Heat Loss through the Head
- Thread starter BoltSnap
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
pjhansman
Contributor
Heat loss from any part of the body is largely dependent upon surface area. The only time the head loses more than it's share of body heat is when it is bare while the rest of the body is covered.
OP
But isn't the amount of circulation present in the area has a lot to do with it? Would lose more heat from my feet or my head if I am exposing the same area of both?
But this would apply to any other part of the body. If I cover my head and I expose my hands that are the same area of my head, would I lose more, less or the same amount of heat compared with exposing the head?
The surface area of the head, according to a variety of first-aid books, is about 9-10% of your body.
Blood vessels in the head are closer to the surface and perhaps somewhat denser than in other parts of the body. Maybe this raises the cooling potential of the head to 12% ... 15% if it's windy and cold.
In my opinion it can't be much more than this.
HOWEVER.... in a diving context there is a mental aspect to cold as well as a physical aspect. The physical cooling may be only 10% but if your head, hands and feet are cold then it *feels* colder than it really is. I think this has to do with the body's survival mechanisms and the signals your brain is getting.
For example. When the water is 4C /39F and I'm diving with wet gloves it feels colder then when I'm diving with dry gloves. The difference can be pronounced. I can dive maybe 15 minutes longer with dry gloves than I can with wet gloves in the cold before I feel uncomfortable.
Same with the cap. I've adopted a habit in cold water of inhaling through my mouth and exhaling through my nose. When I exhale through my nose, the warm air coming out of my body goes into the cap and warms up my head. It can make a difference again of 10-15 minutes before I become very uncomfortable in the cold.
Before I discovered these tricks, I was shivering at 30 minutes into a dive in 4C water and wondering what the hell I was doing there..... Since applying them (dry gloves, breathing into the cap) I can easily manage 40-45 min without feeling uncomfortable at all.
R..
Blood vessels in the head are closer to the surface and perhaps somewhat denser than in other parts of the body. Maybe this raises the cooling potential of the head to 12% ... 15% if it's windy and cold.
In my opinion it can't be much more than this.
HOWEVER.... in a diving context there is a mental aspect to cold as well as a physical aspect. The physical cooling may be only 10% but if your head, hands and feet are cold then it *feels* colder than it really is. I think this has to do with the body's survival mechanisms and the signals your brain is getting.
For example. When the water is 4C /39F and I'm diving with wet gloves it feels colder then when I'm diving with dry gloves. The difference can be pronounced. I can dive maybe 15 minutes longer with dry gloves than I can with wet gloves in the cold before I feel uncomfortable.
Same with the cap. I've adopted a habit in cold water of inhaling through my mouth and exhaling through my nose. When I exhale through my nose, the warm air coming out of my body goes into the cap and warms up my head. It can make a difference again of 10-15 minutes before I become very uncomfortable in the cold.
Before I discovered these tricks, I was shivering at 30 minutes into a dive in 4C water and wondering what the hell I was doing there..... Since applying them (dry gloves, breathing into the cap) I can easily manage 40-45 min without feeling uncomfortable at all.
R..
CT Sean
Contributor
It's a myth, based on a flawed military study.
see here:
Scientists debunk myth that most heat is lost through head | Science | The Guardian
see here:
Scientists debunk myth that most heat is lost through head | Science | The Guardian
I believe that when cold the body reduces blood flow to some areas. The head is an area it does not reduce flow since the brain is critical.
For another similar slice, go to: https://www.msu.edu/user/manns/myths.html and see what Dr Bookspan says at #18.
The rest of the article is interesting too.
The rest of the article is interesting too.
OP
I read it and I am even more confused now, here is what it says:
"18. LOSE MOST OF YOUR HEAT FROM YOUR HEAD? This is a popular myth. Head heat loss is not the majority of heat lost. Not even close. The heat you lose from your head is small compared to the rest of your body, and varies with temperature and exercise.
Head heat loss is linear with temperature, meaning the lower the temperature, the higher percentage head heat loss. At 0 degrees Centigrade, up to about 30 to 35% of heat could be lost through your head at rest. When exercising at about a work rate of 50% of aerobic capacity, head heat loss falls to less than half that.
Even though head heat loss is less than one-third to one-fifth of total heat loss, that is a good amount considering that your head is only about 7-9% of your body total surface area. (But, some people have bigger heads than others in proportion to their stature.) To reduce heat loss, wear a hat."
Bottom line seems to be that you do not loose MOST of your heat through your head. However, it is also suggesting that you loose a lot of heat through your head.
Heat loss is linear with temperature, but it is not proportional. A simple cooling law is that the rate of heat loss is proportional to temperature difference. So if the water temp is 98.6 you lose no heat. Constant of proportionallity depends on materials, any insulation, etc.
So in going from 98.6 to 58.6 the rate of heat loss is 4 times as fast as at at 88.6 ignoring all other factors.
Heat loss is linear with temperature, but it is not proportional. A simple cooling law is that the rate of heat loss is proportional to temperature difference. So if the water temp is 98.6 you lose no heat. Constant of proportionallity depends on materials, any insulation, etc.
So in going from 98.6 to 58.6 the rate of heat loss is 4 times as fast as at at 88.6 ignoring all other factors.
Similar threads
