We had a new "25 year" roof put on 12 years ago. The house was originally built with soffit vents and gable vents. When the new roof was put on the roofer added the roofline vents. The plywood is now rotted because of condensation and the roof will have to be replaced again. I had a different roofer come out to try and determine what had caused this to happen. It was his opinion that is was due to the gable vents not being closed off when the roofline vents were installed. We are the second owners of the house. We never had condensation problems in the attic until after the old roof was replaced. The previous owners took very good care of the house and I doubt they would have not fixed a problem like that.
Beats me. Until this problem was discovered I didn't know diddly squat about attic vents. I assumed that the person I paid to do the job would do it correctly. I wouldn't have known to ask about the gable vents and relied on his professionalism.
When the guy I had come out to diagnose the problem gave me his opinion, I asked him directly if the roofer who did the job had been negligent in not closing the gable vents. He said yes, he was. If that's the case, his mistake is going to cost me a good deal of money. It seems to me that his negligence, if that's what it was, is the cause of the damage. Why should I be responsible for paying any part of it?
It's not what he did, it's what he didn't do. Failing to do something you're supposed to is just as bad as doing something you're not supposed to.
IMO, I find it very hard to believe that adding can vents to an attic that already has gable vents and soffit vents is responsible for moisture causing roof failure. The flow of air is from the soffits up. Previously it went only out the gables, now it can flow out those plus the can vents. You'd have to have a hell of a lot of moisture coming from somewhere to get enough moisture to create a problem. There are millions of homes that have all kinds of mixes of attic ventilation and this is the first one I've every heard of where adding more vents created a moisture problem. And exactly what in the roof is failing? Sounds like it's the plywood rotting?
I would make sure all sources of moisture have been identified. Where do all the bath exhaust fans go? It's not unusual to see these either discharged incorrectly into the attic or routed to a soffit, with the hose just laying next to the existing soffit, rather than have a proper outlet.
I'd get a good home inspector in to take a look at the problem and give an opinion.
You're assuming the air is flowing out of the gable vents. Maybe it's flowing in because more air is flowing out of the can vents?
Someone responded elsewhere in this thread: "when they did my new roof they closed the gable vents and put in ridge vents along with the soffits already there." Why would they close the gable vents if, as you are proposing, they would have made the ventilation more effective? It may have as much to do, or more, with the relative position of the different vents as how many vents there are. I don't know, but it sounds plausible.
Yes, the plywood. The shingles look fine. Looking at the outside of the roof you'd never guess there was a problem.
We have an upstairs and a downstairs bathroom. The upstairs bathroom is the one that is used 99% of the time for showering and bathing and it is unvented. I'm told this is because it has a window that opens so venting is not required by code. The downstairs bathroom is vented. I'm not sure if it's vented into the attic or through the attic and out a vent. Since it hardly ever gets used, though, I guessing it wouldn't matter one way or the other.
Exactly which way the air flows at any given time is probably a complex issue depending on among other things, wind speed and direction. If a strong wind is blowing at a gable, then yes, I would expect air to be going in, instead of out. And I still believe that with adequate soffit vents, adding more vents in the upper atttic, whether gable, can, ridge, power, etc will only make things better, not worse.
Because there are various theories to optimum ventilation and you can find roofers that subscribe to one or more of them. The idea here is that some air will come in from the gables and flow out the ridge, rather than have the air flow all the way up from the soffits, which is optimal. There are two factors here. One is if this does in fact occur, or does most of the air really follow the logical path from soffits up and out. The second is, how big of a factor is it? I could see it possibly causing the ventilation to be less than optimal, but that is a long way from being able to create a problem like yours with rot due to moisture. I've never heard of moisture rot in an attic with any reasonable amount of ventilation, unless there was some other major defect creating a source of moisture. And I would say your attic with two gables, can vents, and soffit vents is reasonably vented, provided they are all unblocked and an adequate amount.
