A specialist reference on dividing a single modular cold-room footprint into multiple temperature zones — covering internal partitions, anterooms and air-locks, and the refrigeration, sealing, and control implications of each.

A modular cam-lock enclosure does not have to be a single uniform box. Because the panels are interchangeable and demountable, one footprint can be subdivided into a chiller and a freezer, a chiller and a buffer anteroom, or three or more independently controlled rooms — without pouring new walls or commissioning separate buildings. This article explains how to design those zones so each holds its setpoint, how partitions differ from external walls, and where an anteroom or air-lock earns its floor area. It is written for refrigeration engineers, designers, installers, and facility managers, not only for buyers of a particular product line.

Quick answer: Split a single footprint into zones with insulated cam-lock partition walls, giving each zone its own evaporator and control circuit. Size the partition for the temperature difference between the two rooms, not the outdoor delta — a chiller/freezer partition (≈ +4 °C vs −20 °C, a 24 K difference) typically uses the same 100–120 mm panel you would put on an external freezer wall, and must be insulated on the freezer face to stop the warm side condensing. Insert an anteroom or air-lock (an intermediate buffer at ≈ +8 to +12 °C, or a vestibule with two non-simultaneous doors) ahead of any deep-freeze or high-traffic zone: it cuts door-infiltration load, frost, and condensation at the transition. Each added zone adds an evaporator, a control loop, and partition cost — so zone only where the product genuinely needs it.

Why zone a single cold room?

A multi-zone room stores products with different temperature or humidity needs under one roof, one structure, and (often) one plant connection. The modular cam-lock system is unusually well suited to this because the same panels, joints, and doors used for the outer shell build the internal divisions.

Typical drivers:

• Mixed product range. A caterer needs fresh produce at +2 to +4 °C, dairy and meat at 0 to +2 °C, and frozen stock at −18 °C or colder — three setpoints, one delivery bay.
• Traffic separation. A high-traffic picking chiller opened hundreds of times a day should not share air with a stable, rarely-opened long-term freeze store.
• Process flow. Receiving, processing, and dispatch may each want their own controlled condition in sequence.
• Future flexibility. A demountable partition can be moved or removed as the business changes — a property site-built masonry cannot match.

Partition walls: the core of zoning

An internal partition is a cam-lock wall that separates two conditioned zones rather than separating a conditioned zone from the outdoors. It is built from the same sandwich panels as the shell, but the engineering logic changes in three ways: which temperature difference it must resist, which face it must protect against condensation, and how it is structurally tied in.

Size the partition for the inter-zone difference

The first instinct — to make an internal wall thinner than an external wall because "it's only inside" — is wrong for a chiller/freezer partition. The heat flow across a wall is driven by the temperature difference across that wall, not by the outdoor temperature.

The rule of thumb: the bigger the ΔT across the partition, the thicker the panel — and a chiller-to-freezer partition deserves the same thickness you would specify for that freezer's external walls, because the chiller side, although "indoors", is still ~22 K warmer than the freezer.

Frostbox standard range. The Frostbox / Algor catalogue is built around 80 mm and 100 mm panels for chill/cold rooms and 100 / 120 mm for freezing rooms. A chiller/freezer partition is normally a 100 or 120 mm panel from that range. Thicknesses such as 60 mm, 150 mm or 200 mm shown in generic industry tables (including the deep-freeze row above) are not part of the Frostbox product line and should be read only as broad engineering context. Likewise, deep-freeze setpoints below −22 °C (e.g. −30 °C) are generic industry context — the standard Frostbox freezing-room range is −18 to −22 °C.

Protect the warm face from condensation

Across any partition, the warmer side is the side at risk. Warm, humid air from the chiller meeting the cold partition face can drop below its dew point and condense — or, on a freezer partition, frost. Two consequences follow:

• Vapour control. The panel's vapour barrier and, critically, every joint, corner, and floor/ceiling junction of the partition must be sealed so warm moist air cannot migrate into the core. A leaking partition joint condenses internally and slowly destroys the insulation's R-value.
• No cold bridges. The cam-lock joint pulls the foam cores fully home so there is no thermal gap at the seam; the same discipline applies where the partition meets external walls, floor, and ceiling. Seal every wall junction and corner joint properly — the continuous wall panels lock directly to each other at the corners, and a metal-to-metal path that bypasses the foam will sweat or frost.

Tie the partition in structurally

A partition is also a structural element. It is locked to the floor and ceiling panels with the same cam mechanism and corner profiles as the shell, which lets it carry its own weight and resist the small pressure differences that door cycling creates. Where a partition is long or tall, the design may call for an additional ceiling tie or floor channel — confirm spans with the panel supplier. Because the joint is mechanical, the partition can later be unlocked and relocated, which is the whole point of choosing a modular system for a layout that may change.

