Plant rooms are one of the most common sources of noise complaints in commercial buildings. Whether it’s rooftop HVAC systems or internal mechanical rooms, managing airflow without excessive noise is a design challenge for everyone and compliance to building regulations is essential. This is where acoustic louvres come in. But, specifying them correctly is essential, if you get it wrong, it can lead to poor performance, compliance issues and/or costly redesigns
This guide explains how to specify acoustic louvres.
What are acoustic louvres?
Acoustic louvres are ventilation systems designed to:
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- Allow airflow
- Reduce noise
- Maintain weather protection
They are used in plant rooms, rooftop enclosures, generator compounds and data centres. Unlike standard louvres, they incorporate acoustic infill to absorb sound while maintaining air movement.
When are acoustic louvres required?
You’ll need acoustic louvres when:
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- Plant equipment exceeds local noise limits
- Buildings are near residential areas
- Planning conditions require noise mitigation
- There is a risk of noise breakout through ventilation openings.
This is often linked to local authority noise conditions and environmental health requirements.
Key factors when specifying acoustic louvres
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- Acoustic Performance (dB reduction)
The most important factor is how much noise reduction is required? This is usually expressed as:
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- dB reduction
- Insertion loss across frequencies
Important: low frequency noise from large plant is harder to attenuate and must be considered separately.
2. Airflow requirements
Acoustic performance always impacts airflow.
You need to define:
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- Required airflow (m3/s or l/s)
- Acceptable pressure drop
Higher acoustic performance = more resistance to airflow, which can mean larger louvre areas are required.
3. Free area
Free area determines how much air can pass through the louvre. Standard louvres – higher free area, acoustic louvres – lower free area.
Always check the percentage free area and resulting face velocity
Incorrect sizing is one of the most common specification mistakes.
4. Weather performance
For external applications, louvres must also prevent rain ingress and handle wind-driven rain.
5. Location & installation
Consider:
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- Rooftop vs facade installation
- Proximity to noise source
- Ducted vs direct airflow
- Poor positioning can significantly reduce acoustic performance.
6. Fire rating (if required)
In some plant room applications, fire rated lourves may be required. Always check building regulations and fire strategy documents.
Common mistakes to avoid:
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- Undersizing louvres (causes airflow issues)
- Ignoring low-frequency noise
- Focusing only on dB without airflow impact
- Not considering weather performance
- Late-stage acoustic fixes (more expensive)
Acoustic louvres vs other solutions
Depending on the project, alternatives may incude acoustic enclosures, attenuators and screens.
Louvres are often preferred because they integrate into building facades, combine airflow and noise control and require less space than separate systems.
Getting the specification right
Engage with us in the early design stage and work with us on sizing. We have decades of experience. Ensure you use performance data (not assumptions) and consider both acoustic and airflow together.
Need help specifying acoustic louvres?
If you are working on a plant room project and need acoustic performance calculations, louvre sizing or technical drawings, contact us.
