Spandrel Glass

Spandrel glass is rendered near-opaque through specialized coating technologies applied to heat-treated glass, creating products suitable for non-vision areas of curtain wall systems. By strategically combining vision and spandrel glass, architects achieve the illusion of a fully glazed building envelope, enhancing modern architectural aesthetics while concealing structural necessity.

Understanding Spandrel Glass Applications

Spandrel glass occupies the non-vision areas of building facades, positioned between sections of transparent glass. These locations typically correspond with floor slabs, mechanical spaces, and structural elements that must be hidden from exterior view. The defining characteristic of spandrel glass is its opacity, which provides complete visual screening while contributing to the thermal performance and safety standards the building envelope requires.

Unlike transparent vision glass, spandrel glass does not need to provide views or natural light transmission. Instead, it serves functional roles including concealing building systems, providing thermal control in areas without natural ventilation, contributing to overall facade aesthetics, and meeting safety requirements for heat-treated glass in curtain wall applications.

OPACI-COAT-300® Spandrel Paint

OPACI-COAT-300® is a water-based silicone paint specifically formulated for spandrel and wall cladding applications. This coating technology can be applied to conceal structural and mechanical elements including ductwork, concrete subfloors, insulation, electrical systems, and piping while providing complete opacity and extensive colour flexibility.

Application Process and Quality Control

At PFG Glass, we apply OPACI-COAT-300® using the spray method, which reduces waste and improves setup times compared to roller applications. This approach ensures uniform coverage, consistent thickness, and the smooth surface finish contemporary curtain walls demand. The spray application happens after glass has been heat-treated, avoiding potential strength reduction concerns associated with some other coating methods.

Our quality control procedures ensure every spandrel panel meets rigorous standards before leaving our facility. Testing verifies no bubbles, peeling, crazing, cracking, tunneling, shrinking, staining, discolouration, or delamination. This comprehensive inspection provides confidence that installed spandrel glass will maintain its appearance and performance throughout the building’s service life.

Technical Advantages of OPACI-COAT-300®

The water-based silicone formulation provides distinct advantages for contemporary building projects. The coating is lead-free and ultra-low VOC, supporting LEED certification pathways and aligning with modern sustainability goals. Unlike ceramic frit coatings that must be applied before tempering, OPACI-COAT-300® is applied after heat treatment, allowing application to any glass type from annealed through fully tempered without affecting glass strength.

When applied at 1.3mm thickness on fully tempered glass, OPACI-COAT-300® provides fallout resistance, meaning the coating helps hold glass fragments together if breakage occurs. This characteristic adds a safety dimension beyond simple opacity, particularly valuable in overhead applications or locations where glass fallout could present hazards.

The coating accommodates exact colour matching and maintains batch consistency across production runs. This consistency matters critically for curtain wall projects where multiple panels must present uniform appearance across large facade areas.

Colour Options and Customization

Stock Colours for Immediate Availability

We maintain inventory of the most commonly specified OPACI-COAT-300® colours, allowing rapid turnaround for projects requiring standard options. Our stock colours include Primary White for clean, bright facades, Medium Gray for neutral contemporary aesthetics, Harmony Gray for warmer grey tones, Warm Gray for softer appearance, and Black for maximum contrast applications.

Custom Colour Matching

For projects requiring specific colours that match surrounding materials or comply with unique design specifications, we provide custom colour matching services. Our virtually unlimited opaque colour palette allows architects to specify exact hues for seamless integration with cladding, window frames, or corporate branding requirements.

Custom colour development typically requires approximately 2-week lead times, accounting for colour formulation, testing, and approval processes. We work with architects to understand colour requirements early in project timelines, ensuring custom colours are ready when fabrication schedules demand.

Colour Selection Considerations

Colour selection for spandrel glass requires careful consideration of the underlying glass type. Standard clear glass contains iron oxide that creates a noticeable green or blue-green tint. This tint can shift the appearance of lighter spandrel colours, particularly whites and pastels. For projects where colour accuracy is essential, we recommend specifying low-iron glass as the substrate, which removes iron impurities and provides colour-neutral transparency that allows spandrel coatings to display true colour values.

Configuration Options for Diverse Project Requirements

Monolithic Spandrel Glass

Monolithic spandrel consists of a single pane of heat-treated glass with opaque coating applied to the back surface. This configuration provides the most cost-effective spandrel solution while meeting safety requirements for heat-treated glass in curtain wall systems.

