There are three basic wall types, all of which can be made in essentially any shape, including: window walls, which include “closed” or four-sided fenestration openings; spandrels, which are common for parking structures and ribbon window designs; or column covers, mullions, and other customized shapes.

• Solid. Solid precast concrete walls contain no integral insulation, with walls being typically 4 to 8 inches thick. These traditional wall systems require an interior finish wall system with insulation to complete the envelope.

• Thin shell. This is a newer concept, with walls made by attaching as little as 1.5 inches of concrete to a back-up frame which, though typically comprised of metal studs, can also be produced in concrete. The two are then joined by thermally resistant connectors. The designer can specify a layer of insulation between the exterior concrete wythe and the back-up frame. The back-up frame system allows for drywall to be attached to provide the interior finish. Glass fiber-reinforced concrete (GFRC) precast concrete panels (typically about 1 inch thick of concrete) are another option in which a mix of concrete and glass fibers is sprayed into a mold. GFRC panels are another example of thin-shell systems, which are often used to produce intricate shapes. Thin shell systems allow for lighter weight and help reduce the size of foundations.

• Insulated sandwich wall panels. Typically including 2 inches or more of rigid insulation between two wythes of concrete, insulated sandwich wall panels provide high energy efficiency, meeting the continuous insulation requirements of ASHRAE 90.1, as well as an interior concrete wall that can be painted and used as the interior finished surface, avoiding the need for furring strips and drywall. Precast concrete's high thermal mass also minimizes energy consumption naturally. Historically favored for industrial buildings such as distribution centers and warehouses, sandwich wall panels allow a range of finishes and benefits that has expanded the component's applications to schools, offices, retail, residential, and other uses.

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