12 Hanover Street, Walcot, Bath
12 Hanover Street forms part of a Grade II late 18th - early 19th century terrace, 7-12 Hanover Street, situated within the Bath conservation area and World Heritage Site. 12 Hanover Court forms the southernmost end of the terrace with a dual frontage overlooking London Road. The terrace is a typically elegant example of its housing type with a uniform shared façade of Bath stone ashlar that steps down the north-south slope towards the valley floor, made up of a series of two bay dwellings transitioning into grander three bay dwellings towards the southern end.
BPT does not typically comment on internal alterations without the benefit of a site visit. However, we note that proposals include the installation of underfloor heating across both south-eastern rooms at ground and first floor, and we query whether the floor structure would be capable of bearing the additional load. We trust that this detail will be appropriately considered by the case officer.
The use of lime plaster and breathable paints to address damp issues at basement level is supported as a more sympathetic material intervention which would work with the breathable qualities of the Bath stone. We additionally suggest further assessment of the areas affected to see if previous unsympathetic repairs may be responsible, such as cementitious pointing, etc.
In light of the declared Climate Emergency, BPT is supportive of sensitive sustainability retrofits, where deemed appropriate, within the historic environment, as well as the sympathetic upgrade of traditional and listed housing stock to better meet modern standards of living. As such, we therefore note a positive opportunity for the sensitive implementation of energy efficiency retrofits and thermal improvements where this does not result in harm or the loss of significant historic fabric.
We appreciate that there are very few examples of ultra-slim double glazing such as vacuum glazing and we are therefore strongly supportive of the principle of trialling this technology, with potential benefit for future retrofit with high thermal performance and negligible visual impact.
The glazing would be fitted into the existing sash frames and sash boxes, allowing for these existing elements to be retained and upgraded. We are supportive of the retention of a 6-over-6 sash fenestration style. However, we encourage submission of further details regarding possible alterations required, such as accounting for any weight/balance changes between the sashes.
However, this application currently provides inadequate information regarding the age and significance of the existing windows and glazing. Whilst the D&A Statement notes that “some of the sashes to Hanover Street elevation have been replaced in recent years”, it is unclear as to whether 12 Hanover Street has been subject to similar alterations. The ground floor window can be assumed to be a later addition attributed to its larger-pane fenestration style, but there remains a lack of clarity regarding the multi-pane sashes across the upper floors. Where historic glass survives, this retains high significance in relation to the original construction and detailing of the listed building and removal would need substantial justification to outweigh the proposed harm to the building’s special interest. Without further details pertaining to the value of the existing windows, it is unclear as to the extent of impact proposed by this development. We maintain that further research should be undertaken as part of this application proportionate to the significance of the listed building to determine whether this application would result in the loss of historic fabric before this scheme can progress further.
We strongly recommend that existing and proposed sections of the windows pre- and post-glazing installation should be submitted to clarify the proposed change of thickness and appearance.
We additionally note that the technical specifications of Fineo glazing includes reference to the use of “20 mm grid micro-pillars” between the individual glazing panes, which may result in the windows having a ‘speckled’ appearance and detract from the overall appearance of the listed building. This detail is included within the data sheets available from the Fineo website, but is not included within the data sheet attached to this application. We therefore strongly recommend that the material specifications of the glazing proposed as part of this application are clarified with regards to this detail. The submission of a sample would be welcomed as an opportunity to see how the proposed glazing would look in situ and how the appearance of the internal support pillars may be suitably mitigated.
Therefore, whilst we are supportive of the principle of this scheme and welcome the opportunity to trial new thermally-efficient retrofits in Bath’s historic housing stock, there is currently inadequate information to assess how the special interest of the listed building and the character and appearance of the conservation area would be affected.
BPT is very interested in working with the applicant to reach an acceptable solution and to assess the performance of the windows before and after retrofit to create a ‘best practice’ case study. This information could then be used to more accurately assess the suitability of slim and vacuum double glazing installation in Bath’s historic building stock, and inform future upgrades of listed buildings.