A HIGH-PROFILE development that transformed a B-listed school building into upmarket flats has been hit by a row over claims it has "non-compliant" windows at risk of failing.

Apartments in Edinburgh's old Boroughmuir High School are currently on the market for between £499,000 and £620,000.

But industry body the Glass and Glazing Federation (GGF) has raised concerns that the insulating glass units (IGUs) used in the development's double glazing do not comply with regulations and are at risk of failing and "misting up".

John Agnew, managing director of the GGF, said that based on his information the "product that's installed is in breach of the CPR [Construction Products Regulation]".

Cala insisted it has worked closely with Edinburgh Council and Historic Environment Scotland to restore the original sash and case windows "while abiding by all statutory approvals".

It said that in "the unlikely event of any issues, customers will be fully supported by our after-care service and the 10-year NHBC [National House Building Council] warranty".

Michael Gaillard, joint managing director of CENSolutions Limited - the UK’s largest supplier of quality certification in this area - and an active member of the GGF, said the units are "illegal" and "not fit for purpose".

He said: "The chances that those units will fail is relatively high."

He said this failure could lead to the windows misting up and condensation appearing between the two panes of glass.

The evaporation of moisture could also leave "little white spots", he said.

Mr Gaillard said there are a lot of non-compliant units being sent into the marketplace across the UK.

Alex Gray, chairman of GGF Scotland, said those buying the upmarket apartments will expect "nothing but the best".

He said he would not accept the current glass units "any more than I would accept dodgy electrical wiring or defective plumbing or loose tiles on the roof".

In an email sent to Mr Gray in September, seen by The Herald, a technical manager at Cala said: "We are informing our customer care team to expect a degree of failures on IGUs at Boroughmuir and will be prepared for carrying out the repairs and replacements on behalf of our clients."

Mr Gray is the managing director of Blairs Windows & Doors, which he said was previously in talks to refurbish the windows at Boroughmuir.

Mr Agnew said there is no "cheap fix", adding: "You either reglaze the units with a product that's fit for purpose, or you fit new windows."

The GGF says the units are in breach of European standard EN 1279 and the Construction Products Regulation.

The trade body says this could cause problems such as structural issues or moisture getting into the cavity between the two panes of glass in the double glazing.

A spokeswoman for the NHBC said: “We are investigating the insulating glass units and have no comment on compliance with EN1279 until that has concluded.

"Irrespective of that outcome, we will stand by our 10-year warranty product.”

A Cala Homes (East) spokesman, said: "This is an important heritage building and we fully understand the responsibility on us as its developers.

"We’ve worked closely with the City of Edinburgh Council and Historic Environment Scotland, to retain and carefully restore the original sash and case windows, while abiding by all statutory approvals.

"This has involved replacing predominantly single glazing with a slimline double glazing, that is sensitive to the heritage and appearance of the building.

"The chosen solution, while a huge undertaking, is the most sustainable, and we believe it provides the best outcome for both the architectural preservation and appearance of this important listed building and quality of end-product for our customers.

"We are confident in the careful, and enhanced design and fitment undertaken by specialist contractors at Boroughmuir, and in the unlikely event of any issues, customers will be fully supported by our after-care service and the 10-year NHBC warranty."

A spokeswoman for Historic Environment Scotland said: “We were involved in discussing the proposals for the former Boroughmuir High School in our role as statutory consultees on the applications for listed building consent, however this doesn’t extend to being involved in detailed technical issues dealt with in building standards, or in relation to monitoring completed works.”

An Edinburgh Council spokeswoman said: “We’re satisfied that in this case Cala is following the appropriate approvals process for building standards and planning.”