Calculating Attic Ventilation Requirements

As well, if the ceiling does not have a continuous vapor barrier installed, excess moisture will enter the attic, which, if not removed can cause structural damage to roof rafters and the ceiling of living space below the attic.  Hence, maintaining proper moisture and temperature levels within the attic space is critical.  Both moisture control and air temperature is controlled by proper attic ventilation.

There are numerous methods that can be used to provide proper ventilation to your attic space.  Which is chosen is usually predicated upon the roof construction, style and materials.

The most common method of ventilation employees static vents in the soffits and manual and/or powered vents close to the ridge of the roof.  In this case because of natural air flow (hot air rises) or in the case of a powered vent unit the hot air is expelled near the top of the roof and fresh air is drawn in from the vents in the soffit,

A common variation is to replace the roof vent with a ridge vent that runs the total length of the ridge.  In a similar manner to having air vents mounted close to the ridge of the roof, a ridge vent expels all of the hot air in the attic which is then replaced with fresh air through the soffit vents.

There are many variations, combinations and hardware that can be employed to provide proper attic ventilation.