of the vent to adversely affect its air permeability the base mesh fabric can be secured to the insulation by block insulation fasters and or by adhesive or sealant the skirt 130 typically composed of cured epdm wide cover tape adhered onto the membrane 30 around the vent and sealed by calk or sealant around its inside and outside perimeter to the tube 126 and to the membrane 30 the tape of the skirt 130 can be applied in two strips and sealed along its seam to form approximately a 2 foot by 2 foot skirt as shown in fig2 the tube structure 126 has an upwardly tapered peripheral wall portion 140 terminating to leave a top opening not shown in the upper end of tube 126 the lower end of tube 126 is open to a space 142 provided above the insulation blocks 112 and occupied by the pathway 46 of mesh fabric and the base mesh fabric 129 a cap or hood generally designated 152 is provided for the upper end of the tube or stack 126 to prevent the entry of rain snow and the like and comprises a top wall 154 spaced above the top opening of the tube 126 and has a downwardly divergent peripheral wall 156 extending generally parallel to wall portion 140 but overhanging the wall 140 when wind is present an air stream traveling up between the walls 140 and 156 is converged.