APPLICATION OP REFEIGEEATION TO HANDLING OF MILK. 51 



Planing-mill shavings are better for insulating purposes than 

 sawdust. They are elastic, do not settle rapidly, and will not absorb 

 moisture as readily as sawdust, and, most important, can usually be 

 had in very dry condition. They should be odorless, free from dirt, 

 bark, and chips, and should be well packed into place to prevent 

 future settling. About 9 pounds per cubic foot is considered the 

 proper density to which they should be packed. 



Sawdust has in the past been used to a great extent in rural dis- 

 tricts for insulating the walls of small cold-storage buildings, due to 

 the fact that it is available in most country districts, and generally 

 may be had without cost. It is not a satisfactory material, however, 

 for insulating purposes, as it is always more or less damp. The damp- 

 ness not only destroys its insulating value, but it favors the growth of 

 molds and bacteria, first in the sawdust itself and then in the walls 

 of the building. The rotting and the consequent heating causes the 

 sawdust to settle and leaves open spaces, which further weaken the 

 insulation. It also furnishes an ideal nesting place for rats and mice, 

 and the tendency of these rodents to carry matches into their nests and 

 to start fires is well known. When sawdust or mill shavings are to be 

 used they should be thoroughly dried before being put into the walls. 

 Furthermore, if air is allowed to circulate in the shavings or sawdust 

 moisture will be deposited in warm weather, and then, again, in cold 

 weather it will dry out. This being repeated for several years will 

 cause the boarding and shavings to rot. If, however, the shavings 

 or sawdust is surrounded by waterproof paper and boarded, the con- 

 densation will not occur and deterioration will be prevented. 



In deciding upon an insulating material for cold-storage purposes 

 the following points should be carefully considered: Efficiency as 

 a heat insulator; whether or not it will retain its efficiency indefi- 

 nitely; structural strength; the effect of moistufe; uniformity of insu- 

 lating value; whether fireproof or not; space occupied; first cost; 

 cost of installing, etc. 



The greater portion of the refrigeration required for cooling cold- 

 storage rooms is done to remove the heat that leaks through the walls, 

 floors, and ceilings, and only a small part is required to cool the goods 

 in storage. As previously stated, it is necessary to pump out, so to 

 speak, the heat that enters from the outside after the goods are once 

 cooled to the desired temperature. 



Take for example a creamery cold-storage room 10 by 10 by 10 

 feet, inside dimensions, .which is of sufficient capacity to hold a 

 week's output of butter from a creamery making 2,000 pounds daily. 

 The butter will come from the churn at approximately 58° F. The 

 average outside temperature of room is assumed to be 75° F., and the 

 inside temperature 32° F. It is further assumed that the walls, 

 floors, and ceiling are insulated for a heat transmission of 3 B. T. U. 



