Posted on March 24, 2021 by Bob Geil
The marriage of precast concrete and masonry has existed since the mid 1960’s. The combination of these two trades brings together all the benefits of precast concrete and the timeless beauty and character of hand-laid masonry.
Insulated precast concrete wall panels with a thin-brick exterior have many advantages over traditional masonry cavity walls. First, they eliminate the need for large on-site masonry crews, which in turn reduces the negative impact on a project’s schedule caused by the time-consuming field labor of meticulously building a cavity wall system. The precast wall panels can be manufactured while the site work and foundations are being completed to create a just-in-time strategy to finish the wall system ahead of schedule. The precast just-in-time approach is much faster than traditional masonry cavity wall construction. A wall that takes a field masonry crew weeks to build can be done in days with a precast field installation crew. Indoor plant-controlled conditions provide year-round quality work without delays caused by adverse weather conditions. Furthermore, an insulated precast concrete wall can be designed as a fully insulated envelope system, unlike masonry cavity walls which have many compromises in the insulation envelope.
An insulated precast concrete wall panel with a thin-brick exterior and a masonry cavity wall may look identical, but how they are built and how they perform are very different. Insulated precast concrete wall panels are manufactured in a precast concrete factory and are built in an assembly line process with established quality control measures.
The precast panels are cast on long casting beds where multiple panels are built simultaneously. The first step in the manufacturing process happens when the thin-brick material is laid into the casting bed. The thin-brick is set into a plastic liner that holds them in place and also creates the mortar joint. Once the thin-brick is set, reinforcing is added into the form and a 3” to 4” layer of high-strength concrete is poured over the thin-brick. The thin-brick is encased in a layer of concrete that creates the mortar joints and an exterior protective shell for the insulated wall panel.
The next step is to place 3" to 4” of board insulation over the exterior concrete layer, then non-conductive fiber ties are screwed through the board insulation that penetrate into the recently poured face layer of concrete. The ties extend above the board insulation to secure the exterior concrete face layer to the concrete backup structural layer of the panel.
The final step in the process is to add the reinforcing for the backup structural layer and then pour 4” to 6” of high strength concrete on top of the board insulation. Because the casting beds are steam cured, the panels can be stripped from the casting beds within a few hours and shipped to the job site after some cleaning and detailing.
The wall panels are delivered to the jobsite on flatbed trailers and installed immediately with a crane. Typically, a precast installation crew of six to 10 people can install 12 to 14 wall panels each day. Once the wall panels are installed, the panel-to-panel joints are sprayed with foam insulation and caulked to create a high-performance, water-tight wall system with a continuous insulation envelope.
In contrast, a traditional hand-laid masonry cavity wall is constructed in the field with two masonry walls separated by insulation and an air space. The exterior face of the wall is constructed of brick and the interior wall is constructed of masonry block. The two walls are tied together with metal ties that break through the insulation. This creates a thermal break and a major source of energy loss. Furthermore, the cavity air space collects water. Elaborate flashing, weeping and venting details are required to ensure the water can escape the cavity. The moist environment of the cavity diminishes the performance of the insulation, thus reducing the walls energy performance.
Energy performance is becoming more important in the design of buildings, and with the future of energy codes headed towards Net Zero energy use, inefficient traditional construction methods, such as cavity wall masonry construction, will be replaced with other more efficient wall systems.
The good news is a precast concrete insulated wall panel envelope system delivers superior energy efficiency, shortens the construction schedule and provides all the elegance of traditional hand-laid masonry.