well the amazing scientist Matt Edge found out that nilon is best with some cheese wirte :)
This material is a thermal insulator.
Because it traps the heat that comes from your body from escaping, so you have more heat so it keeps you warm.
It depends, in general I would say body heat.
One material that is known for keeping heat inside is insulation. Insulation works by trapping heat within its fibers or layers, creating a barrier that slows down the transfer of heat from one area to another. Common insulation materials include fiberglass, foam, and mineral wool.
An example of a material that keeps heat from being lost is thermal insulation, such as fiberglass or foam. These materials work by trapping air pockets to reduce heat transfer through conduction, convection, and radiation. By slowing down the movement of heat, thermal insulation helps to maintain a comfortable temperature in buildings.
Your body continuously makes energy that keeps your body warm.
As wool keeps you warm and retains body heat
The material of the body and its specific heat capacity, its mass, the temperature difference between the body and its surroundings, and the duration of heat exposure all affect the amount of heat a body will store.
Aluminumm foil paper keeps many things warm. It keeps things warm because instead of absorbing the heat that wants to get into the material you wrapped foil paper on, the foil paper refelcts back so that the heat does not absorb into the object or material.
Rabbits can retain their body heat pretty well when they grow fur, until then, the mothers fur in the nest keeps them warm. --Newfoundland97
A common material that traps air and reduces heat loss is insulating foam. This material creates a barrier that helps to prevent the transfer of heat and keeps spaces insulated. It is often used in walls, roofs, and insulation products to improve energy efficiency.
Your body keeps its temperature when you're hot because of sweat. It keeps your body temperature cool even if you feel hot. People who don't sweat have to be really careful when they do anything physical or are in the heat. Some of them even have to wear special cooling suits.