Double Glazed Sash Windows

Period Double Glazed wooden Sash Windows

Since 2004 Building Regulations have had to be extended to include period properties. Even back as far as the early nineties Sashpro (not a Ltd company then) was coming up with ways to improve the weather performance of period windows. Sash windows have gone further with major changes in order to provide for the demanding environmental challenges that must be met.

As one of the first ‘modern’ firms to address the preservation of sash windows in general, Sashpro has helped to develop a number of innovations that make it possible for the period sash window

Sashpro draught proofing – durable easy glide

to remain in existence and be accountable ecologically. We developed a weather proofing system that not only addressed the traditional synonymous combination of the words draughty and sash window, now thankfully rendered apart but we did it completely invisibly. In other words it’s one of those clever devices you’ll never see, so sash windows remain unaffected aesthetically. All good so far but not good enough for building regs.

Sashpro glass stillage


Double glazing and traditional sash windows were never terms that sat happily together on the purists tongue however looking at the combination from the perspective that it was inevitable and thanks to a great Scottish inventor (whose needs might perhaps be considered greater up north!) Sashpro took a leap of faith and started to use the innovative Slim Sealed Unit.

A low emissivity glass and the dense inert gas krypton, used instead of argon, along with ‘warm edge technology’ all allowed for the manufacture of super slim double glazing for sash windows, traditional timber casement windows and of course timber doors.

Sashpro slim sealed units

Sashpro slim sealed units





Allow these photos to explain

Here we can see that the sealed unit is virtually undetectable though it provides a U value of 1.5 meeting PartL Building Regs 2014 to current


Complicated sashes can be double glazed (and yes that’s a lot of sawdust)

…and installed looking exactly like the original


Re-made to look exactly like the original below, double glazed and draught proofed

…and how the old looked when we brought it back to Beadman St





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Sashpro Ltd | 1 Beadman St, London, SE27 0DN