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About Bruce A. Ryan II, RRO
Expertise
Commercial/Residential Roofing Waterproofing Building Envelope

Experience
Bruce Ryan has 13 years of roofing, waterproofing, and building envelope consulting experience with PRC, with 5 years of commercial roofing experience prior to joining the firm. He became Vice President of the company in 1998. Bruce Ryan plays a key role in the development of practical, long-term roofing and waterproofing solutions, along with implementation of on-site forensic studies. Bruce also has a high level of experience with regard to the impacts of roofing materials and construction for demanding clients with heavily occupied structures.

Organizations
Oregon Construction Contractors Board Construction Specifiers Institute National Roofing Contractors Association The Institute of Roofing, Waterproofing, & Building Envelope Professionals Oregon Board of Investigators Installation Masters

Education/Credentials
University of Maryland BS Business & Administration Registered Roof Observer - RCI Private Investigator Certified EIFS inspector - Northwest Wall and Ceiling Bureau Certified InstallationMaster™ - The Installation Masters™ Training and Certification Program (developed by American Architectural Manufacturers Association)

You are here: Experts > Home/Garden > Home Improvement/Repair > Roofing > Tongue and Groove Decking

Roofing - Tongue and Groove Decking

Expert: Bruce A. Ryan II, RRO - 10/28/2009

Question
We are installing a new roof on our house which has tongue and groove ceilings. We scraped all the old shingles and cylotex which exposes the T %26 G. We fitted 2 x 10 rafters 2'OC and havae installed kraft faced R30 bat insulation directly on the T&G. We have installed the insulation so the kraft paper is facing the outside toward the shingles. On top of that is the OSB plywood. On the roof, we figured we would get better ventilation with the kraft paper away from the house. Was this the right decision?

Answer
Mel,

I need to assume that your roof sheathing and not the ceiling is t%26g sheathing and that you have sistered 2x10s next to your existing smaller 2x rafters, or replaced them completely.

You generally want to face the Kraft paper toward the 'warm' side of the structure, which in most climates is toward the interior. The paper is coated with an asphalt film that serves as a vapor retarder. The integrity of the vapor retarder is usually questionable after the batts are installed, so this may or may not be a problem for you. The possibility now exists that condensation can form on the Kraft paper on the insulation side of the batts, where it is not subject to the ventilation (drying) effects of your attic air space.

The problem also is that there really can not be much of an air space between the T%26G and the insulation as the R-30 batts must nearly fill the entire joist space. You need 1 but preferable 2 inches of clear space between the top of the insulation and the bottom of your roof sheathing for adequate ventilation.

Energy code, Building code, and practical construction often butt heads and we are sometimes forced to choose a winner.

I hope this helps,

Bruce Ryan II, RRO
Professional Roof Consultants, Inc.

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