 In Europe, homes with precast concrete walls have been built for more than two decades. In the U.S., its use is spreading into residential construction now that precast concrete structures such as buildings, parking garages, and bridges are commonplace.
Precast systems can adopt almost any aesthetic, incorporating a variety of colors and textures, or emulating natural stone. By crafting systems that not only look great, but also act as structural walls and support floor loads, builders and designers can reduce material redundancy—and project costs.
To build a precast concrete home, concrete plants use the house plans from the builder to produce all exterior walls, complete with embedded steel reinforcing, electrical wiring and rough openings, and foam insulation. The panels are then transported to the homesite and lifted into place by cranes. Workers are connect the panels to the foundation and each other.
As with all concrete wall systems, precast concrete homes have many attributes that contribute to "green design." Precast wall systems provide environmental benefits during construction, after occupancy, and if the home is demolished.
Environmental benefits during construction
- Waste Minimization. By manufacturing precast panels in a controlled factory setting, less material is required because precise mixture proportions and tighter tolerances are achievable. Additionally less concrete waste is created due to careful control of quantities of constituent materials. The factory setting also allows waste materials to be more readily recycled. Sand and acids for finishing surfaces are reused as are steel forms.
Since the exact amounts of components are delivered to the building site, construction waste is reduced. Any spare components can be recycled by the manufacturer, and their materials used again in another structure.
- Locally Sourced Materials. The manufacturing process of portland cement, the binding element of concrete, is not tied to a certain region of the country and the materials involved in the process are readily available throughout North America.
- Use of Recycled Components. Precast panels can incorporate recycled supplementary cementitious materials like fly ash and slag cement in two ways.
First, portland cement is often produced by including recycled industrial byproducts such fly ash into the manufacturing process to minimize dependence on virgin raw materials. Additionally, fly ash, slag cement, silica fume, and recycled aggregates can be incorporated into concrete, thereby diverting materials from the landfill and reducing use of natural resources.
- Less Community Disturbance. Less dust and waste is created at a precast concrete construction site because only the needed concrete elements are delivered; there is no debris from formwork and associated fasteners.
Construction time for a precast home can be up to 30% less than for a traditionally constructed home. The panels can be erected in any weather, so interior work is not delayed. Fewer trucks and less time are required for precast concrete construction; particularly beneficial in urban areas where minimal traffic disruption is critical.
During the life of the structure
- Energy Performance. Houses constructed with precast panels achieve energy savings by combining the thermal mass of concrete with the optimal amount of insulation in precast concrete walls. Compared to wood and steel, concrete structures allow minimal temperature fluctuations. Consequently, heating, ventilating, and air-conditioning can be designed with smaller-capacity equipment, saving money and resources. Additionally the wall acts as an air barrier, reducing air infiltration and saving more energy.
- Disaster Resistant. Precast walls offer high durability and strength They are resistant to fires, wind, hurricanes, floods, earthquakes, wind-driven rain, and moisture damage. The use of precast concrete can even reduce fire insurance rates.
- Cool. Light- or natural-colored concrete reduces heat islands, thereby lowering outdoor temperatures, saving energy, and reducing smog.
- Indoor Air Quality. Precast concrete has low VOC emittance and does not degrade indoor air quality.
- Recyclable. Precast concrete structures in urban areas can be recycled into fill and road base material at the end of their useful life (about 5% to 20% of aggregate in precast concrete can be recycled concrete).
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