A block of draughty tenements in Glasgow's south side are now among Scotland's warmest and most energy-efficient homes following a first-of-its-kind project.

Eight rundown one-bedroomed properties were acquired from private landlords through compulsory purchase laws and stripped back to their bare bones to allow construction workers to put in place "21st-century energy efficiency solutions".

The mammoth retrofitting project, on Niddrie Road in Glasgow's south side, has involved air sealing the entire building with the internal and external walls, floor and loft areas insulated and windows triple-glazed.

The Herald:

A mechanical ventilation system delivering a continual supply of fresh air aims to reduce the need for tenants to open windows.

Air source heat pumps have also been installed in four of the pre-1919 flats with a control group using gas boilers.

'We think this is a really important lesson for fuel poverty' 

Tenants moved in just over a year ago and have seen an "astounding" drop in energy bill costs, according to Southside Housing Association, which acquired the flats.

"Given that we were in the midst of an energy crisis, the difference that we have seen in their energy bills, especially coming into that winter period, has been astounding," says Lisa Gillon, housing officer at Southside Housing Association.

"In the middle of winter I've had a tenant say their usage was sitting at around £40 a month and they were using their heating very frequently so I think that itself shows how successful the project has been."

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Those involved in the EnerPHit model project say it was complex and costly, at between £35,000 to £40,000 per flat, but that it is cheaper overall and better for the environment than demolition and rebuild.

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Chris Morgan, Director of John Gilbert Architects, said: "We've done a lot of low-energy retrofitting of buildings but this was the first time it had been done with a stone tenement in Glasgow.

"I think from the contractors' point of view they found it difficult but not impossible.

"From the street side, you don't really see much change but we have made flats here which are more energy efficient than any other flats in Scotland.

"Technically speaking as an architect I think we've moved things along a lot but I think from the clients' point of view you would say it's costly.

"So the issue going forward has got to be how can we make sure this sort of thing is affordable."

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One tenant, who moved from shared accommodation in Springburn, said: "It's a lovely warm flat and the electric is less."

The project was discussed at a conference held earlier this week in Glasgow organised by the UK Collaborative Centre for Housing Evidence, led by the University of Glasgow, looking at retrofitting solutions for older buildings.

Professor Ken Gibb, centre director, said: "This fabric-first mode of reducing energy demand has not just had a phenomenal effect on thermal comfort that residents have but it has significantly reduced their energy costs at a time of financial crisis and we think this is a really important lesson for fuel poverty.

"We recognise that it's been expensive for the housing association and a lot of public money [but we] must look at the other side of the ledger and the benefits.

"We found that compared with demolishing and building, the net benefit was much stronger. The only way you get these deep savings to residents and the only way you get close to net zero is with the Enerphit retrofit model.

"And it goes without saying that if you pursue retrofit you are also protecting the heritage of our tenemental stock."

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Housing is responsible for around 20% of carbon emissions.

There are more than 75,000 pre-1919 sandstone tenements in Glasgow and they make up around a fifth of the city's housing stock.

Prof Gibb said he didn't think it was reasonable to expect that the Niddrie Road project would be replicated in tenements across the city but rather that lessons would be learned and said Scottish Government grants were available for tenement owners.

"This is a demonstration project, it was an experiment to see if it could be done so it has a lot of public money attached to it but we found out that it could be done," he said.

"At some point the tenements need to have repair and refurbishment work done.

"We will inevitably have a series of carrots and sticks to try to encourage people to find efficient ways to do what they can and a lot of that is about clever finance and stretching subsidy."

Retrofitting works have been carried out a multi-storey block in the north of Glasgow owned by Queen's Cross Housing Association.