Photo © Robb Siverson. Photo courtesy Tubelite Inc.
Screw-spline assembly
The screw-spline assembly method utilizes integral splines within the horizontal extrusions. This eliminates the need for shear blocks. Vertical mullions are two-piece interlocking extrusions. Horizontals are attached to the verticals using a screw through the vertical into the screw-spline in the horizontals to form pre-assembled ladders in the shop or field.
Water management
Each lite of glass within the curtain wall is sealed, thereby creating individual zones to manage water infiltration. Water entering the framing system is contained within the glass pocket at the bottom of each glass lite and drained to the exterior through weep holes. These holes are positioned in the upper portion of the pressure plate, and at the bottom leg of the face cap, or ends of the covers.
In equalized pressure conditions, the exterior glass and aluminum faces act as a rainscreen, diverting water. The interior glass face and aluminum glazing pocket are connected by gaskets, which act as an air barrier. Water entering the glazing pocket exits via the weep system.
To minimize infiltration issues, the air barrier system should be tied to the curtain wall and other fenestration products. These systems should be installed prior to insulation and façade cladding.
Depending on the project’s size and schedule constraints, the glazing contractor may prepare the curtain wall in its own facility and then ship the units to the jobsite, or it may have the materials sent directly to the jobsite in sequential phases for onsite installation. It is essential to coordinate the curtain wall installation in conjunction with all other building trades.
Customization and compatibility
Standard curtain wall systems can be customized by incorporating a variety of glazing and infill panels, integrating other solar control and fenestration products, and finishing the framing in unique hues and school colors.
Glass
The curtain wall’s design needs to account for the glass width. This may extend from 6 mm (1/4 in.) to triple-thick glazing. Generally, an insulating glass unit (IGU) measures 25 to 44 mm (1 to 1.75 in.).
Glass types should be considered separately for each orientation of the building, and when it is possible, with respect to each room’s unique function. As examples, a classroom’s viewing areas would commonly be located at eye level, a laboratory may prefer daylight-only areas where all the fenestration products are closer to the ceiling to avoid glare on instruments and monitors, or a library’s south-facing elevations may require higher performance glass to block more of the direct ultraviolet (UV) radiation and solar heat gain.
Glass selection can be fine-tuned to views, daylight, energy-savings, and comfort by balancing visible light and sound transmission along with managing unwanted solar heat gain, thermal transmission, and condensation resistance. For high-performance and specialty glazing options, additional choices include hurricane-impact resistance, ballistic, blast hazard mitigation, anti-eavesdropping, electrochromics, photovoltaics (PV), and bird-friendliness.
Infill and integrated components
Glass is the most popular infill for curtain wall systems, but not the only option. These aluminum-framed systems can also incorporate metal composite panels (MCPs), masonry, or louvers. In addition to different infill material, curtain wall also integrates and connects with other fenestration products.
Storefront
On multi-story buildings, economical storefront systems are installed on the ground level. It can also be installed in limited applications up to the third floor.
Ribbon window
Typically installed between the floor slabs, ribbon window products are used in ‘punched’ openings, or as a connected ‘ribbon’ of horizontal windows.
