By Jody Harrison

THEY are the work of master craftsmen who toiled long before the days when industrial production and lightweight synthetic materials became commonplace.

But now it has been warned that the often unique windows of Scotland’s listed buildings are disappearing fast, as councils nod through upgrades which see them ripped out and cast on the scrap heap.

A study by heritage experts at Heriot-Watt University has claimed that local authorities across Scotland have a “culture of consent” when it comes to the most vulnerable features of the country’s listed buildings.

There are around 47,000 listed buildings in Scotland, and their status means certain features should be retained and not replaced, such as original fireplaces, slate roofs and even windows.

But planning permission to remove and replace historic windows from listed buildings is being given at the same rate as for non-listed homes, with little regard for their protected status.

While international and national heritage organisations have been working to promote the repairing and upgrading existing windows, in Scotland the decision takes place at a local level. Owners of listed buildings apply to their local authority’s planning department for permission to remove windows, or other historic features of the building.

The study looked at Glasgow and Edinburgh, and found that from 2010 to 2015, the number of listed building applications relating to windows in the capital increased steadily from 169 to 304, with an approval rate of almost 90%. In Scotland’s largest city, which has the third-highest number of listed buildings of any council area, approvals rose by 41%.

Dr Craig Kennedy, of Heriot-Watt’s Institute for Sustainable Building Design, said: “Window glass is often overlooked compared to other historically important building materials like stone, metal and timber.

“As such it is most vulnerable to being replaced, and with that a listed building begins to lose its character and aesthetic.”

Kennedy added: “There is no difference in approval rates between listed and non-listed buildings – it’s around 80% across the board at the three councils. What struck us was the increase in approvals from 2010 to 2015. The number of applications related to windows in listed buildings almost doubled, as did the number of approvals. The approval rate rose to almost 90%.

“We interviewed officers in planning departments across Scotland, and some in England. The story was the same everywhere – since 2010, conservation officers have left the organisation and haven’t been replaced, planning departments are under-resourced and under pressure. The result is a culture of consent.”

Many of the windows in listed buildings pre-date the industrial manufacture of glass on a wide scale, meaning each pane is unique and carries imperfections which often enhances their appeal.

They will often be sash or casement windows, wood-framed and moved through complicated weighted pulleys hidden in the walls which can be difficult to replace.

These windows are usually replaced by PVC frames with modern glass, for a variety of reasons. Householders may believe they are more energy-efficient or cheaper than restoring older windows. However, timber windows are often a cheaper and more environmentally-friendly option.

But Kennedy believes that a decision to allow the replacement of historic windows should only ever be taken as a last resort. He said: “The importance of retaining original windows cannot be overstated. They contain a wealth of information on historic practices and manufacturing techniques.

“Nowadays we are used to the glass in windows being perfectly clear. Older windows often contain tiny bubbles, known as seeds, or curved striations that came from the crown glass method of glass-making.”

He added: “The replacement of historic windows must be seen as a last resort instead of a first choice. Our research shows that the efforts of heritage agencies to promote repair and upgrading of historic windows may have been ineffective. They should refocus efforts to ensure that this message reaches the local planners who are in charge of our architectural heritage. We’re concerned that, at the local level, nobody is advocating for historic buildings.”

The Heriot-Watt team developed its own software to conduct the survey, as each of the local authorities recorded window-related applications differently, even within their own organisation.

The team hopes heritage professionals across the UK will use its software to examine decisions affecting listed buildings in their own local authority, and determine the scale of historic feature loss on a national scale.

Both Edinburgh and Glasgow city councils defended their record on protecting listed buildings, with Edinburgh planning convener Councillor Neil Gardiner saying: “We’re very lucky to be home to not one but two World Heritage Sites in the capital. As a planning authority, we’re ultimately the guardians of our historic built heritage, and our listed buildings guidance seeks to protect the character and aesthetic appeal of period properties in the city.

“We recognise that windows are an important feature in the elevation of any building and are vital to the history and architectural integrity of all historic buildings. Not only that, but their replacement with different designs can seriously affect the historic and architectural character of a building. That’s why our guidance on window replacement in listed buildings in Edinburgh emphasises a general presumption against the removal of original timber windows. The repair and rehabilitation of original windows is preferred in terms of sustainability, as well as protecting historical character.”

A Glasgow City Council spokesman said that it was important to note replacing windows in unlisted buildings does not need planning permission outwith conservation areas, meaning that a direct comparison is impossible as this type of work is not recorded.

He added: “Our guidance requires that proposals for the replacement of an original window to listed buildings and properties in a conservation area should be accompanied by a statement to demonstrate that the original window is beyond repair to justify its replacement.”

A spokesperson for Historic Environment Scotland (HES) said: “Our Managing Change guidance, which was created for planning authorities when making decisions, states that original or historic windows should be retained wherever possible. In the guidance, we highlight several ways to upgrade energy efficiency, including draught-proofing and secondary glazing. Our guidance states that original or historic sash windows should only be replaced when they are beyond reasonable repair. If replacement is required, the new windows should be as close a match to the original designs as possible.”