Attic Ventilation Control

The Inclusion of Cold-Side Venting is Essential for Eliminating Attic Vapor Pressure

By Mark J. Donovan

Attic ventilation control is critical for preventing mold and mildew growth in the attic. It is important to make sure air can flow freely in the attic.

If there is inadequate attic ventilation control, moisture that moves through the ceiling will become trapped in the attic.

Fortunately and unfortunately roofing materials do not allow the transfer of moisture between the attic and the outside.

Consequently, when framing and shingling a roof, it is essential to incorporate adequate attic ventilation control in the design of the home.

One method of attic ventilation control is to include cold-side venting into the attic.

Cold side venting effectively involves including soffit vents and ridge vents, and/or gable vents in the attic so that any build up of vapor pressure, or moisture is transferred from the attic to the outside.

Installing soffit vents distributed evenly along the roof eaves and a ridge vent along the peak of the roof is the best way for controlling ventilation moisture.

As the attic air warms it lifts upwards and escapes out the ridge vent, and in the process, pulls in cooler drier air from the soffit vents. The beauty of this type of attic ventilation control system is that no wind or powered fans are required.

Soffit Vents are one component in proper attic ventilation control.

For sufficient attic ventilation control one square foot of ventilation should be provided for every 150 square feet of attic area. In addition to soffit and ridge vents you can also use gable, roof and turbine vents. Gable vents are placed near the top of the gable ends of the roof. Roof vents are installed on the roof. Typically when using roof vents for attic ventilation control, many of them need to be installed on a roof.

Alternatively there are roof turbine vents that include a fan mechanism in them. As wind blows across the turbine, they draw hot and moist attic air out of the attic.

Installing windows in the attic is another solution for providing attic ventilation control, however the windows need to be opened and closed regularly to prevent the threat of rain water damage in the attic. There are also power attic fan vent systems that can be installed in the attic for drawing hot moist air out of the attic.

Another important component of attic ventilation control is the proper installation of attic insulation.

Attic Conversion Bid Sheet

It is essential that when installing attic insulation that the rafter channels are not obstructed with insulation so that air cannot flow properly from the soffit vents in the attic eaves up into the attic. If insulation is jammed into the attic soffit areas, fresh cool air will not be able to be drawn into the attic.

For help on Attic Conversion and Attic Renovation Projects, see’s Attic Conversion Bid Sheet. The Attic Conversion Bid sheet will help to ensure that you hire the right contractor so that your attic conversion project is built correctly, on time and budget.

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