What Is Vacuum Glazing? A Guide to U-Values & Performance”

A comprehensive guide to the “impossible” glass transforming UK heritage homes.

For decades, the glazing industry has been fighting a battle between Performance and Aesthetics. If you wanted energy efficiency, you had to accept thick, heavy double or triple glazing. If you wanted slim, elegant heritage lines, you had to accept cold, draughty single glazing.

Vacuum Insulated Glazing (VIG) has ended that war. It offers Passivhaus-level insulation in a unit that essentially looks like single glazing from a distance.

1. The Science: How a Vacuum Works

To understand why VIG is revolutionary, you need to understand heat transfer. Heat moves in three ways: Conduction, Convection, and Radiation.

• Standard Double Glazing slows heat using a deep pocket of Argon gas. Gas is a poor conductor, but it still conducts some heat.
• Vacuum Glazing removes the gas entirely. It creates a total vacuum between the two sheets of glass.

Because a vacuum contains virtually no matter (no molecules), heat cannot travel through it via conduction or convection. It is the perfect insulator. This allows a microscopic 0.3mm gap to do the thermal work of a bulky 16mm gas cavity.

2. Inside the Unit: Getters & Pillars

Creating a stable vacuum inside a flat glass unit involves some incredible engineering. If you simply remove the air, standard atmospheric pressure will instantly try to crush the two panes of glass together with immense force.

The Micro-Pillars: To stop the glass from crushing inward and touching, thousands of microscopic “pillars” (spacers) are placed between the panes. In premium units like LandVac, these are spaced on a strict 20mm grid and are barely visible to the naked eye.

The Getter: Over a 25-year lifespan, tiny amounts of gas might naturally leach out of the glass material itself. To maintain the purity of the vacuum, a small “Getter” dot is placed inside the unit. This material acts like a sponge, absorbing any stray gas molecules and ensuring the vacuum (and your insulation) remains completely intact for decades.

3. Head-to-Head: VIG vs. Triple vs. Double

How does the new technology stack up against current market leaders? We compared LandVac Heritage vacuum glass against standard industry units.

The “Hybrid” Option (Passivhaus Performance)

For modern homes or new extensions where window frame thickness isn’t an issue, we can supply a “Hybrid” unit (often called LandVac Optimum). This places a fully sealed Vacuum unit inside a standard double-glazed unit with an Argon gas cavity.

The result? A hybrid triple-glazed unit with an astonishing U-Value as low as 0.2 W/m²K—offering space-age insulation specifically tailored for strict zero-carbon homes.

4. The Local Heritage Solution

5. The Acoustic Benefit

It’s not just about trapping heat. Vacuum glazing is arguably the best acoustic glass on the market relative to its minimal thickness.

Sound waves behave very much like heat—they require a physical medium (like air or gas) to travel through. They fundamentally struggle to cross a vacuum. While the internal micro-pillars do transmit a tiny fraction of sound, the main vacuum barrier blocks a massive amount of high-frequency noise (like voices and wind whistling) and low-frequency traffic drone. A standard 8.3mm unit offers noise reduction comparable to high-spec, thick acoustic laminated glass.

6. Advantages & Drawbacks

The Advantages

• Heritage Aesthetics: It preserves the character of older homes by allowing genuine slim sightlines without the bulk.
• Safety First: Unlike much older vacuum technologies, modern LandVac units are manufactured from Toughened Safety Glass as standard, making them five times stronger than standard annealed glass.
• Longevity & Sustainability: The units are fully recyclable and are expected to last significantly longer than standard gas-filled units because there is no gas cavity to degrade or “leak out” over time.

7. Frequently Asked Questions