Extractor Fan Testing

As buildings become more insulated and air tightness is improved, it is essential that any installed ventilation systems are fit for purpose, balanced and commissioned correctly to ensure optimum levels of operation for the well being of the occupants.

Approved Document F of the Building Regulations requires that MHVR Systems (Mechanical Ventilation and Heat Recovery) and intermittent extractor fans (e.g. kitchen and bathroom) have their flow rates checked, are working efficiently and the relevant test results submitted to building control as part of the overall building compliance and sign off process.

Under normal circumstances, we are able to carry out Ventilation Flow Rate testing alongside our on-site Air Pressure Test, thereby enabling you to achieve both Part L and Part F compliance in the most time-efficient, cost-effective manner.

There are four types of ventilation systems as described in Approved Document F, they are referred to as Systems 1–4.

System 1 – consists of background ventilators and intermittent extract fans and is by far the commonly used approach where intermittent extract fans are used to remove moisture and odour from wet areas; however, the general background ventilation to the living spaces is provided via trickle vents housed in windows and/or background ventilators such as air bricks.

System 2 – consists of passive stack ventilation (PSV), this uses passive ventilators, roof level outlets and background ventilators to achieve air changes through natural buoyancy and wind driven ventilation. In this system air is supplied to the dwelling using background ventilators sized in the same way as System 1.

System 3 – consists of continuous mechanical extract (MEV) and System 4, continuous mechanical supply and extract with heat recovery (MVHR), use mechanical systems to distribute air through the dwelling. System 3 discharges it directly to the outside, whilst in System 4 a heat exchanger is used to recover heat from the discharged exhaust air to preheat mechanically supplied fresh air.

If you require advice on which ventilation system to use to achieve compliance with approved document F for domestic extract fan testing. Simply the use our contacts form on this page, or call our offices, to chat about your specific vent testing requirements with our knowledgeable team of consultants.

The extract rates for fans in kitchens, bathrooms and WCs are defined in Approved Document F. These rates apply to all dwelling types and sizes. Extract fans need to meet following minimum extract rates:

a. Kitchen (cooker hood) and utility rooms: 30 l/s
b. Bathrooms (intermittent extract fans) 15 l/s
c. Sanitary accommodation: 6 l/s

If you require advice on what type of extractor fan would be best to achieve compliance with approved document F, Simply the use our contacts form on this page, or call our offices, to chat about your specific vent testing requirements with our knowledgeable team of consultants.

Items to be completed prior to our arrival on site:

a. An Electric supply must be connected to all fans and the fans must be fully operational.
b. All the finishes such as plasterboard and masonry must be properly finished around the vents to enable an air tight finish around the fan.
c. All door and windows should be installed at the time of vent testing.
d. Window trickle vents should be in place.
e. Suitable clear and safe access must be supplied to reach all vents internally and externally.
f. We require the SAP calculation worksheets for each dwelling.
g. All internal doors must be fitted.
h. We require the ventilation/fan specification for all vents.
i. Floor plans and sections for each dwelling will be required 3 days before the test date.
j. The occupant schedule (the expected number of persons living in each property)
k. A parking space not further than 50 metres away should be supplied.
l. Ensure that the completed building envelope is finished. All doors, windows, and cladding must be installed.

Make sure that:

• All wall surfaces in rooms to be tested are complete (including sockets and switches)
• Structural floor and ceiling surface are complete.
• Carpets or timber laminates have been laid in rooms

a. Is the ductwork of the type specified by the manufacturer?

b. Have the number of duct bends been minimised to ensure adequate air flow and least resistance?

c. The Flexible duct provided should only be used to connect the unit to the central diffuser (this is important for the acoustic performance of the product).

d. Have recommended duct jointing collars and components been used to ensure appropriate duct performance (duct runs should be as air tight as possible)? Note: All the joints should be sealed correctly using the collars provided.

e. Have all grilles or ductwork that penetrate the building’s air barrier, as identified in the construction drawings, been sealed to ensure continuity of the air barrier?

f. Is the fan correctly situated, secured and adjusted?

g. Do all internal doors have 10mm undercuts? (as required in “Domestic Ventilation Compliance Guide” Part 2b Table 2.3a)

h. Has the electrician set fan speed using manufacturer’s data table

i. If Air handling units are utilised as part of the system have they been fixed to a stable element of the building fabric (e.g. wall or floor) using manufacturer’s recommended/supplied fixing brackets?

j. Has the unit been installed in a position that will permit access for maintenance purposes.