Ventsetter 4000 Ventsetter 4000 Greenhouse Outstanding Features Superior strength ROLL-FORM truss, purlins and gutters insure unmatched structural integrity. Condensate control features built in. Available with extended columns to accommodate overhead retractable shade systems. Value Components are shipped pre-punched and cut to length, simplifying the installation. ROLL-FORM components nest one into the other during shipment, substantially reducing freight rates.