PROJECT FOCUS GREEN RETROFITTING
ONE MILLION SWEDISH HOMES
When the Swedish government decided to build 1 million new homes within 10 years in 1965, it was a bold solution to a major housing shortage. But as those apartments near their 40th birthday, they have themselves become the problem – poorly insulated, energy guzzling and badly in need of renovation.
“It was a very ambitious programme, but they were quite quickly built, in some cases using new materials that had not been very well tested,” explains Agneta Persson, director of energy at WSP Sweden, who is leading a project for the Swedish Energy Agency to develop cost- effective solutions to retrofitting the homes. “There is a real need for refurbishment to bring them up to modern standards.”
The Million Programme homes – 850,000 apartments and 150,000 single family houses – now account for a very substantial proportion of Sweden's domestic buildings. They are also a major contributor to its carbon dioxide emissions. “When these homes were built, things like insulation were low priority. Now we have the opportunity to make them much more efficient.” The project is aiming to reduce the homes' energy needs by 50%.
WSP is turning the challenge of system-built housing to its advantage – procuring solutions that can be rolled out as
efficiently and cost-effectively as those used in the original build. So far, Persson’s team have worked with the properties’ owners to develop specifications to present to contractors and manufacturers, dangling the carrot of a huge potential market. This time round, the technologies will be rigorously tested. After a theoretical assessment, they will be installed and monitored for up to a year, before WSP negotiates framework agreements to make them affordable for every owner.
WSP is also working with 2,500 residents of housing cooperative HSB Hilda brf in Malmo to
enable them to become energy self-sufficient within 10 years. There it is plugging draughts and installing better insulation, mixer taps and new ventilation and heat recovery systems at a cost of SEK300,000–700,000 per flat.
“There is a growing awareness among property owners that they need to do something because energy prices are increasing all the time,” says Persson. “Since these buildings are in need of renovation anyway, the additional cost is actually quite small.”
The impact of WSP’s retrofitting projects is also likely to spread far beyond Sweden's homes: “In Europe, there are 200 million people living in flats like these, so it’s a major opportunity.”
LAU CHURCH IN GOTLAND
With walls more than 1m thick, the medieval churches of the island of Gotland were certainly built to last. Unfortunately for those who continue to admire them to this day, their solidity means that for many months of the year the temperature inside barely rises above freezing point.
Finding a sustainable way of heating these churches is as hard as retrofitting gets – so it’s lucky that WSP Sweden’s Håkan Nilsson is not scared of a challenge. An associate professor at the Royal Institute of Technology in Stockholm, as well as manager of WSP Environmental’s building physics department in Stockholm,
Nilsson has always been interested in unique architecture. In 2007, working with Professor Tor Broström at Gotland University, he successfully applied for SEK10m research funding from the Swedish Energy Agency.
“I’ve always been interested in old buildings, and the churches are fantastic,” he says. “They’re unique to this part of the world and they also have very good acoustics, for concerts. Sitting in these churches listening to music is a very special experience.”
But it can also be a very chilly experience. “The church is like a big cold store,” explains Nilsson. “In the 1970s, you could heat
them up but today the energy costs are too high. We were looking for solutions that use less energy, and at the same time preserve the wooden carvings and paintings inside the church.”
Their ingenious solution is to heat the people rather than the church. Benches were reinstalled on a new floor hovering 20cm above the stone and heated from within, with radiant heaters fixed in the traditional crown above the heads of the congregation. “When you look at the infrared picture, you can see the people are sitting in a bath tub of heat.”
It’s a deceptively simple image – much calculation and research was involved. “For example, if you have a very strong radiator in a very cold environment it feels uncomfortable. So we looked at how much extra heat we would need from the floor and the seats to compensate.” The measurement system used to
develop thermal models defines a comfortable range as between 10 and 30°C, which meant extra research to validate their models.
Nilsson and the project group have successfully retrofitted his heating solution in two of Gotland’s churches, and carried out tests of similar systems in ruined cathedrals and castles elsewhere in Sweden.
Sustainable heating may be a new concept for Gotland’s churches, but he sees it as just another step in their long history: “When these churches were built 1,000 years ago, they were heated by fires, then by burning coal, then oil, before the switch to electricity. Now we’re going to use heat pumps and radiation. There’s nothing strange in changing the system, it’s just another step in the evolution of heating.”
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