Hey thanks for watching this video is from the second annual hvacr training symposium that we did down here in claremont florida. This session is from rick sims and the title is conductation, which, when some people saw, they thought it was a typo. No, it's not a typo. It's just the session is about condensation on ducks and rick is a clever fellow hands down.

This session was the session that i heard the most feedback that it was really transformative in the way that people thought about the problem of condensation. He went into great depth about the water molecule and how it functions and how we can prevent it from building up on surfaces that we don't want it to so big thanks to rick sims for doing this presentation, and thank you to all of our sponsors and Speakers who made the second annual hvacr symposium possible welcome. My name is rick sims and uh for the next uh course i'll be going through a course. We call conductation it started in 2016., it was developed in climate zone 1, which is the most humid climate in the 48 states, and it grew out of a discussion about sweating air handlers and particularly the way that tech support from the various manufacturers of air handlers Were dealing with their equipment sweating, so the name of that was cold.

Air is not a malfunction, and we grew from that into this. This uh course is all about the dew point versus the surface temperature and so we're to have all kinds of strategies that we're going to evaluate that have to do with controlling the surface temperature, because there's so little that we could do. Oh, we have one strategy to control the dew point: what's the strategy to control the dew point, don't put it outside, don't put it in unconditioned space, so you know if we could do that if we could put all the ducts in condition space at a low Dew point, then that would solve it well, this is for all those times that, for whatever reason you have no choice, you have to put the ducts in a vintage attic in a cool wet parking garage wherever it hap a crawl space wherever you have to do It so the only thing we can do here, since this is all about dew point and we can't control the dew point versus the service temperature. This is all going to be strategies of how you can limit how cool the surface temperature gets.

You will not have to do a lot with this little chart that mr carrier made uh about. All we're going to do this morning is about the equivalent of looking at a map of north america and saying that's texas and that's florida. That's all we need you to do this morning. So, for example, i've plotted the design conditions that i use in naples.

Florida. The ashrae design condition, gives us a 72 degree dew point now. You don't have to do any math with this chart, we're not going to go into it that far, but everybody here does understand that the shape of this chart is because air holds more moisture when it gets warmer, and so the the chart is fat on one Side where it's warmer and it can hold more, but additionally, since we're going to use the term dry, bulb and dew point, i want you to make sure that you understand what other thing about it. This chart, of course, has hotter.

Is this way warm air holds more heat and moisture grains? Is this way how much moisture can the air hold? The dew point is the point where you've hit a hundred percent, and so you have this uh condensation occurring. The thing i need to make sure everybody understands is that we're at 50 percent outside and we're at 50 inside, and you have to understand that concept that, if you're not in the habit, i'm assuming a lot of you are service technicians. If you're, not in the habit of writing down the temperature, that goes with a a relative humidity measurement that you've taken get in that habit, because relative humidity doesn't mean a thing to us. When you tell me it's fifty percent and and customers do it to you.

I got fifty percent. Is that okay, you know, or the service tech writes down 50. These are both at 50 they're, both at 50. It's just that 95 degree.

Air can hold a lot more moisture and so 50 would be 120 grains. I love the math for climate zone, one look at the grains, it's exactly double it's exactly twice as much moisture per pound of air. So how do we use this? Well, i'm going to take and look at the uh how it affects us. It primarily affects us during rainy season and at the beginning of rainy season.

We see it see it start to happen on the the cold parts of the ducks and then toward the end of rainy season. You are more likely to see saturated ducks because it builds up over the course of the season over time. One of the things that's extremely predictable is that the climate zone, one dew point at least at the naples municipal airport over the last 15 years - has been an average of 73 degrees. Now.

The reason that's important is because that tells you where the duct has to be or the air handler cabinet, in other words, in our climate in naples florida. If you're going to have an air handler cabinet, that's cooler than 73 degrees expect it to get wet, and that would not be a malfunction that would just be normal same thing with the duct. If the duct can reach 73 degrees, then you're very likely that you're going to get some condensation, so it should be anticipated now the daily spikes that we record, usually in the early morning hours, we can have an 80 degree dew point and, as a matter of Fact we can have a higher dew point inside an unconditioned space. That's filled with fluffy stuff that pink stuff.

