Before designing or choosing an off-the-shelf temperature-controlled shipping solution, one needs to consider whether to use a seasonal or universal packout. This decision can be easily overlooked, yet can drastically change the direct cost, weight and size of the packout, as well as the freight cost. A seasonal packout is a thermal package that has component and/or temperature conditioning methods that are different depending on the season, typically with packouts designed for summer and winter temperatures. A universal (year-round) packout has the same components and temperature conditioning methods for use the entire year. As a general rule: the more a package is designed to do, the more expensive it becomes. Therefore, universal packs normally will be more expensive than seasonal ones, but that is not the only parameter worth examining.
Seasonal packouts tend to have less components, lower overall weight, and a higher ratio of payload volume to outer shipper volume. For example, a water-based seasonal packout can use less frozen refrigerant in the winter while needing less cold protection in the summer. Together, these lower the costs of actual package, the labor to assemble the package, the warehouse space to store the materials, and the cost of the freight to ship the package—which can be a significant savings.
The big disadvantage to having a seasonal packout is needing to answer the simple question, “Which packout do I use today: the one designed for summer or the one designed for winter?” On the lowest level, this is done by choosing a date to switch from one to the other, usually in October/November and April/May. If the designs are not robust enough, then an unseasonably warm winter day can result in the product experiencing warm excursions during shipment (or vice versa, cold excursions on a cool summer day). There is also the problem of the spring and fall months being highly variable in whether they conform more to summer or winter conditions. To minimize excursions, it might be beneficial to perform a daily comparison of the temperature range that the package was tested against to the forecasted environmental temperature throughout the shipping lane. Another solution is to design a “three season pack” (summer, winter and spring/fall). The spring/fall packout is used to cover the range of time and temperatures that are not very warm or cold, and to mitigate the risk of excursions by making the seasonal transition easier and having a more appropriate middle ground packout for unseasonably warm or cold days.
Universal packouts are by definition much more robust because they are designed to maintain product temperature when exposed to both summer and winter temperatures. The same packout will also cover the range of temperatures between the two seasons, so the problems of the seasonal pack go away completely. These packout designs are best for applications where the need for temperature compliance is very high and the climate is relatively temperate. The universal pack essentially trades the additional cost over the seasonal pack for peace of mind that the packout will work as intended, regardless of the differing daily temperatures. Specialized phase change materials can be used to reduce the overall weight and components, providing a solution that still adds cost but does not have as many usability concessions.
There are exceptions to every rule, of course, and in this area the biggest exception happens when shipping to extreme climates. A universal packout becomes increasingly complex and expensive as the range of seasonal external temperatures widens. As can be expected, a tipping point occurs where it is just not practical to use such a packout. In these extreme cases, it actually becomes easier and less expensive to manage the process of selecting among seasonal packouts. When shipping to the remote north of Canada, for example, a winter packout needs to be designed to withstand temperatures of -20° to -30°C, requiring it to be relatively robust and expensive. This cost can be offset during the summer where the temperatures will be relatively mild, resulting in the most optimized overall system, whereas the required universal packout would be very expensive and complex all year.