How does the location of a ventilation grill effect your system?

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How does the location of a ventilation grill effect your system?
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How does the location of a ventilation grill effect your system?

– by Paul Spoorenberg, 28/10/19

The position of a ventilation grill is crucial to the comfort provided by HVAC systems. To avoid complaints about draughts and hotspots you need to find the perfect location for your ventilation grills. Here’s what you need to know.

The soul of the HVAC system

Supply grills are the very last part of an HVAC system to be fitted. Once they are safely in place, air can freely circulate into and out of the room. You can think of them as the soul of the system: once all the preparatory processes have taken place, supply grills are what enables the system to function properly. But to do their job right, they need to get the air into the room at just the right angle and with the right speed.

The beam

Even if a system is designed with all the care in the world and plenty of capacity to cool, heat and move air at the right humidity, it won’t work right if the ventilation grills are not positioned correctly. Every grill, grid or louvre has its beam, which is defined as the distance from the front of the grill to the point where air ejected from it has a speed of 0.25 m/s.


The Coanda effect

Another property of supply grids is the Coanda effect, which occurs when wall-mounted grills are positioned in the direct vicinity of a ceiling. In this situation, cold or hot air blowing out of a grill results in a highly stable current of supply air which is forced up towards the ceiling by the Coanda effect. This causes the treated air to descend slowly into the room, creating a comfortable feeling for the people inside it.


What could possibly go wrong?

Once we understand how the beam and the Coanda effect work, we understand that the correct positioning of a grill is crucial to its success. If we place a supply grill in a way that its beam is pointing directly at a nearby table, bed or sitting area, it will cause a draught. Obstructions higher up can also undo the Coanda effect, causing the air to drop abruptly with all the associated discomfort.


Another common mistake is placing a supply grill in close proximity of a recirculation or exhaust grill. This leads to a so-called short cut, where supply air is taken away through the extraction grill directly without having had the time to acclimatise and condition the room – instead, the same air simply circulates around the room.

If you have any questions about grill positions, troubles with draught or other uncomfortable situations, get in touch: we would be happy to help you achieve the best solution for your circumstances.

Paul Spoorenberg | Sales Manager

Paul Spoorenberg has been working at H&H since 1994. During his career he gained valuable expertise in HVAC solutions for all kind of vessels in the Commercial, Offshore, Naval & Yacht segments.