Ventilation: Approved Document F, Volume 1 — Dwellings

OFN L1I(N2E ) V, ERR S3I O9N, R42, R44 d. For adjustable terminals with a fixed-volume flow fan, the following apply. i. The fan speed should be set to achieve the desired continuous flow rate. ii. The index terminal flow rate should be set with the terminal fully open and all other terminals should be adjusted to achieve the required flow rates at each terminal. NOTE: Adjusting the terminals only balances the flow. Total flow rate is governed by the fan control setting. Care should be taken not to close the terminals too far, because the fan unit will always maintain a constant volumetric flow rate. Closing the terminals will require the fan to work harder to achieve a given air flow rate. e. For fixed terminals with automatic flow adjustment at the fan unit, the fan speed should be set to achieve the desired continuous flow rate. The flows are balanced by automatic devices within the fan unit, so cannot be adjusted. Air flow rate testing 4.9 The air flow rate of all mechanical ventilation fans should be tested. This includes any of the following. a. Intermittent extract fans. b. Cooker hoods. c. Continuous extract fans and/or terminals. d. Continuous supply fans and/or terminals. 4.10 A calibrated air flow device with a proprietary hood should be used to measure the air flow rates at each room terminal following the procedure detailed below. a. The design air flow rates should be determined in accordance with Table 1.2. b. Both of the following should be confirmed. i. All intended background ventilators or other air transfer devices are open. ii. All internal and external doors and windows are closed. c. Air flow measurements should be performed using an air flow device that complies with all of the following. i. Has a proprietary hood attachment. ii. Has an accuracy of ±5%. iii. Has been calibrated within the last 12 months at a calibration centre accredited by the United Kingdom Accreditation Service (UKAS). d. The air flow for each extract/supply fan or terminal should be recorded in litres per second (l/s) on the commissioning sheet (see Part 3 of Appendix C). NOTE: In exceptional circumstances, the configuration of some fan units may prevent air flow rates from being measured. If so, evidence should be provided to assure the building control body that the flow rate can be determined by following the manufacturer’s guidance. 33 Building Regulations 2010 Approved Document F Volume 1, 2021 edition O N L I N E V E R S I O N