Window wall is the dominant glazing system for Florida's multifamily tower market — and one of the most consistently misunderstood. Many GCs use "curtainwall" and "window wall" interchangeably. They're not the same, and the difference affects your structural coordination, schedule, budget, and code compliance from day one.
Window Wall, Curtainwall, and Storefront: A Direct Comparison
| Feature | Storefront | Window Wall | Curtainwall |
|---|---|---|---|
| Load path | Top and bottom of opening to structure | Bears on floor slabs, slab-to-slab | Anchored at slab edge, cantilevered |
| Typical span | Up to 12–14 ft single run | Multi-story, slab-to-slab | Multi-story, multi-span |
| Primary market | Retail, lobby entries | Multifamily, mid-rise hotel | Office, institutional, high-rise |
| Installed cost (FL) | $45–$90/SF | $80–$160/SF | $150–$350+/SF |
| Engineering complexity | Low–moderate | Moderate | High |
Types of Window Wall Systems
Stick-Built Window Wall
Stick-built window wall is installed piece-by-piece in the field — verticals, horizontals, and glass are installed sequentially after the system is set on the floor slab. It's the most common choice for Florida multifamily projects because it's compatible with the concrete tolerance conditions typical of post-tension slab construction, allows field adjustment at each floor, and requires less upfront engineering than unitized systems. The tradeoff is longer installation time per floor compared to unitized.
Unitized Window Wall
Unitized window wall assembles complete floor-to-ceiling units — framing and glass together — in the factory, then installs them as complete panels on site. Installation is faster once fabrication is complete, and factory glazing produces more consistent quality than field glazing. Unitized is more common on larger, schedule-driven projects where the upfront engineering and fabrication lead time is offset by faster installation. The higher unit cost compared to stick-built is often recovered in labor savings on high-rise projects with 200+ units.
Hybrid Systems
Some window wall systems use factory-fabricated frames with field glazing, or combine unitized spandrel panels with stick-built vision glass. Hybrid approaches can optimize for specific project conditions — schedule constraints, budget targets, or configuration complexity.
Florida Code Requirements for Window Wall Systems
Wind Load
Window wall systems in Florida must be engineered and tested to resist the design wind pressures for the building's location and exposure category. The Florida Building Code references ASCE 7 for wind load determination. For coastal projects, exposure category D applies — the most severe. Component and cladding pressures for window wall on a mid-rise coastal building can reach ±80–100 psf in high-wind zones, significantly higher than equivalent inland projects. The product approval (FL PA or Miami-Dade NOA for HVHZ) must cover the design wind pressure for the specific location and floor height.
Water Penetration Resistance
Florida's Building Code requires window wall systems to resist water penetration at a test pressure of 15% of the positive design wind load, minimum 6.24 psf, under ASTM E1105. The drainage design within the system — weep holes, drainage planes, and sill flashing — is critical. On concrete-frame construction, the interface between the window wall sill and the concrete slab edge is a primary water infiltration risk; this condition must be detailed and sealed correctly per the approved shop drawings.
Thermal Performance
Florida Energy Code (ASHRAE 90.1 or Florida-specific compliance path) sets maximum allowable U-factors and Solar Heat Gain Coefficients (SHGC) for fenestration. Florida's climate zones 1 and 2 (South Florida) have among the strictest SHGC limits in the nation — typically 0.25 SHGC or lower on projects using prescriptive compliance. Window wall systems must meet these requirements as part of the energy compliance documentation, which is reviewed and approved at plan review.
Design Considerations for Florida's Climate
Solar Heat Gain
Florida's solar intensity is among the highest in the continental US. West- and south-facing window wall exposure on a high-rise building can generate substantial heat gain that drives HVAC sizing and operating costs. High-performance solar control glass — products like Guardian SNX 51/23, Viracon VNE-63, or Vitro (formerly PPG) Solarban R67 — significantly reduce SHGC while maintaining visible light transmission. Specifying the right glass for each facade orientation is more important in Florida than almost anywhere else in the country.
Coastal Salt Exposure
Window wall systems within a mile of the coastline face accelerated corrosion risk. Aluminum framing handles salt exposure well when finished correctly — Class I anodize (0.7 mil minimum thickness) or fluoropolymer paint (Kynar 500 or equivalent) are the appropriate finish choices for coastal exposure. Standard Class II anodize or low-quality paint systems will fail prematurely in South Florida's coastal environment. Hardware — strikes, hinges, and operable vent hardware — must also be specified in stainless steel or marine-grade finishes.
The Submittal and Engineering Process
Window wall shop drawings require more engineering than storefront but less than full curtainwall. The typical submittal package includes: structural calculations for the slab bearing conditions and mullion sizing, product approval documentation confirming wind pressure coverage, energy performance data (U-factor and SHGC calculations), anchor and connection details at head, sill, and intermediate conditions, perimeter sealant and waterproofing interface details, and hardware schedules for operable units.
On Florida projects, PE-stamped structural calculations are required for window wall systems. Plan review timelines vary by jurisdiction — expect 4–8 weeks for first review in most Florida counties, with 2–4 additional weeks per correction cycle. Building shop drawing review time into your schedule at buyout is essential; glazing submittals that start late are one of the most common causes of glazing installation delays on multifamily projects.
ACG's Window Wall Experience
American Commercial Glass has installed window wall systems on Florida multifamily and commercial projects including the Lake Park Innovation Center and similar mixed-use developments across the Treasure Coast and Gulf Coast markets. We prepare window wall shop drawings in-house with PE review, which eliminates the coordination friction — and schedule uncertainty — of outsourced engineering packages. If you're pricing or building a multifamily tower in Florida, visit our window wall services page or send us your plans for a scope within 48 hours.
FAQ
What is a window wall system?
A window wall is a non-structural exterior glazing system that spans slab-to-slab, bearing on the floor slab below at each level. It fills the facade between each floor of a multi-story building with glass and aluminum framing, typically from the top of the floor slab to the underside of the slab above. Window wall is the standard glazing system for Florida multifamily towers because it integrates well with post-tension concrete construction, handles concrete slab tolerances better than curtainwall, and is more cost-effective than curtainwall for the repetitive floor-to-floor configurations typical of residential construction.
How is window wall different from curtainwall?
The key difference is load path. Curtainwall is anchored to the slab edge and self-spans between anchor points — it does not bear on the floor below. Window wall bears directly on the floor slab, with the frame sitting on the concrete at each level. This makes window wall better suited for concrete-frame multifamily buildings where direct bearing on the slab is straightforward and concrete tolerances are more easily accommodated. Curtainwall is more appropriate for commercial office and institutional buildings requiring multi-story spans, complex geometry, or higher performance specifications. Curtainwall also typically costs 2–3x more than window wall on a per-SF basis.