Vacuum insulated glass achieves what gas-filled IGU cannot: it eliminates convective heat transfer entirely. This is how a panel 8.2mm thick outperforms triple glazing 44mm thick.
Heat moves through a window system via three mechanisms: conduction through the glass and spacers, convection through the gap fill, and radiation across the gap surfaces. In conventional gas-filled IGU, convection accounts for the majority of heat loss. VIG eliminates it entirely.
A single pane of glass is essentially transparent to heat. Conduction through the glass is high, convection on both interior and exterior air sides is uninhibited, and radiation passes freely with no Low-E coating.
Two panes with an argon-filled gap reduces convection compared to air but does not eliminate it. Argon has a thermal conductivity of 0.017 W/mK — better than air (0.026), but still conducting. Gas-fill degrades over time as argon slowly escapes through spacer seals.
Vacuum pressure below 10⁻² Pascal means there are essentially no gas molecules to carry heat. Convective transfer drops to zero. The only remaining pathways are conduction through the tiny ceramic pillar contact points, and radiation — which is dramatically reduced by the D80 double silver Low-E coating.
U-values are centre-of-glass unless noted. VIG U=0.40 per EN 673:2011 / NFRC 100-2010, confirmed by TÜV Rheinland (Report CN25TTIK, September 2025). Frame and edge effects excluded.
A vacuum insulated glass panel is a precisely engineered system, not simply "two panes with a vacuum between them." Each element — glass substrate, Low-E coating, ceramic pillar, metal seal, and getter — plays a critical and non-interchangeable role in the unit's lifetime performance.
Produced on Glaston FC500 furnaces to achieve world-class surface flatness. Must be tempered, not heat-strengthened — VIG operates under atmospheric differential pressure of ~10 tonnes/m², which only fully tempered glass can sustain indefinitely without creep.
Applied to the inner face of the outer pane. Dramatically reduces radiative heat transfer across the vacuum gap. S1.16 single silver reduces emissivity to ≈0.04. D80 double silver reduces it further to ≈0.02 — the primary reason the 4+V+4 hits U=0.40.
A low-melting-point metal alloy seal runs around the full perimeter, hermetically joining the two panes. Unlike polymer or epoxy seals used in some competitors' products, metal seals are stable at extreme temperatures, do not outgas, and do not creep — rated to −35°C and 90°C.
The only structural elements within the vacuum gap. Typically cylindrical ceramic discs, 0.5mm (micro-dot) or 0.8mm (normal) in diameter, arranged in a precise grid. Each pillar supports atmospheric pressure load at its contact point. Spacing is configuration-dependent: 25–40mm depending on glass thickness. Ceramic has very low thermal conductivity, minimising pillar-path conduction.
A small chemical absorber embedded within the vacuum gap. Over the product's 15-year lifetime, trace gases can permeate through glass and the seal. The getter chemically binds these molecules, maintaining vacuum integrity without re-evacuation. Leadus uses a needle-type getter, which provides a larger reactive surface area than disc-type alternatives. No evacuation port — the unit is sealed without a visible port hole.
Ceramic pillar spacers are the most important performance variable within the vacuum gap. Their diameter, height, material, and grid spacing collectively determine the panel's structural integrity, optical quality, and residual conductive heat transfer. Leadus offers two pillar specifications across its product range.
The conventional ceramic spacer used in 3+V+3 configuration. At 0.8mm diameter, the pillar contact area is small but visible at certain angles under raking light. Used where cost efficiency and structural simplicity are the primary considerations — heritage slim-profile projects with tight tolerances.
The advanced spacer used in 4+V+4, 5+V+5, and 6+V+6 configurations. At 0.5mm diameter, micro-dot pillars are effectively invisible to the naked eye — the contact dots are smaller than a visible pixel on most viewing conditions. Reduced diameter also means lower per-pillar conductive heat transfer, slightly improving the overall U-value at equivalent grid spacing.
Why pillars are under enormous stress. Standard atmospheric pressure is 101,325 Pa ≈ 10.3 tonnes per m². A VIG panel with 0.2mm vacuum gap has the full atmospheric differential pressing the two panes together — a 1m² panel supports over 10 tonnes of compressive load through its ceramic pillars. This is why fully tempered glass (not annealed, not heat-strengthened) is mandatory, and why Glaston FC500 tempering for glass flatness is the production prerequisite, not a marketing claim.
Conventional high-performance IGU fills the gap between panes with argon or krypton gas. These noble gases reduce convection compared to air. But they do not eliminate it — and their benefits degrade over time as gas slowly permeates through spacer seals. Vacuum is a fundamentally different approach.
Noble gas fill reduces convective heat transfer compared to air — argon conductivity is 0.017 W/mK vs 0.026 for air. But gas molecules still exist, still carry heat. Convection still occurs. And over 10–25 years, argon slowly permeates through the warm-edge spacer seal, being replaced by air.
