Beat the heat: how a new type of eco home is helping tackle global warming
3rd April, 2012
As climate change speeds up, the question of how to adapt our homes to hotter temperatures is becoming increasingly important. Now, a pioneering project on the island of Tenerife has been set up to address those concerns. Paul Miles reports
The Canary Islands have long been known as the 'Fortunate Isles'. The mild climate with its year-round warm sunshine and little rain brings tourists in droves and makes for pleasant living conditions. But tourism isn’t all that the Canaries’ pleasant climate has helped usher in. The balmy temperatures have made it the perfect place to trial a new type of eco house, and one that doesn’t need any type of fossil fuel powered heating or electricity. Introducing the bioclimactic home.
It was to meet this (relatively easy) challenge that an architecture competition was organised 15 years ago by the Tenerife government and the Institute for Technology and Renewable Energy (ITER). ‘In those days, these ideas [of not using fossil fuel for heating, cooling or electricity] were not very advanced. Even in this climate, houses were being built with air-conditioning and immersion heaters,’ says Maria Delgado of ITER. ‘The main criterion of the competition was for energy saving during the use of the house,’ she says. Nearly 400 entries flooded in from 38 countries but the 25 winners were all from Europe.
The outcome of the competition is a ‘village’ of so-called ‘bioclimatic’ (or zero carbon) homes, each designed by a different architect. The complex, near the Reina Sofia airport, in the south of Tenerife, had its official opening last March. ‘It has been a challenge for the institute to manage so many different building projects so it has all taken time,’ explains Delgado. The homes, all tastefully furnished and situated amongst endemic, desert plants, near a black shingle cove away from the tourism developments further along the coast, are now available to rent. Each property is built on a 120 square metre plot with three or four bedrooms. All have solar panels for electricity and hot water and are situated near the Centre’s wind turbines and not far from its 24MW solar PV array.
The winning design is by Spanish architect, César Ruiz Larrea, whose house took inspiration from the way that farmers grow grapevines in the Canary Islands. ‘They build inverted cone-shaped holes made of volcanic rock that protect the vine from wind and maximise sunlight,’ says Ruiz-Larrea. Known as “gerias” these stone shelters are ‘also the most beautiful architectural form.’ The house, which could grace the pages of any style magazine, keeps warm at night thanks to the thermal storage provided by its rock walls and is cooled during the day by channelling the wind into a subterranean space from where it is then drawn through the house to cool it without it being breezy. Building materials are local volcanic rock known as tosca but the wood, Douglas fir, is imported from Canada. ‘If I were designing the house today I would use more local materials’ says Ruiz-Larrea, who has since forged a career in designing ‘bioclimatic’ buildings. ‘There is no other way [to build] if we want to create a sustainable world for future generations.’
Unlike the German Passivhaus standard, air-tightness was not a requirement for these homes. Instead, they are monitored constantly for various physical factors. Small measuring devices inside the properties relay a constant stream of data to the ITER offices about interior air flow, temperature and humidity. ‘We want people to come and stay in the houses so that the measurements reflect the human interaction with the building – opening and closing louvers for shade and the like,’ says Delgado. ‘Otherwise we have to keep visiting the houses to pretend that they’re lived in.’ By analysing the data produced, ITER hopes to learn which houses maintain the optimum conditions. A temperature range of 22 to 27 degrees centigrade is considered comfortable (compared to Britain’s standard of 21) and air flow of up to two metres a second is thought to be acceptable but can, to be honest, feel quite draughty as I discovered when I stayed a night in one of the homes, El Rio. One property has walls that have proven so permeable to the elements that not only wind but dust, sand and animals have found their way in. It is constructed of ‘gabions’ – those wire cages of rocks more usually found on mountain roadsides or protecting the coast from erosion. Three British architects were responsible for that house, which is currently uninhabitable. ‘Learning from mistakes is an important part of this project,’ says Delgado, philosophically.
Another British architect, Neil Swift, assistant director of DLG architects, based in Leeds, built a more successful property. ‘I designed it like a church, with large flying buttresses to support the barrel vaulted roof. These help temper the environment by providing thermal mass,’ says Swift. The heat storage capacity of different materials is one of the most important features of building a passive house, explains Swift, which is why several of the designs on the site are partly buried underground, to make the most of the constant temperature of the earth. ‘Around Europe, many new houses will come a cropper as climate change takes hold and temperatures increase,’ he says. ‘The way modern houses are insulated, with lightweight materials that lack the ability to absorb heat and release it slowly – a process called decrement delay - means they will overheat.’
Most passive house design has elements from vernacular architecture – the way our ancestors built to keep comfortable. ‘Old stone farmhouses in the Yorkshire Dales are built on a hill, facing southeast with a windbreak of trees, large windows at the front and small ones at the back,’ says Swift. ‘Bioclimatic (or passive house) architecture is not rocket science but the problem is we’re losing our connection with nature and think that modern architecture needs to be all bells and whistles – heat pumps and the like.’ Perhaps we need to think more simply? Swift thinks so. ‘Pigeons know more about architecture than some architects. Pigeons know which buildings have crap insulation and where to be in the sun to keep warm and how to avoid the wind.’
As the climate changes, we’re going to have to reappraise how we build our homes. Already the bioclimatic houses on the Canary Islands are experiencing problems due to increasing rainfall. The volcanic rock is porous and so allows water to seep through. When it only rains once or twice a year that wasn’t so much of a problem but rainfall patterns appear to have changed says Swift. ‘How we build passive homes will have to evolve as the climate changes.’
For more information, see casas.iter.es
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