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Sustainable buildings should differ across Europe

The Nu-Office building in Munich has small, triple-glazed windows and thick, insulated walls to keep out the winter cold. Image courtesy of Nu-Office.
The Nu-Office building in Munich has small, triple-glazed windows and thick, insulated walls to keep out the winter cold. Image courtesy of Nu-Office.

Sustainable buildings should be different depending on where they are in Europe - that's according to the developers of one of the world's greenest office buildings.

Nu-Office, a highly energy-efficient building in Munich, has small, triple-glazed windows and thick, insulated walls to keep out the winter cold. Another new sustainable building, CARTIF III, is in Valladolid, central Spain; it has glass walls and louvre blinds that manage the sunlight to maintain a comfortable temperature. In northern Italy, a third such building, the New Technology Park, will take advantage of the underground hot water available locally in the city of Bolzano.

The different features of the three buildings, each part of the co-EU-funded project DIRECTION, demonstrate an important point about low-energy buildings. While they will pool a lot of basic techniques, they are likely to be carefully adapted to local conditions, from the weather to local energy supply.

These factors will influence three crucial aspects that make the building sustainable: insulation and use of sunlight; energy generation, as far as possible from locally available sources and renewables such as solar panels and biomass; and system control, permitting the smart management of energy needs, including heating and cooling systems. 

‘There is no single technology that enables sustainable buildings,’ said Sergio Sanz, Deputy Manager of the Energy Division at CARTIF, a technology centre, and the coordinator of the DIRECTION project. ‘Instead we have to combine three different pillars in the best way for the conditions. The main key is an integrated approach.’

For much of the twentieth-century, energy was abundant and climate change was not yet a concern, so low power use was not a major part of building design. But use of natural light did play a part in designing some of New York's early skyscrapers: artificial lighting was primitive, so architects made buildings with large windows and tall ceilings to allow sunlight to reach deep inside.

Nu-Office, which was completed in November 2012, also gets as much natural light as possible despite its small windows. An inner courtyard provides more sunlight and also creates natural breezes. The roof is covered partly with solar panels to generate electricity, and partly with plants, which provide insulation. Groundwater is pumped through a heat exchanger, cooling the building in the summer.

In the basement, a control system coordinates the building's heating, cooling and lighting, and is linked to Munich's district heating system. This feeds in heat produced by electricity generation via a city-wide network, which should by 2040 run solely on renewable sources, in particular a hot water reservoir three kilometres underground.

In from the start

The key to the radical design: inviting energy experts – in this case the German Fraunhofer Institute for Building Physics (IBP) – to participate at an early stage. Though many new buildings are completely glass on the outside, which is a fashionable, modern look, the IBP proposed just 30 to 40 % glass façade, and strong insulation. Then it had to find a way to let more daylight into the building.

‘You need to find a compromise between natural light and insulation requirements,’ said Michael Krause, Group Manager of Systems Engineering at the Department for Energy Systems at IBP. ‘This is not possible if your ideas are integrated too late in the planning process. It needs investors who are open to the idea of efficiency and interested in getting energy problems involved early in the process.’

90 % energy saving

Nu-Office itself could consume a mere 30 kW hours per square metre per year in heating, cooling and lighting costs, said Krause, adding that he is still monitoring the performance. That would compare to the average of 100 to 150 kW hours in a typical new building, and would be an energy saving of up to 90 % compared to older offices. This expected performance won Nu-Office a Leadership in Energy and Environmental Design (LEED) Platinum Certificate with a score that made it one of the world's most energy-efficient office buildings.

'You have to consider the position of the sun when you consider the use of natural light.'

Michael Krause, Group Manager of Systems Engineering at the Department for Energy Systems Fraunhofer Institute for Building Physics, Germany

A building like Nu-Office is more expensive to build than a conventional one, and that cost will be passed on to clients. If they can't see the long-term benefits of lower energy bills, then they won't move in, said Julia Vicente, a member of DIRECTION's coordination team at CARTIF. ‘The user has to be convinced that it is worth paying a little more,’ she said. ‘You need public awareness of the benefits of extra investment in buildings.’

In Munich, energy costs have risen by more than 50 % in the past 10 years. The hoped-for 90 % reduction in energy use for Nu-Office does not translate into total energy bills one tenth cheaper, because other devices running on electricity - such as copiers, computers, and coffee machines - use the same amount as anywhere else. But the owners think the overall consumption will still be significantly less.

Thanks to the lower energy use, they have fixed a flat rate of EUR 2.50 per square metre each month in overheads, compared with a going rate of around EUR 3.30 per square metre for comparable buildings in Munich, said Michael Lentrodt, company representative of Nu-Office developers FACIT GmbH. In addition, the layout means that tenants need about 15 % less office space than usual.

‘The tenants benefit from considerable savings potential,’ said Lentrodt. ‘It's not about sustainability in itself. No one rents or buys from us just because we've received a certificate. People come to us because they understand the advantages.’

Energy costs are rising, and by 2020 the EU wants to achieve a 20 % increase in energy efficiency in part by improving the efficiency of buildings.

By then, EU Member States must ensure that all new buidings are close to zero energy. While countries can opt-out in specific cases, the rule means that sustainable offices are likely to spring up all over Europe in the coming years.

If they do, they’ll have to pay close attention to local conditions. ‘You have to consider the position of the sun when you consider the use of natural light,’ said Krause of the IBP. ‘In southern Spain, the sun is high so less natural light will get through windows. In Sweden, the sun is relatively low on the horizon.’

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