Many ventilation requirements and recommendations are in the form of outdoor airflow rates per person. Ventilation systems are therefore designed to provide a minimum level of outdoor air based on the designed occupancy level multiplied by the per-person ventilation requirement. Because the indoor generation rate of carbon dioxide is dependent on the number of occupants, it has been proposed to use indoor carbon dioxide concentrations as a means of controlling outdoor air intake based on the actual number of occupants in the space as opposed to the design occupancy.
The design of low-energy office buildings requires specific attention to an energy efficient concept for providing good indoor air quality conditions. With this respect, mechanical ventilation shows undeniable advantages: it can be optimally controlled (infrared detection, CO2 control,...), heat recovery is applicable, outdoor noise and pollution penetration can be minimised. Another crucial challenge in low-energy office buildings is avoidance or, if possible, the minimisation of active cooling needs.
The main source of humidity in office buildings is the human occupant. Moisture is therefore a result of heat transmission from the person to the room air. The article covers heat transmission of the human body, humidity and comfort, cooling and dehumidification, and refrigeration capacity.
In the design of natural ventilation systems, there is a wide range of possibilities with regard to the selection of window type and the positioning of windows in the facade. Each window type has unique characteristics, which affect air flow and thermal comfort conditions in the occupied zone. A combination of various window types and faade locations in a room should be capable of improving thermal comfort and minimising draught risk.
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