And all new, non-domestic buildings, including offices, shops, factories and leisure centres will, from 2008 onwards, have to comply with new thermal performance standards. Any building intended for sale or to let from the beginning of 2009 will be issued with a certificate indicating its BER along with an explanatory document outlining ways in which the building's energy efficiency might be improved.

"Any suggestion that these new regulations will affect property prices is purely speculative at this stage, " said Deirdre Flood of Sustainable Energy Ireland (SEI), the national energy agency with responsibility for establishing the new standards.

"If, in future, you want to rent or sell a building, it will have to be rated. If for one reason or another . . .

poor insulation, perhaps, or an absence of double glazing . . . the building scores badly, the purpose of the certification is to alert interested parties to the fact that this is not an energy efficient premises."

SEI is currently working on establishing a measurable scale that will be used as a template to grade energy efficiency of buildings.

In accordance with EU requirements, the new building energy performance standards will be reviewed every five years.

"There may very well be significant cost implications in all of this for landlords and investors in the commercial sector, " said Marie Hunt, head of research with CBRE Gunne.

"It's quite possible there will be less demand for properties with a low rating. Rents may stay flat or could actually fall. It may be the case that companies looking to rent or purchase a premises will in future pass over a property with low ratings, " she added.