Installing an O’Hagin Vent on a Shingle Roof

What is an O’Hagin vent?

In this video, I’m gonna show you how to install an O’Hagin low-profile vent on your shingle roof. O’Hagin vents are one of the best vents, in my opinion, on the market today. They’re both slick, look nice, and have a great venting per square inches. It’s 72 square inches per O’Hagin vent. Now just to let you know, O’Hagin is a brand name. The generic term is low-profile vents. Owens Corning has their own low-profile vents that are pretty much identical to O’Hagin’s. So whether it’s an O’Hagin or an Owens Corning low-profile vent, the installation method is the same. The nice thing about them is they are a lot sleeker. So you can see instead of the big dormers, you only have about two inches sticking up from your roof. The shingles get installed all the way around. They come pre-finished in black, brown, white, I believe light gray, and a conventional galvanized. O’Hagins are also great for exhaust venting. So the way the vent is built is, if you install this near to your ridge, it can serve as a great exhaust, as well as an intake and cross flow vent. There’s a few steps to make sure that your O’Hagins don’t leak. So watch our video, and I’ll show you the tricks of the trade.

How to locate where to install your low profile vent

The first thing we wanna do to get started is cut our wood deck. Now you wanna have your shingles installed up to wherever that you wanna have your vent installed. So you wanna have your shingles pre-installed, and you wanna have your underlayment installed already as well. The low-profile vent gets installed on top of your underlayment, and you don’t have to lap that properly. So you can just work on the roof, and progress until the point that you wanna install the vent.

How to measure and cut your vent opening

Now in order to find the center of the vent, what we like to do is just keep it simple. First thing is we align it to essentially where we wanna have it installed. Now you pretty much lap this like you would any other shingle. So if your shingle were to come down here, you wanna make sure that your vent is aligned there. You don’t wanna install it up, you don’t wanna have these nails exposed. You can come lower. You just don’t wanna go higher than the exposure line. Generally, we like to install it right flush with that exposure line. That way, when our next shingle comes on top, we completely cover this flashing and have a real clean installation.

So once we align it, what we’re gonna do is use a marker to lift this up and mark the center of this vent. Once we have the center marked out, we wanna measure out an 11×11 square, and cut that out using our Skilsaw.

So now that we have our roofing membrane, the underlayment, and the top of the shingle cut out, what we wanna do is pull any nails that are in our 11×11 square. Really, when you’re aligning these vents, it’s not important that you don’t hit a rafter, you can just put it where you please. If there’s a rafter going straight down the middle, that’s totally fine, and we actually have that in this example. So we’re gonna pull the nail. One thing we always wanna make sure is that we don’t have nails when we’re cutting with a Skilsaw. That can cause the Skilsaw to kick back and it also ruins our blade. So we’re gonna remove all the nails, then we can go ahead and cut the square out with our Skilsaw.

Now that we’ve got our 11×11 opening cut and ready to go, we’re ready to install our O’Hagin. Like I mentioned, you can see that we have our rafter here. That’s not a problem, that does not impede proper ventilation. So we just need that 11×11 opening.

Place mastic at the opening and install your O’Hagin Vent

Now, one thing that the manufacturer recommends and we like to do, is install a bed of mastic around this opening. So you wanna make sure that you’re installing it on your roofing membrane, and you wanna lay about a quarter to half inch bed of mastic around that opening. This is both something that Owens Corning and O’Hagin recommends, and is a secondary or third line of defense for leaks. Now that we have our mastic in place, we’re ready to install the low-profile vent.

What kind of nails should you use to install an O’Hagin vent?

The type of nails that we’re gonna be using is the same nails that we use for shingles. Essentially, they’re electro galvanized coil nails that go in a nail gun. You can nail by hand as well, inch and a quarter to inch, to inch and a half, depending on what deck it is. Generally, the manufacturers recommend penetrating past that wood deck, half inch to three quarter of an inch penetration for a proper grab. So these are the nails that we use. We like using a nail gun, it just makes our job a lot faster and a lot easier.

