Curtain Wall vs Storefront: Choosing the Right System for a Colorado Commercial Facade (2026)

Storefront is a non-load-bearing framing system installed between floor and header inside a structural opening, typically at grade, typically one story tall. It is self-supporting within that opening: the weight of the frames and glass runs down through the vertical mullions to a sill anchored to the slab. Most storefront is site-glazed — the framing goes up in pieces on the job and the glass is set into it by hand.

Curtain wall is a non-load-bearing exterior envelope that hangs in front of the building structure rather than sitting inside it. Its weight is transferred back to the floor slabs or spandrel beams through engineered anchors, and it is designed to span continuously past the floor lines, so the framing runs uninterrupted across multiple stories. The anchors are designed to accommodate movement — thermal expansion, live-load deflection of the slab above, seismic drift, and building sway — without transferring that movement into the glass.

Everything else follows from that difference. Because curtain wall is hung and must move independently of the structure, it needs deeper mullions, engineered anchor design, more sophisticated joinery, and higher-performing water management. Because storefront sits in an opening and is not asked to do those things, it can be lighter, simpler, faster, and considerably cheaper. Neither is a premium version of the other; they are different tools.

Storefront is the workhorse of ground-floor commercial glazing in Colorado. Retail bays, restaurant frontages, medical and dental offices, office building lobbies, light industrial entries, and the street level of mixed-use buildings are overwhelmingly storefront. It is a stick system: mullions and horizontals are cut to length, assembled on site with screw-spline or shear-block joinery, anchored at head and sill, and glazed with the glass set from the interior or exterior into a pocket and secured with a snap-in stop and gaskets.

Thermal performance depends heavily on whether the system is thermally broken. Non-thermal storefront — a solid aluminum extrusion with no break — is inexpensive and still shows up in unconditioned or semi-conditioned spaces, but in a Colorado winter it conducts heat straight through and condenses on the interior face. Thermally broken storefront uses a poured-and-debridged polyurethane pocket or a polyamide strut to separate the exterior and interior aluminum, which is what makes the assembly workable in a conditioned building. On energy-code-driven projects, the thermally broken version is usually the practical baseline.

Storefront is also where entrances live. Aluminum medium-stile and wide-stile doors, offset pivots or butt hinges, closers, panic devices, and automatic operators are all detailed into the storefront framing. That is a real advantage of the system: door hardware, thresholds, and accessible clearances are ordinary, well-understood details in storefront, whereas integrating an entrance into a curtain wall run requires a purpose-built receptor and more coordination.

Curtain wall is the envelope system for buildings where the glazing has to span the structure rather than fill holes in it. On a Front Range mid-rise — an office building, a hospital tower, a hotel, a four-over-one multifamily podium with a glass-heavy street face — the exterior wall between the floor slabs is doing structural, thermal, water, air, and sometimes fire and acoustic work at once, and curtain wall is the system engineered for that combination.

The defining feature is the anchor. Steel or aluminum anchors attach the vertical mullions back to the slab edge or a spandrel beam, with one anchor per mullion designed to carry the dead load and the others designed to take wind load while allowing vertical movement. Slotted holes, thermal expansion allowances, and stack joints in the mullion let the system grow and shrink and let the building move without putting the glass in bending. That is why curtain wall detailing looks fussy compared with storefront: most of the fussiness is movement management.

The second defining feature is water management. Good curtain wall is designed as a pressure-equalized rainscreen: the exterior joint is a rain deterrent rather than the primary seal, the glazing pocket is compartmentalized and vented to the exterior so pressure equalizes across the outer plane, and any water that does get in is collected on flashed horizontals and weeped back out. This is a fundamentally different philosophy from face-sealing a joint with silicone and hoping it stays intact for thirty years, and it is a large part of why curtain wall performs better under wind-driven rain.

There is a third system that gets left out of the conversation and then shows up on the drawings: window wall. Window wall sits between floor slabs rather than passing in front of them. Each floor's unit is installed from inside the building, anchored to the slab below and the slab above, with the slab edge exposed or covered by a separate finish. It is common on multifamily and hotel projects across the Denver metro because it can be installed floor by floor without exterior access, which removes swing stages and crane time from the schedule.

Window wall generally costs less than curtain wall and performs better than storefront at height, but it introduces its own issues: the interface at each slab edge is a critical detail for water and air, acoustic and fire separation between floors has to be handled at that joint, and the system has to absorb slab deflection at the head. If a project team is debating curtain wall against storefront on a residential mid-rise, window wall is frequently the system that actually fits, and it belongs in the evaluation.

The reason a specification can meaningfully say one system outperforms another is that both are tested against the same industry standards. Air infiltration is measured under a pressure differential, with lower leakage rates indicating a tighter assembly. Static water penetration resistance is measured by spraying a calibrated water rate at the specimen while a pressure differential is applied; the rating is expressed as the pressure at which the assembly still shows no uncontrolled water on the interior. Dynamic water testing adds a propeller-driven wind field to better simulate wind-driven rain. Structural performance is verified at design pressure and at an overload factor, with deflection limits on the framing members.

