The CSSO currently occupy the 2nd & 3rd floors of The Chancery Building but required additional office space due to expansion. Privacy was high on the Clients requirements and work was undertaken within a live environment. The works required an upgrade of the existing ventilation system which resulted in the installation of new 4-pipe fan coil system providing space heating and cooling to the office staff. Individual fan coil systems were provided to CSSO office staff with cross talk attenuation. Software package IES was used for calculating heat losses and solar gains based on existing fabric to enable ventilation / AC systems to be sized and designed allowing for comfortable conditions in peak summertime conditions. A full LED lighting upgrade which includes for daylight dimming and absence detection was also installed along with new electrical & data wiring to suit the client’s new office layout. the clients new office layout. DIALux was used for natural daylight calculations to maximise daylight to office spaces. It was also used for artificial light design to establish lighting levels in open plan space and cellular offices.