34 Oak Street, Westmoreland, Bath

34 Oak Street forms part of a Grade II early 19th century terrace of residential dwellings, situated within the Bath World Heritage Site and the immediate townscape setting of the Bath City-Wide Conservation Area. The terrace is modest in scale and form at two storeys with a two bay frontage in Bath stone ashlar, stepping down the slight south-north slope towards Lower Bristol Road. The terrace as a whole encompasses two ‘halves’ - 1A, 1-5 & 33-38 Oak Street, and 20-28 Oak Street – which were bisected by the introduction of the St James Viaduct, now Grade II*, in 1840.

The terrace as existing features a varied mix of window fenestration types, indicative of later alterations, including 1-over-1, 4-over-4, and the more traditional 6-over-6 form. The terrace as a whole has recently been the focus of retrofit works, with listed building consent granted for the introduction of slimlite double glazing at 1A, 23, and 25 Oak Street. Alternate measures have also been permitted for thermal improvement works, such as the use of secondary glazing at 27 Oak Street. There is therefore a local precedent for the introduction of a slim-profile double glazing within the local street scene.

In response to 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. Alterations are expected to be sustain or enhance the special architectural or historic interest of a listed building.

Where the existing windows are of a mix of material and fenestration types, this is indicative of later alteration where historic fabric has already been lost or replaced. The existing windows to the rear of the property are evidently modern additions and as such replacement is considered acceptable in-principle.

The existing 1-over-1 and 1-over-2 timber sashes in the front elevation are noted to be materially congruent with the building and the group value of the terrace, but are a later replacement where the original 6-over-6 sash windows have been lost, and as such are attributed a lesser significance in relation to the original form and construction of the building. The opportunity for replacement, where the new units are demonstrated to sustain the traditional window construction and appearance of the terrace, would therefore be welcomed.

Works would be considered to offer the following benefits:

• The replacement of existing, deteriorating windows, which are indicated to be in a poor condition and susceptible to rot despite attempts at repair.
• The replacement of materially inappropriate windows to the rear, and an opportunity to reinstate windows of a more appropriate materiality and profile.
• Reinstatement of traditional 6-over-6 sash profile across the principal elevation, with little to no loss of historic fabric.
• Upgrade to double glazing and resulting improvements to energy efficiency and the windows’ thermal performance, though we maintain that any energy efficiency gains need to be considered from a holistic, ‘whole house’ perspective, which considers the ‘energy hierarchy’, including behaviour change and measures to reduce energy waste.

There continue to be very few examples of ultra-slim double glazing such as vacuum glazing being used in Bath. There would be an exciting opportunity to trial this technology, with potential benefit for future window retrofit with an increased thermal performance and reduced visual impact.

Where Fineo glazing would include the use of “20 mm grid micro-pillars” between the individual glazing panes, it is recommended that further clarification is provided regarding the degree of visual impact to the appearance of the building, as well as its contributions to the wider terrace. The use of internal pillars would result in the windows having a ‘speckled’ appearance, though previous applications for Fineo installation elsewhere in Bath have suggested that the micro-pillars are more visible in immediate, close-range views. We encourage that this aspect of the proposals is explored further, potentially with the provision of a relevant sample to determine whether there would be any aesthetic disparity with neighbouring properties in publicly-experienced views.

There is a further question regarding the proposed profile of the replacement units, as the proposed drawings and sections of the front windows appear to show the use of both through and applied glazing bars. We continue to express a strong preference for the use of through glazing bars where these would sustain the traditional construction qualities associated with the special architectural interest of a listed building, and reinforce its material authenticity. The use of applied glazing bars, would not uphold the integrity of traditional craft used in the construction of historic buildings. By virtue of their non-traditional sash window construction, they would be an incongruous visual and material addition across the principal façade of a listed building. This would result in adverse impact to the established fenestration style and traditional construction not only of the building, but the integrity and group value of the wider listed terrace.

We recognise that there are identifiable public benefits in the installation of slim double glazing and the associated contribution this would make towards the adaptation of our historic building stock to meet the challenges of climate change, as well as their sustainable future use. However, we consider that this would not be outweighed by the harm to the special architectural and historic interest of the listed building, and would detract from the character or appearance of the conservation area.

The use of applied glazing bars would result in harm to multiple heritage assets, contrary to the Planning (Listed Buildings and Conservation Areas) Act 1990, Section 16 of the NPPF, and Policies B1, D, D2, D3, and HE1 of the Core Strategy and Placemaking Plan. We strongly recommend that this aspect of the scheme is suitably amended.