Walk-In Freezer for a Gelateria: Sizing, Setup, Cost
Table of contents
A walk-in freezer is the least glamorous purchase in a gelateria and the one that quietly decides how your gelato tastes on day nine. Size it from production, set it from physics, and it pays you back every week. Get it wrong and you are storing ice crystals.
A walk-in is a quality instrument before it is a storage box.
A walk-in does three different jobs, and only one of them is storage
Most gelaterie ask a single room to do work that belongs to three machines. Understanding the split is what keeps you from buying the wrong box.
Hardening takes gelato from draw temperature down through the zone where ice crystals grow fastest. That is the job of a blast chiller, which uses very cold air moving very fast. A walk-in cannot do it: its air is neither cold enough nor moving fast enough, and loading warm product into a storage room warms everything already in there.
Storage holds already-hardened product cold and, above all, holds it steady. This is the walk-in's real job.
Service holding keeps product at scooping temperature, around -12 to -14 °C. That belongs in pozzetti or a ventilated display case, not in the freezer.
If you take one thing from this article: a walk-in is a stability machine. Ice crystals in gelato do not stop growing when the product is frozen. They grow every time the temperature moves, because a small warming melts the smallest crystals and the following cooling refreezes that water onto the larger ones. That is recrystallization, and repeated cycling is heat shock. A room that sits dead flat at -22 °C beats a room that swings between -25 °C and -16 °C every hour, even though the second one has a lower nameplate.
Size it from weekly output, not from the floor plan
The common mistake is to buy the room that fits the corner. Size it from the numbers instead. Finished gelato at 30 % overrun has a density of roughly 0.85 kg per litre, because a mix of about 1.10 kg per litre has been inflated by a factor of 1.30. That single number turns litres of shelf into kilograms of stock.
| Step | What you need | Worked example |
|---|---|---|
| 1. Peak week output | kg of finished gelato | 300 kg |
| 2. Buffer held in the room | days of stock | 5 days, so 214 kg |
| 3. Pan yield | 360 x 250 mm pan filled 60 mm deep = 5.4 L | 4.6 kg per pan |
| 4. Pans to store | buffer divided by pan yield | 47 pans |
| 5. Pans per bay | 6 per 1200 x 600 mm shelf, 5 shelves high | 30 pans |
| 6. Bays needed | round up | 2 bays |
| 7. Room footprint | racking plus a 900 mm aisle and door swing | about 6 m² |
Then add headroom deliberately. Two rules keep the room honest: never fill more than about 70 % of the shelf volume, and never stack product into the evaporator's air path. Leave 300 to 450 mm clear in front of the coil and above the top shelf. A room packed solid does not circulate, and a room that does not circulate develops warm pockets that undo everything the compressor is doing. The same discipline that governs batch freezer sizing applies here: buy for the peak week, not the average one.
The setpoint is a quality decision, not a legal one
This surprises people. In the European Union, Council Directive 89/108/EEC sets the familiar -18 °C rule for quick-frozen foodstuffs, and it also says, in Article 1, that "ice-cream and other edible ices shall not be regarded as quick-frozen foodstuffs." Gelato is carved out of that directive entirely. There is no EU-wide number handed to you.
What you have instead is Regulation (EC) No 852/2004, which requires food business operators to put in place procedures based on HACCP principles. In practice that means you set the storage temperature, justify it, monitor it and record it. Your HACCP plan is where the number lives, and an inspector will ask you to defend it.
So defend it with physics. Ice crystal growth slows as you approach the glass transition temperature of the freeze-concentrated matrix, below which molecular mobility falls away and the structure is effectively locked. Practical storage rooms sit well above that point, which is why colder and steadier keeps ice crystals small for longer.
| Room setpoint | What it is good for | Trade-off |
|---|---|---|
| -18 °C | Short buffer, a few days of turnover | Fastest crystal growth of the three; least forgiving of door traffic |
| -22 °C | The common working compromise | Good stability at moderate running cost |
| -25 °C and below | Long holding, seasonal stock, wholesale | Highest energy cost; needs a properly specified plant |
Quick reference. Set the room 6 to 10 °C colder than your service temperature and hold it flat. Aim for -22 °C for a gelateria that turns stock over weekly, and treat a swing wider than 2 K as a fault to investigate rather than normal behaviour.
