GREENHOUSE CONSTRUCTION AND HEATING 



31 



The ridge ventilators may be hinged to the ridge or to 

 the header. Some growers prefer hinging them at the 

 ridge (Fig. 1), because the sash practically prevent snow 

 and rain from entering the houses, even when the ven- 

 tilators are open very wide. Other growers prefer hing- 

 ing at the header (Fig. 18), claiming that to be the proper 

 place because of the fact that the condensed water on the 

 glass of the ventilators runs off instead of forming ice to 

 interfere with the closing of the sash a frequent 

 occurrence when the sash are hinged at the ridge. 



The ventilating sash may or may not be continuous. 

 When the ends of the sash are properly fastened to each 



Fig. 18. Semi-iron house. Note large door and ventilators on sides and end. 



other, there should be no difficulty in operating them. A 

 run or two of glass between the sash is preferred by 

 many growers, but continuous ventilators are increasing 

 in popularity. Sometimes ventilators are placed at the 

 ends of the houses, as shown in Fig. 18. 



The ventilating machines should be of the most ap- 

 proved type, and conveniently located. It is often best to 

 have them near the doors at the ends of the houses. 

 There are several excellent machines on the market. 



