI of 40 kBtu/sf/year based on actual performance over one year of operation. If the performance falls short of the mandated EUI, the owner must pay a fine, up to $4 per square foot for a variance of 30 percent or more. Half of the fine can be invested in corrective actions in the building to improve performance (retrofit or retro-commissioning), with the rest paid to the jurisdiction.

While sustainability frameworks like LEED helped drive market transformation toward healthier and higher-performance building over the past two decades, we have not seen the universal adoption needed to fully address the broad environmental and climate impacts of buildings. These frameworks have however served as a proof-of-concept for industry adoption of more aggressive performance-based efficiency standards. We are now seeing some codes moving from just preventing the worst practices, toward requirements that encourage creativity while challenging project teams to do better. I believe that more aggressive code requirements and novel compliance options, along with mechanisms like building energy report cards, will create a push and pull, spurring development of more efficient building components and innovation in design, thus hastening the necessary transition to low-carbon building.

Alan Scott, FAIA, LEED Fellow, LEED AP BD+C, O+M, WELL AP, CEM, is an architect with 30 years of experience in sustainable building design. He is a senior associate with WSP, in Portland, Ore. To learn more, visit and follow him on Twitter @alanscott_faia.