Putting It All Together: Net Zero Operations
and Reduced Embodied Carbon
Houston Advanced Research Center
The Houston Advanced Research Center (HARC) is a “not-for-profit research hub providing independent analysis on energy, air, and water issues.” HARC collaborates with universities, private organizations, governmental agencies, and community groups to develop solutions to environmental issues and affect policy related to sustainability.
In 2014, HARC’s original campus no longer supported their mission and they sought to build a new headquarters that directly reflected its mission and served as a living example for regionally appropriate sustainable design in the Gulf Coast region. It was also essential that the design respect the financial realities of a not-for-profit research institution.
Minimizing Environmental Impact
Early integrated design sessions illuminated HARC’s project goals and their focus not only on operational energy efficiency, but also on minimizing environmental impacts due to the materials used within the building, including embodied carbon. While the project achieved LEED Platinum Certification under the current version of LEED at the time (LEED v 2009), Whole Building Life Cycle Assessment (WBLCA) was not included in the main body of the rating system. However, based on the owner’s interest in reducing embodied impacts, the team elected to pursue a LEED Pilot Credit that allowed the team to apply the LEED v4 WBLCA language in LEED 2009.
As is typical for most projects, HARC’s structural design team investigated different structural systems during the project’s schematic phase. However, atypically, the team also used a WBLCA tool to compare several structural systems and investigate which assemblies and subassemblies contributed the most to each environmental impact indicator and used those results to drive the design.
Strategy Behind Net Zero
As part of the schematic design, and to establish a benchmark, the design team first considered what would constitute a “typical” structural system for this type of building located in this region. In suburban Houston, a building of this size—two stories and 20,000 sq. ft—is frequently constructed of site-cast concrete perimeter bearing walls and interior steel framing. The plan dimensions of the building were set at 240 ft x 62 ft based on programming requirements and the desire to ensure that all spaces could effectively have access to natural light. For the bearing wall case this resulted in a single row of columns down the middle of the building with composite steel framing at the second level and steel bar joists at the roof. Belled drilled footings, bearing 15 ft below grade, and the bearing wall scheme required three lines of drilled footings.
The preliminary WBLCA run of a single bay of the building indicated that a significant amount of the global warming potential, or embodied carbon, was attributed to the concrete panels and the concrete foundations. Walter P Moore then developed an alternate steel framed scheme with wide-flange girders and composite steel beams spanning between the girders. This allowed the girders to be supported on two column lines with cantilevers to the exterior walls. This framing system, while slightly increasing the steel tonnage, allowed for the perimeter wall to be a non-load-bearing and framed from cold-formed steel studs that spanned continuously from the top of the perimeter grade beam to the underside of the roof. The continuity of the steel studs allowed a more efficient stud design and eliminated joints in the building envelop at the second floor level. The steel system also permitted the removal of one line of drilled footings. Drilled footings were only required below the interior column lines and the non-load-bearing perimeter wall was able to be supported on a perimeter grade beam—a strategy that resulted in a significant reduction in the total project concrete volume.
Lessons in Reducing Carbon
Modifying the structural and enclosure system and also refining the concrete mixes to use less cement, resulted in impact reductions in most categories and a 20% reduction in the carbon footprint without increasing the construction cost or schedule. Perhaps more significantly, these carbon savings occurred immediately unlike operational energy savings that build incrementally over the whole lifetime of a building.
The use of WBLCA to inform the structural and enclosure design of HARC’s headquarters provided the team additional insight regarding material sourcing and structural system choices and allowed the full design team to better understand the project’s embodied carbon. It also provided lessons that can be employed by other teams seeking to reduce embodied carbon.
- Establish Baseline representative of typical local construction practices
- Perform initial WBLCA and identify “Hot Spots”
- Perform schematic level WBLCAs of alternatives at component level
- Validate alternate assemblies, procurement premiums (if any) with material suppliers
- Require suppliers to provide Environmental Product Declarations (EDPs)
- Update LCA model based on as built conditions
WBLCA allowed the team to understand the full impact of the building and push as close to a zero-carbon building as possible. In fact, in 2018 HARC received a grant to place additional photovoltaic panels on the roof, an added capacity that exceeds the building’s annual electrical demand. The surplus renewable energy will be fed back into the grid and allow the project to begin to offset the emissions associated with the materials used to construct the building—bringing the zero-carbon goal closer than ever.
- LEED Platinum
- 2017 Engineering News Record (ENR) Texas and Louisiana Best Project
- 2018 Houston Business Journal Landmark Awards finalist
- Gold Level (highest level) APEX Award from the Association of General Contractors of America (AGC) Houston Chapter
- 2018 AGC Award: Office Building: Under $20M
- 2019 ULI Houston Development of Distinction Non-Profit Winner
- 2019 Project of the Year – US Green Building Council Texas Chapter