Separate refrigeration per zone

Each temperature zone needs its own evaporator and its own control circuit. You cannot reliably hold a chiller at +2 °C and a freezer at −20 °C from one shared evaporator and thermostat — the setpoints, defrost behaviour, and humidity targets are different.

What "separate circuit" means in practice

• One evaporator per zone, sized to that zone's heat load (envelope gain + product + door infiltration + lighting + fans + people).
• Independent temperature control — its own thermostat/controller, defrost schedule, and alarm thresholds.
• A condensing unit (or units) feeding those evaporators. Two common arrangements:

Separating circuits also isolates door traffic: the frequently-opened chiller's infiltration load is handled by its own evaporator and does not drag down the stable freezer beside it, avoiding cross-contamination of temperatures (and of odours/humidity) between zones.

Refrigerant note. Match each zone's unit to its duty and to current F-gas rules — see the regulation summary in § Compliance & efficiency. In the Frostbox range these are the real Daikin condensing families (GS, SP-O for quick-connect, DB-O, SAR, SAS, plus R-290 packaged units), specified per zone rather than as a single generic "small/medium/large" unit.

Anterooms and air-locks

An anteroom (also vestibule or air-lock) is an intermediate buffer zone placed at a transition — most valuably ahead of a deep-freeze room or at a high-traffic external entrance. Its job is to break the direct path between two very different conditions so that warm, humid air never meets the coldest room directly.

Why a buffer pays for its floor area

When a door opens between two zones with a large ΔT, dense cold air spills out of the lower half of the opening and an equal mass of warm, humid air flows in through the upper half. That infiltration is one of the largest and most variable heat loads on a freezer, and it carries the moisture that becomes frost on coils and ice on floors. A buffer attacks this in two ways:

• Intermediate temperature. An anteroom held at, say, +8 to +12 °C means the freezer door now opens onto +10 °C air instead of +20 to +30 °C ambient. The ΔT — and therefore the infiltration energy and the moisture load — across the critical door is dramatically smaller.
• Two doors, never both open. A true air-lock has two doors in series with only a short space between them; staff (or an interlock/automation) ensure the inner door is shut before the outer opens. Air is exchanged with the small buffer, not with the cold room behind it.

Where anterooms and air-locks earn their place

Complementary infiltration controls

A buffer combines well with the same devices used at any cold-room threshold:

• Fast doors — high-speed roll-up or automated sliding doors cut the time the opening is exposed; the faster the cycle, the less air is exchanged.
• Air curtains and strip (PVC) curtains — reduce exchange while a door is open, useful inside the air-lock or on a busy doorway.
• Self-closing doors and door interlocks — ensure a door is not left standing open and enforce the "one door at a time" air-lock discipline.

For the door hardware itself, see Door types & specifications.

Floors across zones

Zoning interacts with floor design, because adjacent zones can sit at very different temperatures over the same slab.

• Freezer zones need an insulated, frost-protected floor. A sub-zero room over the ground risks frost heave — moisture in the soil under the slab freezing and expanding, lifting and cracking the floor. Freezer floor panels must be insulated, and large or permanent installations may need a thermal break and a perimeter or under-slab frost-protection (heating) loop to keep the ground above freezing. (See Floor insulation & construction.)
• Match the floor rating to real traffic. MTH Algor offers three floor types, chosen on traffic intensity rather than room size: pedestrian 1,500 kg/m² (foot traffic, shelving), reinforced 3,000 kg/m² (hand pallet trucks, pallets) and drive-in 4,000 kg/m² (forklifts, powered pallet trucks) — verify the actual figures against the manufacturer's data for your panel (download the documents). The rating is a distributed load; wheels and pallet feet press the same weight onto a much smaller area, so design to local pressure and to the published point load, not just total weight. Zones with different traffic can take different floor types.
• The "without-floor" option is chiller-only. Omitting the floor panel (placing the room on a suitable existing insulated slab) is offered for the Cold Room 80 mm configuration only; a freezer zone always needs its own insulated, frost-protected floor.

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Compliance & efficiency context

Smart, centralised control

A multi-zone facility is far easier to run from a centralised monitoring/control system (or a Building Management System, BMS) than from a wall of independent thermostats. One system can:

• track temperature and humidity in every zone simultaneously, with per-zone alarms (essential for HACCP and for GMP/pharmaceutical IQ/OQ/PQ validation, where each zone must prove temperature uniformity and stability);
• coordinate defrost schedules so zones don't all defrost at once and spike demand;
• log door-open events and react to door sensors;
• enable demand-based ("adaptive") defrost that runs only when frost actually accumulates, saving energy and reducing humidity swings.

