Tips for Roof Eave Venting on Roofs with no Overhang or Soffit

Adding intake venting at the lower edge of roofs that have no overhang or soffit for the usual intake vent openings
- How to Correct Inadequate Attic Venting to Stop Attic Condensation, Ice Dam Leaks, Attic Mold, & Roof Structure Damage
Questions & Answers about attic moisture, condensation & ventilation: how to vent a roof with no overhang
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This article describes alternatives for venting attics and cathedral ceilings by providing air intake openings at the lower edge or eaves of roofs that have no building overhang or soffit or eaves. Our page top photo shows a cape Cod home in Poughkeepsie New York. This building was constructed with no roof overhang, making roof intake venting tricky to obtain, and risking extra damage from ice dams or gutter overflow leaks.

This article is part of the series ROOF VENTILATION SPECIFICATIONS and also ATTIC CONDENSATION CAUSE & CURE.

Our photo at page top shows a modern synthetic mesh type ridge vent (with modest airflow capacity) and our photo at left shows a typical installation of continuous soffit or eaves intake venting at the lower roof edges of a building.

Problems With Roofs Lacking Any Overhang - No Soffit?

Don't give up on providing roof intake ventilation openings just because your building was constructed with no roof overhangs. In fact, providing exit venting (at a roof ridge or at gable end vents) on a building with no intake venting at the building eaves will increase the building heating costs and can also add to attic or under-roof condensation, moisture, and mold problems.

buildings such as the cape Cod shown at page top may be constructed with no roof overhang whatsoever. While this design offers the advantage of more light entry at the building windows (not shaded by a soffit), owners of buildings built with this design need to watch out for several problems:

Ice dam formation is likely in freezing climates if there is no under-roof ventilation. Ice dam leaks on any building but particularly buildings with no roof overhang increase the chances of water passage on or even inside the building wall, inviting mold, rot, insect damage, and wet insulation.
Gutter overflow leaks, should they occur, will send water running down the building wall, inviting the same problems just listed above, even in climates where freezing and ice dams do not occur.
Increased building heating or cooling cost will occur in heating climates if roof exit venting is provided with no eaves or intake venting. That's because warm air leaks and heat lost into the attic or roof cavity will create a building up-draft of air movement that, unsatisfied by a ready source of makeup or intake air from outside, will draw conditioned air out of the occupied building space instead.
Increased risk of attic or roof cavity condensation, mold, or insect damage will occur for the same reasons just described. In cool or cold weather, moisture laden air drawn into the attic or roof cavity will leave its moisture as condensation on the roof deck underside or in the attic or roof insulation.

Venting Solutions for Roofs with No Overhang or Soffit

Install special roof intake venting products that work at the lower edge of the roof decking, underneath the first course of shingles. Example: Smart Vent™, a special roof eaves vent product that provides a 3/4" opening about 6" above the top of the roof drip edge.

The Smart Vent is a tapered plastic vent product that is combined with a one-inch slot cut into the roof deck six inches from the lower edge of the roof. You will need to be sure that the air vent opening is not blocked by attic or under-roof insulation.

A similar product, the Hicks Starter Vent, patented by Massachusetts inventor Robert M. Hicks, is a combination of roof edge "starter vent" and drip edge. is cited at Roof Venting: Un-Vented Hot Roof Solutions. (We have had trouble finding this product).

Roof fascia vent or eaves vent (C) Daniel Friedman

Construct a hidden roof intake vent at the top of the building wall by removing the wall top trim or top siding board, cutting away any building sheathing or blocking at the wall top, nailing 1" spacer blocks 16" on center, nailing a new spaced-out wall top trim board along the roof eaves, and screening the opening against insects.

This design is used more often when there is an existing roof overhang but no soffit has been constructed to enclose the overhang.

If you follow this design on a building that has no roof overhang whatsoever, the gutter will need to be removed and re-hung on the new spaced-out fascia board or siding board, and you may need to extend the roof drip edge by 1 3/4" to assure that roof drainage enters the new spaced-out gutter. It should not be necessary, however, to actually extend the roof decking and rafter tails.

Our photo (left) shows a roof fascia vent at the eaves of a home in the Northeastern U.S. though in this case the builder also trimmed out a faux-soffit and fascia board (with no gutter yet installed). Our pen was stuck into the fascia vent opening to demonstrate it's width.

Soffit vent construction detail (C)Daniel Friedman

Construct a soffit, or eaves overhang, combined with assuring that an opening is provided all along the top of the building wall by removing any blocking between roof rafters at the top plate, combined with use of roof insulation baffles to assure an air inflow pathway under the roof deck.

Using this approach it may also be necessary to extend the roof deck out to cover the roof edge extension.

Provide continuous soffit or eaves intake venting as we describe at Roof Venting: Soffit Intake Vent-Continuous.

This is probably the most-costly solution to an un-vented no-overhang roof design, and is practical only in cases where the building is being modified for other reasons. On buildings where the top of windows are close to the top of the building wall, there may be insufficient space to construct an overhanging roof eave without blocking the windows.

See Roof Venting: Proper Locations for another sketch of soffit construction and soffit ventilation details.
Un-vented roof solutions to buildings with no roof overhang and which are a more distant second-best approach, are discussed at Roof Venting: Un-Vented Hot Roof Solutions.

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Related Topics, found near the top of this page suggest articles closely related to this one.

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The Smart Vent™ by DCI roof intake venting provides an intake at the lower edge of roof decking for difficult cases. See www.dciproducts.com/html/smartvent.htm
The AccuVent™ attic ventilation roof baffle produced by Berger permits insulation to extend over the top plate as far forward as possible. See www.bergerbuildingproducts.com/pdfs/AccuVentAtticVent.pdf
GAF Cobra® and other GAF roof ventilation products: see www.gaf.com/Content/GAF/RES1/ROOF/RS_whyuse_ventchart.asp?viewer=&module=
Thanks to reader Steve P. for suggesting this roof vent discussion for providing roof intake venting when there is no overhang on a roof 7/23/09

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"Energy Savers: Whole-House Supply Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Supply_Vent.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
"Energy Savers: Whole-House Exhaust Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Exhaust.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
"Energy Savers: Ventilation [copy on file as /interiors/Energy_Savers_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Natural Ventilation [copy on file as /interiors/Energy_Savers_Natural_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Energy Recovery Ventilation Systems [copy on file as /interiors/Energy_Savers_Energy_Recovery_Venting.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
"Energy Savers: Detecting Air Leaks [copy on file as /interiors/Energy_Savers_Detect_Air_Leaks.pdf ] - ", U.S. Department of Energy
"Energy Savers: Air Sealing [copy on file as /interiors/Energy_Savers_Air_Sealing_1.pdf ] - ", U.S. Department of Energy
Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
"Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
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