GCs encounter the curtainwall vs. storefront decision on almost every mid-rise commercial project. Sometimes the spec is clear. Sometimes it isn't. And sometimes the GC's instinct is to substitute one for the other to hit a budget number — which creates problems that cost more than the savings. This guide explains the technical and cost differences, when each is correctly specified, and what happens when GCs try to make a substitution without going through the right process.
The Technical Difference: It's About Structure
Curtainwall and storefront are fundamentally different structural systems. Understanding that difference is the foundation of everything else in this guide.
Storefront is a relatively lightweight aluminum-framed glass system designed to fill a single-story opening — typically a ground-floor retail or office facade. The framing is supported by the building structure at the head and sill. Storefront systems are designed for openings up to about 10–12 feet in height. They transfer lateral (wind) loads to the structural elements at the perimeter of the opening. They do not span across floor slabs.
Curtainwall is a non-load-bearing exterior cladding system engineered to span from floor slab to floor slab — continuously, across multiple floors, without intermediate structural support. Wind loads, gravity loads, and thermal movement are transferred back to the building structure through engineered anchor systems at each floor level. The system is designed to accommodate building movement, differential settlement, and thermal expansion without transferring these forces to the glass.
Window wall sits between the two. Window wall is a slab-to-slab glazing system that fits within a structural opening between slabs — it's supported by the slab above and below, not by intermediate floor anchors. Window wall is commonly used in multifamily residential and hospitality projects where consistent floor-to-floor glazing is desired without the full structural engineering complexity of curtainwall.
When the spec says curtainwall, it's because the architect and structural engineer determined that the building's design — spans, loads, thermal performance requirements, or aesthetic intent — requires a system that can span multiple floors and handle those engineering conditions. Storefront cannot do that. They are not substitutes for each other from a structural standpoint.
Cost Comparison
The cost difference between curtainwall and storefront is substantial — and it's driven by legitimate engineering and fabrication differences, not by manufacturer pricing strategy.
Commercial storefront systems in Florida typically run $50–$90 per square foot installed, depending on system complexity, glass type, impact rating requirements, and project location. This range covers standard aluminum-framed storefront with insulating glass.
Curtainwall systems typically run $150–$350+ per square foot installed in Florida. The wide range reflects system type (stick-built vs. semi-unitized), glass specification (standard IGU vs. high-performance triple-silver coating vs. fritted glass), Florida code compliance requirements (standard FL PA vs. HVHZ NOA), building height, and site access conditions.
Window wall typically falls between the two: $80–$160 per square foot installed, depending on the system and glass specification.
The cost premium for curtainwall over storefront is driven by: more complex aluminum extrusion profiles, higher engineering content (PE-stamped calculations, thermal modeling, anchor design), more complex shop drawing production, longer fabrication lead times, and more involved field installation (floor-by-floor anchor installation, more complex glass setting procedures, full-perimeter water management system).
When Each System Is Specified
Storefront is typically specified when: The glazing is at grade level, filling a single-story opening. The building is low-rise (1–3 stories). The design does not require continuous glass across multiple floors. The wind loads can be transferred to perimeter framing within a single story height. Budget constraints favor the simpler system and the architect has designed around it.
Curtainwall is typically specified when: The facade must span continuously across multiple floors without visible horizontal structural breaks. The building is mid-rise or high-rise. The thermal performance specification requires a thermally broken system with high-performance glazing integrated into the curtainwall cavity. The structural frame doesn't provide intermediate support points between slabs. The aesthetic intent is a glass tower or glass-dominant facade.
Window wall is typically specified when: The building is multifamily residential, hospitality, or mixed-use with repetitive floor plans. Each floor has a structural slab at head and sill. The client wants floor-to-ceiling glass without the full curtainwall budget. The design allows for horizontal slab covers at each floor line.
Florida Code Implications for Each System
Florida Building Code requirements don't treat curtainwall and storefront identically — and the compliance path for each is different.
For storefront: Every storefront system installed in Florida must carry a Florida Product Approval (FL number). The PA validates the system's structural performance under the design wind pressures at the installed location. In the HVHZ (Miami-Dade and Broward counties), a Miami-Dade NOA is also required. Storefronts in wind-borne debris regions must be impact-rated or protected by an approved impact protection system.
For curtainwall: Florida Product Approval is also required, but curtainwall PAs are more complex — they cover the full anchor system, not just the frame and glass. Engineering documentation for the specific building's wind load conditions must be part of the submittal. In the HVHZ, Miami-Dade NOA requirements apply to curtainwall as well, and the testing and documentation requirements are more extensive than for storefront.
This matters because not all glazing subs are equally qualified to manage the curtainwall compliance process in Florida. A sub that routinely handles storefront but rarely does curtainwall may not have the engineering resources to produce a complete curtainwall submittal package for a Florida mid-rise. At ACG, curtainwall and storefront are both regular scopes — we've managed the compliance process for both across hundreds of Florida projects.
What Happens When GCs Try to Substitute
The most common scenario: a GC has a mid-rise project with curtainwall specified. The glazing budget comes in over target. Someone asks whether storefront can be substituted to close the gap.
The short answer is: not without architect and EOR approval, and usually not at all.
Substituting storefront for curtainwall will result in a rejected shop drawing submittal. The architect has designed the facade around the structural and aesthetic properties of a curtainwall system. The structural engineer has designed the anchor points for curtainwall loads. The building envelope consultant has modeled the thermal performance of the curtainwall assembly. Storefront cannot replicate any of these conditions.
If the budget gap is real, the right path is to work with the glazing sub and architect on a formal substitution request — proposing an alternative curtainwall system that provides equivalent performance at a lower installed cost. This is a legitimate process, and ACG has helped GCs close budget gaps through system substitutions that the architect accepted. The key is doing it through proper channels with full documentation, not by hoping the inspector doesn't notice.
ACG's Experience with Both Systems
ACG installs both curtainwall and commercial storefront across Florida — and the full range of window wall and specialty glazing systems in between. We've delivered YKK AP curtainwall at HCA Cape Coral Emergency Center, Eurowall systems at Lake Park Innovation Center, Trulite curtainwall at SROA Vero Beach, and ESWindows storefront at Dale Mabry Retail in Tampa, among hundreds of other projects.
When you send ACG plans, we read the spec, identify what's actually specified, flag any conditions where the spec and the design may be inconsistent, and give you accurate pricing for both the specified system and any value-engineered alternatives that maintain code compliance and design intent.
That's what a commercial glazing subcontractor with 14+ years in Florida looks like. Send us your plans and we'll have a scope back to you in 48 hours.