Why the two thin woolen blanckets are warmer than a thick blanket?

Answer 1

Because there is a layer of air between them.

As strange as it may seem, air is a great thermal isolator, even better than most clothing.

The reason it seems it is not is because its movement evaporates water on the surface of our skin, thus diminishing the temperature, making us feel cooler.

The air between the thin blankets is not moving around and will form an isolating layer that acts exactly like another blanket, thus improving the thermal isolation.

This can be seen in action in isolating windows. Most of these windows are basically two sheets of glass separated by air (or a rare gas, but the effect is the same). Since the air is a great thermal isolator, the windows prevent heat exchange better than one made out of a single thick sheet of glass.

Answer 2

Two thin blankets are warmer than a thick one. This may seem strange, but see the "Why are two thin blankets warmer than one single thick blanket?" question to know why it is true.

Although the previous answer was based on the right principle (trapping air), the reasoning was slightly off target.

Answer 3

A partial explanation without getting too technical is that air is a very poor conductor, despite the fact it is a great convector.

When you use several thin blankets you create "dead" (non-moving) air spaces between them, and air that is not in motion will not conduct heat very well, so the heat from your body remains trapped under the blankets and you stay snuggy warm - the more layers of "dead" air the better.

When air is in motion, or is free to move, it transfers heat quite readily, simply by attempting to equalize the warm areas with the cold areas. This is called convection, and is the principal behind the forced air furnace in your home, the heater in your car, and the convection oven on your countertop. Liquids, such as oceans, lakes and cups of tea also distribute heat through convection. When you top up the cup of tea, the cold tea becomes warm quite quickly through convection currents until the entire cup equalizes to one temperature.

Answer 4

Because there is a layer of air between them.

As strange as it may seem, air is a great thermal isolator, even better than most clothing.

The reason it seems it is not is because its movement evaporates water on the surface of our skin, thus diminishing the temperature, making us feel cooler.

The air between the thin blankets is not moving around and will form an isolating layer that acts exactly like another blanket, thus improving the thermal isolation.

This can be seen in action in isolating windows. These windows are basically two sheets of glass separated by air. Since the air is a great thermal isolator, the windows prevent heat exchange.

Answer 5

The exact situation would surely depend on the specific blankets. However, between two blankets, there would be an additional layer of air, that helps to isolate the heat, in addition to any isolation provided by the blankets themselves.