IN this world of ever-increasing fuel prices, any means for maintaining business competitiveness by reducing CO2 emissions and hence costs has to be welcomed.

For the biggest businesses energy costs and the implications of being more sustainable are already enormous.

One East Midlands university told us just this week that they spent £6.5 million on fuel last year and paid £500,000 in carbon taxes – figures to concentrate the mind for sure.

We've just completed a new 60,000 sq ft HQ for Dunelm Group at Watermead Business Park in Leicester.

The company, which is both the owner and the occupier of the premises, was prepared to invest in creating a highly sustainable building which would give them a longer term return in terms of lower ongoing energy costs and improved staff well-being.

As a result they now have an airy modern office building with electrical running costs a third of what is generally accepted as best practice and a much enhanced internal working environment.

Taking this a step further, we have also just completed a new regional HQ for Interserve Construction who appointed the Nottingham team of CPMG, CPW and BWB to design their Passivhaus Office. Interserve is taking a lease from the developer Raynsway Properties.

Interserve were moving from a grossly inefficient 1960s building and were able to build a strong case to their PLC board for an ultra energy-efficient building by proving a payback period of only seven years.

So how is this payback going to be achieved?

The answer lies in PassivHaus, a well-established low energy design and build method, already widely used in mainland Europe.

The clue to how PassivHaus works is in the name.

Leave aside renewable energy sources, such as wind turbines, and instead concentrate on getting the primary energy demand down.

This is achieved by using efficient office computers and lighting, orientating the building correctly, keeping out the summer heat with external blinds, providing a well insulated, air tight fabric and using high efficiency mechanical ventilation.

The only really "out there" idea is a system of pipes beneath the car park that uses the constant temperature of the earth at 1.5m depth to warm incoming air by 6C in winter and cool it similarly in summer.

The results are astonishing. The building uses only about a tenth of a non PassivHaus best practice office building.

In fact the base energy use is so low that by providing solar panels on the south-facing roof of the building, we have shown we will reduce its Energy Performance Rating to less than zero – making it not merely a carbon neutral building but in fact carbon negative.

As a happy by-product of this approach the building is also really pleasant to be in – the large South-facing windows provide outstanding daylight and a great natural ventilation opportunity.

Passive cooling is exemplary – during the recent hot spell the temperature outside reached 27C whilst the highly occupied office areas were held at 24C without any air conditioning.

So is this approach to building design affordable?

In these two examples there were specific reasons why the companies choose this route, but as energy prices increase, more and more companies will be able to make an economically-driven business case for this kind of approach – which has nothing to do with a wish to be seen to be green.

Indeed Tom Watkinson, of developers Raynsway, put the question to me the other way round – can we afford not to?

Tenants, when you can get them, are signing up to shorter lease terms and the developer may find himself re-marketing a building in seven or 10 years time.

What will energy prices be like then and how will a building built today, compare with one built in 10 years' time?

Perhaps buildings can be retro-fitted instead.

CPMG has been commissioned by the Technology Strategy Board to research into adapting buildings for future climate change, using a current project as a test case. More on this next year.

In the meantime how will the market go?

There is massive interest in the Raynsway project.

We are conducting seminars at the building fortnightly on Wednesday evenings and they are all packed out with dates now extending through to Christmas.

Everyone goes away with food for thought and other developers are approaching us with potential projects.

How many will come to fruition – who knows?

As for the wider sustainability agenda, it is not necessarily marginalised by this approach, and surely such major reductions in CO2output can only be good, not just for business, but for all of us.

Richard Flisher, is director of Nottingham architectural practice CPMG. Ashley Cowdrey is director of Nottingham Engineering consultancy CPW