GREENHOUSE CONSTRUCTION AND HWEATING 33 
most popular size. Glass of this size is generally laid 
with the sash bars 16 inches apart, although a small per- 
centage of vegetable growers lay the glass with the sash 
bars 24 inches apart. Except in full iron construction, it 
is doubtful whether the roof-bars should be so far apart, 
because of the increased breakage by the weight of snow, 
and the difficulty of making and maintaining tight joints 
at the laps. There is probably no objection to the bars 
being 20 inches apart; this distance makes it possible to 
use 20 x 24-inch glass, which costs only a trifle more than 
16 x 24-inch glass. 
Fig. 20.—A corridor leading to the packing room in a large range. 
The greenhouse grower has been quite successful in 
guarding against losses caused by snow, hard winds and 
very cold weather, but his houses are at the mercy of 
destructive hailstorms. To protect him against this loss, 
hail insurance companies have been organized. One of 
the leading companies charges 8 cents a 100 square feet of 
single-strength glass and 6 cents for double-strength. It 
is just as important for the grower to protect his property 
from losses by hail as from those by fire. 
