Trickle ventilators: effective natural background ventilation for offices.

Approved Document (AD Part F1) of the Building Regulations [1] for England and Wales identifies trickle ventilators as an option for providing natural background ventilation in commercial buildings. This paper reports the results of a field measurement study carried out at BRE during the winter of 1994/95 to assess the effectiveness of trickle ventilators. Two occupied office rooms were equipped with trickle ventilators and measurements were carried out for a fortnight period in each office, with the ventilators closed during the first week followed by a week with them open. Internal and external parameters of significance were monitored including level of metabolic CO2 within the rooms, draught speeds near the ventilators and occupancy. The study has confjmed results of a previous modelling study [2] which showed that trickle ventilators of sizing given in the AD Part F1 provide adequate background ventilation of about 5Vs per person in typical UK offices. Furthermore, it has also confirmed the results of an earlier laboratory study [3] where it was shown that for average and high occupancy (8-10m² per person) trickle ventilators with similar sizing were capable of providing the fresh air required to maintain CO2 levels at or below 1000ppm (which equated to about 5Vs per person) for average UK external weather conditions. In conclusion, the present field study in occupied ofices has shown that trickle ventilators of suitable design and openable area of 400mm² per m² (of floor area), as advocated in AD Part F1, are effective in providing adequate background fresh air in UK offices during the heating season without creating occupant discomfort.