Curtain wall systems are typically published with higher water-resistance pressures and tighter air-leakage rates than storefront systems from the same manufacturer, which is precisely the performance the extra depth, gasketing, and pressure-equalized design buys. On larger or more exposed buildings, the specification may also require project-specific mock-up testing — a full-size sample of the assembly built and tested before production release — which is a schedule and budget item that needs to be identified early rather than discovered at submittal.

Thermal performance is expressed as a whole-assembly U-factor, along with condensation resistance. The important discipline here is to compare assembly numbers, not center-of-glass numbers. A high-performing insulated glass unit installed in a non-thermal frame gives back much of its advantage at the frame, and the assembly value is what an energy model and a code compliance path care about.

Altitude is the one most people outside the region forget. Insulated glass units sealed near sea level and shipped to Denver arrive with internal pressure that wants to bow the lites outward; units fabricated for Front Range elevations are either assembled locally, built with capillary breather tubes, or engineered for the elevation change. This affects glass sourcing and lead time on both systems and is worth confirming with the fabricator rather than assuming.

Temperature swing is the second. A 50-degree day-to-night delta is unremarkable here, and a dark-finished aluminum mullion in full sun can move meaningfully across a long run. Movement joints, stack joints, and expansion allowances that get treated as boilerplate in milder climates are load-bearing details in Colorado, and they are one of the practical reasons curtain wall's engineered movement accommodation earns its cost on taller runs.

Wind and hail matter too. Design wind pressures along the Front Range vary substantially with exposure and site conditions, and the structural engineer's stated pressures determine mullion sizing and reinforcement. Hail exposure pushes some owners toward laminated or heat-strengthened laminated outboard lites on exposed elevations. And solar intensity at altitude makes the Low-E coating selection consequential rather than cosmetic — an ordinary spec choice with an outsized effect on comfort and mechanical load.

These are planning ranges for the Colorado Front Range in 2026, expressed per square foot of installed system, and they are for budgeting conversations only. Real numbers depend on the specific system, glass makeup, finish, height, access, quantity, structural conditions, and the schedule you need. No responsible glazing contractor quotes a facade from a table.

Thermally broken aluminum storefront with a standard insulated unit and a clear or standard anodized finish commonly falls in the range of roughly $75 to $140 per square foot installed at grade. Non-thermal storefront in an unconditioned application sits below that. Entrances are priced separately and carry their own hardware costs, which climb quickly with panic devices, closers, card access preparation, and automatic operators.

Stick-built curtain wall commonly runs in the range of roughly $130 to $260 per square foot installed, with the low end reflecting captured systems on a straightforward low-rise elevation and the upper end reflecting structural silicone, higher performance glass, custom finishes, or difficult access. Unitized curtain wall typically starts near the upper part of that band and moves up from there; its economics improve with repetition, so a tall building with identical typical floors narrows the gap that a small irregular facade widens.

The bigger budget lesson is that the system is often not the largest variable. Glass makeup — laminated versus monolithic, dual versus triple, spectrally selective coatings, low-iron, oversized lites — can swing the number as much as the framing choice. So can access: the same panel costs one thing at grade off a lift and something quite different at the fifth floor off a swing stage with a downtown lane closure. Custom paint finishes, spandrel and shadow-box conditions, operable vents, sunshades, and required mock-up testing all add real money.

Schedule differences are often more decisive than cost. Storefront moves quickly: shop drawings and submittals are comparatively simple, standard finishes and common glass makeups are readily available, and a modest storefront package can commonly move from approved submittal to installed in a matter of weeks. It also tolerates being measured late, because it is fitting into an opening that can be verified once the structure is up.

Curtain wall is a long-lead package. Engineering and shop drawings take longer, structural calculations and anchor design need review, custom finishes add weeks at the paint line, high-performance or oversized glass goes into a fabrication queue, and unitized panels require assembly time before anything ships. On a mid-rise, the curtain wall release is frequently one of the earliest procurement decisions on the job — long before the frame is topped out — because the enclosure date drives interior trades, temporary heat, and ultimately the certificate of occupancy.

The practical implication for a project team is that the system decision should be made during design development, not during value engineering after permit. Switching from curtain wall to storefront late means revisiting structural attachment, energy compliance, and often the elevations; switching the other direction means absorbing a lead time the schedule may no longer have.

Start with height and span. If the glazing is one story, sits in a defined structural opening, and does not need to pass the floor line, storefront is the default and the burden is on the facade to justify anything more. If the glazing runs continuously past floor lines, storefront is not the system, and the choice is between curtain wall and window wall.

