The modern pack-out: liner + box + refrigerant
A cold shipment needs three parts: a corrugated box for structure, an insulated liner to slow heat transfer, and refrigerant (gel packs or dry ice) to absorb the heat that gets through. Molded foam coolers do the same job but cost more to buy, ship and store — a collapsible insulated box liner delivers comparable performance and stores flat (about 75% less warehouse space).
Match the liner to the transit time
| Transit | Liner series | Construction |
|---|---|---|
| Up to 24 hrs (refrigerated) | FB / SL | Foil-bubble or recyclable mono-LDPE bag |
| Up to 48 hrs (frozen or refrigerated) | PL | Curbside-recyclable paper liner |
| 48–72 hrs (frozen, pharma) | PU | Pop-up foam panels, pairs with dry ice |
Full construction details and minimums are on the liners page; flat and small items ship in insulated pouches and mailers instead, and palletized loads get insulated pallet covers.
Sizing the refrigerant
Rule of thumb for refrigerated (not frozen) product: roughly one 24–32 oz gel pack per 12" of carton dimension for a 24-hour summer transit — so a 12×12×8 shipper typically takes two packs. Frozen product doubles the refrigerant or moves to dry ice. Place packs on top of the payload (cold falls), and use sweat-proof packs when condensation would damage labels or cartons. Always pre-chill the product — refrigerant maintains temperature, it doesn't create it.
Test before you ship at scale
Reputable suppliers test pack-outs against ISTA summer profiles in environmental chambers. We can arrange payload testing of your exact product and box before you commit to a program — cheaper than learning from a melted first shipment.
Frequently asked questions
How do I ship frozen food overnight?
Use an insulated box liner rated for 24–48 hours inside a corrugated box, pre-freeze the product, and add gel packs on top of the payload — roughly one 24–32 oz pack per 12 inches of box dimension, doubled for frozen goods, or use dry ice for longer transits.
Are insulated box liners as good as foam coolers?
For most parcel shipments, yes — modern foil-bubble, paper and foam-panel liners match molded cooler performance for 24–72 hour transits while shipping and storing flat, cutting storage space by about 75% and cost per shipment significantly.
How many gel packs do I need per box?
For refrigerated product on a 24-hour summer transit, plan roughly one 24–32 oz gel pack per 12 inches of carton dimension — e.g., two packs for a 12x12x8 shipper. Frozen product needs about double, or dry ice.
Tell us your product, box size and transit time — we'll spec the liner and gel-pack combination and quote it.
Request a Quote