Heat question?

Question

Why you would fill the walls of a house you were building with fiberglass insulation? to keep heat in but how does that work?

Answer 1

fiberglass doesn't conduct heat

Answer 2

Fiberglass is an insulator, so unlike a conductor, heat does not pass easily through it.  So basically, it is like a barrier for heat.

Answer 3

fiber glass is a poor conductor of heat but more than that it is finely bundled and prevents free air movement within it, without the ability of air to move it cannot transfer heat, works the same way as a blanket or a sweater.