In practice, simply increasing the number of layers past a certain value will not improve performance. As the no. of layers increases, radiative heat transfer becomes small compared with conductive “shorts” between layers and other losses. Taking all these factors into account, about 25 layers usually suffice to obtain a minimum overall conductance value.

==== Working of MLI ====

Lets understand this with an example.

Imagine a square meter of a surface in outer space, at 400 K, with an emissivity of 1, facing away from the sun or other heat sources. From the Stefan–Boltzmann law, this surface will radiate 1452 watts. Now imagine placing a thin (but opaque) layer 1 cm away from the plate, thermally insulated from it, and also with an emissivity of 1. This new layer will cool until it is radiating 726 watts from each side, at which point everything is in balance. The new layer receives 1452 watts from the original plate. 726 watts is radiated back to the original plate, and 726 watts to space. The original surface still radiates 1452 watts, but gets 726 back from the new layers, for a net loss of 726 watts. So overall, the radiation losses have been reduced by half by adding the additional layer. <br \>