Why attenuation shouldn’t be an afterthought

Posted by Paul Compton on 31/05/12 09:59

Acoustic louvreIf you are in the early stages of designing a ventilation system for a power generation plant, have you already thought about attenuation? Is the power plant near a residential area? Do you need to ensure that the ventilation system doesn’t allow unacceptable noise levels to come out of the building? It is important to make these considerations early on, as attenuation can have a big impact on the design.

The impact of attenuation on design

There are three ways attenuation can affect your design:

  1. Pressure drop: the addition of an attenuator will increase the pressure drop, so that you will need a bigger ventilator to provide the desired level of ventilation.
  2. More weight: a bigger ventilator will result in additional weight on the steelwork, so you need to make sure that the structure can carry this extra load.
  3. More space: depending on the degree of noise reduction you need to achieve, the attenuator can protrude considerably into the building. This may have an impact on the layout of the equipment, which will need to be placed further from the wall, leaving enough space for the attenuator.

What’s the big deal?

You may think that these are issues that can easily be resolved, but in many cases the impact can be considerable and it can be tricky and expensive to sort them out at a later stage. Adding attenuation to a ventilation system typically requires a 15 to 20% larger free area, which with an inlet system can mean an additional 100 to 200 square metres.

Take the example of a recent project Colt was involved with, which is fairly typical: had we not considered attenuation from the start, we would have found that we needed to add an extra 15 square metres to the inlet system, increasing its area by 25%, the steelwork would have needed to support an extra 110 kg/m2, and the inlet system would protrude a further 1.25m into the building.

I am sure you will agree that having to accommodate these changes at an advanced stage of the design process would have added significant complexity and costs to the project!

Paul Compton Paul Compton is Technical Director for Colt, experienced in smoke control, HVAC, solar shading and louvre systems.

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Topics: Natural ventilation, Climate Control, Power Plants