Ventilation Grille Exterior Gravity Louvre 350x350mm PVC Grey, Vents-Group

Quick Facts — Vents-Group Ventilation Grille GRM-350

• Outer dimensions 350 x 350 mm, mounting holes 286 x 286 mm
• Automatic gravity louvres in grey PVC
• Single, undivided louvre construction
• Grille frame in powder-coated metal, grey colour
• One-way airflow — prevents backdraft
• Weather- and impact-resistant, colour does not fade
• For mounting on vertical surfaces (walls) only

The GRM-350 ventilation grille terminates the extract duct and protects against weather and draughts by closing automatically when the fan is off. The grey PVC louvres are lifted open by the airflow during forced extraction and fall back to the closed position as soon as the fan stops.

In strong wind or with a large pressure difference between indoors and outdoors, the louvres may produce some noise when opening and closing — this is normal and does not affect function.

Why installers choose the GRM-350 for smaller ducts

At this size, the GRM-350 suits ducts with a more limited diameter, such as in bathrooms, utility rooms and smaller technical spaces. The grille frame is coated with a weather-resistant and mechanically durable polymer coating, letting installers rely on the function even in locations with limited oversight, without risk of the colour fading or the frame rusting.

How do the louvres open and close automatically?

The lightweight PVC louvres are pushed open by the airflow as soon as the fan starts, releasing the air freely through the duct. When the fan is switched off, the louvres fall back under their own weight and close the opening, preventing cold outdoor air and draughts from re-entering the room.

Where does the GRM-350 perform best?

The grille is installed outdoors on vertical wall surfaces as the termination of smaller extract ducts, for example for bathroom or kitchen ventilation in homes. Beyond the backdraft seal function, it provides a decorative and neat end fitting while also protecting against debris and precipitation entering the duct.

Model and dimension overview, GRM series

Suitable for: HVAC installers, bathroom and kitchen renovators, and private individuals installing extract air in smaller spaces.

Industries: HVAC and ventilation, home renovation, construction.

Frequently asked questions (FAQ)

Can the Vents-Group ventilation grille GRM-350 withstand direct sunlight or cold without the louvres seizing up?

Yes, the PVC louvres are weather-resistant and withstand temperature swings and UV exposure without becoming stiff or ceasing to move freely. Should a louvre still stick, check the hinge area for dirt or ice build-up.

How often should the GRM-350 be checked after installation?

A simple visual inspection once or twice a year is enough to confirm that the louvres move freely and that the grille frame's polymer coating is intact. No lubrication or adjustment is required under normal operation.

Does the GRM-350 offer the same backdraft protection as a motorised backdraft damper?

The GRM-350 provides fully adequate passive backdraft protection through its gravity louvres, without requiring an electrical connection, control or maintenance of moving electrical parts as a motorised backdraft damper does. The difference is that gravity louvres open and close purely based on airflow, while a motorised version can be controlled and monitored separately.