Our homes are capable of consuming huge amounts of energy and producing large amounts of carbon dioxide emissions. But they don't have to. Building in energy efficiency can shrink our carbon footprints.
Danish architect Olav Langenkamp and his family moved into their new home a few months ago – a sleek black box nestled among pine trees and looking out onto a vast green horizon. But as well as stylish looks and a great location, the house boasts climate-friendly credentials. It uses 80% less energy than a standard house of similar size, saving two tonnes of carbon dioxide emissions per year.
When Langenkamp started designing the house in 2006, he chose ‘passive house’ building techniques that dramatically reduce energy consumption. These include positioning the building to collect heat from the sun, extra thick insulation, super efficient windows and a special air circulation system that helps maintain a constant temperature.
“One of the most difficult tasks for an architect is to design his own house,” said Langenkamp at the 12th international passive house conference in April 2008. However, he was determined from the start that his house would be as efficient as possible. “It had to be a passive house,” he said.
The hard work paid off and two years later it became the first building in Denmark to gain certification as a passive house – a voluntary set of criteria demanding much lower energy use than traditional building standards.
Although the passive house approach is more expensive than standard construction, in countries where the concept is most widespread – such as Germany and Austria – prices are coming down as technologies and building techniques become more common.
Langenkamp said he had proved it was possible to build passive houses in Denmark at a reasonable price and that there had been considerable interest in the project. "Potential clients are calling and writing for more information and the second passive house in Denmark is already on the way," he said.
A growing concept
The concept originated in the 1980s, and the first series of buildings was completed in 1990 in Darmstadt, Germany. By 2001, the EU funded project CEPHEUS (Cost Efficient Passive Houses as European Standards) had helped to construct 250 buildings in five countries, showing it could be commercially viable.
Interest in low-energy buildings has been increasing in recent years, reflecting growing concerns over climate change and high energy prices. According to the organisers, the Passivhaus Institut, more than 1 100 architects, planners, builders and members of the public attended this year’s annual conference in Nuremberg (DE) to hear about projects such as Langenkamp’s – up from around a hundred enthusiasts just over a decade ago.
There are now more than 10 000 buildings across the world certified to passive house standard, ranging from small individual houses to office buildings, schools, and shops. A large number of these are in Germany and Austria, where the concept originated, but interest is growing fast in other countries.
In addition, the approach is being used to renovate existing buildings. Past projects have shown the increase in efficiency to be up to ten times greater than before the method was introduced, helping to cut energy bills dramatically in large public buildings, such as hospitals and schools.
Passive house technologies follow a series of principles, rather than hard-and-fast design rules. These include:
- Using nature. ‘Passive solar design’ means reducing the buildings’ surface areas, with windows positioned towards the equator (south in Europe) to maximise solar gain.
- Wrapped up. Super insulation minimises the heat lost through walls, roofs and the floor. Special attention is paid to eliminating ‘thermal bridges’ – small gaps in buildings that allow heat to escape.
- Hi-tech windows. Passive houses use triple-glazed windows, which have special coatings and are filled with gases such as argon or krypton. On average, south-facing windows in a passive house in central Europe will gain more heat than they lose, even in the middle of winter.
- Fresh air. Mechanical ventilation and heat recovery systems are used to maintain air quality and recover enough heat to dispense with a conventional heating system. This can also use tubes buried in the ground that exchange heat from earth to the air or vice versa to either heat or cool the intake of air for the ventilation system. This also ensures a continual supply of fresh air.
- Sealed off. Ensuring that each construction joint is extremely airtight minimises the amount of warm or cool air that can pass through the structure, enabling the mechanical ventilation system to recover the heat before discharging the air externally.
The variety of climates across Europe means that a range of approaches is needed.
A number of other approaches are also being used to lessen the impact of buildings on the environment:
- ‘Zero energy buildings’ actively generate their own energy through turbines or solar panels. In some countries householders are paid a premium rate for electricity that they feed back into the national grid.
- There are a number of innovative designs for large office buildings or factories that use large roof areas for solar panels or the currents of air around them to drive wind turbines.
- When completed, a new office block in Stockholm will gain up to 15% of the heat it needs from the body heat of passengers passing through the central station next door.
- Roofs covered in soil and plants are becoming more popular around the world. These ‘green roofs’ provide extra insulation and absorb the carbon dioxide (CO2) that causes climate change.
- An engineering company in the Netherlands has developed a system that draws heat from the tarmac in roads in summer. The heat is stored underground and then used in winter to heat neighbouring buildings. In addition the system ensures the road remains ice free in winter.