Vacuum-insulated glass vs. low-emissivity glass for facades - What is The Difference?

Vacuum insulated glass significantly reduces heat transfer by creating a near vacuum between panes, enhancing thermal insulation for facades. Low emissivity glass minimizes infrared heat radiation, improving energy efficiency by reflecting interior heat back into the building.

Table of Comparison

Introduction to Advanced Facade Glazing Technologies

Vacuum insulated glass (VIG) and low emissivity (Low-E) glass represent cutting-edge advancements in facade glazing technologies designed for enhanced thermal performance. VIG uses a vacuum layer between two glass panes to minimize heat transfer, achieving superior insulation without adding bulk, while Low-E glass incorporates a microscopically thin metallic coating that reflects infrared energy, reducing heat loss and solar heat gain. These technologies contribute significantly to energy-efficient building envelopes by optimizing transparent thermal insulation and daylighting in modern facades.

What is Vacuum Insulated Glass?

Vacuum Insulated Glass (VIG) consists of two glass panes separated by a vacuum space that drastically reduces heat transfer, offering superior thermal insulation compared to conventional Low Emissivity (Low-E) glass. Unlike Low-E glass, which uses a thin metallic coating to reflect infrared heat and improve energy efficiency, VIG minimizes conduction and convection by eliminating air or gas between the panes. This advanced technology significantly enhances facade performance in buildings, providing higher energy savings and improved indoor comfort.

Understanding Low Emissivity (Low-E) Glass

Low Emissivity (Low-E) glass features a microscopically thin coating that minimizes infrared and ultraviolet light penetration without compromising visible light, enhancing energy efficiency in building facades. Unlike vacuum insulated glass, which relies on a vacuum layer for superior thermal insulation, Low-E glass primarily reduces heat transfer by reflecting radiant heat, thereby maintaining comfortable interior temperatures. Incorporating Low-E glass in facades optimizes solar heat control and reduces HVAC energy consumption while preserving natural daylight.

Thermal Performance Comparison: VIG vs. Low-E Glass

Vacuum insulated glass (VIG) offers superior thermal performance by minimizing heat transfer through a near-vacuum space between panes, achieving U-values as low as 0.3 W/m2K compared to standard double glazing. Low emissivity (Low-E) glass enhances thermal insulation by reflecting infrared radiation, typically lowering U-values to around 1.0 W/m2K, but it cannot match the thermal barrier provided by the vacuum in VIG. For facades, VIG excels in reducing energy loss and improving insulation without significantly increasing glass thickness, while Low-E glass balances thermal control with cost-effectiveness and sunlight management.

Energy Efficiency and Cost Savings

Vacuum insulated glass (VIG) offers superior thermal insulation by eliminating conductive and convective heat transfer, resulting in lower U-values compared to low emissivity (Low-E) glass, which primarily reduces radiative heat loss through coatings. Energy efficiency gains with VIG can reach up to 50% in extreme climates, significantly reducing heating and cooling costs over time, whereas Low-E glass typically offers a 20-30% improvement. Although VIG has a higher initial cost, its enhanced insulation performance leads to greater long-term cost savings and reduced environmental impact, making it ideal for high-performance building facades.

Acoustic Insulation Properties

Vacuum insulated glass offers superior acoustic insulation for facades by eliminating air gaps that transmit sound, reducing noise pollution significantly compared to traditional glazing. Low emissivity (Low-E) glass primarily enhances thermal performance but provides moderate sound reduction, as its single pane construction is less effective at blocking sound waves. For urban environments demanding high acoustic comfort, vacuum insulated glass is a more efficient solution due to its dual-pane vacuum layer that attenuates noise transmission.

Aesthetics and Design Flexibility

Vacuum insulated glass (VIG) offers a sleek, slim profile that enhances facade aesthetics by minimizing frame depth and allowing for larger uninterrupted glass surfaces, ideal for modern architectural designs. Low emissivity (Low-E) glass provides versatile coatings that can be customized for various tints and reflectivities, offering architects greater control over visual appearance and solar control without compromising transparency. Both technologies improve facade performance, but VIG excels in maintaining a minimalist design with superior thermal insulation, while Low-E glass allows for diverse aesthetic treatments to match specific design intentions.

Durability and Maintenance Requirements

Vacuum insulated glass (VIG) offers superior durability due to its robust vacuum seal that prevents condensation and thermal stress, reducing the risk of glass breakage over time. Low emissivity (Low-E) glass is coated with a microscopically thin, transparent layer that enhances energy efficiency but is more vulnerable to coating degradation, requiring periodic inspection and careful cleaning to maintain performance. Maintenance requirements for VIG are minimal since the sealed vacuum space is protected, whereas Low-E glass demands routine cleaning and occasional recoating to preserve its emissivity properties and overall facade efficiency.

Environmental Impact and Sustainability

Vacuum insulated glass (VIG) offers superior thermal insulation by minimizing heat transfer through a near-vacuum layer, significantly reducing energy consumption in buildings and lowering carbon emissions compared to conventional glazing. Low emissivity (Low-E) glass enhances sustainability by reflecting infrared radiation while allowing visible light, improving energy efficiency but typically with higher embodied energy due to coating processes. In facade applications, VIG provides greater long-term environmental benefits through improved insulation and durability, while Low-E glass contributes to sustainability by optimizing solar heat gain and reducing HVAC loads.

Conclusion: Choosing the Ideal Facade Glazing Solution

Vacuum insulated glass offers superior thermal insulation with minimal thickness, enhancing energy efficiency and occupant comfort in facades. Low emissivity (Low-E) glass reduces heat transfer by reflecting infrared radiation, making it more cost-effective for climate control. Selecting the ideal facade glazing depends on balancing performance requirements, budget constraints, and building design goals to optimize energy savings and aesthetics.