How do you soundproof and insulate an air-source heat pump?

An air-source heat pump can produce several types of noise: fan noise, compressor noise, resonance in sheet metal, vibrations in the wall mount, and structure-borne noise that spreads into the building. For this reason, it’s rarely effective to simply think of “noise reduction” in general terms. First, you need to understand whether the sound is transmitted through the air, through the structure, or via reflections from hard surfaces around the pump.

Airborne sound is often heard as a whooshing noise, fan noise, or a steady machine noise outdoors. It can be perceived as louder if the outdoor unit is located near a wall, a corner, a balcony, a fence, or a neighbor’s patio. In such cases, directional shielding and sound-absorbing materials near the sound source can help, provided that airflow and service space are not blocked.

Vibrations are more often perceived as a humming, pulsating, or low-frequency sound. If the pump is mounted on a wall bracket, the vibrations can travel through the facade and into the room. If it stands on a hard surface, vibrations can be transmitted down into the ground, concrete, wooden structure, or patio deck. In such cases, the first step is to reduce contact between the pump and the surface using vibration-damping products.

We therefore recommend starting with troubleshooting: listen closely to the pump, inside the room behind the installation, and at the surfaces where the pump is mounted. Check to see if the wall, pipes, bracket, or stand vibrates when the compressor is running. If the sound is noticeably louder inside than outside, this is often a sign that structure-borne noise and vibrations are a major part of the problem.

It is also important not to enclose the air-source heat pump too tightly. A tightly sealed enclosure can impair airflow, affect performance, and make servicing more difficult. A better solution is to dampen vibrations at the mounting points, reduce resonance in hard surfaces, and use sound insulation where it can be placed without interfering with the pump’s operation.

For many installations, the best solution is a combination of measures: vibration dampers under the stand or machine feet, sealing or damping strips at contact points, sound-absorbing material on resonant surfaces, and a flexible noise barrier where sound needs to be directed away. This approach addresses both the source and the sound path.

Major sources of noise from an air-source heat pump.

• Fan noise: airborne noise from the outdoor unit that is often most noticeable outdoors or near the building facade.
• Compressor noise: mechanical noise that can be perceived as a hum, especially under high load or in cold weather.
• Vibrations: movements from the pump that can be transmitted through the bracket, stand, wall, pipes, or foundation.
• Structure-borne noise: vibrations that are transmitted through the building’s structure and become audible in other rooms.
• Reflections: Sound that bounces off the facade, siding, corners, deck, or other hard surfaces.

How to Soundproof and Sound-Dampen an Air-Source Heat Pump

To reduce noise from an air-source heat pump, you first need to determine whether the problem is caused by fan noise, vibrations, structure-borne noise, or reflections from hard surfaces. Follow the steps in order, starting with the solution that best suits the type of noise.

Step 1: Identify the type of noise that is disturbing you

Listen closely to the outdoor unit of the air-source heat pump and compare it to how the sound is perceived indoors. A steady hum or distinct fan noise is usually airborne sound. A dull rumble, pulsating sound, or vibrations heard through the wall more often indicate structure-borne noise.

Step 2: Check the stand, bracket, and contact points

Gently feel the wall bracket, ground stand, pipe penetration, and supporting surface while the pump is running. If these parts are vibrating, you should start by damping the vibrations. For machine feet, pumps, and equipment that transmit vibrations down into hard surfaces, Dampio PRO may be a suitable choice.

Step 3: Reduce vibrations before applying sound absorption

Install vibration damping where the pump makes firm contact with the stand, feet, or base. If there are small gaps, joints, or contact surfaces where sound leakage or vibrations are transmitted, SilentDirect Seal can be used to reduce both sound leakage and vibrations.

Step 4: Dampen resonance and harsh reflections near the installation

If sound is amplified by sheet metal, hard surfaces, or an enclosure, SilentDirect Polaric may be appropriate for hard surfaces where mass, sealing, and vibration damping are needed. For mechanical noise, resonances, and technical surfaces, SilentDirect Neo or SilentDirect Egg can also be used where they are compatible with the installation and airflow.

Step 5: Shield the sound if it is disruptive in a specific direction

If the noise primarily disturbs a patio, a neighbor, or a window, a sound barrier can be placed between the pump and the affected area. SilentDirect Sound Barrier 2.48 m can be used for temporary or flexible sound isolation in an accessible area where a barrier can be conveniently placed.

Step 6: Do not enclose the pump too tightly

The air-source heat pump must have free airflow around it. Therefore, never place sound-absorbing materials or screens in a way that blocks the air intake, exhaust, or service access. A good sound solution should reduce noise without compromising the pump’s operation.

Step 7: Test the results and combine measures as needed

Listen again both outdoors and indoors while the pump is running. If the hum decreases, the vibration-damping measure has been effective. If the fan noise is still bothersome, shielding or sound-absorbing material may be needed. Many air-source heat pumps require a combination of vibration damping, sealing, resonance damping, and shielding.

Did you know that…

Did you know that a low, rumbling sound from an air-source heat pump is often caused more by vibrations than by the actual noise level of the fan? If the vibrations are transmitted into the facade, wall bracket, or deck, the sound may be perceived as louder indoors than right next to the outdoor unit. That’s why vibration damping is often an important first step.

Products for soundproofing air-source heat pumps.

When soundproofing an air-source heat pump, it is important to select a product based on the sound path. Vibrations require damping at contact points; airborne sound may require shielding; and resonance in hard surfaces may require damping mats or absorbent materials near the sound source.

Dampio PRO is a powerful vibration damper for machines, pumps, and equipment that are in contact with hard surfaces and risk transmitting structure-borne noise further into the building.

SilentDirect Sound Barrier 2.48 m can be used for temporary or flexible sound isolation in an accessible area where a barrier can be conveniently placed.

SilentDirect Neo is a smooth sound-dampening mat for vibrations, resonances, and mechanical noise where a flat surface is more suitable than a profiled foam structure.

SilentDirect Neo Roll is suitable for larger areas where you want to combine some sound absorption with the damping of vibrations and resonance in technical structures.

SilentDirect Egg is a profiled sound absorber for machinery and technical spaces where you want to capture sound close to the source while dampening harsh reflections.

SilentDirect Egg roll is practical for larger or irregular surfaces, where the roll format makes it easier to cut to size.

SilentDirect Polaric is a self-adhesive barrier mat with an aluminum surface designed for sheet metal, metal, and hard surfaces where sealing, mass, and vibration damping are needed in a single layer.

SilentDirect Seal is a self-adhesive sealing strip for gaps, joints, and contact surfaces where small air leaks or vibrations can compromise sound insulation.

SilentDirect Aluminum Sealing Tape can be used to seal joints in sound-insulating structures, especially where leaks could compromise the performance.