Ridge Vents – Should I put them in?
DesignBuild
| Posted in Construction Techniques on
It is officially raining INSIDE me house now so I think it is time to re-roof. Question is: should I cut in ridge vents while I’m in the process?
The house is a one-floor ranch. Most of the details of the existing roof are in the attached image. I just installed rafter vents above the kitchen since I had removed the ceiling there during the kitchen remodel. I will get the rafter vents throughout the rest of the house once the temps come back down and I can work up in the attic semi-comfortably.
Would love to here your recommendations, thanks!
Sean
EDIT: forgot to mention I’m in the Northeast – Jersey to be precise
Edited 7/10/2008 11:29 am ET by DesignBuild
Replies
I would, but remember to get a ccontinuous ridge vent to work right you need ccontinuous eve vents, it works as a package.
Wallyo
I agree with Wallyo. The best system is continuous soffit vents with continuous ridge vents and no gable vents. Bob's next test date: 12/10/07
Edited 7/10/2008 12:25 pm by Jim_Allen
As long as you have enough regular soffit vents you'll be fine.
Agreed.The formula calls for a balanced intake at the bottom with the outflow at the top. It doesn't have to be perfect but the forumla calls for 1/2 of the vent at the bottom and half at the top. Bob's next test date: 12/10/07
I would cut in the ridge vent.
As others have said in order for the ridge vent to perform properly, the soffits need to be vented and you should not have any gable vents as they short circuit the designed air flow through the attic.
The smaller net free vent area of either the ridge vent or the soffit vents will control the amount of air which can actually move through the attic.
Hypothetical case using totally bogus numbers:
Cut in ridge vent which provides 6 sqin NFVA per linear foot - 100' of ridge - provides 600 sq in of NFVA at the ridge.
Soffit vent at 2.5 sqin NFVA per foot - 200' of soffit - provides 500 sqin NFVA at the soffit.
Since 500 < 600 - the system will perform at the 500 level since that is all the air it can draw. Even if one enlarges the ridge vent area to 1000 sqin - it will still perform at the 500 level - soffit vent area is the limiter in this example.
What to do about that pesky gable end vent and gable end fan? I would be inclined to leave them in place for the time being. However, to avoid short circuiting the air flow from soffit to ridge vent, they would both need to be sealed (plywood or some such on the inside).
Jim
That's what I'd do...seal them up. Bob's next test date: 12/10/07
thanks for the replies -- sounds pretty much like a unanimous yes. I do have the perforated undereave vents similar to those in the attached illustration, and they are continuous around nearly the entire roof line which I have to assume provides plenty of intake air, especially once I get all the rafter vents installed properly. The eaves are also very deep - approx. 24".Closing up the gable vent and attic fan I don't think will be that difficult either. The fan I will probably just pull out since I was considering replacing the siding on the gable with some Azek or similar - its in pretty tough shape at the moment anyway. And the gable vent I can just paint plywood to match and install from the inside.
sounds like you are making the right moves!
I would leave well enough alone, never had them, why ask for possible problems. Moisture in the attic is a nightmare (read) MOLD. New construction yea, remodel NO. IMO.
What does installing ridge vents have to do with getting mold?
My expierence with retrofit has not been good. My own home. 100yrs.plus. Ballon const. I boxed in the rafter tails with solid wood installing 2" rd. vents in each bay. Then had to go into the attic and drill thru each bays blocking for the venting to continue, install those crappy styrofoam shoots. Keeping the insulation away from the top plate. I felt it was a tremendous amount of work FOR WHAT. It had survived very nicely for 90yrs. without the ridge vent. I GUESS the balance of air flow was not proper, cause it ended up sucking heat into the attic, which when meeting the cold/freezing roof sheathing MOISTURE and then MOLD. Based on this expierence when dealing with clients who have older homes, I recommend Leave well enough alone.
Why bother to insulate then? Somewhere you have created a problem in your house. My fealing is that you didn't create proper amount of venting along your eaves, with too little insulation in the attic. Proper amounts of ventalation will eliminate the moisture in the attic. More insulation will reduce and almost eliminate the flow of heat to the attic space.
If you recommend this to your clients, to leave well enough alone, you are doing your customers a large disservice. Somewhere you have misswed something in your house, and because of this, you are passing this along.
It sounds like you did not seal the gaps around all the pipes, wires, and other holes that have been poked in the ceiling over the years. They have been stealing the heat out of the house for 100 years. With no insulation, it was never noticed. Sealing those gaps should be priority #1. They are going to have the biggest impact in reducing fuel bills for little cost although it is not a fun or glamorous job.