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Roofing/Roof fungi and ventilation


Hi, thanks for your time and expertise. I had a salesman come by ( uninvited) and tell me two troubling things about my roof: first, the moss/ fungus growing on the east side of my roof means there is "guaranteed" water damage under the shingles and would probably need to be replaced. Second, we had a ridge vent with the roof 15 years ago. They said we should NOT have box vents with a ridge vent and we should have soffit vents installed. They were clearly looking to sell us an expensive job ($10,000-$20,000). I don't believe or trust them, especially about the fungus, but the venting made sense to me. How much is true and can the box vents be sealed from outside? ( we had the house energy starred a few years ago and the trap- door attic is covered in loose insulation - they did not build a barrier around it) Also wouldnt they have sealed the box vents?) How about installing soffit vents? How big a job would the box and soffit vents be? What might it cost roughly? It is a big roof- probably 25 feet long. I live in upstate NY...not upstate like 1 hour away from NYC, but True upstate, an hoUr from Canada. I hope I have given you what you need, I am neither handy nor knowledgable. The house is 100+ years old. Thanks again! Todd


Trust your instincts!  Moss growth can occur anywhere the environmental conditions are suitable, generally areas that are cooler and where moisture lingers.  This condition is not indicative of nor is it a certainty that water damage is present on your roof sheathing on that east side.

As for your attic venting, I have to ask, "Are you having any performance concerns in your attic space such as condensation or extreme heat buildup?"  Building code requires attic venting to be split between high and low points with a least three feet of elevation difference.  The point of attic venting is to prevent structure damaging moisture buildup within the attic space.

Shingle manufacturer's like venting for the prevention of heat buildup which can significantly reduce the service life of the shingles, so the only way these ridiculous 30 and 40 and longer warranties work is if your attic venting is perfect - like yours, most are not.

Box style vents can work in combination with continuous strip ridge venting if they are toward the low ends of the roof, so if installing soffit venting is not practical and can be cost prohibitive (likely on a home not constructed with this in mind) this is the next best thing.  Removing and installing box vents are a nominal cost and usually is done from the roof side not underneath.  Access your attic and see if the box vents are closed off, I would not expect them to be.

As for what to do, your roof is 15 years old now and not knowing what type of shingle you have and how they are performing to date, I would suggest that you start saving for a replacement in the next 5 years.  Generally when the shingles start to curl, lose granules, or start falling apart (embrittlement), they need to be replaced.  I suggest you leave your current installation undisturbed until the roof needs to be replaced and then have new box vents installed down toward the low end of the pitch within the attic space.

Historical performance is always a good indicator of what to do, so if you have had no performance issues within your attic for 100 years and you are getting reasonable service life out of your shingles, why change anything?

Bruce Ryan II, RRO
Professional Roof Consultants, Inc.


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Bruce A. Ryan II, RRO


I offer solid knowlege of all types of Commercial and Residential Roofing, Waterproofing, and, Building Envelope systems. Experience ranges across low slope and steep slope roof systems. I am also well versed in matters regarding condensation and ventilation. I enjoy donating some of my time and knowledge to the betterment of others.


Bruce Ryan has 20 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.

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

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)

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