How Important Is Ventilation In Roofs?

How important is ventilation in roofs? Check with your local building codes to find out what the proper ventilation is for your climate. Proper ventilation is extremely important in protecting your roof,...

Proper ventilation is extremely important in protecting your roof, says John Humphreys, who is the president and CEO of DaVinci Roofscapes. Without proper ventilation, heat and moisture can build up in your attic and cause premature damage to your roofing materials, not to mention mold, mildew, bacteria, and damage to the attic structure itself. Ventilation is built into properly designed roofs through the use of undereave or soffit vents, ridge vents, and gable vents. A balanced ventilation system works off the negative pressure created by blowing wind and the natural action of rising heat and doesn't require the use of any energy resources.


Particularly in extreme climates ventilation is very important in the prevention of moisture build-up and damage to roofing materials. Attic ventilation allows for the release of heat and moisture caused by appliances, furnaces, and hot water use in the winter and the naturally occurring heat during the summer months. The formation of ice dams on roofs during the winter is sometimes the result of improper ventilation. Trapped heat can also lead to increased energy costs to cool a house in the summer.




Humphreys recommends checking with your local building codes to calculate the required amount of ventilation per cubic square of the attic space since needs can change depending on the climate of a region. As a general rule of thumb you can calculate the amount of ventilation needed by the 1/300 rule, meaning that you need 1 square foot of vent area for every 300 square feet of attic space.

Some of the problems that can occur as the result of unventilated attics and roofs include condensation, rusting, warping, cracking, and dry rot. If your roof deck is made of plywood, excessive heat and moisture will lead to dry rot that can make your roof structure unstable. When moisture condenses in an improperly ventilated attic space, the condensation can rust nails in ceiling joists and even the metal straps that suspend air ducts. In very cold climates condensation can cause frost to form on the underside of the roof or lead or ice dams. If the insulation in an attic collects moisture it becomes a breeding ground for mold spores and other bacteria in addition to lowering the insulation value.

There are any number of venting systems available including soffit vents, gable vents, cupola vents, ridge vents, turbine vents, power vents, and static vents. A roofing specialist can help you determine which type would be best for your home depending on climate, size, and roof slope configurations. Proper ventilation requires both intake vents and exhaust vents. Intake vents, which let air in, are usually located at the eaves or edges of the roof, and exhaust vents, which release air, are usually located along the ridge or uppermost portion of the roof. This allows for the earlier mentioned natural effects of wind pressure and rising heat to ventilate the underside of the roof and attic. Be sure to check that attic insulation is not blocking any of the vents. If this happens, baffles can be used to hold it back.

© High Speed Ventures 2011