How to make 5 mil wetsuit warmer

[Akimbo]

Wetsuit thickness is less important than fit. A poor fit not only allows water circulation, thus substantial heat loss, it also causes water to pump in and out of the suit with body movement. You really need a goldilocks fit because too tight is detrimental to comfort, respiration, and mobility.

Zippers are often a culprit along with loose fitting cuffs at the ankle and wrists. You still need a consistent thin film of water between you and the suit or body movement will cause pumping. Do you feel a cold trickle of water down your spine when you first jump into the water? Then you need a spine pad. All concave areas are problematic.

Head Heat Loss
There are a lot of misconceptions about heat loss from the head due to over simplification of study data. Depending on temperature and thermal protection about 50% of your total heat loss is through respiration. Studies have shown that under just the right conditions half of the remaining heat loss can be through the head, more specifically above the shoulders. But that relates more to people in a life jacket nearing hypothermia since the body restricts circulation in the limbs to save heat for the vital organs and the brain.

Head heat loss is normally much higher for a given surface area of skin than other parts of the body. Though highly variable, there are two primary reasons. First is the relatively high blood circulation rate near the surface of the neck and head, which acts as a radiator. Second is respiration cools the skull from the inside. There is a lot of surface area in the sinuses.

Heat Loss Studies
The great majority of thermal studies of immersed bodies in sea water have been for ship wreck survivors floating in life jackets. I have yet to see a useful study for recreational divers of heat loss in the head with the body fully immersed because it is highly variable depending on temperature, thermal insulation, and the state of hypothermia. Water is about 25 times as thermally conductive as air. The Navy has done a bunch of studies and data is all over the place, plus they tend to focus on hypothermia onset rather than comfort.

Recreational divers are in trouble once the body starts to limit circulation in limbs and should never allow it to get that far.

 

[WhyMe]

I feel good at first, no cold water tricking in. But once we are swimming around and I have my head looking up and ahead with my body horizontal, then move my arms that is when I start to feel the cold down my back a bit. Also if I curl forward like going into fetal position the I think I feel cold water down the back of my neck then too. I should have paid more attention while I was diving.

 

[tbone1004]

Go with a hooded vest that goes under your current wetsuit, you won't regret it.

 

[Eric Sedletzky]

Look into a tropical drysuit. A lot of people with cold issues are going that route.

 

[Dive Right In Scuba 2]

Perhaps look into a Thermocline or Lavacore vest/top and a drysuit hood. The tops I mentioned are neutrally buoyant and add the equivalent to a 2/3mm to the core area. I have found that using a drysuit hood(one without a tuckable skirt) are a good solution for divers who are prone to claustrophobia.

 

[Akimbo]

I feel good at first, no cold water tricking in. But once we are swimming around and I have my head looking up and ahead with my body horizontal, then move my arms that is when I start to feel the cold down my back a bit...

Sounds like pumping. The cut of the suit is critical as well as the fit to solve this. Generally speaking, one thicker layer of an ideal fitting wetsuit is more efficient than two layers because there is only one layer of water for your body to heat. Many divers use another layer to make up for a poor fit and leaky neck area.

Another important factor is depth. Wetsuit material compresses so the deeper you go the less insulation value remains. Do you notice any difference and how deep do you normally dive?

 

[WhyMe]

I don't dive that deep. Usually 80' max and in Cozumel anyway, you seem to drop down to the greatest depth first, which this last trip was on one dive 100' or so, then as the dive goes on you seem to be at 50'-40' for quite a while. I feel colder at the end of the dives which are shallower so I think it's a function of time not depth. Though the 10' to the surface seems to feel much warmer than even just 20' deep so the last few minutes are better

Y'all have given me a few options to consider. The concept of getting warmer is simple but achieving that depends on many factors and your experience has helped me determine what my biggest issues are!

 

[uncfnp]

...Generally speaking, one thicker layer of an ideal fitting wetsuit is more efficient than two layers because there is only one layer of water for your body to heat...

I had often wondered which was more efficient, single or multilayers but could find no research on it. I think I even asked that question on SB once but never really got an answer.

I like the versatility that layering gives me and that I can focus on core yet leave my arms and legs relatively free. I have never noticed a problem with my extremities in fewer mils than my core.

To the op, I don't know if it is a factor for you but the hooded vests also makes it easier to deal with longish hair.

 

[WhyMe]

I really like how the cap holds my hair back and keeps it from getting tangled in the strap for the mask! I can see the hood being even better in that respect.

 

[Akimbo]

…I like the versatility that layering gives me and that I can focus on core yet leave my arms and legs relatively free. I have never noticed a problem with my extremities in fewer mils than my core.

To the op, I don't know if it is a factor for you but the hooded vests also makes it easier to deal with longish hair.

Efficient isn’t always the most functional. For example the material can become so bulky that it actually causes pumping because it doesn’t move with your body as well. Adapting to different temperatures is another important consideration. Sure, one 14mm layer would be more thermally efficient than two 7mm layers, but I wouldn’t want it in my armpit.