Curtain walls are one of the most common facade systems on commercial buildings, yet many facility managers and property owners interact with them daily without understanding how they work, what can go wrong, or when they need attention. This guide breaks down curtain wall construction, components, types, performance, and maintenance for anyone managing a commercial property in the Denver Metro or Rocky Mountain region.
Quick Answer: What a Curtain Wall Is and Why It Matters
A curtain wall system is a non-load-bearing exterior facade made of metal framing and glass or opaque panels. It hangs off the building’s structural frame, typically anchored at floor slabs, and forms the outer skin of the building envelope. Unlike load bearing walls, a curtain wall carries only its own dead load and resists environmental loads such as wind load, temperature swings, and seismic movement. Floor and roof loads stay with the primary structure.
When people refer to a glass curtain wall, they usually mean a full-height glazed facade on an office tower, hospital, campus building, or mixed-use high-rise. Curtain walls are common on commercial buildings because they allow larger spans of glass and open floor plans. If you are unsure whether your building has a curtain wall or a storefront system, the differences between storefront and curtain wall are worth understanding because repair strategies differ for each.
For facility managers and general contractors across Colorado and Wyoming, curtain walls matter because they directly affect natural light, energy efficiency, air infiltration, and long-term maintenance costs. Curtain walls should be evaluated as complete building-envelope systems, not as individual pieces of glass. ONE Glass Service repairs and diagnoses commercial curtain wall systems across the region, focusing on long-term performance and minimal disruption to building operations.
Three takeaways:
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Curtain walls are non-load-bearing; they protect, not support
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They control weather, thermal insulation, and acoustics for the entire facade
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Problems with one component (sealant, glass, framing) affect the whole system
How a Curtain Wall Works as Part of the Building Envelope
The building envelope is every element separating conditioned interior space from the outside. A curtain wall forms that exterior side on glazed elevations, acting as the weather protection, thermal barrier, and acoustic insulation layer all at once.
Basic curtain wall construction starts with vertical mullions anchored to slab edges or structural beams. Horizontal transoms span between mullions, creating a grid. Infill panels, either vision glass, spandrel panels, or metal panels, sit within that grid. Curtain walls are designed to withstand wind and seismic loads, which vary by location and building code, and they accommodate building movement through engineered slip joints and flexible connections. They are also designed to prevent water penetration through pressure-equalized cavities, gaskets, weep holes, and drainage paths.
When detailing degrades or sealants age, water tracks inside the wall assembly. If your building has intermittent leaks along the facade, especially at mullion intersections or slab edges, the article on commercial window leaks covers what to look for. In Colorado and Wyoming, cold-climate specifics matter: back pans behind spandrel areas, vapor control layers, and insulation at slab edges prevent interior condensation and frost formation inside the system.
Key envelope functions of a curtain wall:
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Weather barrier: resists driving rain, snow, and wind-driven moisture
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Thermal barrier: reduces heat transfer in winter and summer
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Acoustic barrier: attenuates traffic, aircraft, and street noise
Key Components of a Curtain Wall System
Curtain wall systems are assemblies of coordinated components. Knowing what each piece does helps you troubleshoot problems and plan repairs before small issues become expensive ones.
Curtain wall framing consists of aluminum mullions (vertical) and transoms (horizontal), secured to the structure by steel brackets or anchors at each floor slab. Integrated thermal breaks, usually polyamide strips within the aluminum extrusion, minimize heat transfer through the frame. Without intact thermal breaks, interior mullion surfaces can drop below dew point in cold weather and collect condensation. Pressure plates and exterior caps clamp glazing into place and protect primary seals from UV and weather.
Vision glass is typically insulated glazing units (IGUs) with double or triple panes, low e coatings to limit infrared heat flow, and sometimes tinting or fritting. Glass thickness and makeup are selected for the project’s wind load requirements, acoustic insulation goals, and energy performance targets. Options range from laminated glass for safety to high performance glazing for solar control.
Spandrel panels cover floor slabs, structural elements, and mechanical systems behind the facade. To learn more, read about what spandrel glass is and how it’s used to hide floor lines and structure. Curtain walls can also use metal panels, composite materials, or stone veneer for opaque infill where the design calls for varied textures. Factory-applied finishes on the aluminum framing help it resist weathering.
Seals and accessories tie the assembly together: EPDM gaskets between glass and frame, sealant joints at corners and splices, setting blocks to position glazing units, backer rod behind sealant, and weep holes for drainage.
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Component |
Function |
Common Failure Mode |
|---|---|---|
|
Mullion / Transom |
Structural frame, load transfer |
Thermal break degradation, corrosion at anchors |
|
IGU (vision glass) |
Transparency, thermal insulation |
Seal failure causing fogging, heat loss |
|
Spandrel panel |
Hides structure, insulates |
Cold spots, deformation from moisture |
|
Sealant / Gasket |
Air and water tightness |
UV cracking, flattening, detachment |
|
Pressure plate / Cap |
Holds glazing, protects seals |
Loosening, corrosion, allowing leaks |
Types of Curtain Wall Systems and Glazing Approaches
Most curtain wall systems fall into two categories based on how they are fabricated and installed: stick built systems and unitized curtain wall systems.
Stick Systems
Stick systems are assembled on site, piece by piece. Individual glazing units, mullions, and transoms arrive separately and are fitted together at the construction site. Stick built curtain walls are typical for low rise buildings, mid-rise Denver-area offices, schools, and medical facilities. They offer flexibility for irregular facade geometries and on-site adjustability. Because field assembly introduces variability, stick systems are often water tested after installation.
Unitized Systems
Unitized curtain walls are prefabricated in a factory environment. Large units, typically about one story tall, arrive with glass and panels already installed. Crews hoist prefabricated panels into place and interlock them. Unitized systems are factory-tested for air and water integrity before shipping, providing higher quality control and faster installation on high-rise curtain wall projects.