Speaking of blocking, have you made sure the soffits are open? It's very common for insulation to be pushed up against them to totally block them. There are plastic baffles available that will keep the insulation away.
Do you have a vapor barrier on the insulation? Considering the problems you are having, I'd definitely get a bath vent installed, as all that moisture has to go somewhere. IS the failing roof area near the bathroom?
Frankly, the assertion that installing extra venting has somehow caused moisture buildup leading to damage seems bogus to me. And I would be very surprised if the guy who "negligently failed" to close off the gable vents will accept it without some proof beyond "this other guy said so." Nor should he, IMHO.
If the thesis is true, it seems to me the damage should show a pattern related to the allegedly short-circuited air flow. Is there such a pattern?
Well, I don't subscribe to the thesis, so it's kinda hard for me to say, but I would think it would be concentrated around the areas that are no longer getting adequate ventilation as a result of the gable vents. So it would presumably be away from the gables and near the soffits (i.e. low on the roofline), particularly at the ends of the house toward the offending gables. But somebody who actually believes in the theory should be better able to say.
If it's replacing hot air with cool, it'll result in convection. That cool air coming in from the gables will drop as the hot air near the soffits rises. So it's not clear to me that anything has been lost.
You may have said that already somewhere, but thanks for repeating it.
I have a friend who was talking about a new roof, I think, and I rushed to remind him that he should get a roofline vent. Then when I was there later, I saw he had gable vents, so I weakened what I had told him. The gable of course is not all the way at the top, like the ridge/roofline is.
OTOH, fressh air could be coming in through the soffitts**, and the gables and even the ridge vent, and all of it blowing out because of the powered fan. I think that would be fine too.
**Oh, yeah, make sure the soffitts aren't obstructed by insulation. Did the roofer who came recently look at that?
If you have time, Before it gets too hot, go up in the middle of the day, or 10AM or 4 or 5 or 6 PM with a cigarette or something else that makes smoke** and check out the air currents.
**I don't mean to smoke it, but they seem to make smoke sometimes just by being lit. There must be something non-flammable that is visible.
You didn't bring this up, but as an aside, if you are looking for him to share the cost of the new roof, as opposed to just coming over for an hour and blocking off the gables, I suspect another problem you have legally is that you had 12 years to notice the problem and mitigate damages. I don't know if you knew or should have known that you had condensation, or that the condensation was damaging the wood, but I think that would be relevant.
OTOH if there really are different theories of attic ventilation among pros (I am no pro) your 12-year ago roofer probably wouldn't be found negligent. Sometimes no one is negligent, even when things don't work out right.
But what differencd does it make?. The goal is to exchange the hot air in the attic with cooler air outside, the humid air in the attic with less humid air from outside.
For every bit of air that enters, some air has to exit somewhere.
Even if the air near the bottom of the attic wasn't moving, because the gables usurp the air flow to the ridge vent, iiuc, the humidity in the lower air would still disperse into the rest of the attic unrelated to air movement. Separate gasses, partial pressures, physics is a blur to me, but that's what I think.
Like the smell of a dish of gasoline fills a room even when there is no breeze. Does it do that? What about the smell of cooking. Doesn't that fill the adjacent rooms faster than the air as a whole moves to that room?
I realize that theory, even if reasonable sounding, doesn't trump fact.
To get facts, aren't there things that make smoke, like smoke bombs? Are there July 4th smokebombs or are they only found in the military? Can recreational smoke bombs, if any, be broken into smaller pieces?
I don't think the post that follows sounds bad, but if so I apologize. This particular topic, or at what I related it to, raises my blood, for reasons you'll be able to figure out when you read my reply. And I got all caught up in it. But now that I'm NOT writing, I've cooled off. I don't see anything that should be rewritten, but I can't tell how it will sound to someone else. I apologize if it has too much punch to it.
If the new guy is right, you make a good point.
