Plan
Besides understanding the manufacturer's instructions and recommendations for installing cooktop ventilation duct, find out what local building codes apply. Planning the route for the ventilation pipe may save time and makes for a smooth installation in the end. Many installers run the ventilation pipe up and out an opening in the roof. Often, the shortest and easiest method consists of running the ventilation pipe out an outside wall. Check the route to make sure it is clear of obstacles, such as other pipes or fire stops.
A straighter run results in a more efficient operation of the exhaust system. Most manufacturers recommend avoiding 90-degree bends in the piping. Follow the manufacturer's suggestion for the maximum length for pipe runs. Under no circumstances should the ventilation pipe terminate in an attic.
Ventilation Ducts
Generally, the ventilation duct consists of round stainless steel pipe. Usually, the cooktop ventilator requires the installation of an adapter to connect the rectangular duct on the ventilator to the round ventilation pipe. Use the exact size duct recommended by the product manufacturer. Rigid stainless steel galvanized pipe offers a solid long-term installation. Employ metal screws to connect ventilation pipes and wrap all connections in metal duct tape to prevent air leaks.
Installation
When conducting a roof installation, route the ventilation pipe between two rafters. At the point where the pipe exits through the roof, most local building codes require a minimum distance of 2 feet from the chimney or other pipes protruding through the roof. Making sidewall installations between two studs involve following the same basic steps. Cutting through a masonry wall presents more of a challenge and may require the help someone with the requisite skills.
Most regulations require strapping the solid connections at the joints. The installer must place a collar or wall thimble in the opening where the pipe passes through a wall or ceiling. These devices provide clearance between the pipe and combustible materials.
Finishing and Sealing
The opening where the pipe exits the roof or wall to the exterior requires the placement of a wall cap or roof vent cap on the end of the ventilation pipe. This flashing helps waterproof around the opening joint. The top and sides of the flange, which are the flat extensions of the flashing, fit under the siding or the roofing shingles. Many installers use mastic to ensure a watertight seal around the joints.
