What Is Curtain-Wall Glazing? A Plain-English Guide for Triangle Business Owners and GCs

Curtain-wall glazing shows up in architectural plans, GC bid scopes, and building-owner conversations all the time, but the term rarely gets explained clearly. Here’s the plain-English version, built for business owners, developers, and general contractors working on commercial projects across the Triangle and surrounding NC counties.

What Curtain-Wall Glazing Actually Is

A curtain wall is a non-load-bearing exterior wall system made up of aluminum framing and glass panels. It hangs on the outside of a building’s structural frame like a curtain, hence the name. It carries no structural weight beyond its own. Its job is to keep weather out, let light in, and give a building its exterior appearance.

You’ve seen curtain wall on mid-rise and high-rise office buildings, medical campuses, university facilities, and modern mixed-use developments. That floor-to-ceiling glass facade on a corporate headquarters? Almost certainly a curtain wall system.

The defining characteristic is that the glass and framing transfer wind load, thermal movement, and their own weight back to the building’s structural floor slabs or columns. The structure itself does none of that heavy lifting through the glass wall.

Curtain Wall vs. Storefront: What’s the Difference?

This is the question GCs and building owners most often need answered before a bid goes out.

Storefront Systems

Storefront is the aluminum-and-glass framing you see on retail shops, restaurant fronts, and single-story commercial buildings across Raleigh, Cary, and Wake County. It’s designed for ground-level use, typically spans floor to ceiling within a single story, and is anchored to the surrounding wall construction. It handles standard wind loads and is a proven, cost-effective solution for lower-rise commercial work.

Curtain Wall Systems

Curtain wall is engineered for multi-story applications. The system attaches to the building’s structural frame at each floor level, allowing it to span continuously across multiple stories without relying on the wall behind it. It has to accommodate thermal expansion and contraction across large glass expanses, manage water infiltration at every joint, and meet higher structural performance requirements.

The glass in a curtain wall system is almost always an insulated glass unit (IGU), meaning two or three panes bonded together with a sealed gas-filled cavity between them. Low-E coatings are standard. Energy code compliance in North Carolina requires careful attention to U-factor and solar heat gain coefficient (SHGC) on commercial envelopes, and curtain wall specs are a big part of meeting those numbers.

A Quick Comparison

• Storefront: Ground-level, single-story, anchored to surrounding structure, lower cost, ideal for retail and commercial tenant buildouts
• Curtain wall: Multi-story, structurally independent, engineered for wind and thermal loads, required for tall facades and large glass expanses

How a Curtain Wall System Works

Most curtain wall systems fall into two categories: stick-built and unitized.

Stick-Built Curtain Wall

In a stick-built system, individual aluminum framing members (the vertical mullions and horizontal transoms) are installed piece by piece on the building. Glass panels are then set into the frame on-site. This approach works well on smaller or more complex projects where prefabrication isn’t practical. It’s also more common on lower-rise commercial buildings in markets like the Triangle, where curtain wall projects tend to be mid-scale rather than high-rise.

Unitized Curtain Wall

Unitized systems are pre-assembled in a factory as complete panels, then craned into place on the building. Each unit interlocks with the next. This method is faster in the field and is standard on large high-rise projects where speed and consistency matter. It requires more lead time and coordination upfront, but installation moves quickly once panels arrive.

How Water and Air Stay Out

A curtain wall system manages water through a pressure-equalized rainscreen design. The outer seal isn’t meant to be the only line of defense. Instead, the system creates an inner chamber that equalizes pressure between the outside air and the cavity behind the glass. Water that gets past the outer surface drains out through weep holes at the base of the system. This is a fundamentally different approach from a simple caulked joint, and it’s why curtain wall performs well over decades when specified and installed correctly.

Glass Specs That Matter on a Commercial Build

The glass itself is a major part of both the performance and the cost of a curtain wall project. Here’s what the specs on a set of plans actually mean.

