Here are some examples of good insulators:

* Air: This is why double-paned windows are more energy-efficient. The air trapped between the panes acts as an insulator.

* Fiberglass: Commonly used in insulation for homes and buildings.

* Foam: Used in packaging, cups, and even some building materials.

* Wood: A good natural insulator.

* Wool: A common material used for clothing and blankets.

* Rubber: Used in many applications, including electrical insulation.

The opposite of an insulator is a conductor, which allows heat to pass through easily. Metals like copper and aluminum are good conductors.