Noise from heat pumps and HVAC units: what to address before building completion?

Why address noise already at the design stage

Noise from heat pumps, air-handling units, fans, cooling equipment or air conditioning should be addressed before the equipment is installed and the building is ready for completion. Retrofit measures are usually technically more difficult, more expensive, and sometimes limited by space or building operation.

A common problem arises when equipment meets the manufacturer's catalogue parameters, but at the specific location the noise proves noticeably greater than the investor expected. Distance from windows, position relative to façades, roof or courtyard placement, night-time operation, simultaneous running of several units, and possible transmission of vibration into the building structure all play a role.

Before building completion it is therefore appropriate to verify whether the proposed solution can meet requirements for protection against noise in the protected outdoor area of buildings, and where relevant also in the protected indoor area of buildings.

Outdoor units of heat pumps

For heat pumps, the location of the outdoor unit is usually decisive. Problems can arise with equipment placed under windows, at the plot boundary, in a narrow courtyard, between façades, or facing residential development.

The catalogue noise value on its own is usually not enough. For assessment it is important to know whether the manufacturer states sound power level or sound pressure level, under what regime the value was determined, and whether the equipment will also operate at night. For heat pumps it is also necessary to take into account changes in output, defrosting, night-time reduction, and possible simultaneous operation of several units.

For family houses, impact on neighbouring residential buildings is often addressed. For apartment buildings, guesthouses, hotels or commercial premises the situation is more complex, because there may be several units, several protected locations, and simultaneous operation of other technologies.

Roof-mounted HVAC units and cooling equipment

Roof-mounted air-handling units, fans and cooling equipment can be a significant source of noise even when they are not placed directly next to residential development. Noise can spread through open space, affect upper floors of surrounding buildings, or be reflected between façades.

For this equipment, exact position on the roof, height above ground, intake and exhaust direction, sound power of individual parts of the unit, operating regime, and any silencers are important. For larger buildings, a frequent mistake is to assess each unit separately without evaluating their combined effect. If several sources run simultaneously, their combined impact must be assessed.

Night-time operation is often decisive

Equipment that is acceptable during the day can be problematic at night. The night period is more sensitive from a noise perspective, because background noise in the surroundings is usually lower and regular or tonal noise from technologies is perceived more clearly by residents.

For heat pumps, HVAC units and cooling equipment it is therefore necessary to know whether they will operate only during the day or also at night. If equipment is to run continuously, it is not enough to document only the daytime regime. Assessment must also include night-time operation, or where relevant options for output limitation, night-time reduction, or adjustment of the operating regime.

Protected outdoor area of buildings

When assessing noise, it is not only the equipment itself that is evaluated, but its impact in protected areas. For buildings, the area in front of windows of living rooms, hotel rooms, sleeping accommodation in healthcare facilities, or other protected areas where noise arrives is often addressed.

The worst location is not always the nearest building in plan. For roof-mounted technologies, upper floors, direct visibility of the unit, or reflection of noise between buildings may be decisive. It is therefore important to evaluate the specific spatial arrangement, not only the air distance from the source.

What to provide for noise calculation

For noise assessment or a noise study, it is necessary to provide in particular the site layout, exact location of units, equipment data sheets, acoustic parameters, height above ground, and a description of daytime and night-time operation. For more complex buildings, a roof drawing, façade elevations, a building section, and information on all technologies that may run simultaneously are also useful.

It is important that the input documents include the sound power of the equipment where available. A general statement about "noise level" without regime, distance and type of quantity may not be sufficient for calculation. If there is already a requirement from the Regional Public Health Authority or the building authority, it is appropriate to provide it at the outset so that the purpose of the output is clear.

When to measure after installation

After installation, noise measurement is carried out when the actual state needs to be verified. This may be a requirement from the Regional Public Health Authority, the building authority, building completion, the investor, the operator, or a response to a complaint.

Measurement should be carried out under representative conditions. If night-time operation is being addressed, measurement at night is usually necessary. If the issue is simultaneous operation of several units, the corresponding operating state must be ensured during measurement. It is not enough to measure the equipment in a random or reduced regime that does not correspond to the situation being assessed.

Post-installation measurement is also appropriate when a noise study proposed specific measures and their effectiveness needs to be verified. This may typically involve silencers, a noise barrier, change of unit orientation, adjustment of the operating regime, or resilient mounting of equipment.

How noise can be reduced

The appropriate measure depends on what is the actual cause of the problem. Sometimes changing the location or orientation of the unit helps; at other times it is necessary to add a silencer, noise barrier, resilient mounting, or to choose a quieter type of equipment. For night-time operation, output limitation, night-time reduction, or adjustment of the combined effect of several sources may be effective.

It is best to address these measures already in the design. After installation, the scope for changes is limited and some measures may be structurally, spatially or operationally difficult.

Typical mistakes before building completion

Before building completion the same problem often repeats: the equipment is already installed, but noise was not assessed in advance. It then turns out that acoustic data are missing, the night-time regime is unclear, simultaneous operation of several units was not addressed, or it is not clear where the nearest protected area is.

Another common mistake is confusing sound power and sound pressure. These quantities cannot simply be interchanged. If the wrong value is used in the calculation, the result may be misleading.

Recommended procedure

If heat pumps, HVAC units, cooling equipment or other outdoor noise sources are part of the building, it is appropriate first to verify whether the Regional Public Health Authority or the building authority requires a noise study or measurement. Equipment data sheets should then be prepared, their exact position marked on drawings, daytime and night-time operation described, and the nearest protected areas assessed.

If the calculation shows a risk of limit exceedance or problematic night-time operation, it is appropriate to propose measures before installation. After the equipment is put into operation, measurement of the actual state is carried out according to the authority's requirement or as needed.

Summary

Noise from heat pumps, HVAC units and roof-mounted technologies should be addressed already before building completion. What matters is not only the catalogue noise level of the equipment, but also its location, operating regime, night-time operation, reflections from façades, simultaneous operation of several sources, and distance to protected areas.

Before installation it is appropriate to prepare a noise assessment or noise study. After installation, noise measurement of actual operation is carried out according to the requirement of the Regional Public Health Authority, the building authority, building completion, or in response to a complaint.

Send us equipment data sheets, the site layout, unit locations, and the requirement from the Regional Public Health Authority or the building authority. We will verify whether a noise assessment, noise study, or post-installation noise measurement is appropriate.