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What are the Most Efficient Heritage Windows?

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Heritage windows with vacuum glazing in a grade II listed property after renovation

What are the Most Efficient Heritage Windows?

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Published on: October 5th, 2020

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What are the Most Efficient Heritage Windows?

Heritage windows have changed considerably through the years and there are now highly energy efficient Heritage windows on the market, which also reflect the traditional appearance. The invention of vacuum glazing has revolutionised the Heritage window market, delivering exceptional U-values better than triple glazing while also match the aesthetic required in older or Listed buildings.

What is the history of Heritage windows?

Historic windows were manufactured with single glazing. These glass panes would achieve U-values between 4.8 and 5.8W/(m²K). The construction methods used on these windows involved antiquated or non-existent seals, multiple small panes, putty glazing systems and older style ironmongery, which could further reduce the performance of the windows.

As climate change and sustainability issues have come into focus in recent years, the window and door industry has tried to respond by utilising more efficient glazing units and modern window profiles. These products may seem like good compromises, but they are typically either not in keeping with traditional buildings (like standard double glazing) or they have significantly reduced lifespans (like slim double glazing). Until now, this has meant that owners of Listed buildings or properties in conservation areas must make significant sacrifices in comfort, maintenance cycles, or appearance in order to replace their windows.

Vacuum glazed Heritage Windows

In 2014, when our team first came across Vacuum glazing, we knew that it was potentially game-changing for new Heritage window manufacture. A vacuum cavity is super-efficient and therefore can be over 50 times thinner than a conventional double-glazed unit while delivering a better U-value (as low as 0.48 W/(m²K)). The ultra-thin cavity means that there is no discernible double reflection in the unit (a tell-tale sign of modern double glazing) and that makes it perfect for Heritage windows. There were no new windows on the market encompassing vacuum glazing, so we set about designing a full range of Heritage windows and doors to revolutionise market.