Nestling in the shadows cast by the iconic St Pauls Cathedral, occupying the south side of Paternoster Square stands the Grade II* Listed Chapter house. Designed by Sir Christopher Wren and his son and built between 1712 and 1714, this beautiful, classically proportioned building has had a chequered history. Both the Cathedral and Chapter House survived a direct hit during the Blitz in 1940. Chapter House was renovated during the 1950s and adapted into offices. Recently major work has been undertaken to make the building more ecologically and thermally efficient. During its restoration Chapter House’s insulation has been brought up to 21st century standards in order to retain heat and reduce energy bills. Heat loss reduction of up to 50% can be achieved using bespoke secondary glazing units. Suitable products from the range were selected for each window opening, depending on the benefits required. Secondary glazing is fully reversible and therefore widely accepted as an adaptation in Listed buildings. Great care was taken to ensure that the colours of the secondary glazing frames would blend with the existing interior. Since this project was completed the Series 30 has been superceeded by the Series 31 lift-out.