Glass Options: Performance-Based Selection

The selection of appropriate glazing materials represents one of the most critical decisions in storefront design, directly impacting energy performance, occupant comfort, security, and long-term operational costs. Modern glass technology offers numerous options for optimizing thermal performance, solar control, and safety characteristics to meet specific project requirements.

Insulated Glass Units (IGUs)

Insulated glass units form the foundation of modern commercial glazing systems, utilizing two or more glass panes separated by spacer systems and sealed to create insulating air spaces. The thermal performance of IGUs significantly exceeds that of single-pane installations, with standard 1-inch units providing U-factors of 0.47 compared to 1.10 for single-pane glass.

The construction of high-performance IGUs involves several critical components that collectively determine thermal and optical performance. Primary and secondary seals prevent moisture intrusion and maintain the integrity of the insulating air space, while spacer systems minimize thermal bridging at the glass edge. Desiccant materials within the spacer system absorb any residual moisture to prevent condensation between glass panes.

Gas fills represent an important performance enhancement for IGUs, with argon gas providing improved thermal resistance compared to air-filled units. Argon-filled IGUs typically achieve U-factor improvements of 0.02-0.03 compared to air-filled units, representing a 5-7% enhancement in thermal performance. Krypton gas provides even greater thermal resistance but at significantly higher cost, making it suitable primarily for premium applications where maximum performance is required.

The durability of IGUs depends heavily on seal integrity and proper installation practices. High-quality dual-seal systems with structural and moisture seals provide redundant protection against seal failure, while proper glazing techniques ensure adequate support and drainage. Expected service life for quality IGUs ranges from 15-25 years, with seal failure typically manifesting as condensation or fogging between glass panes.

Low-E Coatings: Advanced Solar Control

Low-emissivity coatings represent the most significant advancement in commercial glazing technology, providing dramatic improvements in thermal performance while maintaining high levels of visible light transmission. These microscopically thin metallic coatings selectively reflect infrared radiation while allowing visible light to pass through, effectively reducing heat transfer without compromising natural lighting.

The performance characteristics of Low-E coatings vary significantly based on coating type and application method. Pyrolytic (hard coat) Low-E coatings are applied during glass manufacturing and provide good durability and moderate performance enhancement. Sputtered (soft coat) Low-E coatings are applied in vacuum chambers after glass formation and offer superior thermal performance but require protection within IGU assemblies.

SOLARBAN 60 Solar Control Low-E Glass represents a high-performance option particularly suitable for New Jersey's climate conditions. When assembled in 1-inch IGUs, SOLARBAN 60 achieves a U-factor of 0.29 and Solar Heat Gain Coefficient (SHGC) of 0.38 while maintaining 70% visible light transmittance. This combination provides excellent solar control for reducing cooling loads while preserving natural lighting quality.

SOLARBAN 70 High Performance Low-E Glass offers even greater solar control with an SHGC of 0.27 and U-factor of 0.28, making it ideal for applications where maximum energy performance is required. The 64% visible light transmittance maintains good natural lighting while providing superior heat rejection for buildings with high internal heat gains or extensive glazed areas.

The selection between different Low-E coatings depends on building orientation, internal heat loads, and energy performance targets. South and west-facing exposures typically benefit from lower SHGC values to reduce cooling loads, while north-facing glazing may prioritize higher visible light transmittance to maximize natural lighting. Energy modeling can optimize coating selection for specific projects and climate conditions.

Laminated Safety Glass

Laminated glass provides enhanced security and safety performance through the incorporation of polymer interlayers that hold glass fragments together when broken. This construction method creates glazing systems that resist forced entry while maintaining optical clarity and providing protection against injury from glass fragments.

The interlayer material in laminated glass, typically polyvinyl butyral (PVB) or ethylene vinyl acetate (EVA), determines the performance characteristics of the finished product. Standard PVB interlayers provide basic safety glazing performance, while specialized interlayers offer enhanced security, acoustic control, or structural capabilities. The thickness and number of interlayers can be varied to achieve specific performance targets for different applications.

Security applications often utilize multiple interlayers or specialized materials to resist forced entry attempts. These systems can withstand repeated impacts from hammers, crowbars, and other common tools while maintaining structural integrity. The time required to breach laminated security glazing provides valuable delay for security response, making these systems particularly valuable for banks, jewelry stores, and other high-risk retail applications.

Acoustic performance represents another important benefit of laminated glass, with the polymer interlayer providing vibration damping that reduces sound transmission. This characteristic makes laminated glass particularly valuable for storefronts in high noise environments or applications where interior sound control is important.

