Working or living in the extremely cold atmosphere requires the fabric that protects the human body from heat loss. Thermal comfort of a fabric is necessary along with low thickness, lightweight, and low bulk. Extraordinary thermal insulated fabric can be achieved by combination with nanotechnology. This book reveals fundamental concepts of heat and mass transfer through a fabric along with the synthesis of amorphous silica nanoporous material. Various attributes and levels of precursors provide information of the particle size and their distribution. These nanoparticles get embedded into the knitted fabric that has various process parameters chosen to get lowest possible thermal conductivity. A scientific approach with statistical proofs lands with perfect process parameter of knitted fabric combined with the nanoporous material forms a composite that has the ability to protect the human body against extreme cold.