Follow Up: Problems with Cobra III Ridge Vent

GADad · 09-28-2009, 10:56 AM

These are a few pics of our brand new ridge vents during a rain this weekend. The vents are dry (no condensation at all) when it is not raining. Does this look like an installation problem or could it be a negative pressure issue (bringing the outside weather inside). This weekend, we left the attic fan off during the rain (it also has a problem it seems...water splashing off the deck and coming in through the screening). This attic space was originally vented with three gable vents and an attic fan. Only since the new roof was installed, are we getting moisture. And specifically, the moisture is accumulating on the new ridge vents and new fan.
Thanks for anyone's comments.

AaronB · 09-28-2009, 11:23 AM

If you're using ridge vent AND attic fans, this is a big no-no. Likely to be pulling outside air in through the ridge vent via the attic fan. Roofer should have known better than to mix the two.

GADad · 09-28-2009, 11:37 AM

We did not have the fan running when this rain event occurred. And still, you can see the amount of water that built up on the vents. Would that mean that they are installed improperly?

Slyfox · 09-28-2009, 11:55 AM

Even when your power vent is not running it is still open and allowing air flow in or out.
That much water in the ridge vent is most likely a wind driven situation,
it happens with all types of exhaust vents. If the vent was installed properly the amount of water getting in will be minimal to the point of doing no harm.
In my experience I would say the amount of wetness showing in your pictures is high and I would check to make sure the ridge vent is fastened properly and has a proper amount of ridge cap overhang.

GADad · 09-28-2009, 12:11 PM

The roofer recommended the attic fan for one half of the attic. This particular side is very steep and apparently doesn't have a long enough ridge to accomodate a working ridge vent. Unfortunately, what we discovered after the installation was that the roofers actually cut open the short run of ridge on the same side of the attic as the fan. Now they are saying that they can just close it up. (We are a little concerned with how they plan to do that so that we don't have future problems. They said it is not a big deal; that they will install ridge cap shingles and place another piece of ridge vent on top for asthetic purposes (which is what they were supposed to do in the beginning).

There is a plywood partition wall between the two sides of the attic. The other side of the attic has the longer section of ridge vent. (We do also have a large gable vent on the same side that they said would not be a problem.) The roofer originally indicated that there would be no problem utilizing ridge vent for ventilation on that half of the attic ...while using the venilator fan on the other side.

Now we are thinking that maybe we should just have them close up all of the ridge vent and go back to just merely using the gable vents and the new fan. ??

AaronB · 09-28-2009, 12:24 PM

One or the other.

I have never seen a situation whereas the roof was too steep for ridge vent. A steeper pitch means faster hot air rise and vent.

Slyfox · 09-28-2009, 05:57 PM

8/12 was the steepest for the exposed metal ridge vents, but I have not used any cap over styles that have a limit on steepness.

Power/Solar Fans work,
Box vents work,
Ridge vent works the best.

Take some pictures of the ridge vent "exterior" and maybe we can spot a problem in the installation. Take the picture with the power vent viewable as well if possible.

oldfrt · 09-28-2009, 07:22 PM

From what I can try and see,it looks as though the vent holes may be cut improperly.

In the first pic it looks like the there is a strip of plywood just to the right of the ridge and then a cut section of decking for venting.
On the second picture,it looks like the vent cut in the plywood is too wide.
This would mean that the ridge vent doesn't overhang the shingles enough and your getting splash in from the rain.

Typically,the decking is cut 1" from each side of ridge and the ridge vent would overlap the shingles by about 3".

GADad · 09-28-2009, 09:32 PM

That is what we were thinking...that the opening is too big. Now what? Is it safe for them to just close them up and utilize the original ventilation (gable vents and attic fan)? What is the appropriate method of closing the ridge vents?