Soffit vent stripRoof Soffit Intake Vent Specifications
How to Install Soffit Intake Vents to Stop Attic Condensation, Ice Dam Leaks, Attic Mold, & Roof Structure Damage

  • ROOF VENT SOFFIT, CONTINUOUS - CONTENTS: Continuous soffit intake venting to Stop Attic Condensation, Ice Dam Leaks, Attic Mold, & Roof Structure Damage. How to detect roof venting deficiencies, attic insulation defects, and attic condensation problem
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Roof Soffit or Eave Ventilation Specifications:

Continuous intake venting is desirable in vented roof designs.

This article describes how to properly inspect, place, and size ventilation air intakes at the lower edges of a building roof - its soffit, or eaves.

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Continuous High Capacity Eaves or Soffit Intake Venting Provides Adequate Intake Air Under Roofs

Soffit intake venting

This article describes inspection methods and clues to detect roof venting deficiencies, insulation defects, and attic condensation problems in buildings. It describes proper roof ventilation placement, amounts, and other details.

These recommendations are based on roofing industry standards, roof covering manufacturer recommendations, and on review of the literature on building insulation and ventilation, as well as on 30 years of building inspections, on the observation of the locations of moisture, mold, ice dams, condensation stains, and other clues in buildings, and on the correlation of these clues with the roof venting conditions at those properties.

We have also measured changes in airflow, temperature, and moisture before and after installing roof venting.

As we show in this pair of photos (above and below), continuous soffit intake venting will provide optimum intake air flow between every rafter pair.

On buildings with very large gable end vents, lots of insulation in the attic floor, and perhaps lucky house siting, I have seen attics that were perfectly dry and free of condensation, ice dams, and mold.

But these have been the exception, not the rule, at least for inspections in northern climates subject to cold winters and hot humid summers.

Home made soffit ventInstalling Continuous High Capacity Eaves or Soffit Intake Venting Works Best to Avoid Attic Moisture, Mold, & Ice Dams

Here are examples of inadequate intake ventilation: vents at the soffits are intermittent or "spot vents" or are simply too small.

Continuous soffit/eaves intake venting is the proper location for the intake air, in order to assure that the entire under-side of the roof sheathing is vented and kept dry.

Where I inspect attics with "spot vents" in the soffits (those little round louvered vents ranging from about 3/4" diameter to 2" in diameter, are completely ineffective, never moving enough air.

Venting needs to be provided between every rafter pair at the eaves and ridge. You won't achieve this if venting is intermittent along the soffits or eaves of a home.

Don't install intermittent or occasional or faux soffit intake venting or vents with too little opening area such as we show in the photo at left.

Not only are the openings too small to pass enough air (obstructed further by the louvers and insect screens), intermittent soffit intake vents or little round or rectangular soffit spot vents are singularly ineffective in providing good under-roof or attic ventilation.

Poorly vented home soffitWhere we inspect attics where even larger vent openings are provided in the soffits or eaves, if the openings are intermittent, we see wet and often moldy roof sheathing on those roof sections where no venting is provided, even though at other roof sections where vents are present the sheathing often looks clean and dry.

This is very strong evidence that air is not moving up the under-side of the sections of roofing where no vents are present.

Continuous ridge venting is the optimum exit path for warm rising air in an attic, thus pulling new cooler, drier outside air into the under-roof area from between every rafter pair. (C)Daniel Friedman - copyright violation trap.

But also remember the danger of adding a ridge vent without soffit vents (the worst) or soffit vents without a ridge vent (bad) or only gable-end vents (usually bad).

The up-draft of air from the building (convection current of rising warm air which moves up through most buildings) will be increased and will mean unnecessary heat loss if you have a ridge vent to vent air out without also providing good intake venting at the soffits or eaves.


Continue reading at ROOF VENTILATION SPECIFICATIONS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see ROOF VENTILATION INTAKE if NO OVERHANG for roofs that have no soffit or eaves overhang to provide an intake opening, see

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