Natural ventilation has the potential to replace or supplement air conditioning, comfort cooling and mechanical ventilation. Whilst there are obvious environmental advantages, there are problems to achieving adequate control as the flow of air must be controlled to limit energy consumption and maximize thermal comfort. This "Technical Note" provides guidance on the application of BMS (Building Management System) controls to natural ventilation. The use of automatic controls is not a panacea for ventilation problems. A vent under occupant control should generally be provided, thus allowing the building occupants to manipulate their own environment. However, the provision of automatic control of air inlet vents and inaccessible air outlet vents results in improved ventilation rates, particularly in the summer, thus enhancing the working environment. Further to this, automatic controls offer the opportunity for night cooling techniques, thus helping to ameliorate daytime heat gains.
This publication presents a number of generic control strategies for natural ventilation, mixed-mode ventilation and night cooling, which are used to control this enhanced daytime ventilation and night cooling. Procedures for commissioning and fine-tuning buildings using these strategies are described, together with appropriate control setpoints. An analysis of the costs of buildings utlizing various ventilation types is also provided. The guidance is reinforced with the results of monitoring carried out in three naturally ventilated buildings. A description of the buildings is presented, together with details of the control strategies and the results of monitoring. General conclusions regarding the control strategies and the performance of the ventilation system in each of the buildings is presented. Finally, a description and details of the control strategies of eight further buildings utilizing controlled natural ventilation are presented.