- When you're building a new residential home,
and you're thinking about conditioned attic
versus vented attic,
there's a couple of different things to think about there.
Plus your metal roofing assembly.
Today, we're on site with Matt Risinger,
at one of his projects.
We're gonna talk about the differences.
Let's get into it.
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What's up, guys?
Welcome to the Metal Roofing Channel, I'm Thad Barnette.
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We release metal roofing and metal construction content
every Monday and Wednesday.
Matt Risinger.
- Hey, Thad!
- Great to have you on the channel again.
- Thanks for coming out to my job, man.
- Yeah, absolutely.
So we got a brand new metal roof going on right here.
And we're talking about conditioned versus vented attics,
in the assembly right here.
- That's a good topic. - Absolutely.
So tell me about it.
You've done conditioned attic spaces for years.
And tell me why and kind of what that means.
- Well, let me back up a little bit,
and talk about what's normally done.
You know, throughout this entire neighborhood,
this is a 70s neighborhood.
But even if you went to new construction neighborhoods,
the majority of attics in the South
are what they call vented attics.
It's true in the North as well.
A vented attic, you might have gable vents,
you might have Airhawks, you know, e-vents.
The idea is you've got airflow in the attic
so that if the roof has a small amount of leakage,
you know, condensation, whatever,
it's gonna dry out and not rot your structure out.
That's good in terms of an assembly that's gonna last.
You know, my neighbors in the 70s neighborhood,
have roofs that are asphalt shingle roofs,
and they've lasted because when they leaked,
they dried out and there wasn't a problem.
However, vented attics are also dumb.
In this day and age, vented attics mean that,
you know, every neighbor here has rat poop
throughout their entire attic.
I've had raccoons in my attic before I switched
to an unvented attic.
I had a lemur in my attic.
(Thad laughs) I've had a snake in my attic.
You know, my duct work, and most people's duct work
is in their attic when it's 150 degrees
on a typical summer day.
And you've got little R6 duct
keeping your 50 degree air from your 150 degree air.
So for many, many reasons, vented attics,
from an energy efficiency perspective,
from a healthy house perspective are dumb.
However, if we're gonna go to an unvented attic,
we need to think about the details.
So most builders in the South
when they go to an unvented attic,
they spray open cell foam in the entire attic assembly.
They close everything off.
They think about their traditionally gas maybe,
vented appliances and switch those
to high efficiency appliances
that are maybe gonna use a solid PVC for the venting
in and out to the, for the combustion air.
You can't use, you can't use B-vents for the attic,
you know, that metal vent anymore.
However, over the years, I've kind of evolved to think,
well, maybe there's two different ways to do this.
And this house is kind of an interesting example.
This house, Thad, has your Sheffield metal roof on it.
And it is a spray-foamed, closed attic assembly.
I have closed-cell foam in here,
but I have a Hunter Panel, insulated panel,
on the roof deck.
And so that Hunter Panel, if you look at the cross section,
it has two-inch polyiso.
And on top of the polyiso is a one-inch wood spacer block.
And then on top of that is a 5/8 CDX plywood deck material.
And that's basically what your panel got screwed right to,
was that deck on top.
- Well, tell me how that's different
from the assembly we did for your house.
- Okay, so what's happening at my house
was I did a sandwich of decking,
you know, Huber ZIP System, sheathing,
a couple of inches, four inches of polyiso,
and then another layer of ZIP System.
And then I did a 3D mesh product.
I think I used Keen's product and I used some one by fours
for ventilation underneath the metal.
So my metal is ventilated. However,
my roof sheeting is not ventilated.
And so I want to make sure that I'm doing everything I can
to make sure that sheathing is not getting wet.
So for instance, I taped all my seams on my Huber.
And then I also came back and put a fully adhered
underlayment.
I used Sharkskin Ultra SA over the top
of the entire roof. That way all my fasteners,
everything was a hundred percent covered.
Then I put my 3D mesh on
and then I put my Sheffield metal on top of that.
