When you go to the sauna you may sit in a room with 90°C+. If it is a "commercial" sauna it will be on for the whole day. How does it come that when you sit on the wood you don't get burned?
I believe this question is different than the "classical" one concerning the "feeling" of heat, which may be explained with a low heat transfer. After a much shorter time other objects seem much "hotter", and the heat transfer is not different (as it's still a room filled with the same air).
My guess would be that the reason is the heat capacity but I cannot really explain it. In my understanding a capacity is the ability to store something (heat, charge, …). Why should an object be cooler if it can store less heat? Also, cannot this be ignored in this case, as the wood is exposed to the temperature for a very long time?
Best Answer
First of all, I hope you sit on a towel. But even when you touch wood with your bare skin, you don't get burned. This indeed has to do with thermal conductance.
The point is not the heat transfer between the wood and your skin, but rather the heat flowing within the wood. When you touch the surface, your skin and the wood at the very surface equalize their temperature. But because it's only a thin film of wood at the surface, not much heat is transferred. This relatively small amount of heat is quickly transported away from the skin into the body by the high thermal conductance of the human body (many processes play a role here, including blood flow carrying heat away). To further heat up your skin, heat from deeper down in the wood needs to get to the surface, so it can be transferred to your skin. This is the process that is slow whenever a material has low heat conductance, like wood, and allows the skin to transport energy away quicker than it can come from the bulk to the surface, so you don't get burned.
Compare this to touching metal, where the heat stored deep in the bulk of the material can rush to the surface rather quickly, if something cool is touching the surface. Much more heat is transferred and you will burn your hand.
The low heat capacity of a wooden bench certainly also plays a role, simply because if there's little heat stored in the material, it has less energy to heat up your skin with.