3 20 



VENTILATORS 



an angle of about 30 degrees with the vertical. A wind or a storm will 

 close the windward shutter and open the leeward shutter wider. The 

 eaves of the monitor are made to project, so that very little of the storm 

 enters. 



Cost. The shop cost for louvres is ordinarily about I cent per 

 pound. To this must be added the cost of the sheet steel and the cost 

 of the framework and details. In 1900 louvres without frames cost 

 about 25 cents per square foot. 



Circular Ventilators. Circular ventilators are often used for ven- 

 tilating mill buildings in place of the monitors, and on buildings requir- 

 ing a small area for ventilation. They are made of galvanized iron, 

 copper or other sheet metal, and are usually placed along the ridge line 

 of the roof. 



'STAR" VENTILATOR 



Globe Ventilatoi 



GARRY VENTILATOR 



Acorn VentiMtor. BUCKEYE VENTILATOR. 



FIG. 161. CIRCULAR VENTILATORS. 



