Ceiling Grilles
Our ceiling grilles and diffusers cover every common way of getting supply or extract air through a ceiling, from a single bathroom valve to a full suspended-ceiling refit. The range includes 4-way ceiling diffusers, pressed swirl diffusers, round ceiling diffusers with built-in dampers, eggcrate grilles in stock and made-to-measure sizes, and metal air supply and air extract valves, including 1-hour fire-rated versions. You will also find the Terlok Ring Leader fixing ring, which takes the aggravation out of installing air valves, plus plenum boxes for connecting grilles to round ducting.
Which ceiling grille or diffuser do I need?
For supply air into offices, shops and classrooms, a 4-way diffuser or swirl diffuser spreads conditioned air evenly across the room — both are available in sizes that drop straight into a standard 595mm x 595mm suspended-ceiling tile. For extract from bathrooms, WCs and utility areas on 100mm to 200mm ducting, a simple metal air valve is the usual choice; specify the fire-rated version where the design calls for it. Eggcrate grilles give a large open area, making them a popular pick for extract and return-air positions, and can be made to your exact neck size with an instant online price. Where round ducting terminates directly at the ceiling, a round diffuser with an integral damper lets you balance the airflow at the grille.
Sizes, stock and delivery
Most ceiling grilles here are held in stock in standard sizes — air valves from 100mm to 200mm, eggcrate grilles from 100mm to 550mm square, 4-way diffusers with neck sizes from 150mm to 450mm — while eggcrate grilles can also be made to measure up to 1000mm x 1000mm with an instant price online. Product pages list both neck and face dimensions, so you can check the grille against your duct size and ceiling opening before ordering.
Stocked sizes ordered by 3pm are available for next-day delivery, and made-to-order items show their lead time on each product page. As a Leicester-based UK supplier we deliver nationwide, with free UK mainland delivery on orders over £400 ex VAT. Wall-mounted alternatives — single and double deflection, eggcrate and plenum boxes — are in our wall grilles range.
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4-Way Ceiling Diffuser
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Air Extract Valves
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Air Extract Valves – Fire Rated
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Air Supply Valves
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Air Supply Valves – Fire Rated
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Eggcrate Grille
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Pressed Swirl Diffuser
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Round Ceiling Diffuser (with Damper)
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Terlok Ring Leader
Ceiling Grilles for Ventilation
Ceiling grilles are the visible interface between a concealed ductwork system and the occupied room below. They perform a critical function: distributing conditioned supply air uniformly across the space, or collecting stale extract air for removal. The grille design affects room comfort, draught control, noise levels, and the aesthetic appearance of the ceiling.
Types of Ceiling Grille
Egg Crate Grilles
Egg crate grilles feature a grid of open cells that provide high free area (typically 75–85%) and minimal pressure drop. They are suitable for both supply and extract applications and offer a clean, unobtrusive appearance. Available in aluminium or steel with white or silver finishes.
Perforated Face Grilles
A flat or slightly recessed face with a pattern of circular perforations. Perforated grilles give a subtle, modern look and are popular in architectural interiors, hotels, and premium office fitouts. Free area is lower than egg crate (typically 30–50%), so size accordingly.
Multi-Directional Diffusers
Square or round ceiling diffusers with adjustable vanes that spread supply air in multiple directions across the ceiling plane. The Coanda effect keeps the airstream attached to the ceiling surface, preventing cold draughts in the occupied zone below. Ideal for supply-air distribution in offices, retail, and hospitality spaces.
Circular Duct Grilles
Connect directly to exposed circular spiral ductwork for industrial-style interiors. Popular in restaurants, bars, gyms, and converted warehouse offices where the ductwork is left visible as a design feature.
Materials and Finishes
- White powder coat (RAL 9010) — the most popular finish, blending with standard white ceilings
- Silver / anodised aluminium — for exposed ductwork and contemporary interiors
- Custom RAL powder coat — any colour to match your interior scheme
Sizing
Ceiling grilles are sized by their face dimensions (width × height) and specified for a target airflow rate and acceptable noise level. Oversizing the grille reduces face velocity, which lowers noise and improves comfort. Undersizing causes draughts and audible rushing noise. Refer to the manufacturer’s selection data or contact our team for guidance.
Installation
Most ceiling grilles install with concealed spring clips or screw fixings into the ceiling tile grid or plasterboard. A plenum box or flexible duct connection behind the grille links it to the main ductwork above. Ensure the connection is sealed to prevent air leakage into the ceiling void.
Why Choose Alpha Air?
Alpha Air stocks a comprehensive range of ceiling grilles and diffusers for same-day dispatch. With many years supplying the UK ventilation trade, we offer practical advice on grille selection, sizing, and airflow distribution. Free delivery on orders over £400. Call 0116 246 0031.
Frequently Asked Questions
What size ceiling grille do I need?
Grille size depends on the required airflow and acceptable noise level. As a guide, keep the face velocity below 2.0 m/s for quiet rooms (offices, bedrooms) and below 3.0 m/s for general areas. Divide your airflow rate by the target velocity to get the required free area, then select a grille whose free area meets or exceeds that figure.
Can ceiling grilles be used for both supply and extract?
Many grille types (egg crate, perforated) are suitable for both supply and extract. Multi-directional diffusers with adjustable vanes are specifically designed for supply-air distribution but can also be used for extract. Check the product specification for the intended duty.
How do ceiling grilles connect to the ductwork?
A plenum box or short length of flexible duct connects the grille to the main ductwork above the ceiling. The plenum box bolts to the ceiling grid and the duct connects to a spigot on top. Seal all connections with foil tape to prevent air leaking into the ceiling void.