Below 10⁻² Pascal, the mean free path of any remaining gas molecule is longer than the gap itself. Molecules cannot interact with each other to transfer heat. Convective heat transfer is physically impossible — not just reduced. And vacuum, unlike gas, cannot escape.
With convection eliminated by the vacuum, radiation becomes the dominant remaining heat transfer mode. Low-E coatings reduce this by reflecting long-wave infrared radiation — the thermal energy your heating system produces — back into the building. Leadus offers two Low-E specifications across its product range.
A single layer of silver deposited via magnetron sputtering between anti-reflection oxide layers. Provides a strong balance of low emissivity, high visible light transmission, and solar control — the practical standard for most heritage and residential applications.
Two silver layers with additional anti-reflection and barrier coatings. Reduces emissivity further than single silver while improving visible-to-solar selectivity — more daylight, less solar heat gain, better winter heat retention. The coating that makes U=0.40 possible in the 4+V+4 configuration, and is required for Ontario Step Code 5 and Passive House compliance.
Glass flatness is the single most critical manufacturing variable in VIG production. The 0.2mm vacuum gap must be supported by ceramic pillars with sub-millimetre contact points. If the glass surface is not flat within tight tolerances, those contact points cannot support atmospheric pressure uniformly — and the vacuum seal fails. Glaston's FC500 tempering furnace delivers the world-standard for glass flatness. In February 2026, Glaston and Leadus formalised their cooperation to advance VIG manufacturing further.
All four VIG Horizon configurations in one reference view. All values are per EN 673:2011 / NFRC 100-2010 unless noted. For project-specific calculations, contact VIG Horizon Inc.
| Parameter | 3TL+V+3T | 4TL+V+4T | 5TL+V+5T | 6TL+V+6T |
|---|---|---|---|---|
| GLASS SUBSTRATE | ||||
| Total thickness | 6.2 mm | 8.2 mm | 10.2 mm | 12.2 mm |
| Glass pane thickness | 3 mm each | 4 mm each | 5 mm each | 6 mm each |
| Vacuum gap | 0.2 mm | 0.2 mm | 0.2 mm | 0.2 mm |
| Tempering degree | Fully toughened | Fully toughened | Fully toughened | Fully toughened |
| Tempering equipment | Glaston FC500 | Glaston FC500 | Glaston FC500 | Glaston FC500 |
| THERMAL PERFORMANCE | ||||
| U-value (centre of glass) | 0.58 W/m²K | 0.40 W/m²K | 0.44 W/m²K | 0.42 W/m²K |
| U-value test method | EN 673:2011 | EN 673:2011 + NFRC 100 | EN 673:2011 | EN 673:2011 |
| TÜV Rheinland certified | — | Yes · CN25TTIK | — | — |
| Min. operating temp. | −35°C | −35°C | −35°C | −35°C |
| Ontario Step Code 5 (<0.45) | No (0.58) | Yes (0.40) | Yes (0.44) | Yes (0.42) |
| PILLAR SYSTEM | ||||
| Pillar type | Normal (0.8mm) | Micro-dot (0.5mm) | Micro-dot (0.5mm) | Micro-dot (0.5mm) |
| Pillar grid spacing | 25 mm | 30 mm | 40 mm | 40 mm |
| Pillar colour | White / Black | White / Black | White / Black | White / Black |
| Evacuation port | None | None | None | None |
| Getter type | Needle | Needle | Needle | Needle |
| LOW-E COATING | ||||
| Available Low-E options | S1.16 only | S1.16 / D80 ★ | S1.16 / D80 | S1.16 / D80 |
| Recommended for Step Code 5 | — | D80 (for U=0.40) | D80 | D80 |
| PRODUCTION SIZES | ||||
| Minimum size | 300 × 300 mm | 300 × 300 mm | 300 × 300 mm | 300 × 300 mm |
| Maximum size | 1000 × 2000 mm | 1500 × 2500 mm | 1900 × 2800 mm | 1900 × 2800 mm |
| Maximum area | 2.0 m² | 3.75 m² | 5.32 m² | 5.32 m² |
| CERTIFICATION | ||||
| SGCC safety glazing | #9744 COMP+CAN | #9744 COMP+CAN | #9744 COMP+CAN | #9744 COMP+CAN |
| IGCC seal durability | #6076 | #6076 | #6076 | #6076 |
| Canadian standard | CAN/CGSB 12.1-2022 | CAN/CGSB 12.1-2022 | CAN/CGSB 12.1-2022 | CAN/CGSB 12.1-2022 |
| Warranty (VIG Horizon, Canada) | 15 years | 15 years | 15 years | 15 years |
| PRIMARY APPLICATION | ||||
| Best fit | Heritage / slim-profile restoration | Net-Zero / Step Code 5 / most specified | Commercial / curtain wall | High-rise / high wind |
All values indicative. Project-specific calculations available from VIG Horizon Inc. upon request. ★ = D80 recommended for Step Code 5.
Download the full technical data sheet or request a project-specific specification package — U-value calculations, CAN/CGSB compliance mapping, SGCC documentation. In English or French, within 48 hours.