Updated August 2024: In recent years, window technology has made major advances. At Gowercroft, we now use LandVac vacuum glass instead of Pilkington Spacia™ due to its many advantages. LandVac offers superior thermal insulation, enhanced soundproofing, and greater durability, while maintaining a slim profile ideal for heritage applications. This cutting-edge glass allows us to deliver windows that exceed the highest standards of energy efficiency, sustainability, and aesthetic appeal.
Conventional double glazing uses two glass panes separated by a gap of up to 20mm. This cavity is filled with dry air or inert gases like Argon or Krypton to reduce heat transfer. The wider the gap, the better the insulation — up to an optimal point. Beyond that, the gas begins to circulate and reduces the benefit.
Pilkington Spacia™ is different. Instead of using gas, it extracts the air from the cavity, creating a vacuum between two panes of glass. This vacuum significantly reduces heat transfer by eliminating conduction and convection.
Thanks to this design, the total unit thickness is just over 6 mm. That’s one quarter of the thickness and two thirds of the weight of standard double glazing. Radiation heat loss is minimised through a low-emissivity coating, similar to those used in high-performance glazing.
Pilkington Spacia™ was developed in Japan to meet high energy performance targets with less glass per square metre. The goal was to reduce building weight in earthquake-prone regions and improve safety.
Its slimline profile made it ideal for historic windows and buildings where standard double glazing would be too bulky or visually intrusive.
In the UK, Pilkington Spacia™ has been embraced by the heritage sector. Its ultra-thin 6.5 mm thickness avoids the double reflection seen in standard units and fits within traditional upstands. That makes it easier to satisfy conservation officers and maintain a period-accurate appearance.
Although still a niche product in the UK market, it has seen rising interest from architects and property owners seeking efficient, conservation-approved glazing. Pilkington Spacia™ currently carries a 10-year warranty and offers excellent thermal and acoustic performance.
Back in 2014, we were actively searching for an alternative to slim double glazing, which had consistently underperformed. When our product team discovered Pilkington Spacia™, we began extensive testing and completed a major installation in Richmond, London.
This convinced us of its potential. We went on to design two high-performance heritage window ranges that integrated this glass:
These windows combined traditional aesthetics with superior energy performance and long-life guarantees for any building.
We now use LandVac vacuum glass, which has replaced Pilkington Spacia™ across our product range. It offers:
If you’re working on a historic building or simply want the best energy performance from your glazing, we have great vacuum glazed options available. Our Heritage Range is perfect for Listed and Conservation properties, whereas our Performance Range is ideal for those seeking advanced levels of thermal insulation.
If you’re working on a period property, refurbishment, or energy-efficient upgrade, we can help. Get in touch with our expert team to discuss your project, request a demonstration, or book a tour of our Derbyshire workshop.