104 DAIRYING 



matched lumber; this is then covered with two thicknesses of 

 damp proof paper with edges overlapping at least two inches, 

 and on this paper another layer of matched ^lumber is placed. 

 This last layer gives the inside finish of the room. 



851. The so-called empty, "dead-air space" should be 

 avoided, or no effect made to secure it, as a strictly dead-air 

 space is nearly impossible to obtain. There will necessarily be a 

 difference in the temperature of outside and the inside wall en- 

 closing such an empty space and this difference in temperature 

 will cause the warm air to ascend on one side, and the cold air to 

 descend on the other, thus creating a current in this "dead air" 

 space and interfering with true insulation. It is also about im- 

 possible to get the walls so carefully built that there will not be 

 cracks or nail holes in them which will allow currents of air to 

 pass through the "dead air" space. 



When such an empty space is filled with dry shavings, saw- 

 dust, etc., these currents of air are prevented and the inside room 

 will be insulated and protected from changes of the outside 

 temperature. 



852. It is very essential, first, that all insulating material 

 should be absolutely dry when placed in these dead air spaces; 

 (if shavings, sawdust, etc., are used, these should be spread out 

 in a thin layer and thoroughly dried before using) ; second, that 

 the walls should be built so that cracks or nail holes are few, if 

 any, as both these defects will diminish the effect of insulation; 

 third, the lumber of the walls should be matched boards, and no 

 tar paper should be used because of its odor; fourth, protect the 

 insulation from dampness that may come from melting ice, by a 

 thin air space and the use of damp proof paper. 



CONSTRUCTION OF FLOOR OF REFRIGERATING ROOM. 



853. A wood floor of any kind is not suitable for a farm 

 refrigerator room, because when it is wet it is a good conductor 

 of heat and it decays easily. Dry wood only is suitable for a cold 

 room, and it is not probable that the floor of a dairy refrigerator 

 will be kept dry all the time. 