How many of you have a psychrometer that has two heads on it field piece makes one you like that in that nice it's got two heads on it. So you always know if one's lying right, because they got to read the same thing next summer, when you're in one of these cases where the ducks are sweating - and you look and you see this pink fluffy blown in insulation, andy os turned me on to this. Stick one psychrometer tip down in the fluff, put the other one up in the air it'll blow your mind. How wet that insulation is so you don't just have one dew point, which was the way i started training.

I put it this way, the other night when i started trading hotel. California was the number one song. So that's you know so anyway, we kind of were trained that uh. You got an indoor dew point and an outdoor dew point with building science in the last 20 years.

One of the things we've learned is the molecules tend to be on the stuff, and so we'll be looking at how that works. Now this is the time of year when we get these fronts from up north, when the polar vortex pushes down some nice dry weather from outdoors, and we, if you have sweating, duct and sweating air handler problems for this part of the year, you will probably find Something that that's wrong. What we find is that for systems that are set up well well commissioned they're, running reasonable static pressures, they're running the anticipated flow rates. What we see with those is that they work pretty good until you get into that rainy season.

It's more likely your air handler is going to sweat in climate zone, one this pointer doesn't work, but if i could point i would point to this naples florida. That's where we're at climate zone, one uh is basically naples to miami, so uh the difference is uh. Is not that you don't get humid steve rogers from the energy conservatory, he sent me a photo of his phone showing an 80 degree dew point in minnesota, so it happens. It's just that it doesn't happen for four months.

That's the difference. Let's see what else is on here, so, let's start with uh materials, we're going to take a look at some of these materials and how they're going to work, and the first one that i'm interested in has probably the most published about it when it comes to This this is familiar to you right, fiberglass, duct board. You can find all of the information that you want about this stuff, an incredible amount of stuff for free from the national association of insulation manufacturers of america and all kinds of stuff you can download and some of the stuff that's on. There is specifically about what to anticipate with regard to is the duck gon na sweat.

Well, the bottom line is the people that sold you this. That made it. They told you it was gon na sweat. So you can't be surprised that it's sweating because they said it would and here's where they told us if you put that stuff in a place where the relative humidity is 90 for any reason at all, it's gon na sweat and it doesn't matter if you use R8.

R6. R4. It's not going to matter because, as you can see, they're telling you we don't do 90 percent. So if you put me in a place where now the other thing you see, this is the area that you'll see as we go through this, where the biggest problem occurs.

I've got it shaded, blue here and right here where this green line. This is where we lose control of r8, and this is where we start to condensate with r6, and so you can see that uh there's quite a bit of exposure there quite a bit. So what? What? If we just insulate our way out of it? Why don't? If we make it thick enough right should work. That's one strategy: you can do that if you want to solve this problem completely with insulation, anybody know who that guy is joe stiebrook, pretty pretty smart guy uh moisture in things joe is showing us these uh foamed ducks here's a picture that paul mass from building Science in tampa took of them foaming in some flex, duct they're, just using this polystyrene foam board as a form and then they'll pull it off when they drywall.

But what they're doing is they're encapsulating this duct to a minimum of r13 paul, and i were discussing this photo. We don't think they did it right. The reason we don't like it is because they've got the flex duct laying right on the wood and they've basically created a composite, and the wood is part of that thermal composite, so the wood is going to get damp and turn black inside of the foam. So if you wanted to do this, don't do it like most people do as a matter of fact.

I never liked this because i never saw one that was done nice and then i saw jason julian in alabama and that changed everything. This is jason julia julian heating and air conditioning in alabama is coating, their sheet metal pipes, hanging them beautifully and uh that i, like the reason i haven't liked: r13 non-permeable foam ducts. I haven't seen one done this nicely. What i've just seen is just somebody just went in there and just you know, just made a a big lump of foam.

