This resulted in a sample of 9,998 buildings for which financial data could be obtained.

There were a total of 1,360 possible buildings at CoStar, but the researchers can find all the required matching data from CoStar on 893 buildings, comprising 694 for which the researchers have rental data as of September 2007, and 199 that were sold between 2004 and 2007.

The research provides the proof on the economic value of the certification of green buildings in the commercial sector and concludes that there is a premium of 3% for the rents that green buildings with the Energy Star rating can command. Additionally, when looking at effective rents (the true rent of a property, considering rental concessions, spread over the life of the lease) the premium is higher still, above 6%.

The researchers have looked at the impact on the selling prices of green buildings, and here the premium is even higher, in the order of 16%. This means that upgrading the average non-green building to a green will increase its capital value by some $5.5 million. Even though, the tenants and investors are willing to pay more for an energy-efficient building, but not for buildings that are sustainable in a broader sense.

Simon Rubinsohn, RICS Chief Economist comments: “This piece of research is an important first step in building an evidence base on the topic of the value of “green” buildings. Previously with only anecdotal evidence available on which to base decisions surrounding development of energy efficient buildings, it is understandable that the uptake of some measures has been frustratingly slow.

“With more comprehensive evidence based research, such as this paper, the economic argument for having an energy efficient building will be strong. Any businesses wishing to maximize profits will have to start looking at increasing the energy efficiency of the buildings in order to remain competitive. By proving that green buildings are economically beneficial due to the savings they can make and the higher rental yields they attract, non-green buildings will eventually become an outdated model.”

This research has been carried out by Piet Eichholtz and Nils Kok of Maastricht University, the Netherlands, and John Quigley of the University of California, Berkeley, US.