Consent secured for replacement windows at St John’s Wood house

London has the highest number of Listed homes in the country. Despite being very desirable, they are often drafty and cold.

Owners attempts to upgrade these desirable properties is often thwarted by regulations that seek to preserve the ‘historic character’ of the building, sometimes at all costs.

Even in instances where the windows are non-original, there is often resistance to improvements. For example, installing double glazing has for many years been resisted by the Conservation Officers in Local Planning Departments.

Seemingly written from a different era, Conservation Officers have often resisted upgrades by referencing guidance that falls short of accounting for the Climate Emergency. Green Conservation and the Financial Times have repeatedly stressed this point, calling for a radical rewriting of the rulebook.

Now, there are signs that policy is slowly changing: Historic England’s latest advice note on ‘Adapting Historic Buildings for Energy and Carbon Efficiency’ has shifted the conversation from the question of what constitutes a positive contributor replacement window towards more pressing issues around the climate and biodiversity emergency. It recognises that for a country with the oldest housing stock in Europe, the necessary steps must be taken to reduce the environmental impacts of buildings construction before 1939, and this includes efforts to improve the thermal insulation of houses and apartment buildings with upgraded windows.

Arguably the most significant outcome of the proposal is the recommendation that ‘the replacement of windows which do not contribute to the architectural or historic interest of a building with double-glazed windows of appropriate material and pattern should now generally be acceptable’. This suggests that sub-standard, poorly insulated non-original windows can now be replaced in line with the specifications of the listing.

Other developments include advice on draught proofing of windows, the installation of secondary glazing to windows, and the installation of slim-profile or vacuum double-glazing within historic frames. Whilst the solution had typically been to either preserve or remove and store existing windows, the new guidance supports these non-invasive interventions, describing them as either ‘generally’ or ‘invariably’ acceptable.

Rodić Davidson welcomes the new policies and guidance from Historic England but believes that policy makers can and should go further to encourage sustainability improvements and upgrades to Listed Buildings.

Earlier this month, the practice received planning permission from the City of Westminster for window improvements to a Grade II-listed Regency townhouse in St. John’s Wood. The consent allows for the replacement and upgrade of the existing sash windows using Histoglass HD12 slim double glazing and MONO single panes. No only will the window upgrades improve the overall composition of the front and rear elevations, crucially, the higher energy efficiency of the new Histoglass units will substantially improve the standard of thermal insulation in the Listed Building and thus mitigate the development’s net carbon impact.