Energy statements for refrigerated warehousing

A cold store energy statement has an awkward starting point: the largest energy use in the building is invisible to the calculation the policy target is based on. Process refrigeration is unregulated energy, so it falls outside Part L and outside the percentage reduction a local plan carbon policy asks for. You can show a large regulated improvement on a refrigerated distribution building while the meters run at many times the figure in the table.

Officers have become alert to this. The statements that pass are the ones that report the process load openly, set out what is being done about it, and explain why the Part L number is small.

Why the regulated and process split matters more here

Regulated energy under Approved Document L covers fixed building services: space heating and cooling, hot water, ventilation and fixed lighting. Process energy, including refrigeration plant serving chilled and frozen storage, is outside that definition.

For an office the split might be reasonably balanced. For a freezer store it is lopsided. The building has almost no space heating demand, modest lighting, and a refrigeration plant running continuously. A compliance calculation under the National Calculation Methodology compares your building with a notional building of the same geometry built to a defined specification, and that notional building is assumed to be heated and lit in a conventional way. Comparing a cold store against it produces a number that is arithmetically correct and practically meaningless.

There is a further wrinkle worth resolving early. Some industrial buildings with low energy demand sit outside parts of the energy efficiency requirements altogether, and how a cold store is treated depends on how it is serviced and how the unconditioned volumes are modelled. Settle that with your building control body before the energy statement is drafted, because the answer changes what the statement can say.

Reporting the refrigeration load

The statement should give the refrigeration load its own section with its own numbers, separate from the compliance tables.

What a reviewer needs is the refrigerated volume by temperature regime, the design plant capacity, the assumed operating hours and load profile, the coefficient of performance or seasonal efficiency assumed for the plant, and the resulting annual electricity consumption. Then state the method used to derive it. A design-stage operational energy estimate prepared to a named method such as the CIBSE approach to evaluating operational energy is far more useful than a single unsupported kilowatt-hour figure.

Separate the loads out as well. Compressors, condenser fans, evaporator fans, defrost, dock equipment, underfloor heating to the freezer slab and lighting inside the cold volume all behave differently, and an officer asking about mitigation wants to know which of them your strategy actually touches.

The electrical consequence belongs here too. A continuous refrigeration load drives the connection capacity, and the timing of a distribution network operator connection is often the real programme risk on these schemes. Our note on substation capacity and the grid connection question covers how that interacts with the planning programme.

Fabric performance in a cold envelope

A cold envelope behaves in the opposite direction to a heated one, and the details that matter are different.

Insulation continuity is the whole game. A thermal bridge in a freezer envelope wastes energy, and then it condenses and freezes, and ice formation in a panel joint is a defect rather than an inefficiency. So the statement should describe the panel system, the treatment of junctions at the floor perimeter, the vapour control strategy and the approach to penetrations.

Underfloor heating beneath a freezer slab is an energy use that exists to prevent frost heave lifting the floor. It is unavoidable, but its source is a design choice, and recovered heat from the refrigeration plant is the obvious one.

Air infiltration at the dock is where a lot of the load actually comes from. Rapid-action doors, dock shelters, air curtains, vestibules between temperature regimes and a door interlocking regime all reduce it, and they are the measures a planning officer can understand without a thermodynamics lesson. Give the door cycle assumptions you used, because that is what the load estimate turns on.

Heat recovery and what is worth claiming

A refrigeration plant rejects heat continuously, all year, which makes it an unusually reliable heat source. That is the strongest part of most cold store energy strategies and it is often understated.

The uses worth claiming are the ones with a matching year-round demand: domestic hot water, heating for the ancillary office and welfare areas, underfloor heating to the freezer slab, and defrost. Where an adjacent building or a future phase could take low-grade heat, say so and describe the connection point you have left, because a network connection commitment carries weight in policy terms even when the network does not exist yet.

What is not worth claiming is a heat recovery arrangement with no demand to serve. A desuperheater feeding a hot water cylinder that is already heated by an efficient source is a line on a drawing rather than a carbon saving, and reviewers with technical support will say so.

Quantify it properly. Give the recoverable heat, the demand it meets, the hours of coincidence, and the resulting reduction. An unquantified statement that heat recovery will be incorporated invites a condition requiring the detail later, which means a discharge application.

Refrigerant choice and its carbon weight

Refrigerant selection has a carbon consequence that sits outside the energy calculation entirely, and it belongs in the statement.

Ammonia and carbon dioxide systems have negligible direct global warming potential compared with the fluorinated refrigerants they replace, and the regulatory direction of travel has been reducing the supply of high global warming potential gases for years. Ammonia brings safety and design implications, including separation distances, plant room design and the regulatory regime for the quantity stored. Carbon dioxide systems operate transcritically at high pressures with their own engineering consequences.

What the statement should contain is the refrigerant proposed, its global warming potential, the charge quantity, the leakage rate assumed over the life of the plant, and the resulting emissions. Where a refrigerant is chosen for safety or operational reasons rather than carbon, say so plainly.

Those life-cycle emissions also belong in a Whole Life Carbon Assessment if one is required, and the RICS methodology sets out where refrigerant leakage sits in the modular reporting. Keep the charge quantity and leakage assumption identical in both documents.

Benchmarking against comparable buildings

Because the Part L comparison is weak, benchmarking carries more weight than usual, and it is where statements most often become vague.

Use an intensity metric suited to the building type. Energy use per cubic metre of refrigerated volume per year is more meaningful for a cold store than energy per square metre of floor area, because the load follows volume and temperature regime rather than footprint. Whatever metric you use, state it, state the source of the comparator, and state whether the comparator includes process energy. A benchmark quoted without those three things will be discounted.

Do not invent a figure. If no published benchmark fits the building, say that, give your modelled intensity, and offer a monitoring commitment instead. That is a more defensible position than a comparison nobody can verify, and it sits comfortably alongside a BREEAM Pre-Assessment where the scheme is pursuing certification.

Presenting the strategy to a planning officer

Structure the Energy Statement so that the officer can find the policy answer and the honest answer in the same document without them contradicting each other.

1. State the policy target and which emissions it applies to, in one paragraph.
2. Give the regulated emissions baseline and proposed figures, with the software and version named.
3. Give the process energy estimate separately, with its method named and its exclusion from the policy target stated.
4. Set out the measures against the energy hierarchy: demand reduction first, then efficient supply and heat recovery, then low carbon generation.
5. Quantify each measure, including the heat recovery, with the demand it serves.
6. Report the refrigerant, charge, leakage assumption and resulting emissions.
7. Offer a metering and reporting commitment, with the metering strategy described.

That last point matters more on a process-dominated building than anywhere else, because the gap between design estimate and operation is wide and the only way to close it is measurement. Where a zero carbon or energy condition is likely, read it before determination, since discharge terms drafted for an office can be awkward to satisfy on a cold store. Our note on zero carbon conditions and how they are discharged sets out what to watch for.

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