So I'm basically vented underneath the metal.
Now this house though,
is vented and slightly different in maybe a better way
really, where I've got this air gap underneath my OS,
or pardon me, my CDX.
And then I vented through all my eaves and all my gables
were vented to believe it or not so that I could have air
flow underneath that CDX.
And then I have a ridge vent across as well,
so that air can flow up and out of the ridge.
And now I have a vented roof, but a closed attic.
- Yeah. And I can tell you,
I like Hunter Panels because now you have that eave to ridge
airflow, complete vented airflow
above that conditioned attic space.
Tell me some other benefits of using a Hunter Panel
versus some other options.
- Well, for us, the one big benefit was labor savings.
You know, those Hunter Panels are all ready to go,
that you just basically screw them down to the deck.
And Hunter did a really interesting thing
where they take some green spray paint
and they're spray painting exactly
where those spacer blocks are that give you that one inch
airflow because we wouldn't want to screw in the field.
It would curve the plywood.
You'd see that on the deck eventually
when that metal roof went on.
So we want to screw through the sheathing,
keep everything nice and solid.
So the Hunter Panel was probably a labor savings,
even though we're paying a little bit more for a panel
that has, you know, that's kind of preassembled.
- Gotcha. And I know you won't mind,
but I kinda want to talk more
about some building science here.
- Yeah, please.
- Joe Lstiburek. I love Joe and I love watching
his videos on YouTube.
Tell me a little bit about the polyiso that you got here.
You have it layered vertically and horizontally
with the seams inter spaced. So tell me about that.
Why that matters with airflow underneath the roof deck.
- Yeah. You know, I learned that from Joe.
Joe wrote an article on fine home building
maybe 15 years ago, where he used eight inch
thick blocks of insulation on the outside of his barn
in Massachusetts. And he had a problem.
He took it apart 10 years later and realized
all those blocks had shrunk and he had these half inch gaps
of insulation throughout the outside of his building.
So the article's proponent was basically, look,
we should always do our exterior installation in two layers
so that instead of having this and shrinkage,
we're having an overlap on those two panels
we're overlapping both horizontally and vertically.
So if we get some shrinkage,
we still have full depth insulation underneath there.
So that's the way to do it.
And the beauty of that exterior installation
is now my framing's not getting hot
so I can use less insulation on the inside of the house.
And this house I still used, you know,
four or five inches of closed cell foam.
At my house I still have an R-30 Rockwell batt
on the inside, but man, that house
when I've got four inches of polyiso
even though it's only R-20, R-21 or so on the roof deck,
that's a lot of insulation on that roof deck.
It's really going to keep that heat away from the house.
And then that metal, you know, that metal is going to go,
as I said earlier, many decades of service,
why not make sure everything in that whole assembly
is top-notch.
If I'm going to put a roof on that's going to last
30, 40, 50 years,
why not make sure everything else underneath
that is going to last that long.
- Absolutely.
- And the same goes with, you know,
if you're going to choose metal already,
if you're already thinking metal, which you should be,
I've used metal for 15 years,
it's a great long lasting roof.
Why not then say, Hey, I'm going to upgrade?
I'm gonna upgrade what's underneath the metal.
Put that rooftop insulation on.
Use a really good underlayment.
Let's make sure that assembly has a really,
really long service life.
- Absolutely. All right, Matt.
Well, thanks so much.
I love, love conversations like these
and I think we need to have more building science
talk on the Metal Roofing Channel.
I think that's really important as well.
Tell me, tell us about the Build Show.
- Man, we publish every Tuesday and every Friday.
I'd love to have you guys come over to my channel
and check it out. Lots of nerdy, talk like this over there.
- Awesome. Comment down below with any questions.
I love talking with you guys, building that community.
That's really important as well.
Subscribe here to the Metal Roofing Channel. Anything else?
SheffieldMetals.com and as always I'm Thad Barnette.
We'll catch you next time.
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