FRUIT STORAGE 95 
waste cotton, mineral wool, and even shavings or saw- 
dust have been used with good results. 
Insulating Materials.—The construction of a modern 
storage house calls for 
great care and attention 
to details of the work. 
Carelessness or the use of 
poor material will often 
result in the inability of 
the operators to control 
the temperature of the 
house. All of the differ- 
ent materials used in con- 
struction have different 
insulating values. The de- 
gree with which they will 
prevent the passage of 
heat or cold is different 
with each materfal used. 
For determining the insu- 
lating value of the dif- 
ferent materials, certain 
units in measuring heat 
have been established. 
One used in England, 
and to a considerable ex- 
tent in the United States, Fig. 83.—FIBER-FELT 
is commonly known as the 
British Thermal Unit, or, as ‘it is usually written, 
B. T. U. It means the amount of heat required 
to raise the temperature of one pound of water 
one degree Fahrenheit. The French and German 
Fig. 81—PRESSED CORK 
Fig. 82—MINERAL WOOL 