Tempered Safety Glass

Tempered glass provides safety glazing performance through heat treatment that creates compressive stresses in the glass surface, resulting in strength approximately four times greater than annealed glass. When broken, tempered glass fractures into small, relatively harmless fragments rather than large, sharp shards that characterize annealed glass failure.

The tempering process involves heating glass to approximately 1200°F and then rapidly cooling with air jets to create the desired stress pattern. This process cannot be reversed, and tempered glass cannot be cut or modified after tempering, requiring precise sizing and edge work before heat treatment. All holes, notches, and edge polishing must be completed prior to tempering.

Building codes require tempered glass in numerous storefront applications, including all door glazing and glazing within 24 inches of door openings up to 60 inches above the floor. These requirements ensure occupant safety in areas where human impact is most likely to occur. Proper identification marking is required for all tempered glass installations, with permanent etching or labeling indicating compliance with safety standards.

The optical quality of tempered glass may exhibit slight distortion due to the tempering process, particularly in larger sizes or thinner sections. This distortion is generally acceptable for commercial applications but should be considered for installations where optical precision is critical.

Tinted and Reflective Glass

Tinted glass provides solar control through the incorporation of metallic oxides during glass manufacturing, creating colored glass that absorbs solar radiation and reduces heat gain. Common tint colors include bronze, gray, green, and blue, with each offering different combinations of solar control and aesthetic appearance.

The performance of tinted glass depends on color intensity and thickness, with darker tints providing greater solar control but reduced visible light transmission. Bronze and gray tints offer good solar control with neutral color rendering, while green and blue tints provide distinctive aesthetic effects but may alter color perception of interior spaces and merchandise.

Reflective glass coatings provide solar control through reflection rather than absorption, utilizing metallic coatings applied to the glass surface. These coatings can be applied to clear or tinted glass substrates to achieve specific performance targets. Reflective coatings typically provide superior solar control compared to tinted glass alone but may create glare issues for adjacent properties or roadways.

The selection between tinted and reflective glass depends on aesthetic preferences, solar control requirements, and local regulations. Some municipalities restrict the use of highly reflective glazing to prevent glare impacts on neighboring properties or traffic safety concerns.

Spandrel Glass

Spandrel glass provides opaque glazing for concealing structural elements, mechanical equipment, or floor slabs while maintaining visual continuity with vision glazing areas. These systems utilize painted, ceramic-coated, or laminated glass to achieve the desired opacity while providing weather protection and thermal performance.

The thermal performance of spandrel areas requires careful consideration, as these locations often experience higher heat gains due to reduced thermal mass and insulation compared to conventional wall construction. Insulated spandrel systems with thermal breaks and appropriate insulation can achieve thermal performance comparable to conventional wall systems.

Color matching between vision and spandrel glazing requires careful coordination during design and procurement phases. Lighting conditions, viewing angles, and glass thickness can all affect color appearance, making sample approval and mock-up construction important quality control measures.

Switchable (Smart) Glass

Switchable glass technology enables on-demand privacy and solar control through electrochromic, suspended particle device (SPD), or polymer dispersed liquid crystal (PDLC) systems. These technologies allow glazing to transition between clear and opaque states, providing dynamic control over privacy and solar heat gain.

Electrochromic glass provides variable tinting through electrical activation, allowing continuous control over visible light transmission and solar heat gain. These systems can be integrated with building automation systems to provide automatic solar control based on time of day, solar conditions, or interior temperature requirements.

SPD and PDLC technologies provide rapid switching between clear and opaque states, making them particularly suitable for privacy applications in conference rooms, medical facilities, or executive offices. The switching speed and opacity levels vary between technologies, with each offering distinct advantages for specific applications.

The cost of switchable glass systems remains significantly higher than conventional glazing, limiting applications to specialized uses where dynamic control provides substantial operational benefits. However, energy savings from automated solar control can provide partial cost offset in appropriate applications.

Performance Comparison Table

Glass TypeU-FactorSHGCVLTRelative CostBest ApplicationsClear IGU0.470.7079%BaselineBasic applicationsSOLARBAN 600.290.3870%+15-25%Balanced performanceSOLARBAN 700.280.2764%+20-30%Maximum energy efficiencyLaminated IGU0.470.7075%+25-40%Security applicationsTempered IGU0.470.7079%+10-15%Safety glazing areas

Performance data for 1-inch IGUs with 1/2-inch air space. Source: Vitro Architectural Glass