The Ins and Outs of Unitized Storefront Systems
May 31, 2014
A glass and aluminum storefront or curtain wall that is fabricated and installed as a panel system is referred to in the industry as a unitized system. Until now, unitized systems have only been used for curtainwall high-rise and multi-story building applications. However, the industry has increasingly demanded unitized storefront systems for largescaleapplications. This has led to further development of complete unitized storefront panels—or units—that can be easily delivered to the field for installation.
Unitized storefront systems utilize the same operational and water management mechanisms as traditional storefronts. Water is diverted to a sill flashing (or can) and directed out through weep holes at the bottom of the system. Unitized storefront systems are typically installed in multi-level, floor-to-floor, straight single floor runs, and punched openings. Some manufacturers even design floor slab covers that can give unitized storefront exteriors the appearance of a curtain wall, when in fact they are installed floor to floor. Unitized storefront systems are available in center and front load 2-inch by 4 ½-inch panels and front load 2 ¼-inch by 6-inch and 2-inch by 6-inch units that have the option to be thermally broken.
Unitized storefronts feature the same design elements as stick-built storefront systems, including aluminum mullions and panel-mounted IGUs in prefabricated aluminum frames. However, instead of assembling the glass and aluminum storefront in the field, all unitized system components are cut to their appropriate sizes and assembled in a controlled shop environment. They are then sealed according to the manufacturer’s instructions and screwed together. Once the frames are assembled, they are glazed either standing up or lying flat on saw horses. This ultimately promotes quality assembly procedures, faster fabrication and a more efficient installation. The units are now ready to be packed or crated, and transported to the job site.
Unitized storefronts are designed to be assembled and installed on the building as panels. Once the units are delivered to the job site, the bottom receivers (or flashing) must be properly installed. At this point, the aluminum mullions should already be fabricated as half sections instead of tubular sections so they can mate during installation to form the unitized system. The panels should then be installed in a sequential manner, interlocking one panel into the next. Make sure to follow the manufacturer’s instructions for sealing and anchoring the system, which might require additional equipment depending on the size of the individual panels.
|CRL-U.S. Aluminum Series TT601 Top Notch Unit Glazed Window Wall System with slab edge covers and Series 250 narrow stile entrance doors|
It is important to have an excellent and well-coordinated project management team in place when designing and installing a unitized storefront. The process begins with meeting the general contractor to review the project site to ensure sufficient rough openings for the storefront. Next, the project manager should coordinate with glazing shops, submittals, and the approval for assembly and installation. Once approval and rough openings are established, the project manager’s job is to work with the vendors to procure glass, storefront units, caulking, anchors, and even arrange for transportation throughout the project. Securing a good project manager is the key to a successful unitized storefront installation.
Key information to remember
Clients, architects and glazing contractors alike can benefit from fast installation and lower field costs that unitized storefront systems can provide. These economic benefits are especially evident on large-scale projects that would normally require a substantial field labor budget and a longer project timeline.
When assembling and installing standard storefront systems, field labor costs can consume 70 percent to 80 percent of the project’s entire labor budget, which can increase the risk of damaging the glass or causing leakage. Seventy percent of the labor takes place in the shop when assembling a unitized system, keeping costs down. The controlled shop environment minimizes the risk of accidental damage to the system.
Unitized storefront systems require a glazing contractor to have a facility large enough to fabricate, assemble and possibly store the completed units. Overhead cranes and forklifts are required for moving, packaging or crating storefront panels, especially when working on large projects. Because every storefront panel is assembled separately, multi-story buildings require a substantial amount of preparation. Careful planning, scheduling and storage are needed for projects of this magnitude.