Energy and F-gas considerations

Zoning is itself an efficiency measure — you only spend deep-freeze energy on the volume that truly needs it, rather than freezing a whole footprint. Reinforce that with thick partitions, tight joints, fast doors, and buffers as above. Two further points for the plant feeding the zones:

• Right-size and modulate. Variable-speed (inverter) compressors that match output to the real, varying zone loads outperform fixed-speed units in a multi-zone facility; consider waste-heat recovery from condensers for water or space heating.
• Specify refrigerants for the current regime, not the last one. The governing instrument in the EU is now Regulation (EU) 2024/573 (in force 11 March 2024), which replaced Regulation 517/2014 and accelerated the HFC phase-down. Key consequences for new multi-zone builds:
• A GWP-150 cap on self-contained commercial refrigeration applies from 2025, pushing plug-in equipment to R-290 (propane); under IEC 60335-2-89:2022 the allowable hydrocarbon charge is now up to 500 g per circuit (not the older 150 g limit), widening where R-290 can be used.
• R-448A and R-449A are now retrofit/"bridge" blends only (GWP ≈ 1273 / 1282 — above the GWP-150 self-contained cap). They keep legacy R-404A plant running but are not a future-proof basis for a new installation. Genuinely durable choices are natural refrigerants — CO₂ (R-744), R-290, or low-charge ammonia (R-717) — or, where a synthetic is required, ultra-low-GWP HFOs.
• Ammonia is efficient but is a B2L refrigerant (toxic and mildly flammable); keep it out of occupied space (central plant + secondary loop) and design to EN 378 / ISO 5149. Hydrocarbon GWP is low (≈ 3), not zero.

For the full architecture-and-refrigerant decision, see Refrigeration system selection and Refrigerant regulations & compliance.

Design checklist for a multi-zone room

1. List the zones and setpoints — temperature, humidity, traffic level, and product for each.
2. Compute the ΔT across every partition and pick panel thickness from the largest difference, not the average.
3. Identify the warm face of each partition and confirm vapour sealing and corner detailing there.
4. Assign one evaporator and one control loop per zone; choose independent units vs. a multi-zone pack vs. central + secondary loop by scale.
5. Place an anteroom/air-lock ahead of any deep-freeze or high-traffic transition; add fast doors, air or strip curtains, and self-closers.
6. Detail the floors — insulated and frost-protected under freezers; rate for real traffic; remember "without floor" is 80 mm chiller-only.
7. Specify a centralised controller with per-zone logging, alarms, and coordinated defrost.
8. Choose refrigerants for (EU) 2024/573 — naturals/low-GWP, sized per zone.

To turn a zoned concept into specific dimensions and units, use the Frostbox size calculator for each zone in turn, then request a quote for the combined layout — Frostbox can advise on partition thickness, evaporator split, and anteroom placement for your products.

Related articles

• Holistic design example
• Door placement & design
• Floor insulation & construction
• Ventilation & airflow management
• Refrigeration system selection
• Heat load calculation

Sources & further reading

• 2022 ASHRAE Handbook — Refrigeration, chapters on Refrigerated-Facility Design and Refrigeration Load (infiltration through doorways; vestibule/anteroom load reduction) — American Society of Heating, Refrigerating and Air-Conditioning Engineers — ashrae.org
• ANSI/ASHRAE/IES Standard 90.1, Energy Standard for Buildings (vestibule requirements for door air-loss control) — ashrae.org
• EN 378-1:2016+A1:2020 / EN 378-2/3/4, Refrigerating systems and heat pumps — Safety and environmental requirements (also ISO 5149) — European Committee for Standardization — standards.iteh.ai
• Regulation (EU) 2024/573 on fluorinated greenhouse gases (in force 11 March 2024; repealing Regulation 517/2014) — EUR-Lex — eur-lex.europa.eu
• "Fluorinated greenhouse gases (F-gases) — EU rules" — European Commission, Climate Action — climate.ec.europa.eu
• IEC 60335-2-89:2022, Household and similar electrical appliances — Safety — Particular requirements for commercial refrigerating appliances (flammable-refrigerant charge limits, up to 500 g) — International Electrotechnical Commission — webstore.iec.ch
• EN 1186 / EU Regulation (EC) 1935/2004 on materials in contact with food, and HACCP principles (Codex Alimentarius CAC/RCP 1-1969) — for hygienic zone surfaces and monitoring — eur-lex.europa.eu
• "Airflow and Energy Simulations to Assess Energy Savings from Vestibules and Air Curtains" — ASHRAE Transactions / PNNL (infiltration data with and without a vestibule) — pnnl.gov

Specifications reflect the MTH Algor panel system supplied by Frostbox; partition thicknesses, evaporator splits, and anteroom layouts are project-specific. For a zoned design tailored to your products and site, contact [email protected].