From Prague to Plovdiv, engineers and architects are giving a second life to communist-built apartment blocks in Central and Eastern Europe, ready for the climate change era.

One of the oldest residents of one of the tallest building in Gabrovo city, Bulgaria, is former engineer Hristo Hristov. At nearly 90 years old and “still obsessed” with how things fit together, Hristov has lived in the block since it was built three decades ago. The block was designed in the 1970s, before the arrival of energy efficiency standards in Bulgaria, and completed in 1994.

Until 2020, this 16-storey tower block was typical of the apartment buildings that dominate the skyline of not just Gabrovo, but cities across Central and Eastern Europe. Many of these blocks are cold, draughty and expensive to heat. Today, Hristov’s block is warm and dry and energy bills in the block are half what they used to be.

The change is down to a full energy retrofit of the tower, coordinated by Hristov. It required getting the agreement of every resident in the block to proceed – but, incredibly, this was achieved. “A final few had us like a slow roast on a spit,” he says, making use of an old Bulgarian phrase. “But there are 80 families here and even with full funding some people, understandably, needed persuading,” he says. “These are their homes.”

Now the concrete block, left bare for decades, is well insulated, its old balconies are enclosed, and it is clad in clean pastel colours. As one of the first blocks to be renovated in Gabrovo, the tower signaled the start of a slow change to the post-industrial city. And Gabrovo’s transformation is in turn part of a change happening across hundreds of cities in the region, as post-communist countries look to upgrade their crumbling apartment blocks.

As climate change puts pressure on cities to use less energy to heat and cool buildings, and to help insulate residents against temperature extremes, the race to retrofit these apartment blocks is only getting more urgent.

Monolithic skylines have become symbolic in Central and Eastern European cities. While brutalist apartments can be found in many parts of Europe, the rapid urbanisation of former-communist countries in the second half of the 20th Century means large, concrete blocks make up a high proportion of their building stock today. Though there were several evolutions of design – from the prefabricated panel blocks to modernist towers – they usually had something in common: bare outer walls made of concrete or brick, with little insulation.

Approximately one third of the Bulgarian population lives in apartments built during communism, a similar proportion as in the Czech Republic and Poland. In Latvia more than 50% live in the ex-communist blocks, while in Estonia the figure is as high as 70%.

Miles Glendinning, professor of architectural conservation at the Edinburgh School of Architecture and Landscape Architecture, says that modernist housing blocks in Central and Eastern Europe usually don’t receive the same level of public stigma as those in Western cities. They are simply a part of daily city life.

But as the blocks age and become inadequate in terms of energy efficiency, there’s the question of what to do with them – demolish or retrofit?

Demolition is often not popular and rarely feasible. In Bulgaria, a high level of private ownership, at around 85%, means the buildings would be problematic to tear down and build anew. Plus, rebuilding housing is costly. A study by researchers at Tallinn University of Technology, Estonia, found that tearing down blocks to rebuild similar housing in the country would cost three to four times more than even an intense retrofit.

“For many reasons, the blocks are likely here to stay,” says Dragomir Tsanev, director of EnEffect, an energy efficiency non-profit in Sofia, Bulgaria. Although many Bulgarian apartments have outlived their intended lifespans of 50 years, “some studies have shown they should be no less structurally sound than newer buildings, so long as they are well maintained”.

That said, more data is needed to fully understand the picture, Tsanev says, especially on energy efficiency. Most of the blocks fall into EU energy classes E, F and G – the worst performing bands.

And while several post-communist states are addressing this inefficiency, it’s less of an organised joint project across states than “a movement, or even several parallel movements” spurred by many factors, says Glendinning. Among the strongest drivers are national decarbonisation goals and European Union-backed renovation programmes.

According to EU Commission estimates, buildings are responsible for 40% of its energy consumption and 36% of its greenhouse gas emissions. Governments have widely decided that modernising the continent’s building stock is key to combatting climate change. A strategy published by the European Commission in 2020 aims to double energy renovation rates by 2030.

Tsanev sees “huge appetite” for building renovation in Bulgaria. In the last funding cycle for a full grant, 3,068 hopeful buildings applied. There was only enough funding for 756. “The unsuccessful proposals represent time and money the residents put into their buildings,” he says. They all would have had to obtain 100% consent from neighbours, a huge challenge, and would have spent money on a technical and energy audits, he says. “Residents end up disenchanted with renovation. On the technical side, refits go too slowly.”

For Tsanev, the wave of energy retrofits will only take shape with easy, streamlined involvement for residents and “fairer” financial mechanisms.

The Bulgarian government was contacted for comment but did not reply by the time of publication.

Back in Gabrovo, Mogiliov Boulevard gives a snapshot of the Bulgarian situation. Here, a dual carriageway is lined with cheek-by-jowl panel blocks, a type of building constructed in the old Communist style from prefabricated concrete panels. Nine of the blocks applied for the recent funding round and just one block won. One half of a block, renovated in the last round, even won awards for best facade. Its conjoined twin remains concrete.

Under the unrenovated portion, a restaurant is packed with locals at lunchtime. Diners share plates of grilled kebapche (a type of sausage) and talk over house music on radio N-JOY.

“We wanted to apply,” says one diner who lives in one of the flats above, requesting anonymity because of the tense nature of the subject in the neighbourhood. “The majority of us were in agreement [to seek full state funding for a retrofit] but a few hold-outs wouldn’t bite.”

“We applied, but it didn’t work,” says another diner, Teodora, who lives in a block down the boulevard which was unsuccessful in getting funding. “We want to be more energy efficient so we will just do it ourselves.” She says she will insulate her apartment with wraparound external insulation.

To buffer an individual flat in this piecemeal way is something Tzveta Naniova, an energy efficiency expert, strongly advises against. “It can scupper a building application down the line,” she says, and it also presents fire safety hazards. But she can understand the thinking. “People want to save money and are frustrated with the uncertain grant cycle,” she says.

Naniova is the owner of a “one-stop shop” in the capital of Sofia. The aim of the shops – a lynchpin of the European Union’s plan for buildings – is to act as the first point of contact for residents to get up to speed with retrofit requirements and give them easy access to the contacts involved. “Not everyone should have to get a degree in engineering or architecture,” she says. “We have experts in the field,” she says of her colleagues. “We should use them.”

Bulgaria, Naniova believes, must move away from requiring 100% resident support, to a majority of homeowners per block. She also believes Bulgaria should move towards a more market-based model. “There is not enough state money to finance all the renovations,” she says.

Other countries take a different approach. Naniova points to Lithuania as an example of good practice, such as the city of Vilnius and the “renovation capital” Marijampolé. “The country changed from a grant-only approach and instead harnessed public funding to de-risk the private investment,” says Naniova. “But what helps the most is that the loan is connected to the building, not individual residents.”

In other words, if an apartment sells, the loan stays with the property, not the person. For the lowest-income residents, financial assistance is also available.

“[Lithuania] got started 10 years ago and we are trying to catch up,” agrees Tsanev. “Without attractive loans to be paid back from energy savings, we cannot expect people to accept the changes.” For Bulgaria, he would also like to see clarified, full grant support for apartment dwellers with low income. (The Bulgarian government was contacted for comment but did not reply by the time of publication.)