Refrigerated shipping — also known as chilled shipping, cold shipping or frozen shipping — means sending temperature-sensitive products via a regular parcel carrier without breaking the cold chain. In this guide you'll read exactly how that works: which packaging to choose, how many gel packs you need and how to keep shipments cold or frozen for up to 72 hours. All based on our own test data — from our own production since 1972.
How does refrigerated shipping work?
The principle is simple: insulating packaging slows down the heat from outside, while a coolant inside absorbs the heat that gets in anyway. The combination determines how long your shipment stays cold. Three factors are decisive: the insulation value of the packaging (wall thickness or number of layers), the quantity and temperature of the coolant, and how full the packaging is — still cold air is fine, circulating warm air is not.
Step 1: choose your packaging
For refrigerated shipping there are three main routes. Polystyrene boxes (EPS) are the classic: excellent insulation, lightweight and economical per unit — the standard for fish, meat and pharma. Insulated bags are the flexible route: you ship in your own cardboard box with the bag as an insulating inner layer — flat in storage, light on shipping costs and comparable to EPS in performance. Cardboard cool boxes are the fully recyclable alternative: paper and honeycomb board with EPS-level insulation, ideal for brands that put sustainability front and centre. You'll find the complete overview of all types among our cool boxes.
Step 2: choose your coolant
For chilled shipments (2–8 °C) you use gel packs: flexible, leak-proof and available per case. For power and reusability, choose hard-shell cool packs. For frozen shipping (-18 °C) you use more cooling mass and thick-walled packaging; with dry ice, products stay frozen for up to 72 hours. Rule of thumb from our tests: always place the coolant on top of the products — cold air sinks and so cools the entire contents evenly.
Step 3: calculate your transit time
For shipments of up to 24 hours, a polystyrene box with 2 to 3 gel packs is enough, or a 2-layer insulated bag with a gel pack. For 24 to 48 hours, choose extra insulation and more coolant: a 4-layer insulated box liner with gel packs. For 48 to 72 hours — international shipments or bridging a weekend — combine maximum insulation with generous cooling: a 6-layer insulated box liner or EPP with plenty of gel packs, and preferably a data logger. In doubt? Request a sample and test with your own product; actual performance depends on fill level, outside temperature and route.
Common mistakes
The three mistakes we see most often: too much empty space in the box (fill up with the products themselves or extra coolant), placing the coolant at the bottom (cold air sinks — so on top), and coolant that isn't fully frozen when packing (at least 24 hours at -18 °C). Also ship at the start of the week, so your shipment doesn't sit over the weekend.
Refrigerated shipping for every sector
Butchers, fishmongers and meal kit companies ship daily with this setup; pharmacies and laboratories use the same method with validated 2–8 °C configurations; and for pallet shipments and air freight there are thermal pallet covers that protect entire loads. Shipping from a kitchen rather than a warehouse? Then take a look at thermo boxes for foodservice and catering. Whatever scale you ship at: the physics is the same, only the size changes.
Questions about your specific shipment? Our specialists are happy to run the numbers with you — from a few boxes to full pallets, straight from our own production and available from stock.