Drainage ventilation expert Studor has responded to market confusion about Air Admittance Valves (AAVs) and whether they can be used externally.

Technical director Steve White said: “There does seem to be confusion in the market and we’re frequently asked whether AAVs are suitable for exterior use. Both our own Studor Maxi-Vent, as well as the Wavin branded OsmaVent 110, can all be used externally. The latest BBA Agrément Certificates clarify this and specifically refer to their external use.”

The BBA certificates verify that the AI rated valves perform in extreme temperatures, from -20°C to +60°C in accordance with EN12380. However, it should be noted that the independent testing actually carried out exceeded the requirements of the standard and proved that the valves operate in temperatures down to -40°C without the insulating cap. In addition, the ABS plastic which the valves are made from includes a UV stabiliser to protect against any degradation effects from ultraviolet radiation.

The certificates note that these external AAVs should be installed with the Aluminium Cover (Alu Cover) and insulating cap which fits on top of the valve to protects the unit from birds, wildlife and accidental damage. The Alu Cover, which can also be painted if there is a need to match a particular RAL colour, can be purchased independently of the AAVs as needed and is very easy to fit.

Steve White added: “Our company has over 40 years of specialist knowledge in drainage ventilation. Installing an AAV externally protects against pressure fluctuations due to ‘wind effect’ which can lead to traps self-siphoning. Another key benefit of using an AAV externally is that it allows a vent pipe to be terminated close to a window or other opening – removing the need for additional pipework to locate it further away. It can also improve the aesthetics of a building by allowing the soil stack to be terminated below the roofline, avoiding the need for the protrusion of an ugly vent pipe above the roofline.”