Ventilation Grille Exterior Gravity Louvre 300x300mm PVC Grey, Vents-Group

Quick Facts — Vents-Group Ventilation Grille GRM-300

• Outer dimensions 300 x 300 mm, mounting holes 236 x 236 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-300 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.

What sets the GRM-300 apart in the smaller grille class?

The GRM-300 is built on the same principle as the other sizes in the series, but in a compact format for smaller duct dimensions. The grille frame has a weather-resistant and mechanically durable polymer coating that withstands both sun and precipitation over time, while the lightweight PVC louvres open and close fully automatically with no electrical components.

How the automatic backdraft seal works

As soon as the fan starts, the louvres are pushed open by the airflow and let the air out unobstructed. When the fan is switched off, the louvres fall back and close the opening, preventing cold outdoor air and draughts from flowing back into the space through the duct.

Is the GRM-300 suited to spot extraction and smaller installations?

Yes, the size makes the GRM-300 a natural choice for spot extraction, for example from bathrooms, storage rooms, garages or other spaces with limited ventilation volume. The grille is mounted outdoors on a vertical wall as the termination of the duct, while also protecting against debris and precipitation entering.

Model and dimension overview, GRM series

Suitable for: HVAC installers, builders and private individuals installing spot extraction from bathrooms, storage rooms and garages.

Industries: HVAC and ventilation, residential property, construction and renovation.

Frequently asked questions (FAQ)

Is the GRM-300 enough to vent a small bathroom or a walk-in wardrobe?

Yes, the GRM-300 with an internal dimension of 250 x 250 mm suits spot extraction from smaller spaces such as bathrooms, walk-in wardrobes and storage rooms well, provided the duct dimension matches the grille's mounting holes of 236 x 236 mm.

Does the grille frame on the GRM-300 need repainting after a few years outdoors?

No, the frame's polymer coating is designed to withstand weathering over a long period without the colour fading or peeling, meaning repainting is not normally needed over the product's service life.

What advantage does the GRM-300 offer compared with installing the duct entirely without a grille?

Without a grille, the duct opening would be left completely unprotected against rain, debris and insects, while air could flow freely in and out regardless of the fan's status. The GRM-300 solves both problems at once: it acts as physical protection for the opening and as an automatic one-way seal that closes when the fan is off.