Igloo Ice Retention & Guidance

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On a lot of Igloo cool boxes, you will see reference to "ice retention", usually measured in a number if days. The way this figure is attained is by testing in controlled laboratory conditions. Each Igloo cool box is filled with a fixed amount of ice, the lid is closed, and it is then placing it in a 90°F (~32°C) oven to simulate a warm outdoor environment. The cool box ice retention level is the amount of time that it takes for the ice to reach 39°F (~4.0°C) and begin to melt.

Please Note
The way you use your Igloo cool box and the environmental conditions often vary, so the actual cooler performance may be different from lab results.

Maximising Cooling Performance

Pre-chill your contents

Before you pack anything into your Igloo cool box, you should pre-chill or freeze the contents well in advance. This ensures your cool box simply has to keep the contents cool rather than cooling them down, and that the ice packs do not melt so fast.

Pre-chill your cool box

Your Igloo cool box is a very efficient insulator, however this can work for both heat and cold temperatures. If your cool box is stored in a warm place, such as a vehicle, garage, shed, etc. it can retain the heat from its surroundings and when you fill it, it will then have to get down to a chilled temperature first, which will significantly reduce the performance and ice retention time of the cool box because ice packs will melt faster. Before you add any contents, it is recommended that you pre-chill your Igloo cool box overnight by keeping it in a cool place and placing frozen ice packs inside it to cool the temperature down, thus giving you the best chance of achieving acceptable ice retention times.

Fill it up!

Try to fill the cooler to at least 90% capacity with ice blocks and ice cubes - the less space for air, the better your cooler will perform. When the ice cubes start to melt, don't drain the water away until you have finished using it or are able to replace with more ice - water is denser than air and will stay cooler for longer.

Ice placement

Whilst it is beneficial to have ice on the bottom of the cooler, the majority of ice should always be placed higher up, where possible. Cold air drops and warmer air rises - the lower the contents are in the cooler, the longer they will stay cool for - when the cooler is opened they are also less exposed to ambient air.

Use ice blocks and ice cubes in unison

It is advisable to use both ice blocks and ice cubes together to assist in keeping contents cool. The biggest enemy in cool boxes (and bags) is air, as every time the cooler is opened any cool air will quickly be replaced by warm air. By using ice blocks, the larger surface area of ice blocks can enhance the longevity of their performance, however ice cubes are just as important as they can get in to all the small gaps that ice blocks and contents may not physically be able to, thus displacing air. The more contents and ice blocks/cubes that are in the cooler, the better the performance!

Keep your cool box cold during use

In addition to chilled or frozen contents, you should always add plenty of ice and try to ensure there is as little unused space as possible. Using large ice blocks (or large frozen bottles of water) helps to retain the ice at a low temperature for long, generally the larger and denser the ice, the longer it lasts. Always try to avoid placing your cool box in direct sunlight, and whilst some Igloo cool boxes feature CoolRiser technology to reduce the amount of contact the cool box has with hot ground, you should always try to place it on cool ground where possible. Open your cool box as little as possible as the more it is open, the more warm air from outside the box will melt the ice, and be sure it is properly closed after opening. Once the ice begins to melt, you should leave the water inside your cool box provided your contents allow it. By removing the water, you allow more air into the cool box, and it is easier for ice to keep cold water cool, than to cool down warm air.

Dry ice use

Although dry ice can be used in rotomolded Igloo cool boxes, we do not currently offer any products that are compatible with dry ice. Doing so may damage your cool box.


For cool bags (or cool boxes with loosely wrapped contents), re-freezable ice substitutes such as gel packs and ice cube sheets allow effective cooling without the wet mess associated with melting ice. A lot of ice retention principles are common sense such as avoiding opening the cool box any more than required (every time the cool box is opened, it allows warm air inside, which reduces performance). Less room for air to circulate also helps, so keeping your cool box as full as possible is beneficial. If you later add any contents that are at ambient temperature, this will also reduce the time the cool box retains ice and temperature.