This is something that pokes at the back of my mind every time I read a story based on encasement that claims it's trying to be realistic. While in a fantasy story it's perfectly fine to suspend inconvenient realities for the purpose of the story, if the goal is realism, the effect is lost by just sweeping them aside (unless you're hoping that your audience can be Dan Browned).
The biggest problem with encasement (particularly long-term) is that the human body generates a LOT of heat. Under normal circumstances, it has to do that in order to continue functioning properly - it has a lot of surface area through which the heat is dissipated. When the body is encased, preventing proper ventilation between the covering material and the skin, that heat has nowhere to go and the body temperature rises to dangerous levels relatively quickly - from personal experience: maintaining a neck-to-toe thin layer of latex for about 2 hours was enough to raise my body temp by 4 degrees Fahrenheit (equivalent to a dangerously high fever temp).
Aside from the direct harmful effects of temperature elevation, there are also several related effects. When the body is immobilized (and even moreso when it is under compression), blood circulation is slowed and restricted, thus reducing even the effect of local ventilation on an encasement: you may cool one area, but the reduced movement of heat through the body will only result in hot and cold spots, rather than equalizing the temperature at a safe level.
Further, encasement also defeats the body's natural cooling mechanism: sweating. Sweating works because water has a relatively high specific heat value, so more heat is moved out of the body in moisture than in air. However, it relies on that moisture then being allowed to evapourate into the air, rather than simply collecting the heated water (and water vapour) against the body. This results in a number of additional complications:
Sweat leeches moisture out of the body. This can lead to dehydration fairly quickly if not addressed appropriately.
Sweat trapped between the body and the encasing material fails to dissipate the heat, thus negating its cooling function.
Sweat trapped between the body and the encasing material also has a tendency to breed fungal and other infections which will cause massive tissue damage to the flesh - and eventually to the vital organs of the body.
The heat dissipation issue becomes significant LONG before questions of nutrition, elimination of other bodily waste, muscle atrophy, madness, or any of the other problems that are addressed in careful detail in encasement stories that claim to be aiming for realism - and yet this one is so rarely even taken into consideration. It frustrates me.
No, I'm not a creative writer, nor do I even have a workable solution to the heat problem, so I can't write any better. However, every time I read a story that addresses the minor or later problems with long-term encasement, but completely ignores the immediate life-threatening consideration, I feel like I've been misled by the claim of a 'realistic' encasement story.
