It began with such good intentions. When work started on Portcullis House, the landmark Thameside project designed to provide modern offices for MPs, it promised to be one of the greenest buildings in London.

The £247m building would use a third of the energy required by a similar-sized prestige office block, Ove Arup and Partners, the project engineer, told the National Audit Office in 2002.

That works out at an annual total energy consumption of about 90 kilowatt-hours per square metre. The current best practice for an air-condi-tioned office block is about 250 kilowatt-hours per square metre per year, not a long way from what you might expect from a modern home.

But it took a parliamentary question earlier this year from Peter Ainsworth, the Conservative environment spokesman, to winkle out the fact that Portcullis House is consuming about 400 kilowatt hours per square metre - more than four times what was envisaged.

The answer went on to add that: “A number of measures are under consideration which could lead to a significant reduction in consumption.” However, it was fairly clear that Portcullis House will never be the low-carbon building taxpayers were promised.

Ainsworth was angry: “It was supposed to be an example the rest of the country could follow and instead it’s an embarrassment.”

A spokesman from Ove Arup told The Sunday Times: “Portcullis House is not a standard office building. It is used for longer and by more people than envisaged or standard . . . Arup is continuing to advise the Parliamentary Works Directorate on the reduction of the building’s carbon footprint.” Portcullis House is just one of many commercial buildings, sold as low-carbon, where the actual performance turns out to be less impressive. City Hall, which houses the Mayor of London’s office, was designed to be one of the most energy efficient and sustainable structures in the capital. It included special cladding, thermal glass and an air conditioning system that uses artesian well water. But staff have complained that working there is like being in a greenhouse - and solar panels recently installed at a cost of £730,000 have proved capable of producing only 1.5% of the building’s power.

It’s not always fair to blame the building designers. Occupants often install far more equipment and staff than their properties were designed for and then fail to run their energy management systems efficiently. The Swiss Re building in the City of London, better known as the Gherkin, was designed by Norman Foster with advanced energy-saving systems including shafts between floors providing natural ventilation and windows that opened. It recently emerged, however, that such systems have been compromised by tenants erecting partitions that block or alter the natural airflow.

A statement from Evans Randall, the investment bank that bought the Gherkin with German property firm IVG in February 2007, confirmed that partitions had been added “to provide the privacy and security needed for subletting”, but said it was too early to comment on energy use. “The building is only now reaching the point where year-on-year comparisons of energy consumption are possible,” Evans Randall said.

Housing developments have similar problems. One of Britain’s best-known attempts at low-carbon housing is BedZed, the Beddington Zero Energy Development, near Croydon, south London. It was meant to get much of its energy from an onsite combined heat and power plant fuelled by woodchips but the system failed, forcing the developers to resort to the national grid.

Although it is easy to look for faults in such innovative developments, it is through their pioneering work that we can learn what succeeds and what fails. David Strong, formerly managing director of the Building Research Establishment’s environment division and now chief executive of Inbuilt, a sustainable building consultancy, believes overcomplexity is one of the emerging themes.

“The more complicated you make these systems for saving energy and cutting emissions, the more likely they are to break down,” he says. “Even if they don’t break, they fail because the occupants and managers of the building simply forget how to run things properly. Bad practices creep in so that all the potentially excellent design features become pointless. Ideally, low-carbon buildings should have passive systems that manage themselves.”

Bill Bordass, of William Bordass Associates, a buildings performance consultancy, says it is wrong to assume that new or refurbished buildings automatically will have lower-energy consumption and emissions. “Businesses tend to put more kit and more people into modern buildings and there is little pressure to make them efficient. Most of the benchmarking systems date back to the 1980s and there has been little pressure to change because, until recently, energy was a relatively small cost for most businesses.”

How much does this matter? A lot, according to the Carbon Trust, the organisation set up by the government to try to reduce greenhouse gas emissions from business. “Nondomestic buildings generate nearly a fifth of Britain’s CO2 emissions,” says Mark Williamson, the trust’s director of innovations. “Reducing those emissions will be an essential part of meeting Britain’s commitment to cut CO2 emissions by at least 60% by 2050.”

Owners and occupiers are coming under increasing pressure to cut emissions from buildings. Since April this year, energy performance certificates have been required as part of the construction, sale or lease of large nondomestic buildings and the same rules will apply to most other commercial buildings from the beginning of next month. And public buildings with a floor space of more than 1,000 square metres will have to display information on energy efficiency to visitors – a naming and shaming tactic that will apply to some of Britain’s most famous buildings, from art galleries to town halls.

Hitting the 2050 target presents a problem for landlords and owners. About 60% of the commercial buildings that will be operating then have already been built – and 40% will predate 1985. How can they be brought up to scratch? “The average commercial building gets a complete refurbishment every 20-30 years,” says Williamson. “By 2050 almost all the buildings now standing will have had the chance to be upgraded and made energy efficient. It is a huge opportunity.”

There is, however, also a big risk. Studies show that most companies carry out refurbishments for reasons such as improving their brand image, expanding office space or achieving higher rental values. Cutting carbon emissions is seldom high on the agenda, so most refurbishments actually lead to higher carbon emissions.

Tom Delay, the Carbon Trust’s chief executive, says: “Low-carbon refurbishment is not constrained by the availability of appropriate technologies. The key issue is commitment.”

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