Thus the purpose of an extractor fan flow rate test is to ensure that the system installed meets the minimum ventilation requirements of the Building Regulations.
Part F Ventilation Testing
What is a Mechanical Ventilation Flow Rate Test?
Part F of the Building Regulations requires that all mechanical extract fans in new dwellings must have a flow rate test carried out to ensure that the extractor performs to the requirement (as below). The resultant report is passed to Building Control as part of the sign off procedure.
We carry out the test by using an anemometer with a specially fitted bracket to maintain air flow.
Due to the nature of the current regulations it has caused the construction industry to lean towards constructing Air Tight Dwellings. Dwellings that achieve low air permeability ratings have lower heat loss through air infiltration, therefore lower emissions. However, with buildings being built airtight it is vitally important that adequate ventilation is installed. Insufficient ventilation can result in damp, condensation and health issues.
Contact us on to discuss your test.
We offer these free with an Air Test.
What can affect the extractors flow?
Factors that affect an extractor fans flow include:
- The location of the extractor can influence is usefulness, placing an extractor far from a source of odour or damp/condensation etc or using an underpowered extractor. It is always better to over specify the flow rate (See below chart for requirements in rooms)
- Lengthy ducting will cause a drop in performance, try to keep distances short for ducting or as above over specify.
- Rigid ducting vs Flexible ducting; Flexibly ducting can become ripped or crushed either by accident or over time, this will eventually prevent air flow. It is best to use Rigid ducting where possible.
- Bends, kinks and obstructions to ducting will adversely affect fan performance. When using flexible ducting it should be extended to at least 90% of its length for resistance to be minimised.
- For connections, use rigid connectors and/or jubilee clips.
- External grilles should be clear of obstructions to ensure flow of air.
What are the minimum flow rates each intermittent extractor fan should achieve?
|Room||Minimum flow rate|
|Kitchen (adjacent to hob)||30 l/s|
|Kitchen (elsewhere)||60 l/s|
|Utility room||30 l/s|
|Sanitary accommodation||6 l/s|