Why is a rigid silencer better than a flexible one for the main line?

A rigid silencer has a smooth inner surface (perforated metal), creating significantly less air resistance than a corrugated flexible tube. This allows air to move freely, reducing fan load and saving electricity. Additionally, the rigid structure is resistant to mechanical damage and can be cleaned with brushes.

Are rigid silencers susceptible to moisture?

Galvanized steel is corrosion-resistant under normal conditions, but it is crucial that the system is airtight. The internal rock wool is protected, but if the system is installed in a cold attic, the silencer itself must be additionally insulated from the outside to prevent condensation.

How do you clean a rigid silencer?

Unlike flexible models, rigid silencers can be cleaned mechanically using special duct cleaning brushes. The internal perforated metal protects the insulation material from damage during cleaning. We recommend doing this every 3-5 years during routine system maintenance.

Rigid Noise Silencers

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Flexible

Heat Recovery Units

For long straight runs and main trunk lines – only rigid silencers will do. Made of galvanized steel with acoustic wool, they offer the lowest air resistance and maximum durability.

The professional choice for installation in utility rooms immediately after the heat recovery unit.

The problem: aerodynamic noise and resistance

Airflow is strongest and fastest in the main duct trunk. If you installed a flexible, corrugated silencer here, it would act as a brake – creating high resistance and forcing the heat recovery unit to work harder. This means higher electricity bills and faster fan wear.

Additionally, low frequencies (droning) travel far. Thin walls and lightweight materials cannot contain the powerful sound of the fan traveling through the main pipe.

The solution: a rigid galvanized barrier

A rigid silencer acts as a solid shield. Its body is made of galvanized steel, and the thick layer of rock wool inside (usually 50 mm) absorbs noise without stopping the airflow. The inner wall is perforated but smooth, so air glides without turbulence.

This is the most durable part of the system. Once installed, a rigid silencer will last for decades. It can be cleaned, does not deform or tear, ensuring stable system operation for the life of the building.

Lowest possible resistance – rigid silencers allow the system to "breathe" easier, saving energy that the unit would otherwise waste pushing air.

When choosing a rigid silencer, diameter is not the only factor. While it must match the duct (e.g., 160 mm), other parameters determine acoustic comfort:

Length (600 mm, 900 mm, 1200 mm) – the rule "the longer, the better" applies here. A 900 mm silencer is the "golden mean," while 1200 mm is the ideal choice for maximum silence. Short 600 mm models are suitable only where physically nothing longer fits.
Insulation thickness (50 mm) – rigid silencers usually feature a 50 mm rock wool layer. This is critically important for dampening low frequencies caused by unit motors.
Tightness class – galvanized silencers with rubber gaskets at the ends (nipples) ensure Class C or D tightness. This means no air leaks at connection points.

Where to install?

The best spot is immediately after the heat recovery unit. Install one rigid silencer on both the supply and extract ducts. This "cuts" the noise at the very beginning, preventing it from gaining momentum in the duct system. Leave flexible silencers for terminal points near diffusers.

Heavy weight – solid support

A rigid silencer is heavy. Due to thick metal and insulation, it weighs significantly more than a simple duct, so it cannot simply be "hung" on a flexible duct.

Mounting – use metal clamps with rubber lining (to prevent vibration transmission to the ceiling) and threaded rods. The silencer must be secured stably so it does not move.
Connection – silencer ends slide directly into ducts. The connection must be secured with self-tapping screws or rivets and sealed with aluminum tape.
Insulation – if the silencer is installed in an unheated space, it must be additionally insulated from the outside to prevent condensation.

Easy maintenance

This is the most hygienic choice. During ventilation system cleaning, a rotating brush can be safely inserted into a rigid silencer. The inner perforated metal protects the wool from being torn out, so you can be sure that after cleaning, the system will operate just as quietly and efficiently, with no insulation particles in the air.

Rigid Noise Silencers

Often bought together with

The problem: aerodynamic noise and resistance

The solution: a rigid galvanized barrier

Where to install?

Heavy weight – solid support

Easy maintenance

Frequently Asked Questions

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Often bought together with

Professional solution for a silent main line

Technical parameters: what to look for?

Installation and system maintenance

Frequently Asked Questions

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