Hey guys, Your expertise would be greatly appreciated here. My question is: Do the new low profile ridge vents work as effectively (CFM airflow) as the standard ridge vents?
The shingles on my roof were recently replaced and a new “low profile” ridge vent was put in. Mechanical installation of the vent looks good to someone who has never installed one (about a 2" gap on either side of the center beam was cut and nails are into the wood to secure the vent). However, there seems to be minimal (if any) gap for air to vent out between the wood roof and the under side of the vent.
Prior to the new roof we had a standard profile ridge vent with less than an inch gap on either side of the center beam. The new extra wide gap in the wood roof seems good w/r/t airflow, but the low profile vent has a very small vertical gap for the air to squeeze out of. From my attic I cant even get a finger into the gap. It seems this small gap competes with good airflow which is what I am after.
Does anyone know if the low profile vents reduce ventilation? I trust the installer who said he will swap out the vent at no charge but I’m not sure if it is needed. It seems low profile is the way of the future.
One more quick question. Because I have a hip roof there is only one gable which a temp controlled exhaust fan is hooked up to. Does that compete with the ridge vent?
i never mix active (powered) venting with ridge vents.
what brand is your ridge vent. we can tell you the net free area of the vent you used in comparison to others. also you need to know what your intake venting is and make sure its not blocked by insulation.
You probably have less net free area in a low profile vent.
But if you have excess heat that the ridge vent can’t handle, the power vent will kick on and take care of that.
Not a problem to mix power and ridge vents.
A little on that here:http://roofersreview.com/PowerVentilators
With all due respect ( and I mean that ), you are completely wrong on this, Sir.
Ventilation is a system, it needs to work together…
It needs to be balanced, if not balanced an excess of intake is preferred.
Insulation plays a large part in this also.
It is a very basic concept that a roof needs to breath in a cold climate.
How you make this possible depends upon the structure.
If you have a flat roof it is a different story…
Passive ventilation is preferred, but in some cases power vents are needed.
On a case by case basis.
Most pitched roofs will breath nicely if ventilation is installed correctly.
It is up to the roofer to determine this, on an existing structure.
It is for the Architect to spec this on new builds.
In my experience Architect’s don’t know Sh*t about roofs…
They are more concerned about the project as whole.
That is their job…
I am a roofer so I am concerned about the roof, it is my problem…
Not much of a problem really…
Give us the freedom to do it right and we will.
The manufacturer will have their stated NFVA, which is Net Free Venting Area, that their ridge vent will provide if installed per their specifications.
Listed NFVA sometimes is not as important as actual performance. A ridge vent which contains an external baffle, such as the Shingle Vent II or the Cobra Snow Country will perform better.
I have more experience with the Shingle Vent II. so their independant lab test results show conclusively that it outperforms ridge vents without an external baffle, which is a trough molded to the side profiles of the product.
Even with a moderate breeze of 3 mph, the performane is increased and it has been tested in 110 mph wind conditions.
The usage of any additional exhaust ventilation product will short-circuit the proper balanced ventilation flowage. When the powered gable vent kicks on, it will attempt to expell more air from it than the soffit vents alone can handle and therefor, also pull air in through the ridge vent exhaust system.
Contrary and in respectful disagreement with what Dennis states, this will and does happen, and that is an improperly functioning ventilation system.
Close off the powered gable exhaust fan by sealing it from the interior of the attic.
Additionally, I have done and also heard of proper ventilation done at the upper 3 foot portions of the hips. Actually, on a cathedral/vaulted ceiling application a little over 1 1/2 years ago, I vented the entire length of all of the hips. The photos I took a couple of weeks ago show conclusively by the snow melt on opposing sides of the hip vent, that they are performing and functioning properly. I will copy/paste my post from another forum and add the photos here later if I can.
Remember, this will improve the total NFVA for the attic exhaust, but not all vent manufacturers state that their product is suited for hip venting applications. For the hip venting portion of the job I did, I used the Vent-Sure from Owens Corning on the hips and the Shingle Vent II for the ridge lines.
Depends on the amount of soffit intake, but, glad to see you’ve come around to my way of thinking.
You are correct, as I did not state that, but only regarding the fact that it depends on the amount, or NFVA, of the intake ventilation.
I am not quite sure I ever made any statements contrary to this, ever. Multiple exhaust vents will fight each other to see which one will expell the air. A powered version will over rule the static air verion, hence creating intake through an exhaust vent, whether it be ridge vents or mushroom vents.
So you would rather have excessive heat in the attic???
I would rather get the heat out of the attic, without creating a short-circuiting of the ventilation flowage or creating intake through the exhaust ventilation product. I would also like to follow the manufacturers specifications and guidelines, so that their and the shingle manufacturers warranty remain intact. I also would not like to be challenged in court someday for going against the manufacturers specifications, because someone had a belief that the manufacturers specifications were wrong and I wouldn’t want to be liable for the ensuing weather inhibition due to doing the ventilation incorrectly, as you suggest.
