Yahoo has unveiled plans for new datacentres that it claims will be the company's greenest yet, and has promised to cut its global carbon intensity by at least 40 per cent by 2014.

Dubbed the Yahoo Computing Coop, owing to its similarity to a chicken house, the datacentres use high pointed ceilings and louvered walls to dissipate heat naturally, eliminating the need for an air conditioning system.

"For datacentre geeks, we expect our new design will have an annualised average power usage effectiveness [PUE] of 1.1 or better," said David Filo, co-founder of Yahoo.

Datacentres typically have a PUE rating of 1.6 or higher, making the new design one of the most power efficient in the world.

The centres, each running at 5-megawatts, will be built in Buffalo, New York, and will use hydroelectric power from the nearby Niagara Falls. The lack of air conditioning means that 90 per cent of the power will be used to run the servers, compared to less than 50 per cent in most datacentres.

Two facilities will be built at the site initially, followed by three more in a second phase of development.

Filo also announced that Yahoo will no longer buy carbon offsets, as promised in 2007, and will instead concentrate its resources on building more environmentally friendly computing facilities.

"We will continue to push ourselves hard to lower our impact," he said. " Today we are committing to reducing the carbon intensity of our datacentres by at least 40 per cent by 2014. In other words, we will decrease our average electricity consumption and greenhouse gas emissions from our datacentres around the world."