The thermal environment in eight naturally ventilated and eight air-conditioned offices, located throughout England, was continuously monitored for one week in winter and one week in the following summer. The occupants assessed their thermal sensation (TS) every half-day on the ASHRAE seven-point scale. In total, 1,692 occupants made 11,450 votes in winter and 1,363 people made 9,505 votes in summer. Weighted regression analysis was used to compute the neutral temperature and acceptable temperature range relating to 3.5 £ TS £ 4.5. The overall comfort range in naturally ventilated offices in winter and summer, 4.9°C and 3.9°C (8.8°F and 7.0°F), respectively, was wider than that found in air-conditioned offices, 2.6°C and 2.4°C (4.7°F and 4.3°F), respectively. The neutral temperature in naturally ventilated offices was 0.7°C (1.3°F) lower in winter and 2.1°C (3.8°F) lower in summer than in air-conditioned offices. However, there was only a marginal difference in clothing insulation and activity levels between the two types of offices. The lower neutral temperature in naturally ventilated offices in summer may partly be due to an overestimation of warmth due to conditions typically being warmer than the previous day. Discrepancies of up to 3.0°C (5.4°F) were found between the observed neutral temperatures and those predicted by ISO 7730 for naturally ventilated offices in summer. In contrast, for the air-conditioned offices in winter and summer and naturally ventilated offices in winter, the predicted neutral temperatures were much closer to those reported, with a maximum difference of only 0.6°C (1.1°F). In winter, the percentage of occupants satisfied with the temperature in the naturally ventilated buildings (76%) was higher than in the air-conditioned offices (70%), whereas in summer, there was less satisfaction in the naturally ventilated offices (69%) than in the air-conditioned offices (73%). The occupants were less dissatisfied in the naturally ventilated buildings in winter than in summer, whereas there was only a marginal difference in dissatisfaction between seasons in the air-conditioned offices.

Units: Dual