So we wanna make sure that we properly align the low-profile vent with the opening. And again, like I mentioned, we always prefer to go flush with this exposure line, the same place you install your shingles, to make sure that you have a nice, clean and waterproof finish. So once we have that in place, you can press it down a little bit to get that mastic nice and embedded in the flashing. After that, we wanna nail every four inches on center, one inch in from the edge of the flashing. So four inches on center, one inch in.

How you can provide extra waterproofing protection around your low profile vent

Now that we have our low-profile vent installed, we can theoretically start installing shingles, however, there’s one step that we like to take that is not necessarily recommended by the manufacturer, but we have talked to our local rep, our technical guy, and he definitely thinks that it’s a great step to take, is installing ice and water shield around this flange. This flange, in my opinion, is a little bit short. Four inches is a little bit too short for my comfort, so we like to install ice and water shield all the way around, as well as the top, though it’s not necessary. At the top, we have a good 8 inches. So we like to install ice and water shield around to really extend this flange out prior to installing our shingle. Now, any time that we’re using any type of self-adhered asphalt-based material, we like to apply a quick bed of asphalt primer to improve adhesion. So this is not a necessary step, again, it’s just a way to make sure that this vent never leaks.

Now we had to wait a few minutes for this primer to dry. Now that it is dry, we can install this. One thing we wanna be sure to do is install a half inch to an inch back from the edge of this vent, and I’ll show you why later, but it’s an important detail to always follow. Now you can either do this in one piece or have separate pieces for the sides, it’s totally up to you. The easiest way is to align it first, hold one side up. And we wanna make sure we’re above our exposure line and leaving a half inch to an inch gap between the low-profile vent and the edge of our ice and water shield.

Now that we have this installed, I think it should make sense on why we really like to do it, and why we think this is a bulletproof way of installing these low-profile vents. Essentially, we’ve turned a four-inch flange into an eight-inch flange, guaranteeing us that we won’t leak. If you’re in different climate zones and have ice and hail and wind-driven rain, I think this is a no-brainer to do. It just takes a few extra minutes, but it will ensure this vent stays leak-free.

How to install shingles around an O’Hagin vent

At this point, we’re ready to start installing our shingles. Now the shingles will be lined up pretty much like you would the rest of the roof with a few differences in installation. Now we wanna line it up and leave it about three quarters to an inch back from this vent right here. What this is gonna allow for is water to drain around that vent, as opposed to getting shoveled underneath. The other thing we want to do is make sure we don’t nail right here at the edge, because we don’t want a penetration in this flashing. We wanna go about 4 inches back and put one nail here. This is gonna be our first nail. After that, we’ll continue nailing our shingle in a regular pattern.

The last detail we wanna make sure to do is what we call dog-earing these shingles. It is essentially cutting a 45 degree, about an inch and a half, off. What this allows the water to do is, in case any water comes down here, it won’t be getting caught on this edge and traveling horizontally. If any water comes here, it’s gonna be diverted essentially down and through our channel. So these are the few steps you wanna take. You wanna make sure that you’re not nailing on the flashing itself, about three to four inches out, and dog-ear all your shingles.

Now that we’ve got our shingles installed all the way up to the side, what we wanna do is put a full piece pretty much right in the middle, and what we’re gonna do is cut out the O’Hagin opening at this point. So we’re gonna put a nail just to keep it in place.

So you can see what that did is allow us to install the top of the shingle so that we’ll have somewhere for the next shingle to properly lap, as well as giving us a good channel. Again, half inch to an inch is what we’re looking for around the O’Hagin for proper water drainage. Now the last thing is we just need to finish these shingles off and we can call this a day.

So we’ve essentially wrapped this up already. I wanna show you the reason for this detail right here, and it’s a very important one. This allows us to have a level base for this shingle. If we were to not install this top portion and just install pieces on each side, what that would do is when we install this last row of shingle, it would create a dip right here and create an opening in these corners. So now that we’ve got this installed, we just lay this on top and continue shingling for the rest of our roof.

So I wanna show you the purpose of this channel that I have been talking about so much. You can see any water that comes here, we really want it to go down and out of this channel, instead of traveling to the side.