According to some property analysts, buildings which are more energy efficient and environmentally-friendly could command a growing premium in the future by drawing tenants and generating higher rents.

In a statement, the companies said the scheme would assess and benchmark the environmental performance of their existing buildings by rating them according to a number of measurable indicators.

These include a property's energy and water consumption, the waste it produces, its carbon emissions and transport links, plus its record on occupier health and safety.

"...The asset performance is assessed on site by an independent third party and can thus provide a sound and concrete decision-making tool for improvement actions," Gilles Bouteloup, global head of compliance and sustainable development at AXA REIM, said.

"Furthermore, this rating will allow us to give evidence of the actual progress achieved year by year and will concern 95 percent of our real estate portfolios," he added.

Real estate accounts for 40 percent of the EU's energy requirements and carbon emissions.

A European Union directive in 2003 provided for the harmonisation of building standards across the 27-nation bloc so that greater emphasis was placed on minimising the energy needs of new property developments and homes.

But there was a gap in the market when it came to existing commercial properties, the statement said.

"The initiative covers hence a real need that is not addressed so far by existing green labels, mostly domestic, heavier to implement and mainly focused on new-builds," said Gabor Kende, GE Real Estate's engineering manager for Europe.

The Global Green Rating system is being developed and tested in 15 pilot sites in Germany, France, Spain, and the UK.

Depending on the results, an open version of the scheme could be launched before the end of 2008.

(Reporting by William Kemble-Diaz; Editing by Elizabeth Fullerton)

(See www.reutersrealestate.com for the global service for real estate professionals from Reuters).