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Down vs. Synthetic Insulation

Down: The Pro's

  1. Insulation: As a rule you can say that the best down gives almost twice the warmth/weight performance of the best synthetic wadding: i.e. down will provide the same warmth as twice its weight of synthetic filling.
  2. Resilience: In spite of seeming fragile, down will retain its loft much longer than a synthetic wadding (two to three times as long).

Down: The Con's

  1. Wetting: Down is a very poor performer once wet and it takes a lot of drying.  So-called ‘waterproof’ downs have improved the situation, but they will still end up soaked, whereas synthetics such as Primaloft simply do not absorb water. 
  2. Cost: Down is initially more expensive than synthetics, but the reverse is true over an extended period (see 'Resilience' above)

Synthetics: The Pros

  1. Damp: Synthetics still offer some insulation when wet (up to 50% of their dry performance), and they dry quickly.
  2. Cost: They are cheaper to buy. And if either low usage or regular replacement are expected, their comparatively quick loss of loft is not so important.
  3. Care: Care of synthetics is usually simpler and quicker than with down.  

Synthetics: The Con's

  1. Bulk & Weight: To provide the required warmth in extremely cold conditions synthetic-filled gear tends to be bulky and clumsy (e.g. polar and high altitude gear). For less cold enviroments (e.g. the Alps & British winter) the same comments apply to synthetic sleeping bags, but synthetic-filled clothing can be very effective, though it cannot compete with down in the pure ultralight stakes.        
  2. Life: In the long term synthetic waddings lose their loft and their performance much sooner than down.

Conclusion:

There are several minor issues ignored in this outline, such as 'what quality of down', 'what type of wadding', etc. But after more than 40 years of experience and research we find the main points above hold as true today as they did at the start. As a simple rule of thumb, go for synthetic insulation:

  • if there's a serious danger of getting the equipment wet
  • if the gear is for limited use and the initial price is important

In virtually all other circumstances down is the clear winner.

If you are interested in reading about these issues in more detail, read our article - The Truth About Sleeping Bags - which goes into much more detail about the warmth / weight performance, cost, and resilience of down vs. synthetics.

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