Curtain Wall Installation: The Building Envelope System for Mid- and High-Rise Construction

Curtain walls are non-load-bearing exterior wall systems hung from building structure. Aluminum framing combined with glass, metal panels, or stone provides building envelope. Mid-rise and high-rise commercial buildings predominantly use curtain walls. Stick-built systems assembled piece-by-piece on site for traditional applications. Unitized systems pre-fabricated as floor-height (or larger) panels installed by crane. AAMA (American Architectural Manufacturers Association) provides standards for testing and performance.

Understanding curtain wall installation helps GCs coordinate this complex envelope scope. This post covers curtain wall installation.

Stick-Built vs Unitized

Two main system types:

Stick-built systems install individual mullions (vertical), horizontals, and infill (glass, panels) on site. Lower material cost but more on-site labor. Unitized systems pre-fabricate floor-height panels (or larger) in factory. Panels lifted into place by crane and connected to anchors. Faster installation, factory quality control. Unitized increasingly common for high-rise; stick-built common mid-rise.

Performance Requirements

Multiple performance requirements:

Performance requirements span multiple metrics. Structural for wind and seismic. Air infiltration low (per ASTM E283). Water penetration resistance per ASTM E331. Thermal U-value per energy code. Solar heat gain coefficient (SHGC). Visible light transmission. Acoustic per project requirements. Fire resistance for specific applications.

Mock-Up Testing

Mock-ups verify performance:

Mock-up testing verifies performance. Performance Mock-Up tested at lab — structural, air, water testing. Field Mock-Up on building tested with actual conditions. Visual Mock-Up for aesthetic approval. ASTM and AAMA test methods. Pass mock-up before production manufacturing. Mock-up failures common opportunity to refine design before production.

Anchorage

Anchorage to building structure:

Anchorage transfers loads to building structure. Slab edge anchors typical — embedded plates or post-installed expansion anchors. Specific load capacity for wind and dead load. Clip angles bolted to anchors and connected to mullions. Tolerance allows thermal expansion/contraction. Wind load transfer to floor diaphragms. System-specific design coordinated with structural engineer.

Glazing

Glazing infill:

Glazing typically insulating glass units (IGUs) — two or three panes with sealed air or argon space. Low-e coatings provide thermal performance. Tinted glass or frit (ceramic pattern) for solar control. Laminated glass for security or hurricane impact resistance. Spandrel glass at non-vision areas. Heat-strengthened or tempered for safety. Specific selection per location and performance.

Installation Process

Installation specific to system:

Installation per system type. Anchors installed during structure work — critical detail. Mullions or unitized panels installed. Glazing installation in stick-built (factory-glazed in unitized). Sealants and gaskets weather-seal. Field testing verifies. Punch list and corrections. Quality control throughout from anchor installation through final.

Field Testing

Field testing verifies installation:

Field testing verifies installation. AAMA 501.2 hose water spray test for water penetration. ASTM E1105 chamber test simulating wind-driven rain. Air leakage testing. Specific test points (typically random sample plus high-risk locations). Pass/fail criteria per spec. Repair and retest if fail. Documentation of testing.

Bottom Line

Curtain wall installation is complex envelope scope for mid- and high-rise commercial. Stick-built and unitized systems serve different applications. Performance requirements span structural, air, water, thermal, solar, acoustic, and fire. Mock-up testing verifies before production. Anchorage transfers loads to structure with thermal tolerance. Glazing typically IGUs with various coatings and properties. Installation specific to system type. Field testing verifies installation. Coordination across structural, glazing, and other trades essential. Tolerance management constant challenge. For GCs on mid- and high-rise commercial, curtain wall is critical envelope scope deserving careful coordination and quality control.