Abstract: A roof ventilator comprising a pipe provided with an opening therein, a shutter means adapted to be raised above or lowered over said opening, a supporting arm associated with a rotating shaft which is rotatably disposed within said pipe, a fan means housed in said pipe below said shutter means and attached to said shaft, means for rotating said shaft and the fan associated therewith, said shutter means being supported on said supporting arm by two pairs of foldable arms, each pair of arms being pivotally connected to each other and to the terminating top end portion of said supporting arm at one end and to the shutter means at the other end so that a unitary upward movement of said pairs of foldable arms and said shutter means is achieved by the rotation of the fan means disposed therebelow.