Applications of thermal conductivity :

1. 

• Thick walls are used in the construction of cold storage rooms.
• Brick being a bad conductor of heat is used to reduce the flow of heat from the surroundings to the rooms.
• Better heat insulation is obtained by using hollow bricks. 
• Air being a poorer conductor than a brick, it further avoids the conduction of heat from outside.

2. Street vendors keep ice blocks packed in saw dust to prevent them from melting rapidly.

3. The handle of a cooking utensil is made of a bad conductor of heat, such as ebonite, to protect our hand from the hot utensil. 

4. Two bedsheets used together to cover the body help retain body heat better than a single bedsheet of double the thickness. Trapped air being a bad conductor of heat, the layer of air between the two sheets reduces thermal conduction better than a sheet of double the thickness. Similarly, a blanket coupled with a bedsheet is a cheaper alternative to using two blankets.