How long does an EPS box stay cold?
How long an EPS box stays cold differs strongly in practice, depending on wall thickness, gel packs and outside temperature. A thin-walled EPS box reaches 8 to 12 hours with gel packs, a thick-walled one 24 to 48 hours, and with dry ice the contents stay frozen for up to 72 hours. The spread is wide, because the cooling time depends on several factors at once.
What does the cooling time depend on?
Four factors together determine how long a box made of EPS stays cold:
- Wall thickness. The thicker the wall, the longer the insulation holds. A thick-walled box (40 to 50 mm) holds the temperature a lot longer than a thin-walled one of 20 mm.
- Number of gel packs. The number of cooling elements you use plays a part.
- Outside temperature. The outside temperature and the time in transit also count.
- Fill level. Empty space is your enemy: the less air is left in the box, the less heat can circulate.
The factors work together, so the cooling time depends on the combination.
How long an EPS box stays cold: the guideline times
The same question applies to a styrofoam shipping cooler. Styrofoam is another name for EPS. The guideline times:
| Setup | Guideline time |
|---|---|
| Thin-walled (20 mm) | roughly eight to twelve hours |
| Thick-walled (40 to 50 mm) with gel packs | 24 to 48 hours |
| With dry ice | up to 72 hours frozen |
Your own result depends on wall thickness, gel packs and outside temperature.
How long a Tempex box stays cold: it is the same material
Asking how long a Tempex box stays cold is the same question, because Tempex is the old brand name for EPS. An EPS box, a styrofoam box and a Tempex box therefore insulate equally well. EPS consists of about 98% air in closed cells. That air slows heat transfer, while the material itself stays light. The difference in cooling time lies in the wall thickness, the filling and the coolant, not in the name. You can read more about the material in what is EPS foam: material and insulation.
How to extend the cooling time
Three things help:
- Place gel packs on top of the product. Cold air sinks and so cools the whole contents evenly.
- Use gel packs. Without cooling mass, the box only slows down the warming.
- Fill the box tightly, if needed with extra cooling elements. See choosing the right box size.
Looking for a different setup? Then read thermal box for 48 to 72 hours. A comparison with dry ice is in cool packs or dry ice.
Shipping frozen with dry ice
With dry ice, frozen products such as ice cream and ice cream cakes stay frozen for up to 72 hours.
Measured: a 400 gram gel pack in a thick-walled EPS box
Our product data contain a measurement series over 48 hours. The conditions: a gel pack of 400 grams, a thick-walled EPS box and a constant ambient temperature of 25 °C. The result applies to that setup.
| Moment | Measured at 25 °C |
|---|---|
| After 12 hours | Temperature still well below freezing, the contents stay deep frozen |
| After 24 hours | Gel pack still below 0 °C |
| Up to about 30 hours | Temperature stays below 0 °C |
| Up to 48 hours | Box warms up slowly, stays below 8 °C |
For the guideline times above (eight to twelve hours, 24 to 48 hours, up to 72 hours), our data state no outside temperature. For this measurement series they do: 25 °C.
Which hours do the product pages mention per size?
For a number of sizes, the product description states a time or a comparison:
| Box | Wall | Product description |
|---|---|---|
| EPS box 12 L, 400 x 300 x 155 mm | 20 mm | For online shops and food companies that ship chilled within about 24 to 48 hours. With gel packs the contents stay at temperature longer. |
| EPS box 10 L, 400 x 300 x 200 mm | 35 mm | A chilled order stays at temperature for 24 to 48 hours, depending on the number of cooling elements. |
| EPS box 4.7 L, 300 x 200 x 200 mm | 30 mm | Bridges a day in transit, also in summer. |
| EPS box 30 L, 600 x 400 x 300 mm | 50 mm | With the same load, a box with a 50 mm wall keeps the contents within range roughly one and a half to two times as long as a thin-walled one. |
| EPS box 45 L, 600 x 400 x 400 mm | 50 mm | More volume gives more thermal mass: a well-filled 45 liter box holds its temperature longer than the same amount of product spread over small boxes. |
Wall thickness per size
The wall thickness is in the product data for every box. A selection, from thin to thick:
| Box | Outer size (mm) | Wall |
|---|---|---|
| EPS box 5 L | 300 x 200 x 155 | 15 mm |
| EPS box 12 L | 400 x 300 x 155 | 20 mm |
| EPS box 25 L | 600 x 400 x 155 | 30 mm |
| EPS box 10 L | 400 x 300 x 200 | 35 mm |
| EPS box 30 L | 600 x 400 x 300 | 50 mm |
| EPS box 45 L | 600 x 400 x 400 | 50 mm |
In this selection, the thin-walled 20 mm from the guideline times matches the 12 liter box. The thick-walled 40 to 50 mm matches the 30 liter and the 45 liter box (50 mm).
Frequently asked questions about the cooling time of an EPS box
How long does an EPS box stay cold without gel packs?
Without cooling mass, the box only slows down the warming. The contents do not stay actively cold. For a stable temperature you need gel packs or another cooling element.
How long does a Tempex box stay cold in summer?
Shorter than at a lower outside temperature, because the outside temperature counts. A thick-walled box of 40 to 50 mm reaches 24 to 48 hours with gel packs.
Can I reuse the box?
Yes, EPS boxes are reusable. If you want to know how to have EPS processed after use, read disposing of and recycling EPS foam.
How long does a gel pack in an EPS box stay below freezing?
In our measurement series (400 gram gel pack, thick-walled EPS box, constant 25 °C), the temperature stayed below 0 °C for about 30 hours. After that the box warmed up slowly, but up to 48 hours it stayed below 8 °C.
What does up to approx. 48 hours mean for an EPS box?
Our collection data give a cooling time of up to approx. 48 hours, depending on wall thickness, gel packs and outside temperature.
Our boxes come from our own production since 1972. If you order before 14:00, a standard order usually leaves the same day. Still unsure about the size after reading how long a styrofoam box stays cold? Then take a look at all EPS boxes.
You will find all names in our glossary.
