Thermal State, Potential of Natural and Fan-Induced Ventilation in Enhancing Comfort of Nine Office Buildings in Southern Ghana

Abstract

This paper presents the outcome of a long-term study of the thermal conditions in nine office buildings in Accra and Kumasi, Ghana. As part of the aim, the authors sought to evaluate the prevailing thermal conditions in the office buildings and to find measures of reducing overheating tendencies via comfort charts and a simulation approach. The outcome of the study suggests high thermal discomfort feeling in the office buildings because the environmental parameters of temperature and relative humidity values plotted on the various comfort charts illustrated uncomfortable conditions. However, air velocities of 0.5, 1.0, and 1.5 m/s could help to increase the percentage of time (POT) in which the indoor spaces are comfortable within a range of 28% and 98% across the various buildings. Mean overheating temperature values ranged from 1.2 to 5.6 K above the neutral temperature across all buildings. This was associated with a high number of predicted percentages of dissatisfied occupants (24%–65%). In addition to this, American Society of Heating, Refrigerating and Air-Conditioning Engineers’s (ASHRAE) reference temperature for summer comfort, that is, 26°C led to a mean overheating temperature of 0.7–5.6 K in the multistory (MS) structures. Given the potential of improved design options in combination with various air change rates (ACHs) in reducing overheating tendencies, predicted mean votes (PMVs) could be reduced from a mean of 2.7 (hot) to 1.6 (slightly warm) across all buildings. There is a strong indication of the inability of Ghanaian office buildings to fully operate in passive mode from the results. Furthermore, the survey revealed that although building occupants voted air quality and thermal comfort as the most important parameters, they also complained about the inaccessibility of building systems (35%). On the thermal sensation scale, occupants indicated a wild range of conditions with a majority (more than 60%) from cool through warm. Efforts to observe time slots where reliance on natural ventilation would be appropriate through scientific monitoring and performance documentation are being studied. The anticipated ecological and economic benefit to Ghana would be positive amidst the current global challenges.