The Sash Restoration Company have been involved in the design, development and manufacture of traditional double hung box sash windows for almost 20 years. Our aim from the beginning has been to produce a refined yet thermally and acoustically efficient window for both new build and replacement in period buildings. Up until one year ago the finest glazing bar we could achieve (within the contsraints of the double glazed units available in the marketplace) was 27mm in width, as can be seen on all the double glazed windows displayed in the rest of this website.

Due to advances in spacer bar technology and the development of a unique "warm edge spacer bar", we have been able to reduce the width of our glazing bars to 22mm. This, as you can see from the photos in this section, has allowed us to create a double glazed box sash window which comes very close visually to it's single glazed counterpart.

Our new design has attracted a great deal of attention from conservation architects and planners. We have installed 30 six over six Georgian replacement windows in a Grade II listed building (principle elevation) in Halifax, with the full consent of West Yorkshire Planning Authority. We are also currently installing 23 Georgian style box sash windows on Picadilly in London, again Grade II listed, with the full consent of Westminster Planning Authority.

For technical details, go to our materials and construction section.

Otherwise, please browse the photos in this gallery section to see a selection of double glazed projects incorporating our 22mm glazing bar.

Large Venetian Box Sash Window

Internal detail	External elevation