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Roofing/ridge vents and power fans

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Question
We live in south Alabama and are about to undergo a re-roof due to hail damage.  We currently have an aluminum ridge vent , and a power fan that is turned on by a thermostat.  We had the power fan installed because the attic space was unbearably hot,and it raised the temperature in our attached garage. One of the contractors has recommended removing this power fan, because he says it works against the ridge vent.  He does use a different style of ridge vent than we have now..  brand name of Cobra vent. Is this vent different enough that the power fan is unnecessary?  Why would the power fan work against the roof vent?

Answer
Kerry,

Not knowing all he specifics of the house, let me offer some general opinions that should address you couple main questions.

Aluminum ridge vents are not readily available or used primarily due to cost.   Factory-fabricated "ridge" vent materials are commonplace due to cost and ease for roofers to use.  Most roofing product manufacturer's also make or market these roof vent products.  The Cobra Vent you mention is one of those.  There is no reason to believe your aluminum vent is not suitable and should be reused, unless you simply do not like the look or changes have been made to the home that the ventilation ratio is not longer satisfactory.  The International Residential Code out lines the venting requirements, but keep in mind it may not be the same as it was when the house was built.  Ventilation requirements have not changed substantially, so that does not raise a concern in my mind. Unless he offers sound reasoning why the aluminum vents are no longer suitable for use, I would plan to simply reuse them.  He may just not want to take time to carefully remove and reuse them and using new is easier for him, which I suspect is the case here.

As for the power vent, theoretically, one could say it conflicts with the power vent when it is in operating mode and exhausting air. But is this not the purpose of ventilation to remove stale air and create air exchange in the attic? So what difference does it make if it is the power vent or ridge vent that is contributing to the air exchange.  When the power vent is not running, it should have little or no impact on the venting of the ridge vent.

In summary, unless a good justifiable reason is offered (other than cost) the existing aluminum ridge vent could be reused. The power vent, as I understand it is being used, is of no quantifiable detriment and could remain.

I wish you the best in your roofing adventure and suggest you think all proposals thoroughly and with a clear mind frame as it can be trying of one's patience and decisions can sometimes be made in haste or frustration.

Steven C. Wadding

Roofing

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Steven C. Wadding RRC,RRO,CDT

Expertise

General questions in regards to most roof types and situations. As the Technical Services Manager for Polyglass USA, Inc. this would not be a forum to address any issues directly related to a product my employer manufacturers.

Experience

I have been active in the roofing and waterproofing industries for more than 30 years with extensive experience from product installation, product development and consulting. I have been active in the Construction Specifications Institute and Roof Consultants Institute for approximately 20 years. I am a member of ASTM and am a voting member of various subcommittees. I have many years of consulting experience in the fields of Roofing, Waterproofing and Exterior Building Envelope disciplines.

Organizations
Roof Consultants Institute Construction Specifications Institute ASTM

Publications
Division 7 Technical Binders for Malarkey Roofing Products and Polyglass USA, Inc. CSI Phoenix Chapter Cactus Comments

Education/Credentials
Registered Roof Consultant - Roof Consultants Institute Registered Roof Observer - Roof Consultants Institute Certifified Document Technologist - Construction Specifications Institute Spray Fireproofing Special Inspector - International Code Council

Awards and Honors
Registered Roof Consultant - Roof Consultants Institute Registered Roof Observer - Roof Consultants Institute Certifified Document Technologist - Construction Specifications Institute Spray Fireproofing Special Inspector - International Code Council

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