The production of this Guide is the culmination of considerable effort by a number of dedicated members who have selflessly given their own time that the membership at large may avail themselves of updated technological and intellectual data. This Guide also provides a landmark in the CIBSE publications process as it marks the start of a policy whereby the Guide will be revised on a more regular schedule. This change in policy reflects the more rapidly changing world and the Institution’s recognition of the necessity to keep members abreast of technical and legislative developments and the demands associated with European and international standards. Preparation of the next edition is already in hand and this work will be facilitated if members communicate suggestions for amendments, modifications and revisions to the Institution’s publications secretariat. Meaningful feedback from members is an essential ingredient of the publications process.