| 摘要 |
A roof ventilator comprises a base plate insertable in a roof assembly and having an opening receiving a panel leaving a free passageway at the lower end. The panel having a plurality of pairs of transverse louvers defining louver openings. Alternate louvers extend outwardly and upwardly and outwardly and downwardly from the panel, the cross-sectional area of the louver openings tapers outwardly and the endmost louvers converge outwardly of the panel. A projecting ridge is formed in the base plate beyond the lower transverse edge of the passageway and has an upper side which is connected by a step to an inclined section of the bottom wall of a duct communicating both with the louver openings and passageway and the attic or rooms below. Irrespective of the direction of currents of air flowing along the roof negative pressure is produced inside the duct. |
