How to insulate a shipping container: protect cargo from heat and condensation

Short answer: for transport, the fastest way to insulate a shipping container is a container liner — a thermal liner hung inside the cargo space that shields the entire container in one go, with no installation. A container you are converting permanently (workshop, storage, tiny house) is better insulated with rigid panels or spray foam on the walls and ceiling. This article covers the first situation: protecting cargo during transport and temporary storage.

Why does a shipping container overheat so quickly?

A steel container in full sun works like an oven: the internal temperature can climb above 60 °C in summer while it is 30 °C outside. On winter routes the opposite happens and the cargo space drops below freezing. Steel conducts heat almost unhindered — without an insulating layer, your cargo is exposed to every temperature spike of the journey.

The second problem: container rain

At least as damaging as heat is condensation. When a container crosses climate zones, the air inside cools at night. The moisture in that air condenses on the ceiling and walls and drips onto the cargo as “container rain” or “container sweat”. The result: mould, corrosion, damaged cartons and rejected consignments. Hygroscopic goods — coffee, cocoa, rice, timber, paper — are especially vulnerable.

The transport solution: liner plus desiccant bags

For cargo that is temperature-sensitive but does not need active cooling, the combination of two passive measures is the standard:

• Container liner. A reflective thermal liner that lines the cargo space. It dampens temperature spikes (typically 10–20 °C cooler in heat), reflects solar radiation and forms a barrier between cargo and container wall. Reusable and fitted in minutes, for 20-foot, 40-foot and HC containers.
• Desiccant bags. They absorb the moisture in the cargo space before it can condense. Hung from the lashing rings, they keep working for the entire voyage.

Together they cover both risks: the liner handles temperature, the desiccants handle moisture. For strictly refrigerated transport (2–8 °C pharma, frozen goods) a reefer container remains the right route.

When are insulation panels the better choice?

If you are converting a container permanently — as a workshop, office or storage space — fixed insulation with PIR panels, glass wool or spray foam makes more sense: one-off installation, higher insulation value, but not reusable and not swappable per shipment. For transport that is impractical and needlessly expensive; there the liner wins on speed, weight and reusability.

Practical rules of thumb for sea freight

• Hang the liner before loading and close it only after the last pallet.
• Count on desiccant bags per running metre of container; more for moist cargo (timber, agricultural products).
• Stow cargo clear of the walls where possible — direct contact with hot or cold steel is the biggest risk factor.
• Measure critical routes once with a data logger — then you know what happens in your chain.

Direct from the manufacturer

Browse our range of container liners and desiccant bags for 20-foot, 40-foot and HC containers — shipped from stock, custom sizes on request. Shipping individual pallets instead of full containers? Then thermal pallet covers are the right solution.