This paper comprises the outcome of a long-term monitoring of the thermal conditions in a selected number of office buildings in Kumasi, Ghana. The observed data was not only used to assess indoor environmental conditions in these offices, but also to calibrate a number of thermal simulation models of the buildings. Thus, a simulation-based exploration of thermal retrofit options towards a general reduction of cooling requirements could be conducted. Moreover, the impact of thermal retrofit measures towards reducing carbon dioxide (CO2) emissions was assessed and the amortization times for investments in such retrofit measures were estimated. The results suggest that improvements in building fabric and controls (with payback times of 3-12 years) can reduce buildings' cooling loads by around 20-35% and CO2 emissions around 27%. Additionally, the outcome of interviews conducted showed that 45% and 70% of occupants in mixed-mode and naturally ventilated buildings were uncomfortable with the air quality during the dry season. The highest dissatisfaction with indoor environment was reported by 85% of the occupants in the naturally ventilated building. The importance attached to the operation of windows and shades was relatively high, 55-80%, depending on building type. (C) 2010 Elsevier B.V. All rights reserved.