Imagine a pane of glass as thin as a smartphone, that installs into an existing frame without any modifications, without Argon gas, without bulky spacers, yet insulates 10 times better than a single pane and equally well as triple glazing!
This is not science fiction. It already exists on the market (though still at premium prices) and it's called Vacuum Insulated Glass (VIG). It is based on the same principle that keeps your coffee hot inside a thermos flask: Eliminating the air. Let's see how this becomes possible in a window, why it's so impressive, and where it finds practical application.
In classic double glazing, we place air or Argon between two glass panes. This gas acts as an insulating cushion, but even the heavy Argon molecules still transfer some heat.
What if we remove ALL the air molecules? What if we create an absolute vacuum between two panes? Without molecules, there is no conduction or convection of heat. The only remaining heat transfer mechanism is radiation - which we already address exceptionally well with a Low-E coating!
Unlike the 12-16mm cavity of a classic double-glazed unit, the vacuum in a VIG is just 0.1 – 0.3 millimetres thick! This allows the total VIG thickness to remain impressively small: just 6-10mm (typically ~8mm).
This is where the greatest engineering challenge lies. In classic double glazing, the air/gas balances atmospheric pressure. In vacuum glass, the atmosphere exerts enormous pressure (~10 tonnes per square metre!) trying to "crush" the two panes together.
Between the two panes, thousands of microscopic metallic or ceramic pillars (micro-pillars / micro-spacers) are placed in a regular grid, typically every 20-40mm.
Each micro-pillar has a diameter of ~0.3-0.5mm and a height of ~0.1-0.3mm. Up close (with very careful observation) they may appear as tiny dots, but at normal viewing distance (1+ metres) they are impossible to see.
The perimeter of the VIG is hermetically sealed, usually with metallic (indium alloy) or glass (solder glass) bonding, which guarantees the vacuum for decades.
VIG is not (yet) the ideal choice for every home. But in specific applications it is irreplaceable:
Entire historic centres of Europe (including Athens) have buildings with single-pane windows, small dimensions and very thin wooden frames. Replacing with classic double glazing (24-28mm) won't fit the existing frame. VIG (8mm) fits perfectly, delivering wall-level insulation without altering the architectural character.
In oversized minimal fixed glass panes, the reduction in thickness means less weight (important for rollers/mechanisms) and slimmer profiles.
Passive Houses (Passivhaus) require Uw ≤ 0.8 W/(m²K). A VIG with Ug ~0.4-0.5, in a modern frame, can achieve this target without triple glazing.
The vacuum blocks noise equally impressively. A VIG can achieve noise reduction of 35-40 dB, ideal for main roads or airports.
Despite the impressive technology, VIG is still in its maturation phase:
A VIG still costs 3-5 times more than an equivalent-insulation triple-glazed unit. Production is more complex (requiring high-temperature ovens and vacuum equipment).
Current VIG units are available in maximum dimensions of approximately 1.5 × 3.0 m (varies by manufacturer). For oversized applications, they don't yet reach jumbo sizes.
Major manufacturers (AGC, NSG/Pilkington, LandGlass) are investing billions in automation and production scale. The industry forecast is that within the next 5-10 years the price will drop dramatically, making VIG a mainstream choice for renovations and mid-to-high-value new builds.
Vacuum Insulated Glass (VIG) is the ideal balance of thickness, weight and insulation. For heritage buildings and renovations, it is already the only solution that sacrifices nothing. For new builds, it's a matter of time (and price reduction) before it becomes the new norm.
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