Cold stores and refrigeration plant noise in planning

Refrigeration plant is the single most common reason a food business gets a noise condition it cannot meet. Condensers run through the night, when the background sound level in a residential street falls away, and an assessment that looked comfortable against daytime measurements fails at three in the morning. If you are installing a cold store, a walk-in chiller or roof mounted condensers anywhere near homes, the noise case has to be built into the plant selection rather than bolted on after the order is placed.

When a cold store needs permission

A cold store inside an existing unit, with no external plant and no change of use, often needs nothing from the planning system. The trigger is usually the external equipment.

Condensers, compressors and their acoustic housing are alterations to the building. Whether they need permission turns on whether the work materially affects the external appearance under section 55 of the Town and Country Planning Act 1990, and on whether any of the permitted development rights in Schedule 2 of the General Permitted Development Order 2015 reach that building type. Rights for commercial premises are narrower than householders assume, and they fall away on a listed building, in a conservation area and wherever an Article 4 direction has removed them.

Two other triggers catch people out. Extending the unit to house the plant is development in its own right. And a new cold store serving a wholesale operation can shift the character of the use, which matters if the permission or a condition restricts what the premises may be used for.

Where the cold store forms part of a wider fit-out, it is usually simpler to apply for the plant and the use together rather than install first and argue later.

Plant selection and siting before acoustics

The decibels you never generate cost nothing to remove. Before anyone measures anything, the specification decides most of the outcome.

Ask the supplier for sound power levels in octave bands rather than a single A-weighted figure, because the character of the sound matters as much as its level. Larger, slower fans move the same air at lower tip speed and lower level than small fast ones. Electronically commutated fans with speed control let the unit run at part load for most of the year and drop further at night when ambient temperature falls. Compressors on the far side of the building from the nearest bedroom window will always beat a better attenuator on the near side.

Distance and screening do work that money cannot buy later. Doubling the distance from a point source reduces the level by around 6 dB in free field conditions, which is usually more than any bolt-on measure achieves.

Assessing under BS 4142 and the night-time background problem

BS 4142:2014+A1:2019 is the method councils expect for industrial and commercial sound affecting people in nearby dwellings. It works by comparing a rating level with the background sound level.

The specific sound level is the plant contribution at the assessment position, over one hour during the day (07:00 to 23:00) or fifteen minutes at night (23:00 to 07:00). Character corrections are then added for acoustic features: tonality from a fan or compressor, impulsivity, intermittency, or other distinguishing characteristics. The result is the rating level. Background is measured as the LA90 over the same reference intervals.

The standard describes the difference between the two as the starting point for an assessment of impact, with a difference of around +10 dB or more indicating a significant adverse effect, around +5 dB an adverse effect, and a rating level at or below background an indication of low impact. Context then modifies the judgement, and the standard is explicit that the numbers are not a pass mark.

Night-time is where refrigeration schemes come apart. A suburban street can drop to a very low measured background between 01:00 and 04:00, and plant that sits 8 dB below daytime background can sit 6 dB above the night figure without changing at all. Insist that the survey covers the quietest period the plant will run in, not a convenient evening slot.

Internal levels help the argument where the external excess looks unattractive. BS 8233:2014 gives guideline internal ambient values of 35 dB LAeq,16hr in living rooms during the day and 30 dB LAeq,8hr in bedrooms at night, which lets you show the effect with windows in a realistic condition. Environmental health officers usually treat that as supporting evidence rather than as an alternative to the BS 4142 comparison.

Night running, deliveries and the hours question

Refrigeration is one of the few plant types that cannot simply be switched off overnight, and officers know it. That makes the rest of the operation the negotiable part.

Deliveries are often the louder event. Reversing alarms, refrigerated trailers running on their own engines while parked, roller shutters and cage movements across a yard all produce short, intrusive events that a continuous LAeq figure hides. Offer a delivery management approach with stated hours, a nominated bay away from the boundary, a prohibition on trailer units running while stationary, and broadband reversing alarms in place of tonal ones. Where the site generates enough movements to matter, a Transport Statement should describe the same arrangements so the two documents agree.

The hours restriction on plant is worth negotiating carefully. A condition that bans plant operation between 23:00 and 07:00 is unworkable for a cold store, so propose a level based condition at the nearest sensitive facade instead, and accept a tighter night figure in exchange. Articles on hours conditions for other uses, including extraction and hours for beauty salons and nail bars, show the same trade being made in reverse.

Structure borne sound in a building with flats above

Where homes sit above or beside the unit, airborne noise is only half the problem. Compressors and pumps transmit vibration into the structure, which then radiates as a low frequency hum inside the flat above. Occupants describe it as a throb rather than a noise, and it is often inaudible outside.

BS 4142 does not deal with this. Human response to building vibration is assessed against BS 6472-1 using vibration dose values, and the mitigation is mechanical rather than acoustic: anti-vibration mounts selected for the running speed of the machine, inertia bases where the mass ratio demands it, flexible connections on every pipe and duct, and resilient support for pipework rather than rigid clips into a party structure.

Get the isolation designed by the mechanical engineer at the same time as the pipework layout. Retrofitting isolation once refrigerant lines are brazed into place is expensive and usually incomplete.

Screens, louvres and enclosures that do not choke the condenser

Mitigation has to respect the airflow the unit needs to reject heat. An enclosure that starves the condenser raises head pressure, increases energy use and can trip the plant on a hot day.

Practical measures, roughly in order of usefulness:

1. Move the plant. Relocation to a flank or roof position with the building between plant and receptor is the strongest single measure.
2. Break the line of sight with an imperforate barrier of adequate mass, sealed at its base, positioned close to the source.
3. Fit acoustic louvres sized on the pressure drop the manufacturer allows, not on the space available.
4. Use attenuators on ducted intakes and discharges where the unit is designed for them.
5. Lower fan speed at night through a control setback, with the reduced duty checked against the worst case ambient temperature.
6. Absorptive lining on the inside faces of a screen or enclosure to control reflections.

Whoever designs the mitigation should state the insertion loss claimed for each element and where that figure comes from. Inspectors and environmental health officers discount unsupported claims, and a scheme that relies on an unsourced 15 dB from a timber fence will not survive a commissioning test.

Conditions and the commissioning test

Expect a condition expressed as a rating level relative to background, typically requiring the rating level from all plant to be no higher than the measured background level, or a stated number of decibels below it, at the nearest noise sensitive facade. Some authorities add a separate limit for tonal content.

Expect a second condition requiring a commissioning test by a competent person within a set period after the plant is first operated, with results submitted and remedial work carried out if the limit is exceeded. Read that one carefully before you agree to it. If the limit is set below what the specified plant can achieve, the obligation to put it right lands on you after installation.

Planning control also sits alongside statutory nuisance. Even with permission and a discharged condition, a council can serve an abatement notice under section 80 of the Environmental Protection Act 1990 if the plant amounts to a statutory nuisance in practice. Compliance with a planning condition is helpful evidence, not a defence in itself.

PlanScope drafts a Noise Impact Assessment and a Ventilation and Extraction Statement structured to the standards councils cite, with missing site measurements flagged rather than guessed. Councils normally expect an acoustician to author or review this kind of assessment, so treat the draft as the framework a suitably qualified consultant completes. Reports should be reviewed before submission, and PlanScope does not guarantee planning approval.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified acoustician before relying on it.