How are window vents measured?

In England and Wales, Equivalent Area has replaced Free Area for all vents installed in new build and refurbishment applications. This change represents a more logical step in achieving the air movement in dwellings with products tested in situ.

What is Free Area?

Free area is the total area (mm²) of the rout on the window profile that the window vent is installed over.

e.g. 4000SBW rout = 2 x 175mm x 16mm with a 10mm gap

The total Free Area for the product would therefore be 5600mm² (2 x 175 x 16mm).

What is Equivalent Area?

Equivalent Area is the airflow which passes through the ventilator when it is in the open position, installed on the window profile.

All of the vents are tested to BS EN 13141-1: 2004 Ventilation for Buildings, as detailed in ADF 2010 to determine equivalent area performance.

The performance at 1 permanently and visibly marked on the ventilator for inspection by building control.

Equivalent Area Diagram

All Greenwood products are tested at third party accredited test houses to all current British and European standards. All performance details are available on request from Customer Services.

BS EN 13141-1: 2004

Ventilation for Buildings

BS EN 1026: 2000

Air Permeability

BS EN 1027: 2000

Water tightness

BS EN 717-1: 1997

Airbourne Sound Insulation (dB)
S Vent - Through Frame Slotvent

Through Frame Slotvent

Up to 4200mm² equivalent area.

S Vent
L Vent

Slimline Through Frame Slotvent

Suitable for low profile window frames.

L Vent
F Vents

Through Frame Slotvent

Clip fit and screw fix installation options.

F Vent
EAR42W Vents

Acoustic Vents

Fresh air in or out – no noise.

Acoustic Vents
2500EA Vents

Aluminium Acoustic Vents

The best of both worlds…

Aluminium Vents
Easy Vents

Easy Vent

Competitively priced window slot vent.

Easy Vents