20 SILOS: CONSTRUCTION AND SERVICE 



importance than has usually been supposed. As will be seen 

 in the following paragraphs, air does not conduct heat away 

 from silage as rapidly as building materials; therefore, as 

 little material as possible should extend continuously from 

 the inner to the outer parts of the wall. Air spaces are of 

 considerable advantage, and the larger the percentage of air 

 space the better. However, it is very questionable if a man 

 who must be careful of his dollars can afford to let this ques- 

 tion of warmth influence his choice of materials to any great 

 extent. 



So many conditions enter into the question of freezing 

 silage, that it is very difficult to form any conclusion without 

 examining carefully a large number of silos which have been 

 cared for in a similar way, having similar good roofs, doors, 

 and chutes, and which are similar in exposure to cold winds, 

 and are fed down to about the same place, at about the same 

 rate. It is very doubtful in the mind of the writer whether 

 or not there is much difference to be found between the loss 

 of heat through a 2-inch stave wall and through a 6-inch 

 concrete wall. The hollow wall, such as cement block, clay 

 block, and monolithic concrete, has some advantage, but it 

 is questionable if an 8-inch clay block wall is any better in 

 this respect than a 4-inch. That is, the air spaces are not 

 separate, and there is more material extending across the 

 wall in the case of an 8-inch wall than in a 4-inch. 



Air Spaces in Walls. It is always a good thing, so far as 

 warmth is concerned, to prevent the circulation of air in the 

 wall spaces. To illustrate, suppose the air space is vertical 

 and the air free to circulate. When the silo is half emptied 

 and the weather cold, the air is slightly warmed in the lower 

 part of the wall by contact with the inner side of the wall 

 next to the silage. This causes it to rise, carrying heat from 

 the silage up to the colder parts of the walls at the top of the 



