Precast concrete members are unique in that they are individually engineered products that can be detached and relocated, facilitating future additions to buildings. When future additions occur, non-loadbearing panels on the end simply are disconnected from the framing, and new panels and framing are added on each side. With the new addition in place, the original end panels can be replaced.

When ultimately removed from service, precast concrete members may be reused in other applications. Because it comes apart with a minimum amount of energy and retains its original qualities, precast concrete is also friendly to downcycling, a process in which building materials are broken down. Concrete pieces from demolished structures, for example, can be reused to protect shorelines, and recycled concrete is frequently crushed and used as fill or road base.

Material Efficiency

Significant efficiencies from both a construction and operational perspective are possible with precast building systems.

• Site efficiency. Factory-fabricated precast concrete minimizes or eliminates dust, waste, and truck traffic at the construction site. Only the needed precast concrete elements are delivered, with the resultant decrease in vehicular activity and noise particularly beneficial in urban areas. Unlike typical cavity wall construction, often comprised of a number of different products installed by different subcontractors, precast is erected by a single Tier-1 subcontractor. Scaffolding, lay-down space, material storage, and numerous subcontractors' field trailers are typically not required, greatly reducing the construction site requirements and environmental impact on adjacent site areas. Because precast concrete units are normally large components, greater portions of the building are completed with each activity, creating less disruption overall. Optimized structural members, spans, and other components lead to minimal material waste and associated economic and environmental savings.

Perhaps precast concrete's most dramatic benefit, though, may be the speed with which it can be designed, cast, delivered, and erected. Since the prefabrication process does not rely on other critical-path activities to begin, it can be started upon approval of drawings, ensuring components are ready for erection as soon as foundation work and other site preparation are completed, giving contractors a significant head start before the site is even available, and shaving weeks or months from the schedule. This flexibility also allows the building's shell, whether loadbearing or cladding, to be enclosed quickly which, in turn, lets interior trades begin work earlier and reduces overall construction time. The fast enclosure decreases concerns for weather or material damage during erection, reducing the contractor's risks and costs.

Because precast components are fabricated under factory-controlled conditions at the plant, harsh winter weather does not impact the production schedule or product quality, and often eliminates the need to add “cushions” to the timetable to accommodate unforeseen schedule creep due to delays caused by weather or site requirements. Precast components also can be erected through the winter months to meet a tight schedule, cutting overhead costs, reducing the possibility of cold weather-related change orders, and readying the building for faster occupancy.

• Energy and operational efficiency. Precast concrete has a high heat capacity, or the ability to slowly absorb and release large quantities of heat, contributing to a high-performance building envelope. Concrete's thermal mass allows it to react very slowly to changes in outside temperature—an advantage that reduces peak heating and cooling loads and delays the time at which these loads occur. The resulting savings can be significant—up to 30 percent of heating and cooling costs.

Another factor affecting the behavior of thermal mass is internal heat gain. This includes heat generated inside the building by lights, equipment, appliances and people; and heat from the sun entering through windows. Generally, during the heating season, benefits of thermal mass increase with the availability of internal heat gains. During the cooling season, thermal mass exposed to the building's occupied spaces will absorb internal gains, shifting peak cooling periods by as much as four hours, and dampening the overall cooling peak load. Concrete exposed to the interior, not covered by insulation and gypsum wallboard, works best to absorb internal gains, saving cooling energy.

Thermal bridging is also essentially non-existent with precast sandwich and thin-shell panels. Most connectors are made from composite or coated materials that do not thermally conduct. When combined with thermal mass and continuous insulation, precast concrete provides an extremely thermally efficient wall system.

The color, or albedo, of precast concrete panels can be used to improve the energy-conserving features of the walls. Panels with high albedo, meaning they are generally lighter in color, can help reduce the urban heat-island effect. Air infiltration, too, has significant effects on the amount of energy required to heat and cool a building, and large precast concrete panels have minimal joints, reducing uncontrolled air infiltration. Precast concrete is also an air-barrier and meets the requirements of the 2012 International Energy Conservation Code and ASHRAE 90.1.

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