So i really like what they're doing up there in alabama and i got ta say in florida. I still i work on sometimes 50 million dollar homes, but i haven't seen this yet i haven't seen anybody do this, this nice, the way he's doing this uh. This is a a basic formula for determining how cold is the duck going to be because we already said well, you know if we're going to be in climate zone 1 and the duck gets cooler than 73, it's going to get wet in the summertime. So we could use this formula, but i will uh point out that this is a very simple formula that does not include any radiant heat.

In other words, this is just conduction, and so this would be the temperature of the duct may be on if it was in an attic with some heat coming down, it would be on the bottom. Okay, so generally it'd be, if anything it'll be warmer than this, but what i'm gon na do here is take these temperatures and we're gon na look at it under a couple of different circumstances, where the air around the duct is 75 degrees. The air around the duct is 80 degrees or the air around the duct is 90.. Then we're going to throw some variables at it, like is the supplier temperature 50.

Is it 55? Is it 60 and we're going to just take a look and see? Well? What does that do to us? So the first comparison that uh you want to make. Is this one? Actually, this is the second point of this today. The first point was: you: can insulate your way out of it, but what does it have to be r13 and what else non-permeable? It can't be permeable foam so that if you can pour water through the foam, that's not the right kind of foam. It's closed cell foam is what it needs to be, and it needs to be r14.

You do that. You got it. This is a comparison now of what happens when you raise the temperature or decrease the td. Now the reason this one's important uh, in my opinion, sweating ducks - is very, very seldom a service call.

What is this guy in this truck going to do about it he's got one move in his playbook: what's the service tech going to do? Well, it's vented. It's vented, i mean you know, we have to you, know dehumidify the outdoors, but i'm with you but see now you're cheating because now you're putting it into conditioned space, and you know that you know if you had that luxury. Why wouldn't you? Why? Wouldn't you put the duct in condition space, but if you don't have that ability to do it and we will say well, we have to put the duct outside for whatever reason, then. My point is that if i'm a service technician - and i'm expected to do something about this sweating air handler and these sweating ducts, well, you know you can take the static pressure and check and see is: is it restricted? Is there a dirty filter? You can look at all: that's moving air, it's just sweating like a pig, well uh.

The only thing he's got he can do is raise the fan, speed right doing it for years. That's sweating! I guess we'll raise a fan speed, even though we really wanted to design it with a low fan speed, and that was the best scenario for what we were doing. We end up sizing, selecting a fan speed just so we don't rain on the duct. So it's a heck of a compromise, but it's the only thing that a service tech can do.

What's the service tech going to do, pull all the duct out on a service call, so he hasn't got. He hasn't got a lot of choices. The uh most of these problems have to be solved before the duct is installed. Here's what happens um a 5 degree we'll look at r6, a 5 degree increase in the supply air duct.

We were running air, leaving the coil at 50 degrees, but the cabinet's sweating. So i'm gon na i'm gon na speed up the air handler and when i do, the air handler is now 55. We raised it five degrees you get about a one degree increase in your duct temperature from a 5 degree rise. So that's your second question answered: how much will i raise the temperature of the ductwork so that it won't sway? Can i get it above? The dew point is what you're trying to do i'm trying to warm this duck up.

Well, if i speed up the air, what if i speed it up so that i've only i got a 60 degree leaving air - that's not great for many reasons, but i got 60 degree leaving air. I only gained 2 degrees, the duck's only 2 degrees warmer. So you have to you have to change the supply air temperature by 5 degrees to get a 2 degree or no by 10 degrees to get a 2 degree difference. You got to change it by 5 degrees just to get 1 degree.

So, that's all that poor service technician can do and what's he going to do right, he's there on a service call, so he doesn't. He doesn't get to uh. Do some of the other things that we'll talk about, because it's just not in the scope of a service, call and look what's happening here? 90 degrees? Look at this! These dew points! These are the surface temperatures of the duct. It's in the 80s.