Figure 1: where a small walk-in gains and loses heat, and the clearances that keep air moving.
Panels, floor and door: where the load actually comes from
Insulated sandwich panel is rated by its core. Polyurethane and polyisocyanurate cores sit around 0.022 W/m·K, so thickness translates directly into transmission load. For a 3.0 x 2.0 x 2.4 m room, the total envelope is about 36 m², and holding -25 °C inside a 25 °C kitchen is a 50 K difference.
| Panel core | Thermal conductivity | U-value | Transmission load |
|---|---|---|---|
| 80 mm | 0.022 W/m·K | 0.28 W/m²K | about 495 W |
| 100 mm | 0.022 W/m·K | 0.22 W/m²K | about 396 W |
| 150 mm | 0.022 W/m·K | 0.15 W/m²K | about 264 W |
Going from 80 to 150 mm cuts steady transmission by roughly half, for the price of 70 mm of floor space per wall. In a freezer that runs every hour of every day, that is usually the easy call.
Two details cost more than they look. The floor of any room held below 0 °C must be insulated and protected against frost heave, either with a ventilated void or with a heater mat under the slab; without it the ground below slowly freezes and lifts. The door is typically the largest single variable load in a small walk-in, because every opening dumps warm humid air inside, which then condenses and frosts onto the coil. Strip curtains, a well-adjusted closer and a habit of pulling a full trolley instead of six single trips do more for stability than another 50 mm of panel.
Defrost, airflow and the slow theft of freezer burn
Every gram of moisture that enters the room leaves the air on the coldest surface available. Usually that is the evaporator, which is why it needs a defrost cycle. Sometimes it is your gelato, and that is freezer burn: surface ice sublimating away, leaving a dry, pale, granular crust and a hollowed flavour.
Three habits prevent almost all of it. Lid every pan, without exception, because an open pan is a free evaporation surface. Schedule defrost for quiet hours and check that the drain line is heated and actually draining, since a frozen drain line turns the coil tray into an ice block. And keep the room genuinely full or genuinely organised, because frozen product has a large thermal mass that damps temperature swings, while empty air does nothing.
What it costs to run
Purchase price varies too much by market to quote usefully, but running cost is arithmetic you can do before you sign anything. Take the transmission load above, multiply by roughly 2.5 to cover door infiltration, lighting, defrost heaters, fan motors and product pull-down, then divide by the coefficient of performance of the refrigeration plant, which for low-temperature duty is realistically in the region of 1.3 to 1.6.
For the 100 mm room: 396 W of transmission becomes about 1.0 kW of total heat, which at a COP of 1.5 needs roughly 0.67 kW of electricity, or about 16 kWh per day. The 150 mm version lands nearer 11 kWh. Over a year that difference is real money, and it stacks with everything else in your energy bill. Build the figure into the opening budget rather than discovering it in January.
Commissioning: the week that decides the next ten years
Run the empty room for 24 hours and log it before you put a single pan inside. You are looking for the pull-down curve, the depth and frequency of defrost recovery, and whether the room returns to setpoint after a door opening. Place a calibrated probe at the warmest point you can find, usually high and far from the coil, not next to the controller sensor. Remember that the controller reads air, and air is not product: a probe pushed into a pan of gelato tells you the truth, and it will lag the display by a long way. Then write the numbers you saw into the HACCP plan as your monitoring limits, and you are done.
Related Concepts
- Blast Chiller for Gelato covers the hardening step a walk-in cannot do.
- Ice Recrystallization in Gelato explains why steady beats cold.
- Heat Shock in Gelato is what a badly commissioned room causes.
- What Temperature Should Gelato Be Served At covers the other end of the cold chain.
- Freezer Burn in Gelato is the slow loss you can design out.
- HACCP Setup for Gelaterias is where your setpoint has to be justified.
