Vent your barrel roof on top of the roof decking when constructing the building. Place the metal vent to one side or the other of the roof-top angle.
Place the 30-pound felt, or roofing paper, on top of the top edge of the roof vent, and underneath the bottom edge. This prevents water from getting underneath the vent.
Determine the number of roof vents needed on your building by checking local building codes. The codes discuss how many vents per cubic feet of air is needed in a building.
Install electrical fans on barrel roof vents that suck hot air out quicker and provide adequate circulation. Ventilation fans are recommended in buildings that do not have air-conditioning.
Enhance your barrel roof ventilation fan by adding a controlled thermostat. Set the temperature so the attic fan comes on automatically. When the building cools down, the fan will shut off.