That's pretty safe! Even in climate zone one so as a general rule, i say that if the air around the duct is 90 degrees or more, it shouldn't be sweating, because the dew point would have to be in the 80s. So that's why we expect most of the condensation that we experience with these things to occur at 80 to 75 degrees, and when does that happen during rainy season in florida every night, every night, it's 95 in the daytime? Is it 95 at night? No it's 75 to 80. and that's when your ducks are getting wet. While you sleep, while you're there on the service, call they're actually drying.

So you can actually go to the customer and say i checked it out they're drying right now. You know see if it works for you, it didn't work for me, but try it okay. So the next question is what, if i use r6 instead of r8 uh, one of the things that we've been uh, what we've proven to ourself in our climate zone for years is there is no energy payback for r8 ductwork, and it's been, you know, i'm on One of the building code committees, where our values are over discussed in my opinion, but anyway the the r8 duck board. If you've ever used, it add four inches to your duck dimension.

So if it's a 10 by 10 duct, it's going to be 18 by 18.. You know or excuse me, that's going to be a 10 inch. Duct is going to plus 14 by 14. uh, the um, the change from r6 to r8, we'll look at it at 90 degrees at 90.

Degrees is where you get the most bang out of it, but you still get less than two degrees warmer. So it really doesn't do much two degrees and really where we need it, which is down here at 75, which is night time when it's uh cold out. We're only getting one degree warmer, so by going from r6 to r8, and that's exactly what nema tells you. So it's not like the people selling the duck board and the insulation are saying that it's going to be better than that they're, not they're telling you that yeah, you get a little better.

So you don't get a lot of bang out of that. Here's the big one, this one's huge with only a five degree increase in your temperature of your air. So, let's say you're thinking about in your mind, you're thinking about ducks in an attic. If the attic temperature goes from 75 to 80, it increases the duct temperature by four degrees.

So that's usable, you know, and the other thing is by the way it can go the other way. For example, um the home was shaded by a tree and then irma came through. The hurricane takes the tree out and now the temperature is warmer, so they change the color of the roof. They put a cool roof on it.

You know now they can make shingles that are colored shingles, that reflect heat and we used to always think about white. They now have technology where colored shingles are reflecting heat, but it's not a white or reflective color. But this is the big one, because if you go from 80 degrees to 90 degrees, if it gets warmer by 10 degrees, that's an 8 degree rise in your surface temperature of your duct. So here's the summary - and this is what this is, what you get when you actually spread it out and look at it.

A five degree increase in your outside air temperature raises the surface temperature of the ducts four degrees, and it is the biggest factor so, for example, that explains why a parking garage is so hard to deal with. You got any radiant heat in a cold parking garage where you're, you know you got lots of air going through the parking garage because it's got these big fans for the the car exhaust, but it's underneath a cold slab. That's a duck that wants to sweat. You know, whereas look how much difference it makes with a little bit of heat, so a five degree increase in the outside the air around the duct will raise the surface temperature of the duct by four degrees.

Going from an r6 r value to an r8 will get you less than two degrees, but where you really need it, which is down in 75 degree range. You only get one. So it doesn't help that much and then the one that everybody does, because it's cheap. It's easy, whether it works or not, for every five degrees that you decrease.

Your td is basically what you're doing, hopefully, you're manipulating fan speeds and not refrigerant charge or something goofy. But if you're just changing the fan speeds and you can get a five degree rise. That'll get you one degree, but it has a lot to do with how it's installed. Now you remember that i said that ducks don't sweat when it's over 90., so here's we got a 73 degree right on the uh right on the edge of wetness 73 degrees.

55 degree air on the inside, we got an 18 degree temperature difference across the wall of the duct everything's going good, and then we do that, and that is going to be a problem as soon as we put this up against this, it's going to get wet It needs a gap, and, what's going to happen, is in between this, you basically you've made a composite you're. Conducting you're touching you're conducting right through you've made a 67 degree area on your duct. That would have been 73, but because you put it up against a piece of wood, you've composited that wood right into your ductwork, the only way you could make it worse and you've seen this is, let's paint mastic over them and make them all one we'll just Mastic the whole thing, so it's one big clump and this is uh, really a very common problem and here's what you want to remember about that. Just a half inch of space is one r value.

