What exactly happens when an insulating material comes in contact with heat through any mode (conduction, convection, or radiation). Something like aluminized mylar will reflect the heat back. How exactly does it block the transfer of heat?

  • $\begingroup$ How does a vacuum stop heat transfer? think of a vacuum flask... $\endgroup$
    – Solar Mike
    May 12 at 11:26
  • $\begingroup$ Metal surfaces (like your aluminized mylar) look like a mirror when viewed in IR. They reflect the photos instead of absorbing them. $\endgroup$
    – Drew
    May 13 at 19:45

2 Answers 2


The difference between an "insulator" and a "conductor" is subjective. All materials transfer heat and reflect some heat at a boundary. Insulating materials are chosen because their reflectivity is high, their thermal conductivity is low, or both.

Note that some materials are chosen because they reflect (or absorb) photons, while others are chosen for their properties related to phonons.


If you see at molecular level the mechanism responsible for heat transfer,the adjacent molecules transfer vibration energy with their neighboring molecules,which results in heat transfer.

Condition in insulating material

The molecules of a typical insulating material are held in place rigidly as compared to heat conducting material,this hinders the heat transfer in insulating materials.

  • $\begingroup$ Not necessarily. vacuum, for one, is a good insulator. $\endgroup$ May 12 at 12:29
  • $\begingroup$ And diamond is a great conductor, and the only things not 'held rigidly' are phonons $\endgroup$ May 12 at 12:31

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