- What's up guys? I'm Thad Barnette from the
Metal Roofing Channel, and welcome to Q&A Mondays. Today, we're gonna be
talking about condensation and the problems that it can cause underneath your metal roof, in your attic, and in your home, and it's a very broad topic. We're gonna cover as much as we can today. You might notice also that I'm not in my usual environment. Today, I'm working from home, just like so many of
you around the country and around the world are, and we're gonna keep rolling with this educational material
every Monday and Wednesday. So, subscribe and stay tuned because we have two months
worth of material ready to go for you guys, already recorded. So, make sure you stay
in the loop for that. Again, we're gonna be talking
about condensation today, and we have roofing expert
Todd Miller on the episode. Again, he's got so much
knowledge ready to share. So, if you're an installer, a homeowner, or building owner ready to
learn about building science, you are in the right place. (grunge rock music) What's up guys? Welcome to the Metal Roofing Channel. Welcome to Q&A Mondays. Today, we're talking about condensation and all the questions
we're gonna be discussing are in the description down below. So, make sure you check that out. If you're new here, please
consider subscribing. We talk about architectural
metal construction every Monday and Wednesday. Well, today, I have a
couple very special guests, Todd Miller from Isaiah Industries, and Adam Mazzella from Sheffield Metals. Thanks guys, both for being here. - Thank you.
- Thanks for having us. - So first of all, I
think a logical step in talking about the
condensation discussion is what is condensation? Let's set a base level for our topic. - Sure, and the best way
I know how to describe it is to give, sort of, an analogy. So, condensation occurs when warm moist air hits a cool surface. So, if you can imagine yourself taking that nice cold glass of lemonade on a hot summer day, and you carry from your kitchen, and you go outside in your backyard, and you know that almost immediately with that warm moist muggy air outside, it starts to condense
and form water droplets on the outside of that glass. Well, that's condensation, and a lot of times folks
will have seen condensation, maybe on glass or a piece of metal, and they start to think,
"Well, there's something "about metal that does that." Well, it really isn't. What really happens is it's a result of the temperature and
differentiation, and the moisture, and basically dew point is being hit. And so, if you can
imagine inside of a house, we do all kinds of things
inside of our homes that create moisture. We take showers, baths, we
do laundry, we do the dishes, we have house plants, we
have vent-less gas stoves. All of these things pump all this moisture inside of our homes, and that moisture is
trying to always drive to a dryer space. Well, that dryer space
happens to be the outside. So, you've got this warm
moist air inside the house that's trying to drive to
the dryer space outside. And if at any point, as
it's trying to do that, it hits a cold surface
that is cold enough, temperature differential-wise
to hit dew point, then it's gonna condense, and that condensation on that
glass of lemonade outside, that's great, that's relaxing, that's fun, but condensation inside your wall or roof assembly can be very dangerous, and that's what will lead to
mildew, and mold, and rot, and all kinds of problems. So, the ultimate goal whenever you look at any home is, "Okay, what are we going "to do to make sure that we
don't end up with condensation?" - Absolutely. - We've seen metal roofs, see 'em early in the morning, sun hits it, you start to see
that water kinda pool up, or running down, you know,
most standing seam roof panel. That condensation's good. That condensation's okay. It's when you're, when
it's trapped on the inside, you know, what are your thoughts on how you get that moisture
out of the house, then? So, let's say one scenario. You've got an attic in your roof assembly throughout the entire roof. We know there's houses that
have vaulted and attics. So, scenario A, you've got a attic. How do you get that
moisture out of your attic? - Sure, and so, once the
moisture has gotten in the attic, and sometimes there are things that we do in construction to help
keep it from getting there in the first place.