Now you remember how you had to you had to drop your td by five degrees just to get one degree and you even if you spent the money in the labor to go from r6 to r8, which is substantial, you would only get one degree you can Get one degree just by not touching this: the r value of a half inch space between the duct and the building component is almost one and when you get into one and a half inches uh, it's our point 1.08. So it's just figure it's about one and you notice that the main thing is that it doesn't touch. You don't get a lot of bang to go from 1.5 inches of space to three and a half inches of space. It doesn't do that much.

You get a big bang just because it doesn't touch so, let's say a half inch. Let's say: there's a half inch because at least we know we get. You know our duct is going to be 73 degrees, not 67., we're in north carolina, but we've had some houses with flex duck in the attics like where it was put in a new construction and was laying basically on the sheetrock, then they came in and blew A lot of insulation on top of it and we've had some cases that we go over there and it's getting water spots on the ceiling and, like you said that insulation is wet down north carolina north carolina. That's exactly what we're talking about.

As a matter of fact, i have a slide of that of exactly what you're talking. What he's talking about is ducks just laying on the ceiling. It's not even that uncommon if you ever check the temperature between the sheetrock and the insulation and above the insulation in the attic it's hotter when you get to the sheetrock than it is on top and you're compressing your insulation on your flex, so you're losing your R value uh did any of you get to see. Uh excellent speaker last year, allison bales allison bales, a phenomenal building scientist phd, certainly better speaker than myself.

He is in a world somewhere beyond climate zone, one where they can bury ducks and they don't sweat and i've had i've had a few beers with him and i've just told him it's just. We can't do it and if you and i get it, you know because he's trying to insulate by putting it under the fluffy stuff, and the other thing i can tell you is that's fine with us for an air return right. An air return is, is gon na, be above the dew point. It's gon na be at 75 degrees.

Now, if the um, if the customer is running at 70, maybe it'll be a little more but should have a duck gain right. If it's, if it's in this situation, where we'd even be talking about it, must have a duck gain all right. Well, let's uh keep going here and so here's our situation and who warned us about this years ago, no audio! It's hammer time, man, camera time! Guess no mc hammer for you, sorry m.c hammer, the five-time nominated grammy-nominated artist was also a visionary in building science and the building science community is never recognized, but he warned us. He told us what did he say and, and is there really that much more to it i mean he, he begged us, but so how do you whoa? I just lost everything how's that go there.

We go yes, sir return air duct would probably be okay. Buried. Return air duct would probably be all right, but the problem with burying uh 50 to 55 degree air in 80 degree dew, point fluffy stuff. Unless it has r14 non-permeable, which then we don't care.

What you do right, then don't do it. So my recommendation is climate zone. Two as well, i'm gon na say: don't do berry ducks, i i don't recommend it in florida yeah. As a matter of fact, i'm going to say: don't touch this, that's what i'm going to say, because what i measure is that the dew point in the attic might be 75 degree dew point, but i stick that cyclometer down in this fluffy stuff and we're going To talk about why that is, you know, moisture molecules, they love surfaces, they don't want to be in the air.

You guys see mr bergman's thing about uh this morning about uh desorption, we're gon na get into that, because it's the same thing. It's just what he's talking about is happening inside copper tubing and what we're doing it's the same thing, but it's on the outside of a of a duct so uh. Actually, we uh, you got to help me out, explain m.c hammer to the millennials just handle that explain it to them. It was actually i that was my daughter for me.

You know my daughter would have bought that you know not me so wrong time period. Now this is one of the most commonly misdiagnosed things. It's so simple in the business. It can be just a horrifying thing for a port royal princess or the realtor or the interior desecrator.

You know they look up at the grill and there's black stuff on the drywall. Oh, my god, you know we've got to do something here. Well, one of the uh lazy things that we do sometimes is just. Oh, that's a duck leak.