Monolithic designs work well for projects where additional insulation is integrated into the curtain wall assembly behind the spandrel panel. Proper installation requires back insulation separated from the glass by at least 1 inch to prevent thermal damage, adequate ventilation to manage moisture, and interior finishing materials to complete the assembly.

Insulated Spandrel Glass Units

Insulated spandrel glass units comprise of two or more glass panes separated by air or gas-filled cavities, with an opaque coating typically applied to surface #4 (the interior surface of the interior pane). This configuration provides superior thermal performance compared to monolithic spandrel glass, reducing heat transfer and improving the building’s overall energy profile.

Insulated spandrel units represent the optimal solution for projects with stringent energy code requirements or those pursuing green building certification. The sealed cavity construction provides thermal resistance values ranging from R-3 to R-10 depending on specific configuration, glass selection, gas fills, and spacer systems.

Laminated Spandrel Glass

For applications requiring enhanced safety characteristics, spandrel glass can be produced in laminated configurations. Laminated spandrel bonds multiple glass panes with interlayers made from polyvinyl butyral (PVB) or structural ionoplast polymers. When laminated spandrel glass breaks, the interlayer retains fragments, preventing fallout and making this configuration ideal for overhead applications or areas requiring maximum fall protection.

Performance Benefits Beyond Opacity

Thermal Performance and Energy Efficiency

Spandrel glass contributes to building energy performance by reducing solar heat gain in non-vision areas. The opaque coating reflects or absorbs solar radiation, reducing the amount of heat entering the building and lowering cooling costs. Insulated spandrel configurations deliver thermal performance appropriate to contemporary energy codes, supporting compliance with standards including ASHRAE 90.1 and regional energy requirements.

Proper detailing remains critical for maximizing thermal performance. Thermal bridging through continuous aluminium framing can undermine the insulating value of even high-performance spandrel assemblies. We work with curtain wall fabricators and architects to ensure thermal break integration and proper detailing that maximizes performance.

Safety and Code Compliance

All spandrel glass must be heat-treated to withstand thermal stress from solar radiation and to ensure safety. We typically produce spandrel glass in fully tempered form, which provides approximately four times the strength of annealed glass and breaks into small, relatively harmless fragments if failure occurs.

Our spandrel products comply with rigorous industry standards including ASTM C1048 for heat-strengthened and fully tempered flat glass specifications, ASTM C1036 for flat glass standards, CAN/CGSB 12.1 for laminated or tempered safety glass, and ANSI Z97.1 for safety glazing materials and performance specifications.

Heat-treated spandrel glass displays a laser-engraved logo in one corner identifying the manufacturer, tempering method, and date. This marking provides documentation of regulatory compliance that building inspectors and project teams expect.

Sound Control and Privacy

Spandrel glass provides acoustic benefits by reducing external noise penetration, particularly valuable in urban applications near transportation corridors or industrial areas. The mass of the glass combined with insulated configurations creates sound barriers that contribute to comfortable, productive interior environments.

Complete opacity ensures privacy for mechanical rooms, administrative offices, and other spaces where interior activities or building systems should remain concealed from exterior view.

Technical Support and Specification Assistance

Colour Selection and Mockup Services

We provide samples and guidance throughout the colour selection process, helping architects understand how different colours will appear under actual site conditions. For projects with specific aesthetic requirements or unusual viewing conditions, we strongly recommend full-size outdoor mockups to confirm colour selection before final production begins.

Mockups provide an inexpensive yet valuable process for evaluating spandrel appearance under actual project lighting, surrounding context, and viewing angles. This practice significantly reduces the risk of misalignment between expectations and final installed results.

Size and Thickness Capabilities

Minimum sizes typically start at 14 inches wide by 9 inches tall for both single-lite and insulated unit configurations, though we can accommodate custom requirements based on specific project needs. We work with architects and curtain wall fabricators during early design phases to optimize panel sizing, minimize waste, and ensure dimensions align with framing systems and installation methods.

Quality Assurance and Inspection Standards

Our spandrel glass inspection procedures follow ASTM C1036 and C1048 guidelines. Inspection is conducted from 10 to 15 feet distance under uniform lighting conditions, with glass viewed by reflected light from the exterior surface against a uniform opaque backdrop.

Quality standards specify that pinholes larger than 1/16″ in diameter are not permitted in 80% of the central glass area, while pinholes larger than 3/32″ are not allowed in the outer 20% of the area. Once installed, reflected pinholes and minor imperfections are acceptable if unobtrusive under normal viewing conditions.

This inspection protocol ensures delivered products meet industry expectations for durability and appearance while recognising that minor characteristics invisible under installed conditions do not compromise performance.