Rachel Calafell, PE, is a Principal in the Structures Group at Walter P Moore. The following piece is an excerpt from the report, Embodied Carbon: A Clearer View of Carbon Emissions.
Overview
REDUCE, REUSE, RECYCLE; three pervasive words related to consumer products. This hierarchy also applies to the built environment since one of the most effective ways to reduce embodied carbon is to reuse a building rather than construct a new one. This not only saves the emissions associated with extracting and installing new materials, but also significantly reduces the waste produced in demolition.
Unfortunately, while building reuse is environmentally beneficial, it can present significant hurdles for the design, permitting, and construction processes. Due to development patterns, there may not be available space where the demand exists, often making location the first challenge. Even when a building is in the right location, there can be many other challenges such as changes in code provisions, societal desires for space quality, or required performance characteristics (floor rating, HVAC system, space layout). To make effective use of existing buildings, we must find strategies that allow us to efficiently renovate existing buildings and save the emissions sequestered within our building stock. The estimated $72 million renovation and expansion of the 270,000-square-foot Sears department store in Houston’s Midtown into South Main’s Innovation District (The Ion), illustrates some of the challenges—and solutions— that are required to achieve these goals.
In 2017, Rice University’s endowment company bought out the remaining years of Sears’ 99-year lease for the property which Rice Management Company, owns. Designed to bring Houston’s entrepreneurial, corporate and academic communities together into collaborative spaces and programs, The Ion will support businesses at all stages of the innovation life cycle and provide resources for Houstonians seeking to participate in the innovation economy as a part of the South Main Innovation District.
The transformation from a retail store to an innovation hub pays homage to the original art deco style of the 1939 structure, particularly at the ground-level storefront. To vertically expand the existing three-story structure by two additional floors, most of the existing spread footing foundations will be strengthened. The existing roof framing has insufficient load capacity to serve as an occupied floor, so new framing will span over it directly to column locations. An additional challenge to repurposing the building includes infilling the existing stairs, elevators, and escalators while framing new stairs and elevators based on the ideal circulation patterns. Introducing daylight into the “concrete box” department store to transform it into a center for technology innovation involves new multistory punched openings in the exterior concrete walls and a new center lightwell angled through the building. Retrofitting the existing structure to accomplish these goals was made more difficult by the fact that the renovated structure will generally not have ceilings and the structural elements will remain exposed. The approach to each retrofitted area had to maintain the aesthetic of the existing exposed concrete flat slab structure with drop panels at each column.
While reusing and repurposing existing buildings is highly effective at reducing embodied carbon, it poses numerous structural challenges. However, it can effectively address challenges while still delivering elegant, redefined buildings.
