15 Milsom Street, City Centre, Bath

15 Milsom Street forms part of a Grade II mid- to late 18th century terrace of townhouses, now with commercial ground floors and shopfronts, situated within the Bath City-Wide Conservation Area and World Heritage Site. Alongside its notable grouped value as part of a contemporaneous terrace, it additionally constitutes part of a high concentration, terraced group of Grade II and Grade II* buildings along Milsom Street, a large number of which are contemporary to the original development of Milsom Street in 1762 by Thomas Lightholder. Milsom Street remains a highly significant commercial streetscape, though originally residential, representative of large-scale Georgian town planning providing intentional sightlines into the city centre. 15 Milsom Street’s value is largely derived from its aesthetic contribution to the wider conservation area and World Heritage Site, and its architectural consistency throughout the rest of the terrace.

As part of the application, the D&A Statement indicates proposals to replace the non-original single pane sash windows with double glazing: “The front elevation windows onto Milsom Street at first and second floor level of No.16 are plain glazed sash windows with horns, which are not the original Georgian windows. It is proposed that these windows are fitted with double glazed units where this can be achieved without altering the appearance of the windows.” Multi-pane sash windows would be retained and fitted with Storm secondary glazing units.

In light of the Climate Emergency, BPT is in-principle supportive of energy efficiency retrofit measures to improve the thermal performance of a building, where changes can be demonstrated to be sensitive to the special interest of a listed building and the wider character and appearance of the historic environment.

We are supportive of the principle of installing magnetic secondary glazing as a less invasive and ‘light touch’ easily reversible retrofit measure to improve the thermal performance and residential comfort of a historic building and ensure its long-term, sustainable use.

The installation of slimlite double glazing is generally supported, where it can be demonstrated that there would be no loss of historic fabric, such as original glazing, and the replacement window units would appropriately replicate a traditional fenestration pattern and profile to sustain the building’s appearance.

We note that the application currently does not provide any details or close-up sections of the proposed replacement window units, or the new secondary glazing units. As such, there is currently insufficient information available to make an informed assessment of the degree of impact to a significant Grade II building within the centre of the World Heritage Site and conservation area. We strongly recommend that further details are submitted as part of this application for the benefit of the case officer.