High up in the Andes, where we are going in November, temperatures could get down to minus 25 degrees. When camping in cold conditions over multiple nights, the down insulation in our sleeping bag and clothing gets damper and less effective every night due to the moisture vapour lost from our bodies condensing out into these layers. Vapour Barrier suits seem to work in several ways to keep you warmer:
• Retaining the moisture from insensible perspiration between the skin and the vapour barrier greatly reduces wetting out of the insulation layers;
• Because the perspiration cannot evaporate, you save the body heat you would use to evaporate it;
• Once humidity inside the vapour barrier approaches saturation, insensible perspiration is reduced, saving water as well as heat.
Vapour Barrier sleeping bag liners are available, but you cannot wear your insulation clothing inside the liner (as it would wet out) so you cannot use the insulated clothing you carry effectively.
There are a few Vapour Barrier suits available from America. However, there is another issue. To put on and take off you vapour barrier suit, you have to strip naked or down to your base layer. Most people would find the suit too hot to walk in, and will only use it at night. Once the tent is up, you can crawl in your sleeping bag to undress and put the suit on. But getting up early in the morning in frigid conditions can be the coldest time. You not only have to strip off, but your skin is wet and as soon as you remove the VB, you lose additional heat evaporating this. Brrrrr. Much better to keep the VB suit on until you’ve started walking and have heated up through exercise. So, we designed VB suits that can be removed without taking off the outer layers of clothing.
Being new to VBs, we first trialled wearing cheap non-breathable waterproofs over a base layer and under other clothing at -11 degrees. Fantastic – a really warm and cosy night in the tent, and the amount of moisture on our skin remained minimal and never uncomfortable. So we designed our removable VB suits and made them out of the lightest silnylon we could get. Unfortunately, our week in February on top of the Cairngorm plateau proved rather mild, and they were only tested at just below zero degrees. They were toastie warm and comfortable and were easy enough to remove once we started walking. They will only really get tested when we use them high up in the Andes.
The photos show my suit. Derek’s is similar but not the same (we never quite agree on the ‘best’ method!). To put it on, the two arms velcro together at the neck and are put on first, then the body of the suit is zipped on over the arms, overlapping tightly round the armpits and with some velcro tabs connecting the two. Each leg of the trousers goes on separately with a large overlap, and elastic cords each side are pulled tight and done up in a bow. The body of the suit tucks into the trousers which are tight with elastic round the waist, and elastic cords are pulled tight at the wrists and ankles. Light rubber gloves for the hands and polythene bags for the feet are put on over base layers for comfort.
The suit can be removed with tight-fitting multiple layers of clothing on top of it. When the elastic is undone on the trousers, the silnylon is so slippery that each leg can be pulled out from the ankle underneath our powerstretch tights. The jacket body un-velcros at the shoulders, the front zip is undone, and it pulls out at the waist. The sleeves un-velcro at the back of the neck, then pull out at the wrist. You do not need to be a contortionist to do any of this.
The total suit weighs 200g almost exact. It should save far more than its weight in insulation layers. We also try to create multiple uses for home-designed items. The elastic cords at the wrists and ankles are designed to pull tight shut, so that each leg and arm can be used as a sausage-shaped almost-waterproof bag when not being worn. These will give additional waterproof protection to items in the pack, and provide good storage bags within the tent. In addition, stuffing a leg with clothes and reversing the other leg over the first, then feeding one end through the elastic cord at the other end, creates an excellent neck pillow for use on the long plane and bus journeys we will be doing.
Our experiments with VBs so far are very positive but limited. Because we have been able to find few reports on using VB suits in cold environments, we intend to report further on ours once properly tested.