Ventilation Grille Exterior Gravity Louvre 655x655mm PVC Grey, Vents-Group

Quick Facts — Vents-Group Ventilation Grille GRM-655

• Outer dimensions 655 x 655 mm, mounting holes 591 x 591 mm
• Automatic gravity louvres in grey PVC
• Dual louvre construction with centre section
• 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-655 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 grille's gravity louvres apart?

The grille frame is made of metal coated with a weather-resistant and mechanically durable polymer coating, giving high resistance to weathering over time without the colour fading. From this size upwards, the grille is divided into two louvre sections with a centre bar, giving more stable blade movement across the larger surface. The lightweight PVC louvres open automatically under airflow, ensuring flow in one direction only.

How do the automatic louvres work in operation?

When the fan is running, the louvres are opened by the airflow and let the air out freely through both sections. When the fan is switched off, the louvres fall back and close the duct, preventing cold outdoor air or draughts from entering the room through the extract duct. This function makes the grille suitable as a termination in ventilation, air conditioning and heat recovery systems.

Where is the ventilation grille best installed?

The GRM-655 is installed outdoors on vertical surfaces, i.e. walls, as the termination of an extract duct. The size makes it suitable for larger duct dimensions in commercial buildings and industrial premises, while the grille also protects against debris and precipitation entering the building.

Model and dimension overview, GRM series

Suitable for: HVAC installers, ventilation contractors, facility managers and builders installing extract air systems in larger buildings.

Industries: HVAC and ventilation, facility management, construction and renovation, industry.

Frequently asked questions (FAQ)

Can the Vents-Group ventilation grille GRM-655 be mounted horizontally, for example on a ceiling?

No, the GRM-655 is intended for mounting on vertical surfaces only, i.e. walls. The gravity louvres rely on gravity to close correctly, which requires vertical installation for the function to work as intended.

Does the Vents-Group ventilation grille GRM-655 require any maintenance?

The PVC louvres should be checked periodically to ensure they move freely in both sections and are not stuck due to dirt or ice. No lubrication is needed, and the weather-resistant polymer coating on the frame requires no repainting under normal operation.

What sets a grille with a gravity louvre like the GRM-655 apart from a standard fixed ventilation grille?

A grille with a gravity louvre like the GRM-655 closes automatically when the fan is off, thereby preventing cold air and draughts from flowing back into the building, whereas a standard fixed grille has no moving parts and allows airflow in both directions at all times. The dual louvre construction also gives more stable function across the larger surface compared with smaller models with a single section.