Mark Flanagan, managing director of Ventrolla, explains why vacuum glazing is a key technology, but holistic retrofit planning is needed to maximise the true benefit.

As the UK continues working towards the net zero 2050 goal, attention is beginning to turn to the performance of existing buildings alongside the new ones being built.

With a significant proportion of the country’s housing stock built before modern efficiency standards and expectations were introduced, retrofit is no longer a ‘nice to have’ option, it is essential.

For heritage and listed buildings, the challenge is much more complex. Heritage buildings, as historic assets that must be preserved and understood, are protected by conservation restrictions, and cannot have non-compliant upgrades undertaken.

But with ever increasing energy bills and volatile weather, in addition to net zero targets, there is a challenge in ensuring heritage buildings can be heated to a comfortable standard without extortionate running costs and environmental impact.

Each business within the industry has their own ESG commitments, so it is especially important that we come together and work towards a collective goal of supporting the homes and overall net zero goals.

At the start of this year, we predicted that we would see a rise in the utilisation of vacuum glazing in heritage properties. It is often considered one of the most promising technologies in modern window works, offering high levels of insulation while preserving the charm of traditional single-pane windows.

Beyond the thermal insulation capabilities, vacuum glazing helps reduce energy consumption and carbon emissions, lowering the overall environmental impact of these buildings. We believed that this type of glazing was expected to become a leading option for owners of heritage, period and listed properties, and we were certainly on the right path with that thought.

For the owners of heritage, listed and period properties, replacing the window in its entirety to enhance energy efficiency is often not an option. This is why careful considerations for glass replacements, and glazing options, is key.

There are some challenges when it comes to the installation of vacuum glazing, especially with traditional sash windows. These types of windows were designed for single glazing, meaning they often have narrow glazing bars and shallow rebates, which limits the amount of material that can be accommodated.

Although vacuum glazing is much slimmer than other modern alternatives, it still often requires more depth than many historic frames are able to provide. An education exercise is needed to tackle this, ensuring professionals do not overpromise the use of vacuum glazing where it is not correct to install it. Many believe it is possible to just expand the gap in the sashes, but this can weaken the wood itself.

As the demand for improved performance in heritage buildings continues to grow, and the UK continues its race towards net zero, vacuum glazing is going to inevitably become one of the key solutions within the retrofit sector.

The ability of vacuum glazing to deliver top levels of thermal performance in a thinner glass profile makes it very well suited to historic and listed properties that need to meet strict guidelines and retain traditional features.

However, while the technology is promising, it must not be considered a universal solution. An alternative such as slim heritage double glazing could be considered but still has its own challenges when trying to retro fit into existing sashes. Secondary glazing could also be considered for some heritage or listed properties.

Heritage buildings require a sympathetic, holistic approach for each property, where the structure and history are understood. If this knowledge and research is not there, implementing the likes of vacuum glazing could do more harm than good.

Experts across the entire construction industry must work together to ensure vacuum glazing is specified correctly and only installed in situations where it is the best possible option for the property. When approached correctly, vacuum glazing could play a significant role in helping bring heritage properties up to modern standards of efficiency and sustainability.