Dressed to impress

Matthew Jones reports on Hydro’s drive to prevent precious energy going out of the window.

Cladding commercial and administrative buildings used to be as simple as clothing their structural elements in stone or some other weatherproof material. While durability, aesthetics and cost were key criteria in the choice, energy efficiency was often lower down the list. But architects, engineers and their clients first started taking serious note of energy saving techniques in façades in response to the spiralling energy prices of the early 1970s. While the raw economic reasons remain compelling today, the emphasis has also shifted since the 1997 Kyoto Protocol on cutting greenhouse gas emissions. Energy loss from buildings, alongside transport, is one of the biggest contributors to carbon dioxide emissions and one of the key target areas for reductions. According to BRE, the leading British building research organisation, non-industrial buildings such as offices, schools and homes account for up to 50% of a country’s primary energy consumption, depending on where in the world they are. The European Union estimates that about 45% of carbon dioxide emissions within its borders are generated through energy use in buildings. And façade design looks set to get even more energy smart from next January, when member states will have to take this into account in the calculation of the overall energy performance of buildings. Hydro, the Norwegian metals and energy group, is one of the companies at the forefront of modern façade design. Over the past 18 months it has developed an aluminium and glass cladding system, known as TEmotion, capable of saving up to 50% of primary energy consumption compared with current standard designs. The system combines two façades separated by a gap within which air is circulated, for ventilation and cooling in the summer and to add extra insulation in cold weather. The outer, fixed double-glazing skin includes a sun-shading device that is more effective than an internal blind, while the inner skin includes turn and tilt windows to let natural air in, even in high-rise buildings. The façade is assembled from pre-fabricated modular units, which saves energy during construction. The panels also incorporate conventional heating, cooling and lighting services controlled automatically in conjunction with the tilting windows and sunshades. One further option available to architects is to include photovoltaic cells in the façade that could potentially generate enough energy to make the building self-sufficient. Werner Jager, managing director of Hydro’s building systems research unit, says the reduced use of artificial light and air conditioning - in some cases no air conditioning at all may be necessary - has been shown to increase comfort levels among building occupiers. He also believes the façade system is sustainable on a whole life cycle basis, in spite of the high initial energy consumption associated with aluminium smelting. Up to 85% of the aluminium content in façades is already recycled and TEmotion components are designed to be easily separated, which will increase recycling rates in the future, he says. So far, eight TEmotion projects are at the consultation stage, and Jager estimates the initial cost to be roughly the same as for buildings designed with standard façades, partly because it brings savings on other construction features: “The fact that all the building services are integrated in the façade means you can do away with suspended ceilings or double-constructed floors, offsetting the higher cost of the system,” he says. “In the long term there are clear advantages for operating and maintenance costs as well as for the environment.” Nick Jones, principal consultant in the BRE’s environment division, is convinced that, with countries under pressure to hit climate change commitments, good cladding systems are becoming an integral part of a building’s ability to deliver carbon savings: “As people realise they can’t just rely on mechanical services within buildings to save carbon, the overall performance of buildings will increasingly come back to the better design of their fabric.” Matthew Jones is assistant news editor of FT.com and a former energy writer for the Financial Times.

20 September 2005

Matthew Jones