Insulation is material designed to prevent heat or sound from being transmitted from one area to another. It's normally used to keep heat and/or sound in or out of your home, or to confine it to certain parts of your house. Insulation can work in a number of different ways, but it most commonly incorporates materials that consist of millions of tiny pockets of air. Still air is an extremely good insulator, and trapped pockets of air are what give most types of insulation their high thermal resistance. 

 

Probably the first type of insulation people think of is some sort of batt, usually glass wool or rock wool; batts are light, fluffy-looking panels of material that sit inside the frame of your home - typically either in wall spaces or in your ceiling. Batts are made of fibrous materials, and work by trapping pockets of air with fibers.