DAIRYING 103 



The construction of the ice storage house and the cold room 

 or refrigerator, however, should be somewhat different because 

 of the purpose for which the two are used. First, the refrigerator 

 should have an insulated concrete floor, while the floor of the ice 

 house should be covered with sawdust or some insulating ma- 

 terial on which the ice is stored. In one case the insulation is 

 above and in the other it is below the floor. 



Second, the construction of the walls of the two buildings 

 must be somewhat different. A thin air space is needed in the in- 

 side wall of the ice storage house next to the ice or the sawdust 

 in order to prevent the dampness of the ice penetrating the insu- 

 lated walls of the ice house. The extra air space is not always 

 necessary in the refrigerator because in this room the air must 

 be dry and the ice is not placed near the walls, consequently they 

 are not exposed to the dampness that comes from contact with 

 ice stored against them as in the ice house. 



849. Dry air is one of the most important things to be 

 secured in a refrigerator. First, because it prevents the growth 

 of moulds which may be responsible for a musty odor in the 

 refrigerator, and second, because it makes the insulation effective. 

 A damp atmosphere will penetrate wooden walls which, when 

 wet, become good conductors of heat, and their insulating value 

 is thus much reduced. 



INSULATING MATERIAL. 



850. The prime object of insulation is to prevent the passage 

 of air currents and protect the space enclosed from changes in 

 the outside temperature. The cold temperature which may be 

 obtained by means of ice is held in the room by the insulation. 

 Protection by insulation is obtained by means of walls varying 

 in thickness, but built in such a way that currents of air cannot 

 pass through them. The construction ordinarily used for this 

 purpose is a board, a brick, or a cement wall on the outside, next 

 to this is a space varying from four to twelve inches, which is 

 filled with some insulating material such as shavings, sawdust, 

 mineral wool, etc., and inside of this a covering or wall built of 



