Chinook Roofing Blog

Unique Ventilation Solution For Steep Slope Roofing

Posted on: January 15, 2015

Steep slope roof in Vashon Island

Steep slope roofing ventilation affects areas like upper rooms and attics

Improper ventilation can make for a “slippery slope” on pitched roof systems, potentially causing lasting damage to the structure of your home. Learn more about why ventilation systems are needed, and find one unique solution that is perfect for the steep slope roofing on many homes.

Conditions for Damage

Veteran industry pro Jeff Avitabile from GAF talks about ways to combat dampness and avoid damage in GAF’s blog. He notes that while good attic ventilation can be a precaution against roof moisture, it can be a challenge in homes with rooms right underneath the roof or vaulted ceilings that don’t allow the space needed for adequate ventilation systems.

Troubleshooting the space and system requirements needed to keep a roof structure dry is important. Many homeowners can relate to this problem, because the typical residential house has pitched or steep slopes—and some of them have little to no attic space.

What Causes Dampness?

Ice dams are an obvious cause of roof moisture, but warmer weather poses its own threats. Hot temperatures mean heat becomes trapped in the upper structure of the house (attics or in the roof system itself), causing poor heat distribution that can be uncomfortable and inefficient. Local climate and humidity also has an effect on moisture and condensation. Freshome Magazine cautions that indoor and outdoor air of varying degrees meets in the attic, creating condensation.

Steep Slope Ventilation

Ventilated nail base insulation creates an external ventilation system, so sought-after interior space is not compromised. The Polyisocyanurate Insulation Manufacturers Association (PIMA) explains that a ventilated nail base contains a layer of polyiso foam topped with spacers and then plywood or OSB, so air can move through the open area created by the spacers. This process can eliminate condensation from collecting onto the substrate.

Ventilated nail base insulation

Ventilated nail base insulation’s airflow

As its name suggests, ventilated nail base offers air movement between the plywood and the insulation. Popular polyiso also benefits the environment, PIMA points out, with recycled content that will not harm the ozone. Learn more about how polyiso works and its features here.

GAF’s Jeff Avitabile believes that ventilated nail base insulation will gain even more popularity as the system of choice for steep slope roofs prone to moisture. Is this choice right for your home or building, or is condensation a problem in your attic? We can help you address it with a free estimate.


Chinook Roofing & Gutters is a full service roofing company with expert cross-trained installers for both commercial-industrial and residential roofing projects. We provide Tacoma roof repair and installation as well as Tacoma gutter installation with a service area that extends throughout the Puget Sound region, including our home base of Fife, as well as Gig Harbor, Puyallup, Milton and more. Contact us today.

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