Will I be warm enough in this?
“Will I be warm enough in this?” It’s the question we are asked most frequently at trade and consumer shows when we are showing our drysuit thermal protection systems. We spend a lot of time talking about our ‘underwear’ and the simple answer to any of these questions is: “It’s all about the layering.”
It’s a time-honoured principle, brought from the wider outdoor sport world, that layering is the correct technique to maintain the best thermal protection. A good baselayer, thermal mid-layer (or two) and an outer shell is a model that most divers have come to adopt over the last 15 years or so, since fourth element launched the first baselayer designed for diving – the Xerotherm.
Choosing your combination of baselayer and thermal layer is a matter of assessing your needs, but the first question is always the same – “What drysuit do you have?”
Suits You Sir
A neoprene drysuit offers some degree of thermal protection. The heavier 5mm and in some cases 7mm neoprene drysuits are designed to do the bulk of the work of keeping you warm under the water and in this case, lighter undersuits are usually sufficient. Thinner neoprene suits tend to offer less in the way of thermal protection but are generally lighter and less buoyant.
Compressed neoprene suits offer much greater predictability in terms of buoyancy and thermal consistency (as they do not compress as much with increasing depth), but in these cases more thermal protection is needed.
Trilaminate suits (such as the Argonaut), are usually a thin layer of butyl rubber sandwiched between two layers of fabric and offer very little in the way of thermal insulation – almost all the thermal protection is provided by the undergarments.
Some thinner membrane drysuits are literally a thin shell with no insulating capabilities whatsoever and the layering principle applies to these in a similar way as with trilaminate suits.
Ready Layer One
A good baselayer is critical — it must manage moisture and keep your skin as dry as possible. Whether you like it or not, there will be some moisture inside your suit, hopefully just from perspiration, but at some stage it is likely that it will also be water from a leaking seal, zipper or a more catastrophic leak. Keeping this moisture away from the skin is the key job of a good baselayer.
Water is wicked
Water is not a good insulator. Water next to the skin absorbs heat, drawing it away from the body. Wicking is the process of moving water through a fabric from one face to another. In the case of the diving baselayer, its objective is to keep the moisture on the outer surface of the baselayer away from the skin, maintaining a layer of air (a much better insulator) as the first line of defence against getting cold. If your undersuit also wicks (as is the case for all fourth element undersuits) then this moisture will be moved even further away, and performance is maximised.
Use the J2 for layering under any undergarment to manage perspiration and small suit leaks without affecting buoyancy. It has a grid-patterned knit, maximising the air next to the skin, but wicks moisture away very quickly. The added advantage of silver ion impregnated fibres minimises the growth of microorganisms such as bacteria, making this the perfect baselayer for drysuit diving trips in which multiple days of diving are planned. We designed it for some of the most extreme diving expedition conditions to maximise performance whilst maintaining healthy skin conditions for the dive team over a continuous period of more than 2 weeks.
Use the Xerotherm to provide good wicking performance, coupled with great thermal protection. Adding this as a base layer to your undersuit makes a significant difference. It’s one of the fastest wicking materials available, and thanks to this fabric technology, it works so well when wet that some divers do not notice leaks in a suit until after the dive!
Choose the right undersuit
Generally speaking, a neoprene drysuit will be cut closer to the body, often allowing no more than a thinner undergarment to be fitted underneath. In this case, look for an undersuit which is low in bulk and will allow freedom of movement, but still offer good thermal protection, or, for warmer waters, choose a thermal baselayer.
Under trilaminate drysuits, we recommend the Arctic Expedition or the Halo 3D, but many divers also choose the Arctic for the ultimate versatility of using it in warmer conditions and layering up more for the cold. In a correctly fitting trilaminate drysuit, there will be more room for undergarments but it is important not to have so much bulk that movement is restricted.
The appropriate combinations will vary with four variables: water temperature, duration of dive, frequency of diving and personal factors – some of us just feel the cold more (or maybe are just prepared to admit it).
1. Choose an undersuit.
The Arctic undersuit is typically used for dives of up to an hour in temperatures from 10 – 16 degrees c (50 – 60 F.)
The Arctic Expedition was developed for temperatures from 6 – 14 degrees c (42 – 57F.)
The HALO 3D was developed for temperatures of 4 – 10 degrees c (40 – 50F.)
2. Add a baselayer to make your undergarment suitable for cooler temperatures or longer dive durations.
3. In extreme circumstances, add an additional baselayer or other insulation to the body core. For example a Xerotherm vest will not change your buoyancy but will add more comfort. The X-Core vest was developed by fourth element as a passive heating garment but provides significantly greater thermal protection. It should be worn either next to the skin or over the baselayer.
4. For some of the most extreme divers doing long dives in cold water, active heating using a battery may be required. This involves task loading, additional equipment and the increased risks of something going wrong. If using active heating systems, we recommend wearing these over the baselayer, but ensuring that adequate passive thermal protection is also worn in the case of equipment malfunction.
5. Repetitive diving in cool water will result in longer term thermal stress to your body, and insulation that felt adequate at the start of a weeks diving may not feel so good half way through the week, especially if dives are long and tiring. In these cases, an extra baselayer top can be employed to great effect to get a little more comfort.
Stay cool and dive smart
Finally, don’t overcook it. There is plenty of emerging evidence that the best way to dive is just comfortable and maintaining this for as long as possible – keeping your body in the thermal neutral zone where it is able to use its own thermoregulatory systems without resorting to extreme sweating for example.
Sometimes the real trick can be keeping the extremities warm. Cold head, hands and feet can make a dive miserable despite being relatively comfortable everywhere else. Good gloves, hood and socks can make all the difference. If there is room, layer thick socks with a baselayer sock. Insulate key exposure areas – the Arctic Expedition and Halo 3D both have additional insulation on the inside of the forearms and panels on the thighs and chest where exposure is greatest in the horizontal trim position.