Q&A – Should I Install Ridge Vents?

Working on reroofing a rental building he owns, this Georgia building owner wants to know if he should install ridge vents. 

Ralph, a building owner from Georgia, asked if he should consider adding ridgevents in his reroofing project. He asked: 

I will be reroofing a rental building that I own. I would like to know if I should be installing ridge vents. Currently no ridge vents are being used. For a better roofing system, should I install them? What would be the best leakproof, longest lasting,lowest maintenance ridge vent available? What are some requirements as far as pitch and proper soffit venting? Current pitch is 4:12 We will be resheathing 4'x8'x1/2". I am planning on using OSB. Would you recommend using a radiant barrier lined OSB board? Some of these buildings do not have any attic insulation installed. Total roof is 288 squares. 1 of 6 buildings that have to get reroofed.

Our roofing expert John Kenney from Cotney Consulting Group had this to say: 

I would recommend installing ridge vents when you reroof the buildings. For a ridge vent to work properly, it needs to pull the flow from soffit venting. I would recommend using a ridge vent recommended by the manufacture of the shingle you decide to use.

Radiant barriers, if installed correctly, are stated to be 97% of radiant heat. The product was designed to work in conjunction with insulation and you must have at least ½” to ¾” space between the barrio and insulation below or condensation will occur in cooler weather.

Another roofing expert, John Stout at Go Roof Tune Up, said: 

Ventilation is always a good thing. It helps cool and provides a way for moisture to exit the attic space. All of the major shingle manufacturers have a ridge vent that is part of their preferred roof system use the vent that goes with the shingles that you pick.

Soffit venting or Low roof venting (intake) needs to be equal in sq in. to the ridge venting (exhaust). 1/300 is the normal calculation some areas 1/150 is recommended or required. Check with your local build department. Your pitch of 4:12 is good for a shingle system.

If you are removing all of the existing substrates and replacing them with OSB then you will gain some “R” value with the radiant barrier, if however you are installing the OSB over the existing substrate you will not. Research has shown that radiant barrier does not perform without open air below.  Attic insulation is always good to add and while you are reroofing access is much easier.

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