Describes experiments carried out in five naturally ventilated offices to measure the indoor environmental parameters such as air velocity, turbulence, intensity and air temperature. Air change rates for various indoor and outdoor climates were determined. The concentration of CO2in the rooms was monitored. Subjective assessment was made to evaluate the thermal comfort and air quality in the offices. The data were used to develop models to assess the indoor environment of naturally ventilated offices. States that results from the present investigation show that the thermal sensation in work environments differs from that evaluated under laboratory conditions. Also shows that the energy consumption for space heating can be reduced by lowering room temperature. Assesses potential energy savings for the UK climate.KEYWORDS: Offices, ventilation, natural ventilation, experiment, UK, thermal comfort, air quality, calculating, indoor, environment, microclimate, room temperature, energy conservation.