Proper Roof Ventilation
There is much more to a good roof install than just properly applied roof shingles. Proper ventilation is key.
Both warm and cold climates require proper roof ventilation to prevent costly issues from occurring inside and out of your home. Many homeowners are unknowingly reducing the normal life expectancy of their roof system because of improper ventilation.
As well as extending the life of your roof system, a properly vented roof will reduce the strain on your A/C unit by cooling the temperature of the attic floor, interior ceiling and your ductwork, therefore reducing your energy costs.
Proper roof ventilation has two key components:
- Intake vents, allowing cool fresh air into your attic
- Exhaust vents, allowing hot moist air out your attic
The goal of these intake and exhaust vents is to keep the air inside your attic as close to the outside temperature as possible and avoid any build-up of condensation.
Keeping this goal in mind, if you have air conditioning pipes running through your attic you should ensure these pipes are thoroughly wrapped with insulation to avoid condensation issues with them.
Having a balanced system (adequate intake and exhaust) will provide the best air conditions for your roof and extend the life of your roof system and roof structure. An imbalanced system won’t work.
Excessive moisture in the attic can cause:
- Mold and mildew issues – negatively effecting your family’s health
- Accelerated rotting of wood trusses and roof structure
Excessive heat in the attic can cause:
- Air conditioning system over working
- Accelerated degradation of roof underlayment and shingles
- Ice damming in cold weather, which can seriously damage shingles, gutters & soffits
Balancing the System
To achieve adequate roof ventilation your roofer should install the either ridge venting or attic vents when installing your roof. They will need to ensure proper soffit venting as well to balance the system. For the system will work with the natural convection process, under no circumstances should the vent exhausting exceed the soffit intake amount. A common rule across most residential building codes calls for one square foot of vented area for every 300 square feet of attic space with a vapor barrier and 1:150 without a vapor barrier. This means a 1,500 sq. ft. attic (with vapor barrier) should have five sq. ft. of vent space. Dedicate half of this for air intake in the soffits and the other half for exhaust through the roof.
Many roof systems can utilize the natural convection process to keep the air flowing. But passive ventilation alone may not be enough to keep your attic cool. Your roofing professional can advise you on whether your roof requires more advanced options, such as turbine or power vents.
When designing any roof ventilation system, it is imperative to ensure adequate intake venting (soffit vents). If there’s inadequate intake or an intake vent becomes blocked, the ridge venting can act as an intake and exhaust, causing weather infiltration.
Soffit Vent Baffles
It’s a good idea for you (or your roofing professional) to do an annual check on your roofs ventilation system. Accordingly, once a year you should clear any screen debris that may be impeding the air flow from your attic and soffit vents. Also now is the time to repair any screen tears or damaged flashing. Check for significant rust or other signs that your vents may need replacement. Finally, from inside the attic, you should clear any loose insulation from the soffit vent openings, ensuring any vent baffles that were installed are still doing their job.
Keep in mind this is fairly general information for a typical home with an attic. Other types of homes will require more specific venting procedures. For example, homes with Cathedral ceilings (no attic) should use continuous ridge venting and ensure there is adequate soffit venting between each and every truss.