BUY a new fridge, dishwasher or car and in many countries it will come with a label telling you about the machine’s energy efficiency. It is all part of efforts to persuade consumers to buy products that are “green”, and help governments meet their targets for cutting greenhouse gas emissions.
Over the next couple of years, houses too will be given energy labels. If you buy a house or any other building in a country in the European Union, you will be told about its energy efficiency and how to improve it.
There are hundreds of millions of buildings within the EU, many of them old, draughty and poorly insulated. Between them they account for 40 per cent of the EU’s carbon dioxide emissions, more than all the vehicles on its roads. And while significantly reducing emissions from vehicles will often require major technological changes, cutting emissions from buildings is much simpler. Yet unlike cars, buildings are often overlooked in discussions of how to reduce global warming.
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The European Commission hopes to change this, and is introducing a directive on the energy performance of buildings that will come into force on 4 January 2006. The commission aims to cut building emissions by 22 per cent by 2010, and its rules will be among the toughest in the world.
The push for greener buildings began in 2001, when the commission’s then president, Romano Prodi, was casting around for ways to meet the EU’s Kyoto protocol targets. With unusual speed, the buildings directive became law in January 2003. “There was a feeling of urgency because climate change was being pushed by Prodi,” says Andrew Warren of the UK’s Association for the Conservation of Energy, who chaired the working group that drafted the directive. By January, member countries must have taken steps to implement the directive, though they have a further three years to comply fully.
Nearly 60 per cent of the energy consumption of the average house in the EU goes towards keeping it warm, so the main aim is to cut heat losses. In most cases this involves low-tech measures such as insulating cavity walls and loft spaces.
A building’s heat loss is normally measured by its “U-value”, the wattage lost per square metre for each degree Celsius of temperature difference between the inside and outside. A modern double-glazed window has a U-value of about 2, whereas single-glazed windows have a value more than twice that (see Diagram).
A major source of heat loss from a building is air leakage. Buildings tend to suck in cold air on the ground floor and puff warmer air out through gaps in the upper storeys. “Forty to 60 per cent of energy losses are caused by air leakage,” says David Pickavance of BSRIA in Bracknell, UK, one of the two largest companies in the country carrying out air-leakage testing.
In the UK, the regulations will say that the rate of air leakage for every square metre of a new building’s outer skin should not exceed 10 cubic metres per hour when the difference in air pressure between the inside of the house and the outside is 50 pascals – about 0.05 per cent of atmospheric pressure.
For the first time, almost all EU countries will test how airtight new houses are by raising the air pressure in the house by about 75 pascals with a fan. The testers then record how much air has to be blown into the house to maintain various pressures, and from these readings calculate the leakage at 50 pascals. If necessary any leaks can then be traced by blowing in smoke.
Europe is not alone in its demands for better energy efficiency for buildings. Many states in the US may follow the EU’s lead by insisting all new commercial buildings are fitted with an “air barrier system”. This means designing a layer of relatively impermeable material around the walls and roof, and sealing common sources of leaks such as the joins between different materials. The proposal is proving highly controversial because of the extra cost, and physical testing of buildings for airtightness is not even on the agenda at the moment.
“A certificate of energy efficiency could provoke headlines of the ’10 worst buildings’ variety”
The success of the EU’s plans depends greatly on how well countries enforce their building codes, and how well they do this is very variable, says Laura Yates, a Greenpeace climate campaigner. In the UK builders already have to calculate the energy efficiency of new houses, using the government’s standard assessment procedure (SAP). This is effectively a forecast of your energy bills. Most new houses do very well, with scores of over 80 on a 0 to 120 scale. Since 2001, construction companies have been required to make the scores for their houses available for buyers to see. But researchers at De Montfort University in Leicester found that this does not yet happen for 98 per cent of new houses.
Last year, when the UK’s Building Research Establishment inspected 99 new homes to see how well they complied with building regulations, one-third failed the standards for airtightness. A common shortcoming was holes round pipes where they went through walls. Property owners that want to ensure that insulation has been properly fitted can use thermal-imaging cameras to spot areas where heat is being lost.
Only a small percentage of buildings in the EU have been built in the past year. So older buildings offer by far the greatest scope for cutting carbon emissions.
The directive singles out large buildings with a floor space of more than 1000 square metres – mainly office blocks and public buildings – for special attention. These buildings will come within the scope of the directive when major works such as renovation are carried out. At this point owners will have to take steps to improve the building’s energy efficiency.
Energy scores
One part of the directive may provide a powerful incentive for companies to clean up their act. The owners of commercial buildings will have to prominently display a certificate of the building’s energy efficiency, which could well provoke headlines of the “10 worst buildings” variety. “This name-and-shame measure could be very effective,” says Warren.
Existing houses too will be given energy labels. Most older houses have an SAP score of between 40 and 60, and only 10 per cent of houses in the UK score more than 60. Energy surveyors will inspect houses when they are sold or rented and give them a rating that will be passed on to the next occupants as part of their homebuyer pack.
The UK government originally planned to make homeowners improve the energy efficiency of their houses when they built extensions. The idea was that an extension would increase the total emissions from a house, so owners should compensate by finding energy savings elsewhere. But this proposal has been dropped, something Warren believes was a mistake. “When you’ve got the builders in they might as well put in some insulation,” he says.
But beyond these regulations, the public also have a role to play in ensuring their homes are as efficient as possible. The houses surveyed by the BRE were each sold with at least three low-energy light bulbs, but the owners soon got rid of them. “People removed most of the low-energy light bulbs because they didn’t suit their lampshades,” says Yates.
