Turbine vent shown on rooftop (C) Daniel Friedman Un-Balanced Roof Intake vs Outlet Venting
Problems created with unbalanced roof venting systems

  • PROBLEMS with PARTIAL ROOF VENTILATION - CONTENTS: problems caused by un-balanced, incomplete, or just partial roof venting include ineffective ventilation, increased heating costs in cold climates, or incresed cooling costs in hot climates. The importance of a balance between venting air intake and outlet is explained.
  • POST a QUESTION or READ FAQs about un-balanced cathedral ceiling under-roof spaces
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Problems with un-balanced roof ventilation intake versus outlet:

This article explains why an incorrect ratio or balance of intake venting and outlet venting in a roof ventilation system can cause more problems than any possible benefit of the roof existing ventilation system.

This article series describes various solutions for un-vented cathedral ceilings and similar under-roof spaces, offering advice on how to avoid condensation, leaks, attic mold, & structural damage when roof venting is not possible.

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Problems with Partial Roof Venting

  (C) Daniel FriedmanSome buildings, by their shape or design, simply don't make it easy to install continuous intake venting at the eaves or lower roof edge, or continuous outlet venting along a ridge.

For example, a house which has no roof overhang at all makes intake venting at the eaves difficult.

A house with a pyramid roof shape or complex roof shapes makes outlet venting at a ridge difficult.

And a home with cathedral ceilings following the roof line may be difficult to vent - a common case where the hot roof design is appealing.

On these roofs, partial venting can be worse than no venting. For example, adding a ridge vent, or several roof "spot vents" or roof turbine vents on a few roof slopes, typically mid-slope or in the upper third of the slope on roof surfaces not visible from the front of the building, may please the installer, but they are worse than ineffective.

Placing an outlet vent on a roof without adequate inlet venting works against the interests of the building and its occupants.

As convection currents and heat loss into the roof space or attic vent out through these vents, the intake air needed to satisfy the exhausted air leaving the building will be drawn from the building interior - increasing building heating costs and possibly increasing particle movement from basements or crawl spaces (if there is a mold concern in the building).


If you can't provide enough intake venting it is probably better to not vent at all in these conditions. Illustration at above left was provided courtesy of Carson Dunlop Associates, a Toronto education, engineering & home inspection firm.

Watch out for real world snafus, damage, leaks in roofs.


Continue reading at HOT ROOF SOLUTIONS for HARD to VENT ROOFS & CEILINGS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES.


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