If you had to work in air-conditioned datacenter and or directly next to it you know how much noise all the machinery can generate.
To be green it would be nice to setup datacenter with low energy consumption servers with passive cooling as well as no air-conditioning.
this solution should help with the no air-conditioning cooling part: http://arstechnica.com/business/news/201…nology.ars
And this is Facebook approach: http://www.matternetwork.com/2011/4/face…server.cfm