Linear Grilles
Linear grilles and diffusers — the long, low-profile air outlets architects specify when ventilation should read as a clean line rather than a square grille. Two families cover the field: linear bar grilles, with continuous parallel bars in a choice of blade angles, and linear slot diffusers, with one to eight narrow slots for ceiling and high-wall supply.
Bar grilles or slot diffusers?
Linear bar grilles present a run of fixed parallel bars — choose a 0 degree profile for a flush, straight-through face, or 15 and 45 degree profiles to deflect air into the room. They are made to measure to your width and height, in standard or plaster-in frames, and suit walls, sills, bulkheads and joinery.
Linear slot diffusers are the ceiling-line equivalent: from 1 to 8 slots, made to length, in standard or plaster-in frames that vanish into the finished surface. A matching linear slot box plenum connects the diffuser to round ductwork.
Made to order, priced instantly
Both families are manufactured to order with pricing calculated instantly on the product page — enter your dimensions and the cost appears immediately, with the lead time shown before you buy. That makes linear outlets, traditionally a quotation product, as easy to order as a stock grille. The plaster-in frame options deserve a special mention for design-led projects: bedded into the plasterboard, they leave the bars or slots floating flush in the finished surface with no visible frame at all. For conventional square and rectangular outlets, see our wall grilles; for the boxes behind the grille, see steel grille boxes. UK mainland delivery is free on orders over £400 ex VAT.
What Are Linear Grilles?
Linear grilles (also called linear bar grilles or slot diffusers) are elongated, narrow ventilation grilles characterised by a series of parallel bars running the length of the grille. They are the grille of choice for architects and interior designers seeking a minimal, elegant ventilation solution that integrates seamlessly into ceilings, bulkheads, sills, and floor perimeters.
Design and Construction
Our linear grilles are manufactured from extruded aluminium, with bars available in various profiles — square, round, and aerofoil cross-sections. Bar spacing (pitch) determines the free area and visual density of the grille. Closer bar spacing gives a more opaque, discreet appearance but lower free area; wider spacing maximises airflow.
Fixed Bar vs Adjustable Bar
Fixed-bar linear grilles are the simplest and most common, with bars permanently set at 0°. They suit extract applications and supply installations where no directional adjustment is required. Adjustable-bar versions allow the bars to be tilted to deflect the airstream, useful for supply applications where you need to direct air along the ceiling or down into the room.
Applications
Linear grilles are widely used in premium commercial and residential interiors:
- Perimeter sill grilles in offices — supplying conditioned air along the window line to counteract cold downdraughts
- Ceiling bulkhead grilles in hotel lobbies and corridors
- Floor-mounted grilles in entrance vestibules and atria
- Continuous slot grilles in suspended ceilings for a seamless, unbroken line
- Kitchen island and worktop ventilation in high-end residential projects
Bespoke Lengths and Configurations
While we stock popular standard lengths, linear grilles are frequently specified to exact project dimensions. We can manufacture grilles to any length and width, with mitred corners, return ends, and junction pieces for continuous runs around corners and columns. Contact our team with your drawings for a quotation.
Finishes
- Mill-finish aluminium — clean, contemporary metal appearance
- Anodised aluminium — satin silver, satin gold, or bronze anodising for a durable, low-maintenance finish
- RAL powder coat — any RAL Classic colour to match the interior scheme
Why Choose Alpha Air?
Alpha Air has been supplying architectural grilles to the UK building services industry. We combine quality manufacturing with expert advice on grille selection, free-area calculations, and finish specification. Standard items dispatch same day; bespoke grilles are manufactured within 5–7 working days. Free delivery on orders over £400. Call 0116 246 0031.
Frequently Asked Questions
What bar spacing should I choose for a linear grille?
Bar spacing depends on the balance between aesthetics and airflow. Closer spacing (e.g. 10-12mm pitch) gives a more opaque, discreet look but reduces free area. Wider spacing (e.g. 20-25mm) maximises airflow but is more visually open. For most commercial applications, 12.5-17mm pitch offers a good balance.
Can linear grilles be used in floors?
Yes. Floor-mounted linear grilles are common in entrance vestibules, atria, and perimeter heating/cooling systems. Floor grilles must be specified with a robust frame and bar profile rated for foot traffic loading. Contact us to confirm the correct specification for your application.
Do you make linear grilles to custom lengths?
Yes. We manufacture linear grilles to any specified length and width. We also produce mitred corners, return ends, and junction pieces for continuous runs around architectural features. Send us your drawings or dimensions for a quotation.