That's a duck leak wet around the grill. That's a duck leak! Well, let's uh: let's send the skinniest smallest guy up there and he can create some thermal bridging now remember how we're not supposed to touch things well. Not only are we touching things we're thermal bridging to all this. Just piling mastic creates thermal bridging you, don't you don't get extra points for mastic mastic, let's see here, i got a square foot of everything today.

I've got a square foot of mastic. Here it is. Is this an insulation? No, this is a sealer and you can't code it up like bondo and get an r-value of it. It's not intended to be used that way, so compounding uh what i mean by compositing piling this stuff up and compositing.

This to this is not a good plan where we're just gon na. Oh we'll just paint the whole thing, we'll just paint it all in together. If you want it to be dry, then that's not a good plan. Now, if you don't want the air to leak, that might be okay, but one of the reasons that this is often misdiagnosed is because it doesn't solve one of the most common problems you guys put in linear diffusers.

Do you ever look at them in thermal? They leak like crazy because they don't have any gaskets and the diffusers that do have gaskets often have crappy gaskets at no extra cost, and so what happens is this is very frequently misdiagnosed. This is not a duck leak to unconditioned space above the drywall, with thermal imaging look a little longer. It's not just that it's damp. How is it damp? You can see with thermal imaging when the air is blowing out from under a diffuser.

You can see it on linear grills and you can even point it out now. If you just look and say well, it's wet if it's damp because it's cold and leaking behind it. It'll, look more like watercolor, you know, it'll be more rounded and and faded into it. It won't look the same when it has pointed feathered edges.

This is clearly the air going between the flange and the drywall, and we got 120 grains of moisture up above that drywall. So it's going to get wet. So what do you got to? Do you have to stop movement? All you've got to do is stop the movement, so one of my favorite products that we're going to be all over today is this stuff love this stuff. It's like a coulee cup for anything.

It's adhesive closed cell foam tape, so it's most often service technicians use this stuff to put on a thermostatic bulb. That might be a good use. This is like pipe insulation with an adhesive on it all right, so that is uh one of the ways we can solve that and let's just keep moving here, there's only 20 degrees difference between this ceiling and the duct. So we go down below and we look at it in thermal and we can see damp cold spots on the ceiling where the flex is laying.

Well, it's easy to fix. That's that's the problem. Does that look a lot like the stuff that was laying on the ceiling yeah, usually the usual suspect is usually involved some sort of a triangle with some sort of a worm coming out of it, and that's usually black. When you pull that out, you know, hang it above.

So what do you do with this? You can't touch this. Give it uh give it a little space here, and what did we say if, if you gave it a half inch you'd get an r value, but i'm saying do better than that. You know pull it on up, get it off that cold ceiling. If you don't want the surface of this duct to be cold, then get it up off that ceiling and what we want you to do is have a 40 degree temperature difference between the inside of the duct and the outside of the duct instead of a zero.

When you put it on or 20 we'll do zero here in a minute there we go there's zero. Well, i can't touch this. What if i put um a 55 degree duct and lay it on top of a 55 degree duck what's the temperature difference? Why would this be anything other than 55? I mean it's trying to get there right. I mean we're doing everything we can to make sure that the bottom of this duct and the top of this duct is going to be cold.

It was installed to be cold, so that's why mc hammer is upset. So that's how you fix it high-tech stuff right, you lift it up. You give it a temperature difference and things change, you'll, also uh people who have some experience, tearing things out and throwing them in dumpsters have seen black marks right, see the black marks on the wood where the old duckwork went. You can see where duct was because it leaves a black mark where it was damp wherever it was touching.

Uh, it's better to use a uh, a galvanized hanger that does not have a lot of thermal mass would be better than using wood. Also, it's non-permeable and mold doesn't really eat metal, but mold kind of likes wood, so i would uh. This is not out of any manual, and this is an opinion. My opinion is: that's a superior hanger to a 2x4 and to tell you the truth, i don't think it costs any more than a 2x4.

