Is it possible to design a cardigan that can outperform most puffer jackets? We decided to find out by building the first Sub Zero Cardigan. Engineered from two incredibly powerful natural insulators – lambswool and superfine alpaca wool – the Sub Zero Cardigan is designed to keep you warm even in sub zero temperatures. So we tested it in the same way we test our puffer jackets, by taking it to a cryochamber.

You normally test arctic vehicles or missile components in cryochambers, not cardigans. But while the average cardigan weighs under 500 grams, at 1.3kg our Sub Zero Cardigan weighs nearly as much as our Titan Puffer. So we put our test subject in the cardigan in the chamber and told them not to move. With the thermostat set to -6°C, our test subject’s arms, chest, back and neck remained comfortable and warm for over half an hour while standing completely still. We only had to take them out as we hadn’t given them any gloves.

Alpaca wool is one of the most extraordinary natural materials on the planet. It’s as soft as cashmere, warmer than sheep’s wool, and contains no lanolin so it’s hypoallergenic. Native to the Andean plateau of South America, alpacas have evolved over millennia to survive the harsh conditions of the mountains where altitudes vary between 3,500 and 5,000 metres, and intensely hot days are followed by sub zero nights. Their fleeces have become a livelihood for native Andean communities, providing them with a constant source of warm clothing and income. 

Alpaca fibres are hollow. So when it’s cold they are highly effective at trapping and retaining heat. When it’s hot, they quickly absorb and wick away sweat much faster than other natural materials, with some studies showing alpaca fibres outperforming Merino wool fibres by more than 80%. This makes alpaca wool one of the most versatile and adaptive natural materials on the planet. The hollow fibres also give it a high ‘thermal capacity to weight ratio’, so even a small amount of alpaca wool keeps you warm. And we used loads of it.

The yarn in our Sub Zero Cardigan is spun by Sesia, a carbon neutral mill in the foothills of the Italian Alps. Known for their responsible approach to fashion, they specialise in organic natural materials and hold multiple ethical and environmental accreditations from bodies including OEKO-TEX, ICEA, and the Better Cotton Initiative. The wool is certified free from the harmful practice of mulesing and the yarn is left totally undyed, so the colours seen in the finished product are a reflection of the natural fleeces of the alpaca and the sheep.