Investigations into the thermal comfort and indoor air quality of rooms in low energy homes using a combined heating and ventilation system

The objective of the research was to identify a suitable heating and ventilation system for the provision and control of thermal comfort in rooms of future low energy homes. This was to be achieved whilst allowing for the provision of good indoor air quality (IAQ) and minimisation of energy consumption. The thesis describes the investigations of individual room airflow and the implications on thermal comfort, indoor air quality and energy consumption. Using a commercial computational fluid dynamics package, numerical simulations were performed to produce airflow patterns and distributions of temperature and pollutants within a room. A numerical model was validated for use in indoor airflow. The model was used, first of all, in the identification of a suitable configuration of supply and extract air terminal devices, over the expected range of boundary conditions. Further to this, parametric and sensitivity studies were performed on the proposed system to establish the influence of the airflow rate, supply air temperature and room specific parameters such as internal heat sources, furniture etc. on the indoor environment. Time dependent variations were considered in order to provide a better understanding of the transient nature of the system. The research also included determination of necessary locations of sensor/measurement points which provide representative conditions of the thermal environment in the room. The investigation found a high level supply combined with a low level extract configuration to be most appropriate over the range of operation expected of the heating and ventilation system. Limits of operation of the system were identified to prevent local thermal discomforts due to excessive vertical air temperature gradients and draught. As a result of the investigations, a simple control strategy was proposed to achieve thermal comfort control, while providing good IAQ and energy efficiency