Insulation works by blocking one or more methods of heat transfer. There are 3 different ways that heat (energy) is transferred (gained or lost): Conduction is the transfer of energy from one molecule to another by direct contact. This is as simple as when you place a pot on a stove to boil. The heat is conducted from the flame or heated surface into the pot and the water.  Convection is the movement of heat by a fluid such as water or air. Think of a hot air balloon. The air is heated from the burner and rises in the balloon creating lift. The cooler air falls to be reheated again. The same effect is seen in the formation of thunderstorms. Hot air rises until it’s cooled, condenses with water vapor and falls back to repeat the cycle. Radiation is the transfer of heat by electromagnetic waves. One of the most familiar forms of radiation is heating via a microwave oven. Microwaves emit a frequency that causes water molecules to vibrate faster and have more energy which we feel as heat. Additionally you can feel thermal radiation after a hot day, the ground and especially concrete sidewalks or streets will radiate heat back into the environment as they cool and try to reach equilibrium.