Roof Venting

Insulating your ceiling is critical for energy efficiency and comfort in your home, but equally important is venting the attic space properly. At Quality Homes & Renovations, we ventilate the attic space to achieve a ‘cold’ roof deck. A cold roof deck places the insulation & air sealing at the ceiling level, and keeps the attic space and roof sheathing at the same temperature as the outside.

Why keep the attic space at the same temperature as the outside air? In the summer this keeps the attic cooler and lets fresh air cycle through. It reduces the cooling load for the homes mechanical system and prolongs the lifespan of the roof covering. In the winter, it reduces condensation caused by any heat loss through the air sealing and insulation.

Passive Ventilation System

There are 3 components to properly venting the roof space. Intake vents in the soffit bring fresh air in, while exhaust vents at the highest point of the roof allow air to escape. In between these two points it is critical to have a continuous unobstructed path for ventilation. This passive system doesn’t rely on any mechanical components, instead using the principle of warm air rising.

There needs to be 1 square ft of ventilation for every 300 square ft of attic space. This ratio is easily met with vented soffits for intake ventilation and low profile ridge vents or Maxi Vents for the exhaust. Combined with good air sealing and the correct amount of insulation in the ceiling the attic will be dry and match the outside temperature throughout the year.

Creating the Passive Ventilation System

If your home has a flat ceiling, foam rafters vents are stapled to the roof sheathing in between each truss. These are 48” long and reach up past the depth of the ceiling insulation. The space between the roof sheathing and wall plate is filled in a fiberglass insulation cut to fit tightly. This prevents the ceiling insulation from drifting into the eaves of the roof. The rafter vent creates a continuous ventilation path from the soffit to the attic space.

A cathedral ceiling is insulated with closed cell spray foam insulation. Quality Homes & Renovations does not install the spray foam directly to the underside of the roof deck. We maintain a cold roof deck and provide continuous venting from soffit to ridge by installing cardboard backing for the spray foam from the eave to the ridge of the roof. This space is at least 6” deep. The spray foam is applied to the cardboard backing, providing the insulation and air sealing for the roof.

Roof venting is a key part of the insulation process. Proper venting, along with adequate insulation and proper air sealing, increases the lifespan of the roof covering and helps prevent condensation and ice damming.