I am curious to know, what make air in itself a good insulator? Just to clarify I am not talking about materials that trap the air and stop the convection current from moving, from a hot surface to a cold one. Is it because of the thermal capacity of air, which I believe is something like 1.0084 kg/c. My reason for thinking this is because air is classed as a fluid. So when I look at something like an island surround by water it take the water long to lose it heat that the island due to have a higher heat capacity.