Installing some type of ventilation mechanism on a metal roof is not a lot different from the addition of vents to any type of roof. However, there are a few simple tips that will help make the process a little easier, and also ensure that the vents are placed to allow the maximum benefit.
Determine the type of vents you wish to install. This may include the round "whirlybird" types that are placed around the roof to allow hot air to escape from the rafters area, or simple slatted vents that are installed in the "A" area of the roof ridge. Deciding which type of vents are best for the situation will make it possible to make use of any of the several designs of prefabricated vents currently available.
Prepare the roof area. This will involve determining the placement of the vents. Various size vents will come with recommendations regarding spacing and placement based on the size of the vents and the expanse of the roof. Use a marker or a chalk line to mark the spot on the roof surface where the vent will be placed.
Measure the body of the vent. Using the tape measure, determine the size of the cut into the roof that will be necessary to insert the vent into the space. Record those measurements on a notepad. Remember to allow for the lip on the vent mechanism that will fit over the opening and rest on the surface of the roof.
Lay out the outline for the roof cuts. Use the marker or chalk line to make an outline of the opening that must be cut into the metal roof.
Cut into the metal roof. This will begin by using the skill saw to cut the outlined space until the hole allows easy visual access to the interior of the attic area.
Use the tar brush to apply a thin layer of tar to the edges of the hole. This will help to create the initial seal between the metal roof and the vent mechanism.
Place the vent into position. Drill starter holes where necessary and secure the unit with the screws provided as part of the installation kit.
Apply a second layer of tar around the perimeter of the vent. This will help to fill in any space that is left exposed between the lip and the metal roof.
Seal the underside. Moving into the attic area, apply more tar on the underside of the exposed hole and place any medallion or cover plate that is included in the installation kit into position. Secure with screws provided.