Ventilation Grille Exterior Gravity Louvre 250x250mm PVC Grey, Vents-Group

Quick Facts — Vents-Group Ventilation Grille GRM-250

• Outer dimensions 250 x 250 mm, mounting holes 186 x 186 mm
• Smallest size in the series — for the narrowest ducts
• Automatic gravity louvres in grey PVC
• Single, undivided louvre construction
• Grille frame in powder-coated metal, grey colour
• One-way airflow — prevents backdraft
• For mounting on vertical surfaces (walls) only

The GRM-250 ventilation grille is the smallest model in the GRM series and terminates narrow extract ducts 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 makes the GRM-250 a strong choice for narrow ducts?

Despite its compact size, the GRM-250 is built on the same construction principle as the rest of the series. The grille frame has a weather-resistant and mechanically durable polymer coating that keeps the colour intact over time, and the lightweight PVC louvres open and close fully automatically based on airflow, with no electrical parts or manual operation.

How do the louvres work during operation and standstill?

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

Where is the smallest GRM model used?

The GRM-250 suits spot extraction with a limited duct diameter particularly well, for example from smaller bathrooms, wardrobes, basement recesses or other spaces where a full-size duct is not necessary. The grille is mounted outdoors on a vertical wall while also acting as protection against debris and precipitation.

Model and dimension overview, GRM series (complete, all 10 sizes)

Suitable for: HVAC installers, builders and private individuals installing spot extraction with a narrow duct dimension in bathrooms, wardrobes and basement spaces.

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

Frequently asked questions (FAQ)

Is the GRM-250 robust enough for outdoor use despite its small size?

Yes, the GRM-250 has the same weather-resistant polymer coating and the same PVC material as the series' larger models, giving fully adequate protection against rain, sun and temperature changes regardless of size. The smaller surface area does not affect the durability of the materials.

Can the GRM-250 be used with a small bathroom fan without external control?

Yes, the GRM-250 requires no electrical connection or external control, as the louvres open and close passively based on the airflow from the fan. This makes the grille easy to combine with most bathroom fans that lack a built-in backdraft damper.

What is the practical difference between the GRM-250 and the next size up, the GRM-300?

The difference is mainly the dimensions: the GRM-250 has an internal dimension of 200 x 200 mm compared with 250 x 250 mm for the GRM-300, making the GRM-250 the right choice when the duct is narrower or when space for the grille is more limited. The function otherwise, including material and louvre construction, is identical between the two sizes.