Wall Grilles
Wall grilles for supply and extract ventilation — single deflection, double deflection and eggcrate grilles, in stocked square sizes and made-to-measure custom sizes, plus the grille boxes (plenum boxes) that connect them to the ductwork. Every neck size quotes its face size too (the visible frame is 45mm larger than the neck in each direction), so you know exactly what will show on the wall.
Three grille types, stocked and custom
- Single deflection grilles — one row of adjustable blades to steer supply air. Stocked squares run from 150mm x 150mm right up to 1000mm x 1000mm, with custom sizes made to order.
- Double deflection grilles — two blade rows for full directional control of supply air. Stocked squares from 150mm to 550mm, plus custom sizes including a version with an integral damper.
- Eggcrate grilles — the high-free-area extract grille, stocked from 100mm to 550mm square with or without a damper, and custom sizes to order.
Grille boxes (plenum boxes)
Behind the grille, a plenum box turns the round duct connection into the rectangular neck. Our stocked grille boxes cover neck sizes from 100mm x 100mm to 550mm x 550mm in a choice of depths (100mm to 500mm depending on size), with spigot connections to suit standard duct diameters. A custom galvanised grille box can be configured online for anything outside the stock run.
Custom sizes, priced instantly
All three grille types can be manufactured to your exact width and height — enter the size on the product page and the price calculates immediately, with the lead time shown before you buy. Stocked squares ordered by 3pm are despatched for next-day delivery, and UK mainland delivery is free on orders over £400 ex VAT.
Wall Grilles for Ventilation Systems
Wall grilles are installed on vertical wall surfaces to supply conditioned air into a room or extract stale air from it. They are used when ceiling-mounted grilles or diffusers are not practical — for example in rooms with solid concrete ceilings, exposed structural soffits, or very high ceilings where wall-level distribution is more effective.
Types of Wall Grille
Double-Deflection Grilles
The most versatile type, featuring two sets of adjustable blades — horizontal blades at the front and vertical blades behind. This allows the airstream to be directed up, down, left, or right, providing precise control over air distribution in the occupied zone. Double-deflection grilles are the standard choice for supply-air applications in offices, meeting rooms, and retail environments.
Single-Deflection Grilles
Feature one set of adjustable blades (horizontal or vertical). Simpler and more cost-effective than double-deflection, suitable for extract applications where directional control is less critical, or for supply applications where only vertical deflection is needed.
Fixed-Blade Grilles
Non-adjustable blades set at a fixed angle, typically 0° (straight) or 15° deflection. The most economical option, suitable for extract duty, transfer air, and applications where airflow direction does not need to be adjusted after installation.
Transfer Grilles
Installed in internal walls or doors to allow air to pass from one room to another without ductwork, equalising pressure across zones. Transfer grilles have angled blades on both faces to maintain visual privacy while permitting airflow. Common in hotel corridors, office partitions, and plant rooms.
Materials and Finishes
Our wall grilles are manufactured in extruded aluminium for lightweight durability and corrosion resistance. Standard finishes include white powder coat (RAL 9010) and natural anodised aluminium. Custom RAL colours are available to order for projects requiring a specific colour match to the wall finish.
Installation
Wall grilles are face-fixed with countersunk screws through the frame or clip-mounted using concealed spring fixings. Behind the grille, a short length of flexible duct or a sheet-metal plenum connects to the main ductwork. For transfer grilles, a sleeve through the wall maintains the aesthetic on both faces.
Why Choose Alpha Air?
Alpha Air supplies a wide range of wall grilles in stock sizes for same-day dispatch, with bespoke sizing available to order. Hands-on ventilation industry experience means we can advise on grille selection, face velocity, and throw distance for your specific application. Free delivery on orders over £400. Call 0116 246 0031.
Frequently Asked Questions
What is the difference between a single and double deflection grille?
A single-deflection grille has one set of adjustable blades, allowing airflow direction in one plane (horizontal or vertical). A double-deflection grille has two sets of blades at right angles, allowing control in both planes. Use double-deflection for supply air where you need precise directional control.
Can wall grilles be used for supply and extract?
Yes. Double-deflection and single-deflection grilles are suitable for both supply and extract duty. Fixed-blade grilles work well for extract and transfer applications. The key difference is whether you need adjustable airflow direction, which is mainly a supply-air requirement.
What is a transfer grille used for?
A transfer grille is mounted in an internal wall or door to allow air to pass between rooms without ductwork, equalising air pressure. They are common in hotel bedrooms (door undercuts or wall grilles), office partitions, and plant rooms to provide a return-air path back to the extract system.
Can I order wall grilles in a custom colour?
Yes. We offer powder coating in any RAL Classic colour. Our standard finish is white (RAL 9010). Specify your RAL code when ordering and we will coat the grilles to match. Allow 1-2 extra working days for powder-coated finishes.