GREENHOUSE HEATING 161 



plant may be used to furnish steam for soil 

 sterilization. 



All the above apply more especially to 

 small ranges than to large ranges. As a 

 rule, hot water is more generally used in 

 ranges covering up to 20,000 square feet and 

 steam in larger ranges, although there are 

 many exceptions. At present the tend- 

 ency seems to be toward the use of hot water 

 rather than steam. 



In an investigation recently made by the 

 author among a large number of greenhouse 

 owners, 86 per cent, of those having 20,000 

 square feet or more under glass preferred 

 steam heat. The chief reasons stated were, 

 "better control," "cheaper maintenance/' and 

 "less shade from pipes." Six per cent, pre- 

 ferred a combination of hot water and steam. 

 The remaining 8 per cent, preferred hot 

 water, stating as their reasons, "steadier 

 heat," "plants grow better," "pipes do not 

 rust out during the summer as with steam," 

 and "cheaper to operate in spring and fall 

 when little heat is required." 



Of those having less than 20,000 square 

 feet under glass, 74 per cent, preferred hot 

 water, giving in addition to the reasons 



