Michael Sweeney 
Most builders rely on vents installed at the eaves and ridge to balance air intake with outgoing flow, with manufacturers such as GAF, Cor-A-Vent, Owens Corning and Air Vent offering products that fulfill code requirements.
Not all roofs can accommodate these devices; should the system fail, warm attic air could leak into living spaces causing mold, mildew and damaged shingles.
Revolving Ventilator
This metal turbine-shaped equipment sits atop your roof and requires wind to set in motion. Once operating, it exhausts an equal amount of air each hour 24×7; helping keep the roof cooler and decreasing attic heat levels in turn.
Wind blowing against outer louvers creates a suction effect; as the turbine rotates, centripetal forces cause centripetal forces to push vanes outward and extract hot air from buildings. Replacement air is drawn into the throat of the ventilator from within buildings causing constant ventilation.
Ridge Ventilator
A ridge vent system is installed along the length of your roof ridge, the highest point in your home. Installation includes inserting an air slot into roof decking before adding a ridge vent itself that helps remove both hot air and moisture from your attic space.
Roof ventilation systems with air ducts can also help prevent mold and mildew growth that could otherwise pose health hazards to you and your family. Professional installation should be sought to ensure an ideal installation process.
These vents work effectively in most climates because they allow a natural flow of air and moisture, essential to keeping your attic cool and prolonging the lifespan of shingles and structures exposed to excessive heat and humidity. Furthermore, they may help extend their lives further as trapped heat and moisture can lead to early deterioration resulting from trapped heat or moisture. Moreover, being covered by ridge cap shingles means less likelihood of leakage during heavy rainstorms compared with box or gable roof vents.
Fan Ventilator
Attic fans use powered attic fans to force air out and replace it with cool outdoor air, in theory creating an airflow cycle which cools the home. But in practice this process may cause depressurization within the house as its source remains unclear and unpredictable.
For these fans to function efficiently, they require large vent openings on both walls and roof. This helps balance air flow throughout your living spaces to eliminate hot or cold spots from developing in specific rooms of the home. They must also be tied into your thermostat in order to turn on and off at regular intervals; otherwise the system could become inefficient over time.
Cupola Vent
Cupolas have long been used as decoration and roof vents on farm buildings. By allowing gases to escape while fresh air enters, allowing hay and livestock not only to stay healthy but also keeping pests out of sheds where paint, sprays, lawnmowers and other equipment is stored.
They work by allowing warm air to move upward through louvers or windows, eliminating mildew, mold and wood rot while making your space more comfortable. Furthermore, a cupola can also be enhanced with the addition of a fan that pulls in cold air while simultaneously expelling warm, moist air from its space and thus helping prevent roofline damage while simultaneously cutting energy costs.
To install a cupola as a vent, it will require using roofing sealant and flashing around its base to ensure proper adhesion to the roof. Before beginning this task, screws from both metal side panels of the cupola should be removed to facilitate proper sealant application and flashing application.
