FUEL AND HEATING 227 



The cost of building sub-irrigation benches properly 

 is two or even three times as great as for the ordinary 

 cypress bench, and as varieties differ in their likes and dis- 

 likes it was found also that some did markedly well by sub- 

 irrigation, while others did not. The cost of a surface 

 watered or ordinary bench may be taken at 22 cents per 

 square foot; the sub-irrigated bench would cost S1.50 to 

 Si. 75 or even S2 per running foot, complete, according to the 

 locahty. It was this question of cost perhaps more than 

 anything else, and the lessening returns from cut blooms, 

 that influenced the growers to retain the old type of bench 

 as against the sub-irrigated one. 



Heating and Fuel 



Regarding the amount of radiation required to main- 

 tain a given temperature in a greenhouse, there is no 

 hard and fast rule that can be apphed in all cases, since 

 so much depends on the type of house, location, size and 

 method of glazing. As a general rule, the following table, 

 giving the lineal amount of 2 in. pipe for hot water heat, 

 with water at a temperature of 160 deg.; also the square 

 feet of steam radiation at 5 lbs. pressure, will show how 

 much is necessary to maintain the temperatures as stated, 

 when the mercury outside is at zero. These amounts 

 are based on the requirements of a greenhouse 100 ft. x 30 

 ft., with cement walls 2 ft. high, 4 ft. of glass on each 

 vertical side, height of ridge 13 ft. 6 in., and both ends 

 glazed and exposed: 



