Unitized Curtainwall

In strictest architectural parlance, a "curtainwall" is any non-load-bearing exterior wall that hangs (like a curtain) from the face of floor slabs, regardless of construction or cladding material. However, in common usage, the term curtainwall usually refers to aluminum-framed systems carrying glass, panels, louvers, or occasionally, granite or marble.
 
"Stick" curtainwall systems are shipped in pieces for field-fabrication and/or -assembly. These can be furnished by the manufacturer as "stock lengths" to be cut, machined, assembled, and sealed in the field, or as "knocked down" (KD) parts pre-machined in the factory, for field-assembly and -sealing only. All stick curtainwalls are field-glazed. Frame assembly requires the use of either, a) "shear blocks" to connect vertical and horizontal framing elements, or b) "screw-spline" construction, in which assembly fasteners feed through holes in interlocking vertical stacking mullions into extruded races in horizontals.
 
Performance of any field-assembled or field-glazed curtainwall is only as good as field workmanship allows, limited by variables such as weather, access, and job site dirt and dust. Many critical seals are necessary, even in systems that are designed to drain or "weep" rain penetration from the system back to the exterior.
 
To accomplish as many of these critical seals as possible in controlled factory conditions, and minimize dependence on scarce and expensive field labor, "unitized" curtainwall systems have been developed.
 6250i HRX
Unitized curtainwalls are factory-assembled and -glazed, then shipped to the job site in units that are typically one lite wide by one floor tall. Only one unit-to-unit splice (usually a silicone sheet or patch) needs to be field-sealed, and only one anchor per mullion needs to be attached to the face or top of the floor slab. Interlocking unitized curtainwall frame members are weatheripped to seal to one another, both horizontally and vertically. This accommodates thermal expansion and contraction, inter-story differential movement, concrete creep, column foreshortening, and/or seismic movement. Most unitized curtainwall systems are installed in a sequential manner around each floor level, moving from the bottom to the top of the building.
 
CHOOSING BETWEEN STICK and UNITIZED CURTAINWALL SYSTEMS
Selection Criteria
Stick Curtainwall
Unitized Curtainwall
Project Size
Small
Large
Wall Configuration
Complex
(Many changes in plane, e.g. soffits, corners, etc.)
Repetitive
(Large expanses of flat wall)
Joint Pattern
Random
Uniform horizontal sill line
Glazing
Field
Factory
Inter-story Movements
Very limited
Inter-locking frames accommodate movements
Quality Control
Subject to site variables
(Both environment and equipment)
Controlled factory conditions
Modification
Can be cut-to-fit in the field
Pre-engineered
Sealing
Subject to site variables
Minimal field sealing
Field Labor Cost
High
(Many parts to track and assemble)
Low
Field Labor Duration
Slow
Fast
(Often setting 75 sqft or more per unit)
Access and Safety
Exterior access required
Set from the interior
(Exterior optional)
  Syracuse Newhouse
. Wausau market managers are available as architectural support resources, and can be reached at education@wausauwindow.com, healthcare@wausauwindow.com, or government@wausauwindow.com.
Featured Project
  University of Colorado Research Complex Phase 2 
 University of Colorado Medical Research Facility
Location: Denver, Colorado
Architect: Fentress Architects
Product(s) Used: Curtainwall and window systems