Deflection Grilles - Single & Double

Deflection grilles are used to control the direction of supply and extract air at the point where ductwork meets the occupied space. Adjustable aluminium blades let you direct airflow horizontally or vertically depending on how the grille is oriented — making them a standard fitting in offices, schools, retail spaces and residential properties with ducted ventilation systems.

Our single deflection grilles offer 80% maximum free area, keeping pressure drop low and helping your system run efficiently. Available in 10 standard square sizes from 150mm to 600mm with next day delivery. If you need a bespoke size, RAL colour, or a double deflection grille, get in touch and our team will come back with a free quote.

What is a deflection grille?

A deflection grille is an air terminal device fitted to the end of a duct run to direct the flow of supply or extract air into a room. The angled blades can be adjusted to control the throw and spread of the airstream. They are commonly used in commercial and residential HVAC systems wherever directional control of airflow is needed.

What is the difference between a single and double deflection grille?

A single deflection grille has one row of adjustable blades, giving you control over airflow direction in one plane. A double deflection grille adds a second row of blades running at 90° to the first, so you can independently adjust both horizontal and vertical airflow. Single deflection is usually sufficient for standard ceiling or wall-mounted supply and return air. Double deflection is the better choice when you need precise control over where the air lands in the room.

What sizes do your deflection grilles come in?

We stock 10 standard square sizes: 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, 450mm, 500mm, 550mm, and 600mm. If you need a non-standard size or rectangular format, we can supply custom-made grilles to your exact dimensions.

Can I get a deflection grille in a custom colour?

Yes. Our standard finish is mill aluminium, but we can supply any grille in a RAL colour of your choice. Contact us with your size and RAL code and we'll provide a quote.

Where are deflection grilles used?

Deflection grilles are designed for internal use on ducted ventilation systems. Typical applications include ceiling-mounted supply air in offices and commercial buildings, wall-mounted return air grilles, and supply outlets in residential ducted heating or cooling systems. For external applications, see our weather louvres range instead.

When should I use a double deflection grille instead of a single deflection grille?

Use a double deflection grille when you need precise airflow control in both horizontal and vertical directions. They’re ideal for offices, classrooms, retail spaces, and large commercial areas where air must be evenly distributed or directed away from occupants. Single deflection grilles are best for simpler supply or return air applications with minimal throw requirements.

Can deflection grilles be used for both supply and extract air?

Yes. Deflection grilles work effectively for both supply and extract systems. On supply air, adjustable blades help shape and control airflow distribution. On extract air, they provide a clean, professional finish while allowing limited adjustment where needed.

Do deflection grilles affect airflow performance?

Absolutely. The grille design directly impacts airflow throw, spread, and pressure drop. High free-area options improve efficiency by reducing resistance, while adjustable blades allow for precise air direction and better comfort control.

Are aluminium deflection grilles suitable for commercial environments?

Yes. Aluminium deflection grilles are widely used in offices, schools, retail units, and public buildings. They offer a strong blend of durability, corrosion resistance, and lightweight installation, with a sleek finish that fits modern commercial interiors.

How do I choose the correct size deflection grille?

Select a grille size that matches your duct opening and required airflow rate. Larger grilles handle higher air volumes and lower face velocities, helping to minimise noise and maintain balanced system performance.