No. 4.] FARM ICE HOUSES. 165 



material for the construction of ice houses. Dead-air spaces may be 

 formed by an extremely careful construction of walls, but this would 

 be entirely impractical in a farm ice house, and if dead air is to be 

 used as an insulating material it must be obtained by the use of 

 sawdust and shavings, both of which materials are fairly available 

 to Massachusetts farmers. When tightly packed between the ice 

 and the walls of the storage house, shavings and sawdust enmesh in 

 their crevices large quantities of air which is practically immovable 

 in character, or dead, as storage-house constructors speak of it. Con- 

 siderable air is also contained in the pores of the sawdust and shav- 

 ings, and it is this immovable air, even more than the material itself, 

 which makes of sawdust and shavings good insulating materials. 

 Hay is less desirable than sawdust or shavings because the air en- 

 meshed in it is not so finely divided, and may circulate to some 

 extent. It takes a larger quantity of hay, and hence more space 

 between the ice and the walls of the building, to give the same amount 

 of protection with this material as with shavings or sawdust. For 

 the most perfect result from the use of hay, sawdust and shavings 

 the material must be dry, as any of these materials when wet are 

 fairly good conductors of heat. For the best result at least 8 inches 

 of well-packed sawdust or shavings should be used between the ice 

 and the walls, and the top of the ice should be covered to a depth of 

 10 inches. If hay is used at least 12 inches should be allowed be- 

 tween the ice and the walls, and 14 or 15 inches on the surface of 

 the ice. 



Drainage is necessary because the water from the melting ice is a 

 good conductor of heat, and if it accumulates in the bottom of the 

 ice house and stands up about the lower tiers of ice it will cause a 

 rapid loss. It will, moreover, soon soak the insulating material and 

 thus permit rapid conduction of heat directly from the walls to the 

 main stack of ice. It is also unsanitary, and will cause a rapid 

 rotting of the timbers in the ice house. 



Drainage is secured by the selection of a well-drained site, or by 

 placing a tile beneath the ice house. Where the house must be con- 

 structed on a soil which does not drain well naturally, an excavation 

 should be made the size of the house and 12 inches in depth. In the 

 center of this excavation should be placed a row of tile leading to a 

 satisfactory outlet, and the entire excavation filled in covering the 

 tile with coarse gravel or cinders. 



Ventilation should be arranged for over the top of the ice stack. 

 Where the building is completely closed, the air above the ice beneath 

 the roof becomes highly heated and causes a rapid loss by direct 

 radiation of heat to the ice. Reliance for insulation is placed on the 

 sawdust, shavings or hay which immediately covers the ice, rather 

 than upon the main body of air above this insulated covering. By 