- Yeah. - So, you wanna make sure
that you've got good seals around any can lights and
things in your ceilings because those, if they're not sealed well, become perfect places
for that warm moist air from the living space to
end up up in the attic. You know, some areas
also use vapor barriers behind the drywall in the
ceilings and the wall, which is basically polyethylene, but that again, helps keep that moisture from driving into your well assemblies where it might condense, but sometimes it does end up in the attic. And so, normally, what
you're trying to do then is you're trying to get it out of there, and you do that through ventilation, and international
building code, of course, has requirements in terms of ventilation, and basically, what that says, in general, and in southern climates, for every 300 square feet
of attic floor space, you've got to have at least
one square foot of ventilation, and that one square foot of ventilation is to be half intake where
fresh air is coming in, and half exhaust where
that air is then going out, carrying the heat and the moisture--
- Yeah, and we've seen this issue with where you're saying, half intake, half exhaust, where if you're only
ventilating your ridge, or if you're only ventilating,
you know, your eave or, you know, your soffits,
that's not going to suffice because usually, the wind
is coming one direction. It doesn't mean that it's gonna circulate all the way through and
go in through the eave and out through the eave, or soffit, or similarly
with the ridge vent. That's good, and one of the worst things that can happen is if your
ventilation actually starts to operate in reverse. So, when you think about ventilation, and go back to your example
of air coming in the soffits, going through the attic,
exhausting out of the ridge, carrying the warm moist air with it, ideally, you want that
to be about half intake and half exhaust. If anything, you want it
to be slightly pressurized with a little bit more intake, and that helps keep the air moving, and gets the airflow, the
convective airflow going properly to carry that air out. Now, if you have a
situation where, let's say, you've got a lot more ridge
vent than you do soffit vent, you can actually start to
suck air in at the ridge, and then, try to exhaust
it out through the soffits. The bad thing about that is
that dries all that moisture into your insulation on
top of your ceilings, and if you start to drive moisture for, I forget what the exact number is, but as you drive moisture
into your insulation, it loses its R-value. So, it's all become,
sort of, self-defeating at that point, and you're gonna end up with
some really ugly situations if that airflow is running the wrong way. - What if I have a cathedral
ceiling, vaulted ceilings, whether throughout or part of the house, how do you handle the ventilation, or if I know I have condensation issue, how do I address that? - Sure, and the nice thing on that is with a lot
of newer construction, we'll see that they
have used vapor barriers and things to make sure
that moisture cant's get into the vault or the cathedral assembly. - But when did that start going up to code though?
- Well, that's-- - I mean--
- That's-- - Yeah, okay.
- That's exactly right. So, we get it to older homes before we were doing that, and for many years,
those homes function fine because they had very
loose windows, and doors, and so, that moisture was able to drive out through the walls, but now, all of a sudden, they've gone in, they put in nice energy-efficient windows, they put house wrap on,
they put sliding on, that all those things that tighten
up the sides of the house, and now, all of a sudden,
they've got problems up in that cathedral assembly because that warm moist air in the house is going right up into there, and will hit dew point at some point.
- Yeah. - And you know, I've
been in on houses before with structural insulated panels, back in the early days
of what we call SIPs before they were properly
sealing the joints and using vapor barriers, and you know, that outer layer of decking was just rotting away because it was continually
hitting dew point. So, when you've got
those extreme situations, fortunately, there are answers. A lot of times, it actually does involve, if there's nothing you can do
inside the existing structure to create ventilation or
to change what's happening, then sometimes, you got
to build on top of it, and you got to create new air chambers. They don't have to be real big, but you'll create new air chambers on top of the existing roof deck so that that moisture can go ahead and rise up into those place, and this, and then, those are vented to get that moisture away, and you can eliminate the problem of condensation doing that. - So Todd, you know, I may be getting into the weeds a little bit here, but let's say I'm going to
put a new metal roof on, and, you know, ice and water shields are all the rage everywhere. Is there ever a situation where I shouldn't use
an ice and water shield, you know, to protect against
potential condensation issues? - Sure, so, a lot of times,
condensation is an issue of the straw that
breaks the camel's back. So, I'll run into houses all the time that, you know, I look at things, and I'm saying, you know, "You are just on the verge "of having condensation issues here, "but yet, what you're doing
right now is working." But suddenly you do
something that changes that, and it's not gonna work, and that example
- The windows, doors, new roof, yeah.
