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Airflow: The Basics of Choosing Grilles and Diffusers

Have you ever spent the night in a hotel room and the air has felt a little stuffy? Or that cold you have feels so much worse when you’re at work than when you’re at home? It could be because the airflow in your office or in the hotel hasn’t been designed carefully to create a comfortable environment.

Air quality inside any building is really important for the health, comfort and productivity of the people inside. It has a much bigger impact than people might think. You may not even notice air quality until you’ve gone from a place where the air flow is wrong, to a place where it has been designed to create a comfortable environment.

An effective HVAC system needs to be made up of the correct components, positioned perfectly in each room in a building to ensure an even air distribution.

Different types of buildings, whether they are for healthcare, education, offices or domestic use, all require different types of air flow and air diffusion.

The correct placement of grilles and diffusers plays an important role in getting the air distribution spot on so you can enjoy a good night’s rest in a hotel or to make sure your cold doesn’t bug you at work.

Architects, consultants and developers working on a new build or a renovation project, want to create the perfect air flow for the requirements of their building, so it’s important to know the difference between grilles and diffusers and what they do.

Grilles and Diffusers: What’s the difference?

Although grilles and diffusers job roles are similar, they do have one major difference.


Grilles can be used to either supply or return air, coming usually in a fixed blade or adjustable format. Adjustable blade versions can direct air in multiple directions if required by the installation and can vary from horizontal air flow to almost vertical.
Grilles can be used for different applications and are often installed in vertical surfaces such as walls or doors.

Aesthetics also need to be considered when specifying a grille. Grilles can be designed not only to meet air distribution requirements, but also fit in with the overall design look of a development, something which architects tell us really helps to integrate the devices into their design.


Diffusers on the other hand can direct air in more directions than just up or down and, depending on the type of diffuser it is, can have a number of configurations which allow for multiple air pattern control.

Diffusers usually have 1 to 4 air distribution slots which can help to blend them into the surface that they are installed into and come in many shapes including circular, square and linear rectangles. They are more commonly installed in ceilings and have a horizontal airflow.
Like grilles, diffusers can be manufactured to not only meet air flow requirements, but also the design of its environment.

Where can they be used?

Depending on the building’s use, Waterloo manufactures a range of grilles and diffusers with different design elements to meet the air distribution requirements of its application. For example, our Louvred Face Diffusers are suitable for projects where the control of air flow is required in a generally small area like a classroom, a hotel room or an office.

Whereas our range of Linear Slot diffusers can meet the air flow challenges of both smaller and larger areas including exhibition halls, terminals and shopping centres. We have a superb little book called the Green Book that you can download which tells you all about where our different types of grilles and diffusers are designed for.

Click here to view all of Waterloo’s grilles and diffusers.