Replacement windows in historic buildings

Readers might wish to note the detailed consideration given by an inspector to an appeal against the refusal of listed building consent for the replacement of a bay window in a Dorset cottage.

To many owners of historic homes it might come as a surprise to find that “Before any decision is made about whether to repair or renew, it is essential that the condition of the joinery is fully understood. It usually necessary to carefully remove the frames so that a detailed examination can be made. It is then possible to prepare an accurate schedule of repair, by reference to each joint, each element of the joinery and each pane of glass.” The inspector goes on to explain in precise terms why the proposed insulated glass units (IGUs) would fail to preserve the special architectural and historic interest of the building (see (DCS Number 400-013-370)). In this regard she draws attention to useful advice on upgrading windows given by Historic England: Traditional Windows: Their Care, Repair and Upgrading, September 2014.

The inspector reports that the HE advice discusses the importance of the scientifically well-established concept of the “whole building approach” to energy conservation in historic buildings, which simply means looking at how the energy usage can be saved throughout the whole property, not just by one measure. It also sets out the evidence gained through research, which has shown how measures such as blinds, insulated curtains and shutters can be a cost effective way of achieving good levels of improvement to the thermal efficiency of older windows.

In the case before her the inspector decided that the limited public benefit in terms of the small reduction in carbon emissions when compared to other ways of improving the thermal performance of the replacement bay window would not justify the harm caused to the significance of the listed building by the visually discordant use of slim profile IGUs.

The following DCP section is relevant: 27.2321