Single-sided natural ventilation—How deep an office?†

Renewed interest is being shown in designing for natural ventilation, as a means of avoiding the need for air conditioning. This has come about as a result of concern about local and global environmental issues related to air conditioned buildings. On the local level there is, for example, the risk of health-related problems such as 'sick building syndrome'. Global issues concern the depletion of the ozone layer and the atmospheric greenhouse effect. It is generally acknowledged that, in operation, ozone depleting gases are released from refrigeration plant of most air conditioned buildings; they consume more primary energy, with an associated greater production of carbon dioxide. To provide adequate ventilation for cooling in summer, traditional guidance recommends cross-ventilation for naturally ventilated offices deeper than 6 m, but this is often not practicable in many modern designs for office buildings. There is little guidance on designing for single-sided ventilation, which may be an option in some cases. This report describes tracer gas measurements of the local mean age of air at different locations within an office room 10 m deep, ventilated through single-sided ventilation. These results show that fresh air is generally distributed over the whole depth, suggesting that if effectiveness of ventilation is the main criterion, natural ventilation may be incorporated into deep open-plan style rooms and wider buildings than is implied by the present limit. The adequacy of the total supply of single-sided ventilation to avoid overheating in summer was assessed using BRE and CIBSE design guidance calculations, and this indicated that comfortable temperatures can be maintained.