Stick vs. Unitized comparison:
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Schedule: unitized systems shorten the exterior envelope timeline; stick systems require more field labor
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Quality control: factory fabrication in unitized systems reduces variability compared to assembled on site stick work
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Coordination: unitized requires more upfront design; stick allows late changes
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Repair access: stick systems allow piecemeal repairs more easily; unitized module replacement can be more complex
Glazing can also be classified by access: interior-glazed systems allow individual glazing units to be replaced from inside the building, while exterior-glazed systems require swing stages or lifts on the exterior side. This distinction matters for reglazing cost, safety, and tenant disruption. ONE Glass Service provides commercial reglazing services for damaged or failed curtain wall glass on both system types.
Performance: Energy Efficiency, Natural Light, and Comfort
A curtain wall is both an architectural feature and a performance system that directly affects utility bills and occupant comfort.
Curtain walls bring daylight deep into floor plates, reducing artificial lighting needs. But glass also transmits solar heat gain if glazing is not selected carefully. Fritted glass, interior shading devices, or external fins can limit excessive heat gain and glare. Orientation matters: east and west facades in Denver receive intense low-angle sun and benefit from solar control strategies. High performance glazing with low e coatings, argon fills, and warm-edge spacers can reduce energy consumption measurably. Thermal breaks in aluminum frames limit heat transfer and prevent condensation on interior surfaces during cold months.
Air infiltration is controlled by tight gaskets, correct sealant installation, and maintained joints. When these elements degrade, drafts and condensation follow, increasing HVAC load.
Retrofitting existing curtain walls by reglazing selected bays, upgrading sealants, or adding interior films can improve energy performance without full replacement.
Questions facility managers should ask about an existing curtain wall:
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Are occupants reporting drafts, cold spots, or condensation along the facade?
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How many glazing units show fogging or haze?
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Has HVAC runtime increased without other explanation?
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When were perimeter sealants last replaced?
Common Issues, Maintenance, and Repair of Curtain Walls
Many commercial curtain walls in the Denver Metro and Rocky Mountain region are decades old, and systems from that era are reaching the point where sealants, gaskets, and individual glazing units need attention.
Typical problems include water penetration at frame joints and perimeter transitions, fogged insulated glazing units from broken hermetic seals, loose or missing pressure plates and caps, staining and oxidation on aluminum surfaces, and air leaks from cracked sealant or flattened gaskets. Perimeter sealants break down fastest on south- and west-facing exposures where UV cycling is most intense. Aluminum frames require careful cleaning to avoid damage to factory-applied finishes; harsh chemicals or abrasive tools accelerate corrosion.
Preventive maintenance includes regular visual inspections, cleaning weep holes to keep drainage paths open, targeted sealant replacement at high-exposure joints, and replacing failed IGUs before condensation damages surrounding framing. When leaks are intermittent or water tracks unpredictably inside wall cavities, professional curtain wall leak investigations and testing pinpoint the source without unnecessary disassembly.
Warning signs that should trigger a professional assessment:
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Active water leaks inside (stains, drips at mullion locations)
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Recurring fogged or hazy glazing units across the facade
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Drafts or cold spots along the glass curtain during winter
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Visible cracks, gaps, or detached caps on the exterior side
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Glass breakage without obvious impact cause
When to Consider a New Curtain Wall or Major Retrofit
Not every curtain wall problem calls for full replacement. Many systems can be extended through targeted restoration: reglazing failed bays, replacing all perimeter sealant, or rebuilding problem details at corners, parapets, and roof-to-wall transitions.
Full replacement or major retrofit should be evaluated when insulated glass failure is widespread, leakage occurs across multiple elevations, framing is warped or corroded beyond repair, or energy performance falls far below current building codes and owner goals. Phased reglazing spreads cost over multiple budget cycles. Adding new corrosion resistant metal cladding over older elements is another option for buildings where the underlying structure remains sound.
Decisions on curtain wall projects of this scale are coordinated among building owners, facility managers, and general contractors. Early involvement of a glazing contractor simplifies budgeting, constructability review, and the installation process. ONE Glass Service supports general contractors on curtain wall scopes and sequencing for retrofit and new construction alike.
|
Good Candidates for Restoration |
Situations for Full Replacement |
|---|---|
|
Isolated IGU failures |
Widespread glass failure across elevations |
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Localized sealant deterioration |
Systemic water infiltration at framing joints |
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Sound framing with intact thermal breaks |
Warped, corroded, or structurally compromised mullions |
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Cosmetic aluminum finish wear |
Energy performance far below current code requirements |
How ONE Glass Service Supports Your Curtain Wall Projects
ONE Glass Service is a commercial-only glazing contractor based in Centennial, serving the Denver Metro area and greater Colorado and Wyoming. Our work focuses on the types of curtain wall issues covered in this guide: reglazing damaged or failed units, leak investigation and diagnostics, sealant and perimeter joint restoration, hardware and operable insert repairs, and glass or metal panel replacement.
We schedule around tenant hours, coordinate equipment access on tight urban sites, and communicate directly with facility teams throughout each project. We can also help determine whether an existing building has storefront or curtain wall and advise on the appropriate repair strategy for each system.
Our typical engagement path:
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Assess: on-site inspection of the curtain wall condition, documenting problem areas
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Diagnose: targeted testing (water spray, disassembly if needed) to identify root causes
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Repair/Restore: scoped work with clear timelines, minimal disruption, and documented results
If your building’s curtain wall shows any of the warning signs above, or you have a repair, retrofit, or new curtain wall project on the horizon, contact ONE Glass Service. Visit our contact page or call (303) 505-3194 to start the conversation.