The proposed changes to Part L of the Building Regulations will create challenging energy targets for all buildings intended to improve performance by around 25%. For air conditioned buildings, a significant contribution to reaching proposed Part L of the Building Regulations targets can be achieved by including free cooling as an integral part of the systems design. This guide has been produced with this in mind and has details of 14 different approaches. It contains a number of useful tools including a table of key attributes which enables a match to be achieved between specific building characteristics and the most appropriate system.