Similar to base layers, block insulators are available in manmade and natural alternatives.
Down clothing has been used for many years in situations where maximum warmth and minimal weight are key issues. The warmth of an item of clothing will depend on the quality of the down/feather mix used (Goose Down generally being considered better than Duck Down, with a higher ratio of down to feather giving more warmth for a given weight) and the amount of fill included. Another factor to consider is construction of the jacket: sewn through construction is cheaper to produce, but the various box-wall methods of construction will eliminate cold spots.
Action Outdoors offers down clothing from Rab and Marmot.
The major draw back of down, is that its insulating properties are seriously compromised if the garment gets wet. The synthetics alternatives retain more of their insulating properties when wet, and with recent improvements in materials are closing the warmth/weight gap when compared to down.
Many of the synthetic jackets can be worn over waterproofs during low activity breaks, such as the mountain top lunch stop, eliminating the need to remove and replace your waterproof layer. Our key products in this area include the Arc'Teryx Atom Jackets and Paramo Torres range.