Then look at exposure and performance requirements. High design pressures, an exposed elevation, a specified water-resistance rating storefront cannot meet, a stringent assembly U-factor, or an acoustic requirement at a busy corridor all push toward curtain wall. Next, consider movement: significant expected slab deflection or seismic drift requirements point to an engineered, movement-accommodating system.

Then weigh access and schedule. If exterior access is impractical or crane time is scarce, window wall's interior installation may decide it. If the enclosure date is on the critical path and the building is tall and repetitive, unitized curtain wall can pay for itself in schedule. Finally, apply budget — but apply it last, and apply it to the systems that satisfy the first four filters. Choosing a system on price and then discovering it cannot meet the specified performance is the most expensive sequence available.

The sequence is broadly similar for both systems, but the intensity differs. It begins with document review: elevations, wall sections, the glazing schedule, the structural engineer's design pressures, energy compliance targets, and the specification's performance requirements. From there the system is selected with the manufacturer and shop drawings are produced showing every condition, anchor, and interface. On curtain wall, structural calculations and anchor details are typically signed by an engineer and reviewed by the design team.

Submittals follow: system data, finish samples, glass and IGU data with the actual assembly performance numbers, sealant compatibility and adhesion testing where structural silicone is involved, and gasket and hardware cut sheets. Approval releases fabrication. In parallel, field verification happens — for storefront, measuring the actual openings once the structure and rough framing are in; for curtain wall, surveying slab edges and anchor locations, which routinely differ from the drawings enough to matter.

Installation follows the system. Storefront anchors at sill and head, assembles, gets glazed, then sealed and weeped. Curtain wall sets anchors first, hangs mullions, installs horizontals, then glazes and caps or bonds. Air and water barrier tie-ins are coordinated with the waterproofing trade rather than left to whoever arrives last. Where the specification requires it, field water testing is performed on completed sections early enough that a detail problem can be corrected before the whole elevation repeats it. Closeout includes punch, cleaning, protection until turnover, and warranty and maintenance documentation.

The most common and most costly mistake is specifying storefront for a condition that needs curtain wall — usually to hit a budget — and then discovering at submittal that the system cannot meet the stated design pressure or water rating. The second is treating the transition between systems as a field problem. The third is ordering from the architectural drawings instead of field-verified dimensions, which on a curtain wall with slab-edge tolerance variation guarantees rework.

Others recur often enough to name: skipping sealant adhesion and compatibility testing on structural silicone work, then finding out the substrate or the finish will not bond; blocking the weep system with sealant during a later trade's caulking and turning a drained assembly into a bathtub; using anchors or fasteners that are not part of the tested and approved assembly; ignoring galvanic separation between aluminum and dissimilar metals; underestimating access and crane costs; and releasing the glass package late, which converts a manageable lead time into a schedule crisis.

One more, specific to renovation: assuming an existing frame can accept a modern insulated unit. Older single-glazed storefront pockets are frequently too shallow for a dual-pane IGU, and the honest options are a new system, a retrofit sub-frame, or a different glass approach — not a forced fit that stresses the seal.

Many Colorado projects are not new construction. A 1980s office building with failing single-glazed storefront, an aging curtain wall with fogged units and hardened gaskets, or a repositioned retail center all present a choice between full system replacement and targeted rehabilitation. Reglazing an existing curtain wall — replacing failed IGUs, gaskets, and sealants while keeping the frames — is often dramatically cheaper than replacement and can be phased around tenants, provided the framing is sound and the pockets accept the new glass.

Full storefront replacement is the more common renovation path at grade, because the systems are lighter, the openings are accessible, and the thermal gain from moving to a thermally broken system with a modern coated IGU is significant. Either way, the assessment comes first: frame condition, anchor condition, glazing pocket depth, water history, and the accessibility and safety-glazing implications of any change to entrances.

Abricos Glass is the architectural glass division of Abricos LLC, established in 2019. We are a glazing contractor: we review documents, coordinate systems and glass with manufacturers and fabricators, verify conditions in the field, and install. We do not manufacture aluminum systems, glass, or insulated units, and we do not perform structural engineering — we coordinate with the manufacturer's engineering and with the project's design team.

On a facade package that means participating early enough to be useful. Reading the elevations and specification before the system is locked in, flagging where a specified storefront is being asked to do curtain wall work, identifying long-lead items while there is still schedule to protect them, field-verifying rather than assuming, and detailing the transitions between systems on paper before anyone is standing on a lift. On the installation side it means the ordinary discipline that determines whether an envelope performs: anchors installed as designed, weeps clear, gaskets seated, sealant joints prepared and tooled properly, and interfaces coordinated with the other trades who touch the same plane.

If you have a set of drawings and are trying to decide between systems — or you have a facade that is leaking and need an honest assessment of reglaze versus replace — that is a conversation worth having before the budget hardens.