VENTILATION
Proper attic ventilation extends the life of a roof and reduces problems because it minimizes the temperature differential between the attic and the air outside. Proper ventilation will remove moisture and heat from the attic. Trapped heat and moisture can raise energy costs, cause ice dams, and damage roof system components as well as structural and personal items located inside the attic where temperatures can easily reach 150 degrees F. Condensation that forms inside attics can be caused by improperly insulated attics, improperly insulated access, the use of washing machines, dish washers, bath tubs, showers, and tumble driers unless these items are properly ventilated through the roof. In some cases the condensation can be bad enough to be mistaken for a roof leak.
There are many types of attic vents available today. There are static vents, power vents, ridge vents, turbine vents, soffit vents, gable vents, starter vents, and cupola vents. These all come in a wide variety of sizes, styles and shapes. Some will ventilate better than others depending on the roof configuration, attic size climate, etc.
To properly ventilate an attic, two types of vents are needed. Intake vents, which are located at the downslope of the roof (aka eaves) and allow fresh air into the attic; and exhaust vents, which are located near or on the ridgeline of the roof allowing air to leave the attic. The use of an exhaust vent in conjunction with an intake vent uses the natural forces of wind pressure and thermal effect, collectively known as stack effect (passive airflow) to ventilate the attic space.
There is always a lot of concern for what the best type of ventilation is. Now remember the idea behind ventilation is maximum air circulation. Most roofing professionals will agree that the best type of ventilation is continuous soffit and ridge ventilation. If a continuous exhaust vent and an equal or slightly greater amount of intake are installed, then the attic will be ventilated for its entire length.
Another common misconception is “more is better”. Many people think that they can improve ventilation of their attic by installing vents throughout the roof surface. What they don’t know is this causes a Ventilation Short Circuit. For instance, let’s say that John has a full soffit and ridge vent system installed. But thinking more is better, John decides to install a couple of vents about halfway up the slope. Instead of improving his ventilation, he has now hampered it because air is now exiting out the vents in the middle of the roof, before it reaches the ridge leaving the attic partially vented. Another problem is installing a ridge and soffit ventilation system and leaving gable vents. The gable vents cause a major problem, and she be removed or blocked off.
Ideally you should have 1 style of intake and 1 style of exhaust vents. NEVER mix or have more than 1 type of each vent style. A Properly vented roof and a properly insulated attic will prevent any future problems with your new roof.
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