Curtain Wall Framing

Storefront and curtain wall are both aluminum framing systems that hold glass on a building facade, but they're engineered for different situations, and choosing the wrong one is an expensive mistake.

Storefront systems are designed for ground-floor, relatively low-height openings — typically under 10–12 feet in height, in a single-story application. The framing sits in the rough opening and transfers wind load to the surrounding structure at the head, sill, and jambs. Storefront is the correct system for the vast majority of retail, restaurant, and office facades, and it's significantly more economical than curtain wall. For storefront work, see our dedicated storefronts & repairs page.

Curtain wall systems hang off the building structure — typically the floor slabs or structural steel — rather than sitting in a rough opening. This allows them to span multiple floors, carry large glass panels, and handle the higher wind and thermal loads that come with taller buildings and larger glass areas. The system is structurally independent of the wall behind it, which is why it can be used on buildings where the wall itself doesn't extend to the full facade height.

The practical trigger for curtain wall: if your facade is taller than about 12 feet, wraps a structural corner, spans multiple stories, or needs to be engineered for higher wind loads (common on exposed or elevated sites), you need curtain wall. We'll tell you which system your project actually requires before any money changes hands.

Curtain wall systems come in several configurations, and the right one depends on your building type, schedule, and budget.

Stick-built (field-glazed) curtain wall is assembled piece by piece on the building. The aluminum mullions go up first, then the glass is installed from inside or outside. Stick-built is the most common choice for mid-rise projects and renovations because it doesn't require cranes to set pre-assembled units, and it tolerates the dimensional variation that's typical of field construction. Nearly all of our curtain wall work is stick-built — it's the right system for the building sizes and project types we work on in the Hudson Valley.

Unitized curtain wall is manufactured in pre-glazed, factory-assembled panels that are craned into place and locked together on the building. It's fast on high-rise construction where the speed of installation justifies the higher cost. For the scale of commercial construction we handle in Orange, Ulster, and Dutchess Counties, unitized is rarely the appropriate specification — but we can advise on it for the right project.

Semi-unitized systems split the difference: the framing is pre-assembled into frames in the shop, then glazed in the field. This provides more dimensional control than fully field-fabricated stick and can accelerate the schedule on medium-complexity projects.

On a curtain wall facade, not every panel is transparent. The glass that you can see through — at eye level and above, between the floors — is called vision glass. It's typically insulated (dual-pane), often with a Low-E coating, and it's responsible for both the view and a large share of the building's thermal envelope. Vision glass selection affects the building's HVAC load, occupant comfort, and exterior appearance. We help specify vision glass that's appropriate for the orientation and use of the building.

Spandrel glass covers the structural elements between floors — the floor edge, spandrel beam, and insulation — so the exterior reads as a continuous glass facade even though much of it isn't transparent. Spandrel glass is typically an opaque or semi-opaque glass (often a ceramic-frit or painted-back glass) that's color-matched to the vision glass so the seam between them is minimized. Getting the color and reflectance match right between vision and spandrel panels is one of the more demanding parts of curtain wall work — a mismatch is obvious and expensive to fix.

We advise on the vision/spandrel specification as part of our scope review and, where the architect has already specified both, we source and install to that specification.

A curtain wall system has to do two things well: keep weather out and manage heat flow. Both depend on details that are invisible once the system is complete — which is why they're also the first things that fail when they're done wrong.

Weather sealing on a curtain wall happens at the perimeter (where the curtain wall meets the building structure), at the joints between vertical and horizontal mullions, and at the glass-to-frame interface. We use high-quality silicone sealants rated for outdoor exposure and follow the manufacturer's joint preparation requirements — clean, primed, and correctly backed — so the seal holds over the life of the building. A sealant joint that fails five years after installation is a remediation job that costs far more than doing it right the first time.

Thermal performance in aluminum curtain wall is addressed through thermal break profiles — a layer of low-conductivity material (typically polyamide or polyurethane) built into the aluminum mullion that interrupts the path of heat conduction between the interior and exterior faces. Without a thermal break, aluminum mullions conduct heat efficiently and create condensation and heat loss at every framing member. We specify thermally broken systems for all heated commercial buildings.

For insulated glass unit selection — which controls a large share of the curtain wall's overall thermal performance — see our insulated & plate glass page.

On a new commercial construction project, the glazing scope typically goes to a specialty subcontractor — us. That scope covers furnishing and installing all the glass and aluminum systems on the building: curtain wall, storefront, entrance doors, and interior glass. The GC coordinates the schedule with the structural and exterior trades, and we work within that schedule to get the building enclosed on time.

Our role includes reviewing the architect's glazing drawings and specs, submitting shop drawings for approval, coordinating material lead times so the glass arrives when the building is ready for it, and executing the installation with our own crew. We don't subcontract the installation to laborers we don't know — our crew is our crew, and Rick Powles is on site for every curtain wall installation.

For entrance door systems on the same project, see our aluminum entrances page. For safety glazing requirements within the same building, see our tempered & laminated safety glass page. All part of our commercial glass & glazing services.

Our Dutton project is the kind of job that illustrates what curtain wall work actually demands. The building has a commercial corner condition — the facade wraps around an exterior corner with large vision-glass panels and a curved transition — requiring the aluminum framing to be custom-fabricated to follow the curve, then installed with consistent sightlines and weather-tight joints across the entire curved section.

Curved curtain wall requires more planning than a flat facade. The mullion spacing has to be worked out geometrically so the glass panels fit the curve without excessive deflection, the glass itself has to be curved or faceted (depending on the radius and budget), and the sealing has to work at compound angles. We managed that scope from measurement to completed installation, with Rick Powles coordinating directly with the GC and reviewing every installation stage.

The finished facade is visible, watertight, and has performed well since installation. It's the kind of project that doesn't get done right unless the people executing it understand what they're doing — and in the Hudson Valley, that's what we bring to the table on curtain wall work.