In one way yes, but to me, in another way, no. Charging for doing something one is not supposed to do, for me, is worse than not charging for not doing something one is supposed to do. For one thing, motives are suspect in my mind when the person gets more money for his mistake. Mere incompetence is not only something I try to tolerate, it is something I expect, given what things have happened to me.
To the extent that one is paying for an expert opinion, they are probably the same, but I never trust anyone's expert opinion anyhow. (I rely on it when I have to, but I never trust it.)
This may have started when I was 13 and was malpracticed on by the first of several doctors, all about different things, and none of which caused me any permanent harm, thank goodness.
But I was treated, given drugs, by two doctors including a neurologist for epilepsy when I never had it. And one of the two, my gp, failed to immobilize my arm when I dislocated it (all he did is xray to see if there was a fracture) and if he had, maybe I wouldn't have had 40 later dislocations and required surgery.
Another doctor at a local little clinic told me I had appendicitis and was ready to do surgery that afternoon, or hand me over to someone, but I went to a specialist on York Avenue, and he saw the *bruise* right there where the soreness was!!! I was only about 20 pounds overweight then, but the fat was in just the right spot that even when I knew there was a black and blue mark there, I couldn't manage to see it. (well maybe I should have tried a mirror :-) but I was in a doctor's office. ) But that first doctor should have seen it. I had no "rebound tenderness" I think they call it, just soreness from the bruise. (I have no idea how or when I got the bruise.)
An orthopedist in a foreign country didn't set my broken leg right, but a different one in the same city did so a week later, after I had the sense to get a second opinion (because I couldn't stand up for more than 10 minutes because of the excruciating pain at that point.) The second orthopedist wanted to know the name of the first one, because he had done such a bad job. I think now that I should have told him.
There are another couple incidents I can't think of right now.
A teeny one: in high school my GP had me soak my inflamed ingrown big toes in potassium permangenate every night for weeks, but I think it was known already that KHMnO3 or whatever the formula is doesn't actually help inflammations. It just wasn't known when he went to medical school. It didn't wash off and I had red feet for weeks. At least I never spilled it on the carpet, and it was in the winter so no one laughed at me. ;-)
My girlfriend has simliar stories, and yet we both go to the doctor when we're sick, because not going would be more reckless.
So if someone fails to nail a sheet of plywood where he should, I think I got off easy. I don't think it is as bad as actually giving drugs for something I didn't have. I know this is apples and oranges, but these doctors and other non-doctors have shaped my feelings. So I don't think doing and not doing are the same.
Or you could take the approach I saw in a coastal town in Louisiana a few years ago. This fellow added a whole second roof, about five feet above the real roof. Basically, he built a no-wall pole barn over his house. Ugly, but I bet it did keep the roof cool. (No real trees around there, being barely-dry mudflat and all, so shade was a rare thing...) It'd be an interesting concept to build into a house from the get-go- make the upper floor a screened deck, with wide overhangs. Water control would be a problem. Rich people down south used to have huge sleeping porches under deep overhangs, just to be able to sleep at all.
The thing is, I'd expect bad venting to contribute to a shorter shingle-life, but it's not at all clear to me that it's a proximate cause of mold and rot. That would require leaks, or venting some appliance into the attic space, else where did the water come from in the first place?
Well, it looks like what I was told about the gable vents interfering with the roof louvers (roof line vents) is correct. I called the roofer who installed the roof and asked him about this. He did not dispute that the gable vents probably should have been sealed, but said that this was "new technology" that was not known when our roof was done. This may be the case, I don't know yet.
Also, a pamphlet put out by the Air Vent company confirms that too many vents, if they are of incompatible types, can interfere with each other. The example they use is roof louvers interfering with a ridge vent. I don't see why the same wouldn't be true of gable vents and roof louvers. The gable vents are supposed to be exhaust vents and so are the roof louvers. Here's a link to the pamphlet...
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