Is Aluminium Foil a Good Insulator of Heat

If used properly, aluminum foil is a good insulator; If used improperly, aluminum foil is a bad insulator. It is a good thermal reflector, and since air/water cannot pass through it, it can also prevent heat evaporation and convection. But its thermal conductivity is very good, so if it directly contacts something, it will not be well insulated.

Aluminum is or is not a good thermal insulation material?

Aluminum is both a great thermal insulation material and a terrible thermal insulation material (or a good thermal conductor). How can this be true?

Don't worry. I also spent a little time to understand this concept, but I will explain it briefly. Understanding it will help you use aluminum foil correctly.

Heat is transferred to and from objects in three main ways.

Conduction

When one object touches another, heat passes through it (imagine a pan on a hot stove).

Aluminum foil is a good thermal conductor, which means it is a poor insulator when it is in direct contact with hot things. It is also thin, and when it is in direct contact, heat can pass through it very easily.

This is the type of heat transfer that aluminum is not good at blocking.

Convection

Heat can flow from one area to another through liquid or gas (imagine a hair dryer blowing hot air through a room or pushing hot water to the other side of a cold bath)

Since water and air cannot pass through, aluminum foil can prevent the evaporation of hot water/gas in food. This prevents a large amount of heat loss due to convection.

Radiation

Heat can be moved electromagnetically by radiation (imagine the sun passing heat to us through vacuum space, or the laser pointer emitting light to the distance)

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