Previous work by the authors has shown the effect that changing climate and small power/lighting equipment can have on heating and cooling loads of typical existing UK offices, for a 2005 baseline. This follow-on study uses an improved office, with reduced cooling loads, and performs retrofit fabric and HVAC measures to further reduce the energy and CO2 emissions associated. The effect of heat recovery on the proposed "2030 office" is then quantified, showing that such an office can tend towards being "passively heated". With adaptive comfort also applied, the office CO2 emissions are estimated for various UK locations. The measures suggest CO2 emissions relating to heating, cooling and ventilation (HVAC) can be reduced by 61% for the specific office-type studied. The proposed measures are carried out while allowing for a change in activity between 2005 and 2030. When all factors leading to changes in energy use are accounted for, namely small power, lighting, HVAC and climate change, total CO2 savings of 65% are estimated when compared to the 2005 baseline. In achieving these theoretical savings, the relationship between internal activity and HVAC is studied, and identified as being a crucial area if challenging CO2 emission targets are to be reached. (C) 2009 Elsevier B.V. All rights reserved.