Roof Venting Question (help!)

happy_will

Hi, hoping someone can give me some advice.

I am building a house with a 6/12 roof pitch and a size of about 25 squares. House has eaves and rakes of 4 feet (no exaggeration) which will be soffitted. The roof is gabled (i.e., not hipped). The roofing contractor wants to use mushroom vents, but I would prefer a ridge vent--it looks nicer. I haven't had a chance to talk to him, but isn't the house a good candidate for a continuous ridge vent considering the size of the soffits?

Does anyone have any tips for me that I could share with the roofer?

Grumpy

First off understand that roof venting is a science unique to the architecure of your home. There are no one size fits all solutions. Also understand that any advice anyone gives you in this thread is based on averages and rules of thumb because we are speaking "site unseen". The point I am trying to make, is attic ventilation is tricky, to say the least. Check out these websites www.airvent.com www.rollvent.com

What type of venting in the soffit? 2" continuous? 4x8? 8x16? Spaced how far apart?

How long is the ridge? Is it a hip or gable roof? Which type of ridge vent (they are not all the same)?

Are you prepared to pay extra for the ridge vent? It will cost more. Are you sure the house is 6/12? I don't like putting ridge vent on less than 6/12.

Alan Hughes

Your roofer isn't looking out for your best interest IMHO. I'd talk to some other roofers before deciding to use him/her.

Ridgevent and soffit vents are the most effective vent system and when installed properly will save you much moola in the long run in several different ways. Shingle life, sheathing life, ac cost, all are directly affected by attic ventilation. It's one of the most important aspects of a longlived roof yet gets minimum attention by many roofing contractors and builders.

Also my experience is ShingleVent II is the most wind resistant and troublefree (of the ridgevents I have experience with). I strongly dislike the roll out ridgevent (Cobra) as it did not do well locally during Hurricane Isabell.

Find a KNOWLEDGEABLE contractor that really cares about quality, your longterm satisfaction, and references (like me and some others here) and you'll be all smiles when you move in knowing the roof is one area you shouldn't have to worry about.

Grumpy

I agree ONLY if the ridge line is adequate for enough ridge vent. If it's a hip roof this might not be the case.

I agree. I also like the Shingle Vent II, but GAF also makes a knock off called Cobra II which is very similiar, and not rolled out. I haven't used it but have seen it at my supplier.

happy_will

Thanks for your help, everyone. I really mean it.

To answer some questions, The roof pitch is exactly 6/12, and the roof is gabled (not hipped). The ridge length is 40 feet, including the rakes on each end. On each gable, the distance from gable end to the ridge is 27 feet. Roof rafters are 10x12's, and space under the roof will be occupied. Roof is 40-year architectural asphalt shingle.

Neither the ridge vent nor the soffits have been installed, and I am willing to select whatever is necessary to avoid the mushroom vents. There has to be a way to make this work with a ridge vent, don't you think? I am willing to select the highest profile ridge vent and soffits with the widest openings, and can spend the extra money (within limits!).

Grumpy, I can even show you the plans, or the house, itself. It is just a few miles east of Glenview! Small world, eh?

Alan Hughes

I assume 2X12s.

as in finished rooms in the attic space? if so or ceilings are to be put up upstairs, make sure the air tunnels are in place before the insulation goes up or it's all for moot anyway. very important!!!

Sounds like a perfect roof for ridgevents. Will there be gable vents also?

Grumpy

From what you described, assuming you have a positive and unrestricted air flow from soffit to ridge, you should be fine. If you are fastening a drywall to the bottom of the rafters(vaulted ceiling) please make sure there is at least 1" of empty space at the under side of the roof deck for air to travel. Also if there is a vaulted ceiling then continuous soffit vent is the way to go IMO so that each rafter "tunnel" has intake and exhaust.

happy_will

Allan, sorry, I meant 2x10's. Rooms in attic will be finished--thanks for the heads up about the air tunnels. There is a place in the gables where we can install gable vents, but I've read in here that it's not good to combine gable vents with ridge vents.

Grumpy, thanks, I suppose I will have them use the air tunnels than Alan suggested.

Alan Hughes

argueable somewhat (each house is an individual) but it's not that big an issue so long as there's unrestricted air flow from the soffit upward.

ps,

and the soffit area exceeds the exhaust area.

thought I'd better add that.

River Rat Dad

The shingle vent II, which I vote for as well will have a net free airflow of 18" per running foot. Airvent also makes continous soffit vent at 9" per foot which balances well with the ridge vent when installed on both sides of the house. I am a fan of skiping the gable vents as they are likely to short circut the system. Air follows the path of least resistence and the ridge would rather draw its makeup air from a gable vent 2 feet down than a soffit vent 20 plus feet away. The 48" overhang presents a question. It is common to run the continous soffit vent roughly down the middle, but I recall a structual engineer who insist's that they should be installed as far to the outside edge as possible.