Insulated Glass Units (IGUs)

An IGU is a sealed assembly of two or more glass panes separated by a spacer, with an insulating gas (typically argon) in the cavity. The seal keeps the gas in and moisture out. When an IGU seal fails, fog forms between the panes. That’s not a cleaning problem; the unit needs replacement. On a curtain wall, IGUs are specified by thickness, glass type, coating, and performance values.

Low-E Coatings

Low-emissivity (low-E) coatings are microscopically thin metallic layers applied to one surface of the glass. They reflect heat while still transmitting visible light. In North Carolina’s climate, the right low-E specification reduces cooling loads in summer and heat loss in winter. Different low-E products have different SHGC values; the right choice depends on which direction the facade faces and what the energy model requires.

Tempered and Laminated Safety Glass

Building codes require safety glazing in specific locations on commercial facades. Tempered glass is roughly four times stronger than standard annealed glass, and when it breaks, it shatters into small, relatively dull pieces rather than large sharp shards. Laminated glass holds together on impact thanks to an interlayer bonded between the panes. Both types are commonly specified in commercial curtain wall work, sometimes together in a laminated-tempered configuration for overhead or high-impact applications.

Spandrel Glass

Not every panel in a curtain wall is transparent. Spandrel panels cover the floor-slab edges between stories, providing a uniform exterior appearance while concealing structural and mechanical elements behind. Spandrel glass is typically opacified with a ceramic frit or backing and is required to meet thermal and fire-containment specifications.

When You Need a Curtain Wall (and When You Don’t)

Not every commercial project needs a curtain wall system. Getting this decision right at the design phase saves money and avoids spec mismatches during bidding.

A curtain wall makes sense when a project involves a multi-story glass facade, continuous glazing from floor to floor, or large glass expanses on a building where structural wind load and thermal performance are key design drivers. Medical office buildings, corporate campuses, boutique hotels, and university buildings in the Raleigh-Durham area regularly fall into this category.

A storefront system is the right answer for ground-floor retail, restaurant fronts, office tenant entries, and single-story commercial buildings. It’s faster to install, more straightforward to specify, and proven in exactly that application. Using curtain wall framing where storefront is appropriate adds cost and complexity without adding performance.

For GCs putting together a commercial bid in Wake County or the surrounding counties, the scope of work should be clear on which system type is specified before the glazing sub is brought in. Ambiguity here creates change orders.

What to Expect from a Commercial Glazing Project

Whether the project is a curtain wall system, a storefront replacement, or commercial window work, the process follows a predictable sequence when a qualified glazing contractor is running it.

1. Scope review and field verification. The glazing contractor reviews the plans and visits the site. Field dimensions are verified against the drawings. Discrepancies get resolved before anything is ordered.
2. Submittal and approval. On most commercial projects, the glazing sub provides a submittal with product data, shop drawings, and glass specs for the architect or engineer of record to review. This step protects everyone.
3. Fabrication lead time. Commercial glass is custom-fabricated to the exact dimensions of each opening. Lead times vary by system type and glass specification. Coordinating the glazing scope with the overall project schedule early avoids delays.
4. Installation. The framing goes in first, then the glass. On a curtain wall, the sequence and tolerances matter. A good installer works closely with the GC on sequencing, especially around waterproofing transitions at the sill and head conditions.
5. Quality control and inspection. Water infiltration testing, air infiltration checks, and visual inspection of every unit are part of a thorough commercial install. On a large project, mock-up testing before full installation is standard practice.

Why the Installer Matters as Much as the System

A curtain wall system is only as good as the installation. The best-specified framing and glass will underperform if the field work is careless. Joint sealing, anchor placement, shimming tolerances, and water management details all require experience and attention.

Maven Glass brings 33 years of glass experience to commercial work across the Triangle, including Wake County, Durham, Johnston, and the surrounding NC counties. We handle commercial glazing from storefront systems to more complex commercial glass scopes, with the same approach we bring to every project: measure precisely, coordinate fabrication to exact spec, QC the materials before they go in, and install it right.