Unventilated Roof Decks Require Roofing and Insulation Expertise

Today we have a timely roofing challenge for your consideration: proper roof ventilation.

In our last blog posting about our recent Green Building seminar, we mentioned that expert Peter Yost, Technical Director of Green Building Advisor, spoke on the importance of examining the building science in each situation. For example, while new insulation materials and methods bring higher “R” values, they also bring new challenges in understanding how all the elements work together in the building over time. We included a photo from Peter (shown again here) of a roof in the Northeast that rotted when good materials were used, but proper roof ventilation wasn’t included in the plan.

Rotted Roof in the Northeast

Surprisingly, this happened to a roof in the Northeast constructed by an experienced building company

In regard to roofing and insulation, if spray foam is to be applied to the underside of the roof deck, an unventilated roof deck could be one result. Or, it could be a situation where there is no ventilation and the rafter bays are going to be filled with dense packed blown-in fiberglass insulation.

How will that impact the roof shingles? How does the lack of ventilation impact the warranty on the roof shingles? Unventilated roof decks are considered “HOT” roof decks, which stirs up some issues with most roof shingle manufacturers. You should check the shingle warranty information of your preferred brand.

Should you wish to have foam insulation done in the roof, but want to provide ventilation so that there are no issues with warranty, National Lumber can provide a system for running a slightly different prop-a-vent the entire length of the roof slopes as necessary to carry air from the soffits to the ridge vent. Pro Insulators can also provide the benefits of spray foam and keep the attic ventilation by spraying foam down from the attic space on top of the sheetrock ceilings, as long as there is access and space to get around within the attic.

National Lumber not only supplies everything needed in building materials, but also expert services to provide solutions to building challenges. If a particular building provides a challenging roofing and/or insulation situation that you have not encountered before, contact our experts for advice.

Pro Insulators, a division of National Lumber, provides installed insulation for residential and commercial buildings. You can subcontract the installation of any kind of insulation for new construction and retrofitting. Spray foam in particular has become a popular choice.

For more information, contact Pro Insulators at 978-423-6051 or insulation@national-lumber.com.

To get a 33% discount on annual subscription to Green Building Advisor, click here to sign up at the National Lumber landing page.

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1 Response to “Unventilated Roof Decks Require Roofing and Insulation Expertise”


  1. 1 Foam Roof August 15, 2011 at 2:36 am

    You said it just right. Insulation without ventilation is of no use because its lifetime do not last for long. Thanks for sharing this with us.


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