described above with the following exceptions described below except for the second set of louvers 270 the reference numbers used in describing features and elements of roof ventilator 220 are the same as those of roof ventilator 20 fig3 but preceded by a numeral u201c 2 u201d so that the description of roof ventilator 20 fig3 can be easily applied to roof ventilator 220 in this alternate embodiment a second set of louvers 270 a mirror image of the first set of louvers 228 a is located in a v shaped configuration such that the second set of louvers 270 extend from the base of the outboard set of supports at a predetermined angle to intersect the inboard set of supports in this embodiment the angle is about 25 u00b0 but any angle up to 90 u00b0 can be used depending on the height and intersection point of the outboard set of supports in this embodiment the band of fibrous material for the filter device 228 includes slits 248 that are cut to a depth that is substantially equal to the height of the support or deeper or even all the way through the filter device 228 the slits 248 run longitudinally and are suitably cut at a distance spaced from each other equal to the distance between each support the filter device 228 is attached over the supports with the slits 248 fitting snugly over each support 226 alternatively the filter device may be attached to the cover member adjacent to or in the second set of louvers so that airflow into the roof ventilator must pass through two sets of louvers before flowing through the filter device fig6 illustrates a roof ventilator 320 formed in accordance with another embodiment of the present invention the roof.