A Guide to Shackleton Insulation

The Shackleton Insulation Guide

At Shackleton, we engineer our outerwear around materials proven to perform. Down is often our first choice when it comes to insulation due to its unrivalled air trapping performance and packability.

Insulation layers usually use two types of insulation materials: down which comes from ducks or geese, and synthetic man-made fibres. Both down and synthetic insulation function as insulating materials by trapping air within their structures, and keeping it stable.

Shackleton designers primarily use RDS certified goose down for our mid and outer-layers and recycled synthetic insulation where performance benefits require.

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What is Down?

Down is the soft cluster that grows beneath the outer feathers of geese and ducks, between the skin and the plumage. It is not a feather. It has no quill, only a round centre, the plumule, from which thousands of fine filaments radiate.

Packed into a jacket’s baffles, those filaments interlock to form a dense web of air pockets. Still air is what holds your body heat, and down traps more of it, for less weight, than any other material.

The result is loft: the ability of down to expand far beyond its packed size. Release a small handful and it swells to roughly the size of a basketball. Because down is mostly air, it compresses small and recovers fully, and the better the down, the faster it springs back.

What the statistics mean?

What is Down Cluster Ratio?

The ratio of down to feather found in a piece of clothing constitutes the down cluster ratio. The higher the ratio, the more down the item contains. The more down the item contains, the better the warmth to weight ratio due to the down's lofting capability. For Shackleton down jackets, we use a down cluster ratio of 90:10, which means the minimum down content is 90%.

What is Fill Power?

Fill power is a number that indicates the relative quality of the down. The number derives from a lab test that measures how many cubic inches of loft one ounce of that down fill produces. Higher fill power numbers indicate greater loft and insulating efficiency. For the Rothera, Ross and Ronne jackets we use a fill power of 850, but for our even more lightweight performance gilet, the Faraday we use 750 fill power.

How is Down Fill-Power Tested?

The test is typically done by filling a large cylinder with one ounce of down. A lightly weighted disk is placed on top which slowly sinks to compress the down. After exactly one minute, the position of the disk is recorded and the volume of down compressed at that point is calculated.

A result of 450 cubic inches of down equates to 450-fill-power down. More resilient down compresses less and will loft higher. It also yields a higher test result—900 fill power is about as good as down gets

The Ethics of Down

The down used in our insulated jackets has been sourced and managed in accordance with the Responsible Down Standard (RDS).

The Responsible Down Standard (RDS) is an independent, voluntary global standard which certifies down against animal welfare requirements and tracks it from the source to the final product. The standard aims to ensure that down and feathers come from animals that have not been subjected to any unnecessary harm. All Shackleton virgin down is certified to the Responsible Down Standard, and you can track where the down in your jacket came from by scanning the QR code on the swing tag.

What is Synthetic Insulation?

Synthetic insulation is usually created from polyester to form either sheets of wadding or lofted structures inspired by down. In this process different sized filaments are intertwined with each other to form a 3D web-like structure which traps air to create a thermal barrier. This structure is held in place by binder fibres which are heat activated (melted) so that they bond where the fibres cross, which holds them in place.

Synthetic insulation's key benefits include that it is fast drying, and remains effective in damp conditions. It is also durable and lightweight. Synthetic sheet insulation is designed to respond to how it is being used, either insulating or breathing to regulate body temperature across a wide range of conditions.

Down vs Synthetic

Synthetic fills have no equivalent test to down fill power, and each brand of synthetic insulation has unique characteristics. So, it’s not possible to use down fill power to compare insulation efficiency to any synthetic fill, and there’s no way to compare the efficiency of two different synthetic fills.

Although both down and synthetic insulation share many of the same properties, there are certain situations where one trumps the other. Down offers unrivalled warmth for weight and is highly compressible and packable, whereas synthetic insulation copes best with moisture, remains warm when wet and is highly resilient and fast drying making it ideal for damp conditions.