Achieving triple glazed performance with just two panes

At the DACH+HOLZ trade fair in Cologne, Germany, VELUX unveiled its new vacuum insulating glass technology — an innovative product designed to take the performance of roof windows to the next level.

Developed in partnership with Guardian Glass, the technology is specifically engineered for roof windows — a far more demanding application than facades due to higher loads and structural requirements. It provides high thermal and acoustic insulation with a reduced CO₂ footprint, contributing to more sustainable buildings and improved indoor comfort.

This new technology allows VELUX to replace the space between glass panes with a vacuum that significantly reduces heat transfer. This enables excellent insulation performance within a much thinner and lighter construction compared to standard triple glazing. Instead of separating panes with argon or krypton gas, this solution uses a vacuum that effectively minimises heat loss.

As a result, the vacuum insulating glass achieves the performance of triple glazing in a slimmer, lighter design. A subtle dotted pattern created by tiny spacers between the panes is characteristic of this technology but does not obstruct the view. VELUX will introduce the technology in two variants: a single vacuum glazing solution and a hybrid version. 

Single Vacuum Glazing

The single vacuum glazing variant is an ultra-thin double pane design that delivers thermal performance comparable to triple glazing. By eliminating the third pane, this new solution is between 1.5 and 5 kg lighter per MK06 unit (depending on the full window construction), making installation easier.

In addition, it offers approximately 30% lower CO₂ footprint when comparing the insulating glass unit alone. A roof window equipped with this glazing achieves an impressive insulation value of Uw = 1.0 W/(m²K). The difference becomes clear when comparing thickness: this new glass measures only 11.5 mm, versus 26.4 mm for standard double glazing and 38 mm for standard triple glazing with similar insulation performance.

It will debut in 2026 in the UK and Ireland within the VELUX Heritage range, ensuring architectural authenticity is preserved while delivering superior thermal and acoustic performance for enhanced indoor comfort.

Vacuum Hybrid Technology

The hybrid version combines the vacuum double glazing with a third pane separated by a gas filling. This construction delivers outstanding thermal insulation and excellent sound reduction while lowering the CO₂ footprint. With a Uw value of 0.83 W/(m²K) and a sound insulation rating of 38 dB, the hybrid solution offers high energy efficiency and acoustic comfort, comparable with the company’s most efficient glazing, IGU 67, with reduced carbon emissions by 5% compared with a full roof window and by 12% compared with the glass alone.

A launch date for the German market has not yet been set. Depending on project interest and availability, VELUX expects to expand the offering to additional European markets.

Background Information

VELUX began testing vacuum insulating glass more than 20 years ago and introduced early versions to the German market. While promising, demand for ultra‑low U‑value products was lower at the time, and performance advantages were not yet significant enough compared to standard triple glazing.

Since then, vacuum glass technology has advanced considerably in durability and performance, especially in facade systems. Tempered glass is now used for greater resilience, sealing methods have improved vacuum integrity, and closed absorber systems remove residual and released gases.

Building on this progress, VELUX spent the past decade developing vacuum insulating glass technology and, since March 2024, has continued development through partnership with Guardian Glass. Improvements include a fully tempered glass solution with fewer supporting spacers between panes — enhancing insulation — and the ability to achieve lower Ug values than standard triple glazing‑ with the hybrid solution. Single vacuum glazing now enables ultra-thin double pane units with sleek profiles and comparable performance to conventional triple glazing.