ROOF VENTING

To properly ventilate an attic, two types of vents are needed. Intake vents, which are located at the down slope edge of the roof (a.k.a. eaves) and allow fresh air into the attic; and exhaust vents, which are located near or on the ridge line of the roof and allow 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 the Stack Effect, to ventilate the attic space.  HINT: Make sure your attic insulation doesn't block the intake vents.  If necessary, use baffles to keep the insulation back from it.

 

Do I have to close off my gable vents when I use a ridge vent?
Yes, the gable vents (a type of exhaust vent) should be closed off whenever a ridge vent (which is also a type of exhaust vent) is installed because vents installed at the roof’s edge or in the overhang should supply the intake air needed by the ridge vents. Air should flow in through the intake vents evenly along the roof line and exhaust out the peak. Any vents in place between the ridge vents and the intake vents may interrupt or short-circuit that flow of air along the roof line. The gable vents will end up becoming intake for the ridge vent — an undesirable situation that could lead to weather infiltration through the gable vents and also could prevent the attic from being properly ventilated.

Condensation Sources

Condensation that forms inside attic can be caused by the use of washing machines, dish washers, bath tubs, showers, clothes driers, and stove use, such as boiling water, unless these items are properly ventilated through the roof or wall. In some cases the condensation can be bad enough to be mistaken for a roof leak. Another source of moisture can come from the crawl space under your house when there is no plastic vapor barrier on the ground to prevent the moisture from rising up into the house.

  

Coravent Shingle Ridge Vent

Filtered Metal Ridge Vent

Adding Insulation to the Outside of your Roof

When adding insulation board to the outside of your cathedral style roof, there should be a ventilated space above the board to allow air flow and to expel any excess moisture. This will help to prevent condensation on the bottom side of the roofing material and prevent the plywood from rotting. Typically we like to use the "Hunter Panel" system shown below. Although the photo shows "OSB" board as the substrate, we only use 'CDX" plywood on our roofs and order the panels accordingly.