How to Install a Direct Vent Horizontal Terminal Cap on Siding

Walk to the exterior of the home and locate the area where the duct will emerge. To locate the area, drive a 6-inch nail from inside the home with a hammer until it penetrates through siding.

Place the square fire stop gasket up to the vinyl siding and center it over the nail. Slide the fire stop up until the top lip rests on the bottom edge of the nearest strip of siding. Draw a line around the outside perimeter of the fire stop with a pencil.

Set the fire stop aside and put on safety glasses. Cut around the pencil outline with a reciprocating saw. If needed, drill a hole through the siding first with a hole saw then cut out the remainder of the hole with the reciprocating saw.

Place the fire stop back up to the siding and insert 1-inch screws through each screw hole with a power drill.

Examine the surface of the vent cap for an arrow or other indicator that designates the proper positioning of the cap. Turn the cap to the proper orientation.

Insert the termination cap into the end of the fire stop until it stops. Look at the side of the cap for the screw holes and rotate the cap slightly until they align with those in the underlying duct or fire stop. Insert 1/2-inch screws into the holes with the power drill.

Apply a 1/2-inch bead of exterior-grade silicone caulk around the termination cap to weatherproof it and seal air gaps.