- That's a good, good example. The other aspect is, although
we don't generally get a lot of breathability through roof assemblies because let's face it,
most roofing materials that we use don't breathe a great deal, but if you do have an extreme situation, and now, all of a sudden, you put ice and water shield on it, you know at that point
that that moisture trying to drive out of the house is trapped. So, I'll often, although I agree, ice and water shields have a place, we see 'em used more and more, they do kind of seal a
structure up like a terrarium. I don't know any other way to put it. So that moisture that is
generated inside the structure, trying to drive out, absolutely can't get through most of those ice and water shields. I don't know if any of them truly breathe. There may be a couple out
there making that claim, which I would dispute, but, you know, now all of a sudden, I put that on there and now, I am gonna have a situation where I'm gonna have
condensation occurring, either on or inside of the roof deck that's gonna lead to problems. - Yeah. So, what do you think? Attic situations, you wanna
make sure you vent that attic. If you've got a vaulted ceiling, you probably wanna
address some ventilation that's gonna take
moisture out of the house. - Yeah, sometimes you've
got to understand better what that cathedral
ceiling is really like. Some people just assume because they have a cathedral ceiling that there's no ventilation
at all occurring, and oftentimes, there is. Oftentimes, people will build it. Even 50 years ago, we're smarter than we wanna give 'em credit to be. So, you really, sometimes, you
might even do a core sample from the roof and start digging down end to find out what's really there. - Yeah.
- And you might found out that there's more ventilation there than you really realize. I think one of the keys, though, and everyone's starting to
pay more attention to this, you know, can lights, I mentioned earlier, have been very popular for
a lot of years in ceilings, but they can be really
sources of letting moisture from the living space into
that cathedral assembly. And so, making sure that those are sealed around can be hugely beneficial also. You know, the flip side of this too is a lot of times those air leaks that lack of ventilation is
what contributes to ice dams in the winter also. So, we have this warm
moist, or this warm air that's trying to escape our house. It gets up into the attic, doesn't get properly vented
out, at, or near the ridge, and it starts to warm the roof deck. In that case, because it's colder outside than it is inside, and now, all of a sudden, the snow starts to melt high up on the roof. That melted snow runs down, hits the cold overhangs, freezes, so we end up with icicles, and ice dams, and all that type of
horrible stuff happening. So, there again, keeping
the living space air inside the living space
tends to be real key to avoiding that as well.
- Yeah. As this relates to metal roofing, you know, 15, 20 years ago,
there was a real big push for SRI, SRI, you know, really keep that thermal
energy outside, you know, and really, improving
the energy efficiency. What we're seeing in
the standing seam world, and this is probably
indicative of all construction is they're really focusing on
the entire building envelope. So, I think one of the
things to be conscious of or at least just be aware of is if you are doing a
renovation, you know, and it's going to be up to code, make sure that building code kind of jives with your current construction. Make sure that, you know, you're building to not just code, but
something that's going to work and not lead to additional issues. - Yeah, I agree wholeheartedly, and yeah, you always have
to look at the structure on its own merit and exactly
what's gonna happen there. I kind of go back, again, an easy analogy in terms of condensation is think about that glass of lemonade. Are you setting up any
situations in your house, realizing that you're gonna
generate warm moist air inside your house? Are you setting up any situations where that's gonna hit
cold surfaces and condense? - Okay.
- And so, just a lot of it really is just a
common sense approach, but absolutely, you have to know how the house was built already, and what code requirements there are. - Yeah. - Well, I think that's a
great place to wrap this up, and we've learned that there's
not a one-size-fits-all when it comes to this topic, and there's a lot of
things that can go into it, but as you said, Todd,
common sense is important, and understanding what condensation means, not only for just your roof, but your entire building
envelope is really important. So please, comment down below
if you have any questions. Subscribe here to the
Metal Roofing Channel. Thanks, Todd, and thanks, Adam. I really appreciate it. As always, I'm Thad Barnette. We'll catch you next time. (grunge rock music)