Do you mean on a cathedral ceiling, or a hipped open attic with short ridge vent?[/quote]
The first set of photos describe a cathedral/vaulted ceiling where I installed the Hip Vents. We also did additional work to allow for the free flowage of air from the Smart Vent along the eave edges to carry through the rafter bays, by inastalling continuous insulation baffle vents from eave to hip rafter or ridge line. We also notched and/ or drilled 6 of 1" diameter holes in each jack rafter intersecting at the hip line to allow for a cross ventilation from one rafter bay to the adjoining ones.
I would think that additional upper air exhaust could also be achieved if the ridge line is not long enough to provide the correct amount of NFVA, by adding additional sections of Hip Vent along only the upper-most section of the hips where they intersect with the ridge line. That supposition is in theory only on my part, since I have never done a partial Hip Vent, but I have seen it on other installations not done by our company. As always the calculations must be done to quantify the correct amouns of both intake and exhaust are being achieved.
Did the photos I inserted into the previous posts show up for you? For the ones that I am currently speaking about, there are written descriptions where they apply.
There is no short-circuiting as the whole of the attic is exhausted through the power vent. Creating intake through the exhaust or ridge vent is relative to the size of the attic and soffit intake.
The short circuiting is when the exhaust vent now becomes an intake vent. I think that we will continue to agree to disagree on the short circuiting aspect.
I have yet to see a manufacturers warranty that voids for ventilation issues other than “inadequate ventilation”.
I have read court case legal documents where the roofing contractor was held responsible for not doing the job precisely as the manufacturers recomendations, for both roofing shingle installations and for improper and unbalanced ventilation. By doing it the way stated and specified by the manufacturer who backs up their proven methods, then a company would be released from that aspect of liability.
I assume you are talking about a hot, sunny day with a cold dry snow falling.
Either that, or, as we just experienced last Saturday around Chicago, a period of several weeks with below freezing temperatures and a recent 12" to 14" snowfall, all melting almost historically fast, due to one day where the temperatures rose to around or above 60*. There may possibly be other scenarios that could occur as well. Such as excessive interior moisture content unable to escape the attic interior due to short-circuiting, or even due to erroneously installed or unsufficient or unbalanced ventilation specifications being provided by the specifying contractor. This environment would be a mold breeding ground, full of potential liability. Mold claims are the legal professions new and improved version of asbestos litigation.
How would that be any different from installing a pot vent a foot down from the peak of the hip. According to your reasoning, any opening below the ridge vent would create a short-circuit.[/quote]
If you read through what I stated, you will see that this position is just my personal and hopefully, professional opinion. Not something that I have actually done. BUT, now read through the Air-Vent position on ventilating homes with ridge lines positioned at different elevations. In that FAQ from the Air Vent seminars, they specifically state that as long as the ridge line elevations are no more than 3 feet in difference, then the proper procedure would be to install ridge vents on all of the ridge lines incurred. (I bet you thought you had me on that one. He-He.)
Now, that is why I stated that a hip vent, and to be more specific, a hip vent on an open cavity attic chamber, would still fall within the scope and guidelines of the manufacturer without causing the short-circuiting of the ventilation flowage.
Dennis or others, will you please answer my question about whether or not my photos showed up properly on this forum for you please. TRG on another forum, stated they did not come up on his computer.
By the way Dennis, although we disagree, I do really appreciate anyone who stands strong with their convictions, especially one who is able to back up their claims with any degree of legitimate validation.
Would you like to find out about another very, very useful and informative roofing forum? If so, please do not abandon this site,l but add this to your knowledge arsenal:
I think the generally accepted definition of “short-circuiting” is when the flow of air from intake to exhaust is interupted. When all the attic air is exhausted through a power vent there is no interuption.
Grasping at straws. A situation where a snow covered roof and attic heats up to turn on a power vent thermostat set at 110 degrees ain’t gonna happen.
As for high humidity, any moisture introduced is expelled. Just as with ridge and soffit.
I agree, even more so if it was a power vent at the hip peak.
Your thumbnails show up fine, but they don’t click to enlarge.
Just supplying the reference for my previous manufacturers suggestion regarding the differing height elevations for multiple exhaust vents and in this particular case, they are specifically speakinf about ridge vents.
Copy/Pasted from a DIY Forum I had previously replied in:
Here is the written response to the question about applying Ridge Vents on homes with multiple ridge line elevations, taken from Air Vent Corp., Ask The Expert Seminars, directed by Paul Scelsi.
How do I ventilate a roof with multiple ridge heights?