The handle of steel or iron handles of kettle gets hot when heat is transferred from the one portion of the body to another by means of conduction. But heat transfer takes time to reach from one point to another. Maximum distance takes maximum time to get hot.Because the vibration of the atom reach there by passing the whole path.
Its very difficult to maintain the same temperature in a room .Heat can escape from the room by conduction of heat through the walls,ceiling ,door or windows, to retain same temperature we use insulator .There are different types of insulators .Use of insulator is to maintain the same temperature through less conduction of heat .The insulator are different for different propose as for ceiling the insulator are different then for window and door it is different .
If we use two glasses in spite of one then it will be better insulator then second one because gap between two window is filled with air and air is not a good conductor with respect to solid glass.