Through the use of concrete and other green elements, the Bethel Commercial Center, a mixed-used transit center in a low income neighborhood on Chicago’s west side, is expected to use 50 percent less energy than conventional construction. The building has been designed to achieve a LEED® Gold rating.
Bethel Commercial Center depends on an insulated concrete wall system to minimize energy use, reduce noise transmission and create a durable structure. The walls are constructed from a core of expanded polystyrene (EPS) foam insulation, like styrofoam coffee cups, strengthened by a reinforcing grid. The foam insulation is then encased in shotcrete, concrete that is dispensed from a hose at a high velocity. The concrete covers the foam and hardens to form a reinforced wall with built-in insulation. It’s all done without conventional formwork.
Such walls have high thermal mass, which limit temperature fluctuations through the day, reducing heating and cooling loads. Basically, the mass of the concrete acts like a holding tank, slowing down the passage of heat from inside to out and the reverse.
The reflective concrete ceiling, along with lightshelves and sunlight shafts, reduce energy use and air conditioning load.
The wall system also contributes to the building’s durability, decreasing air and moisture infiltration, and reducing the use of steel supporting lintels, which can rust. The walls have a two-hour fire rating, and resist water, mold, mildew, and rot as well as insects and rodents. In addition, the walls reduce sound transmission—especially important since Chicago’s elevated train system runs less than 10 feet from the building.
The underside of the precast concrete plank floor serves as the finished ceiling, eliminating the need for additional finishing and materials to construct a drop ceiling. Also, a reflective coating of white paint is applied to the smooth concrete ceiling, which increases the penetration of sunlight into the building. This facilitates the literal harvesting of daylight, reducing lighting energy and air conditioning loads. Concrete is a critical part of an integrated system that uses 50 percent less energy than a merely code-compliant building of the same program and configuration.
In addition, the cast-in-place concrete used in the foundation includes recycled fly ash, a by-product of energy production that would otherwise fill landfills.
The building, which will house a childcare center, employment training facility, and transit-oriented retail stores, has a direct bridge connection to the city commuter train station.