1. Select a low‑noise HRV unit
Every HRV unit generates cabinet noise, but fan type, housing material and control strategy can make a big difference. When selecting the unit, look beyond air flow and controls and compare sound power levels at realistic operating points instead of only at maximum capacity.
For prescribers and consultants, specifying a unit with verified low sound levels in accordance with relevant standards reduces the need for corrective measures later in the project. For installers, this creates a solid basis for a quiet system, provided that the ducting and connections are designed and installed correctly.
2. Dimension ducts for low air velocity
High air speeds in ducts increase turbulence, vibration and therefore noise. Correct dimensioning keeps the air velocity as low as feasible for the required volume flow, which reduces fan effort and noise generation at the same time.
As a rule of thumb, use larger duct diameters on the main trunks and avoid unnecessary reductions that force the fan to work harder. For designers, performing basic pressure‑loss calculations in the design phase helps avoid undersized ducts and noisy systems.
3. Design a smooth duct layout
Right‑angled bends, sudden transitions and complex routing create air resistance and turbulence, which can be heard as whistling or rumbling in the rooms. A smooth layout with gentle bends, limited branch connections and minimal length between unit and terminals reduces pressure loss and noise.
For installers and contractors, careful planning of the routing before installation prevents last‑minute “creative” solutions that compromise acoustic performance. In renovation projects, this often means investing more time in surveying the available space to avoid tight, noisy layouts.
4. Use insulated ducts to damp noise
Ducts do not only transport air; they also transmit cabinet and flow noise from the HRV unit throughout the building. Well‑insulated ducts on both supply and return sides provide thermal insulation and also act as an acoustic barrier that dampens cabinet radiation.
In practice, properly insulated ducts can reduce sound levels from the unit by up to 20 dB(A), depending on system diameter and configuration. This makes duct insulation a highly effective lever for meeting comfort requirements without overspecifying silencers or oversized units.
5. Ensure airtight, flexible connections
Any leakage point in the ductwork can become a source of noise as air and sound escape through gaps and poorly sealed joints. Temperature differences between the air in the duct and the surrounding space can cause joints to move, creating slack and micro‑leaks over time.
Specifying airtight, flexible connections maintains performance and comfort throughout the life of the system. Flexible rubber connections help absorb movements and vibrations, keeping the system airtight and quiet and preventing unwanted transmission of structure‑borne noise.
6. Mount the HRV unit vibration‑free
If the HRV unit is mounted directly on a lightweight wall or weak structure, vibrations can easily transfer into the building and be perceived as low‑frequency noise in living or working areas. Using vibration dampers or a dedicated mounting frame decouples the unit from the structure and significantly reduces this effect.
For installers, it pays off to follow the manufacturer’s mounting instructions and check that the wall or ceiling construction is suitable. For consultants, defining vibration‑control requirements in the specification avoids costly mitigation after handover.
7. Apply silencers where needed
Duct silencers installed close to the supply and return of the HRV unit help absorb noise before it propagates through the duct network. They are especially useful when space or architectural constraints limit optimal duct sizing or routing.
Combine silencers with good duct insulation and airtight joints for the best total result rather than oversizing any single measure. This system approach keeps both investment and operating costs under control while meeting acoustic targets.
8. Keep filters clean and airflows balanced
Clogged or dirty filters restrict airflow, causing the HRV unit to run at higher speeds and generate more noise. Regular filter replacement and inspection are therefore essential not only for indoor air quality but also for acoustic comfort.
Commissioning technicians should balance airflows correctly so the unit operates within its optimal working range. A well‑balanced system can often run at lower speeds during normal operation, resulting in lower noise levels and energy consumption.
9. Avoid rigid, tensioned joints in ductwork
Hard connections or forced alignments between duct components can introduce mechanical stress in the duct system. Under airflow and temperature variation, this stress translates into vibrations that are audible in adjacent rooms.
Using flexible rubber connections and ensuring ducts are installed without tension helps absorb vibrations and prevent noise at the joints. This approach is especially important near the HRV unit and at transitions between different materials or building elements.
10. Specify pre‑insulated duct systems from the start
For new‑build and major renovation projects, designing the system around a pre‑insulated duct solution simplifies meeting thermal, acoustic and airtightness requirements in one step. A coordinated system reduces the number of components, interfaces and potential weak points that can cause noise or condensation problems.
Early coordination between designer, installer and supplier ensures that dimensions, routing and installation details align with the chosen system. This minimises on‑site improvisation and shortens installation time, while delivering predictable comfort performance for the client.
Design your quiet HRV system
Designing a quiet HRV system starts with the right combination of unit, duct design and ducting materials. To see how TQ‑Air can help you reduce noise, prevent condensation and improve energy efficiency in your next project, visit the TQ‑Air product page.
Example solution: TQ‑Air® pre‑insulated ducting for quiet HRV systems
TQ‑Air® is a pre‑insulated ducting system designed specifically for balanced ventilation with heat recovery in residential and small commercial buildings. It combines thermal and acoustic insulation in a single prefabricated solution, helping to prevent condensation, save energy and reduce noise from the unit and airflow.
Key characteristics that support low‑noise HRV installations include:
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An inner tube of polyolefin insulation foam with a vapour‑tight closed‑cell structure that prevents condensation and maintains consistent acoustic performance over time.
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A mechanically strong yet flexible polyethylene outer casing that protects the duct and enables easy routing without compromising airtightness.
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EPDM rubber connections that achieve very high airtightness classes, absorb vibrations, and are quick to assemble on site without additional tape or mastic.
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Sound reduction values of up to approximately 20 dB(A) for typical HRV system diameters, verified according to DIN‑EN‑ISO 5135:1999.
Because TQ‑Air integrates these functions into a single system, designers and installers can meet acoustic, thermal and airtightness requirements with a limited number of components and minimal risk of installation errors.
FAQ
Why is my HRV system so noisy at night?
At night, background noise is lower, so cabinet noise, airflow turbulence or vibrations in the ductwork become more noticeable. Common causes include undersized ducts, uninsulated metal runs, rigid joints and clogged filters forcing the unit to run at higher speeds.
How can duct insulation reduce HRV noise?
Insulated ducts damp cabinet noise and airflow noise that would otherwise be transmitted through rigid duct walls into rooms. Pre‑insulated systems such as TQ‑Air combine thermal and acoustic insulation in one layer, reducing sound levels by up to around 20 dB(A) while also preventing condensation.
What type of ducting is best for a quiet HRV system?
For new projects, pre‑insulated ducting with a vapour‑tight insulation layer and airtight rubber connections offers a robust combination of acoustic damping, condensation control and energy efficiency. Systems like TQ‑Air are designed for balanced ventilation with heat recovery and integrate seamlessly with modern HRV units.
Who should I contact for support with HRV noise issues?
If you experience noise problems or are designing a new HRV installation, contact Thermaflex for technical advice on duct design, insulation and pre‑insulated TQ‑Air solutions. Our specialists support consultants, installers and contractors in optimising thermal and acoustic performance for residential and small commercial projects.
