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Ridge and Soffit Venting

DEFINITION
CONSIDERATIONS
COMMERCIAL STATUS
IMPLEMENTATION ISSUES
GUIDELINES

CSI Numbers:

07800 Roof Accessories
07840 Gravity Ventilators


DEFINITION:

A ridge-and-soffit venting system is a continuous, weather-shielded opening at the peak of the roof in combination with continuous screened openings along the eaves of the house. This system provides air movement under the roof that washes the underside of the roof with air that is exhausted out the top of the roof through the ridge vent.


CONSIDERATIONS:

A continuous ridge-and-soffit vent system is the most effective means to ventilate an attic. It is a passive system (no fans) and can outperform fans. The effect of pulling air from the eaves and out at the ridge is an example of the thermal chimney effect (discussed in the Passive Solar Design section).

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Ridge & Soffit Vent Satisfactory Satisfactory Satisfactory Satisfactory Satisfactory in most conditions Satisfactory
Satisfactory Satisfactory
Satisfactory in most conditions Satisfactory in most conditions
Satisfactory in Limited Conditions Satisfactory in Limited Conditions
Unsatisfactory or Difficult Unsatisfactory or Difficult


COMMERCIAL STATUS

TECHNOLOGY:

Well-developed.

SUPPLIERS:

Well-developed.

COST:

Ridge vents can cost $2.00 – $3.50 per lineal foot. These costs do not include installation.


IMPLEMENTATION ISSUES

FINANCING:

Not an issue.

PUBLIC ACCEPTANCE:

There is moderate interest in continuous ridge-and-soffit vents among energy conscious buyers.

REGULATORY:

Not an issue.


GUIDELINES

1.0 Continuous Ridge-and-Soffit Venting

A continuous ridge-and-soffit attic ventilation system is a passive system that is considered the most effective means of ventilating an attic. This type of venting system can operate effectively regardless of wind direction and velocity. Airflow in an attic created by this type of venting will be a continuous wash of air directly under the roof moving upward from the eaves (soffits) to the ridge.

1.1 Soffit vents run continuously on the underside the eaves.

Locate as far out on the eave as possible (closest to the fascia).

1.2 Ridge Vent types

Metal ridge vents

Typically are not shingle-over vents and aesthetically contrast with shingle roofs.

Roll-out vents

Have lowest profile.

Come in a continuous roll with a fiber matrix.

Install quickly and are cut with snips.

Generate no waste.

Panel Vents

These vents come in 4 foot lengths and are constructed of plastic.

Use foam blocks to seal ends.

Corrugated Plastic Vents

These are made from stacked plastic corrugations, stapled together and cut into strips.

They have a honeycomb matrix, no baffles.

2.3 Ridge vent characteristics:

Baffles in the vents help stop water infiltration. External baffles (vertical flanges in front of the vent opening) are most effective in stopping wind blown moisture.

Foam blocks on ends should be covered by a UV-resistant coating.

Vents that have tabs allow quick aligning and maintaining uniform distance.

Vents with a rounded ridge are easier to sit on for applying shingles but may be difficult to apply on steep roofs. Some vents are scored in the center to easily conform to the roof.

2.4 Ridge vent installation:

Roof sheathing should stop three fourths of an inch before roof peak (no gap within 12 inches of each gable end).

Fasteners may be nails, staples, or screws, according to the manufacturer’s requirements.

The vent should extend to the end of the roof ridge to have a continuous appearance to the ridge even though the opening in the roof stops 12 inches before the gable.

Miter cuts of the vents in ridge-to-ridge and ridge-to-roof intersections will be needed.

Architectural shingles may need to be stripped back since they are thicker and would raise the vent up. Caulk the joint between the vent and the roofing.

If a vent does not have alignment tabs, leave 1/8 inch between the panels to allow for expansion.

Shingles installed over the vent may need to be trimmed.