Generally, ice bar sellers keep the big ice bars covered with jute sacks. Explain why?

Ice blocks and Jute sacks 

Ice-sellers keep big ice bars or slabs covered with jute sacks. They do it to slow down the melting of the ice bars. The ice bars absorb heat from the surroundings and start melting. When they are covered with jute sacks, heat cannot reach the ice bars. The jute sacks function as insulators of heat. The fibers in the sacks prevent the entry of the external warm air inside the ice block which can melt the ice.