These days, metal strap didn't, but a metal strap's a pretty good way to hang a duck. Come how about that full circle? Back to 1950, and still the best way to do it to put it on a metal strap. Thank you mc hammer turbulence. Uh is also a problem because uh this is uh about that mass flow rate.

We were talking about mass flow rate this morning with regard to removing molecules with a vacuum pump. Now we're talking about trying to put those pounds of air down the middle of the duct, and we know from any of you guys do duct traverse, traverse ducts. Okay, most of the air is uh moving down the middle right. That's why we measure it that way and so uh.

We take more readings away from that. I believe uh generally, if you take a velocity pressure reading in the center of a straight duct, that's and divide and multiply times 0.9, that's pretty close to what it's going to be. So most of the air wants to go down the middle until we start putting offsets and turning it. And you know the internet is full of pictures of bad ductwork.

We could make the class that, but you get it run it straight, pull the kinks out of it shorten it, hang it, and these are the common sense things that will help flex collars. Obviously, if they leak underneath the liner, then the liner will get cold, but the other way that's a problem is, if you create thermal, bridging a metal collar is colder than the flex duct, and the metal collar is on the inside see the air barrier is switching From the outside to the inside, so on the trunk line, the air barrier is on the outside, but on the flex duct it's on the inside the tap collar is where it goes from the outside to the inside, and so what we don't want. We don't want to pinch the insulation, we want it fluffed out around the collar. We don't want mastic piled up like.

I show it right here, because mastic is not insulation. That mastic will just turn black and and get damp. We want it like that. We want just enough of an air barrier to carry the air barrier from the inside to the outside, and then we want enough insulation to keep that whole collar.

Underneath in florida you have to tape the outside liner. I know in some states you don't have to do that, but in florida's building code you do have to even if you seal the inside, you can't just fold the outside around and pan. Do it. You can't do that in florida.

You have to seal it. What about ducks that are in the conditioned space? That's one way to do it, one of the. If you don't want to foam and create a a dry low, dew point space up above your ceiling, then uh, one of the things that's done is well. I'm gon na have a vented assembly above the ceiling, but i'm just gon na put all the duct work below it good plan, excellent plan.

In other words, i got a vented attic. I just don't put ducks in it and i certainly don't put an air handler in it. That's a good plan. That's not a bad way to build a building, but if you do that do give yourself a little bit of space, because when you put this duct work up against the drywall, remember.

You've got a 55 degree. Air temperature and you're chilling this drywall down in the dampest part of the house, so all you got to do is don't touch this half inch will do it just give us a half inch, but don't touch don't put the duck all the way up against it Or it's going to get wet. This is business as usual. We have some radiant heat and then we've got this crappy spaghetti duck just splattered all over the home here, and the cool knee wall is a place where you can see all kinds of things happening, because you don't have your typical radiant heat source because you're right Up against this cold knee wall, so everything's different usually looks something like this: here's the cold knee wall, here's the the duck laying on the cold plywood and the air handler and everything's dripping.

If you're going to have a vented space and put a piece of equipment in it, you might want to select an area that has more radiant heat. This is the building cavities that we can't do anything about sweat in those. If you run ducks through those and then you start moving air through those cool cavities, we can't help you. We can't there's, there's nothing.

We can do the builder or the retrofitter somebody's got to give us an air barrier. We need the inside of this house to not try to be the same thing as the outside of the house. There has to be a break somewhere now. The harder thing to be successful at is sealing in the ends of these floor joists.

What you're looking at here is the the ends of the joists that are running through the floor joist. So, in that case, you've got 120 grain moist climate zone 1 air around your duct, but you've only got 70 degree rooms around it. So you've got all the moisture, but you don't have any heat because it's sheltered by the room above so if you move it up on top, it gets a little more heat. But then we usually, if we're going to do things dumb, like we're doing here, we usually put in the big goofy roof cap.

That is also the best method for the rats to go in and out unimpeded is their favorite entrance and exit. They are not installed. They're very seldom installed right the correct location for an attic. Then, if you're going to vin an attic, where is it the top and putting the thing halfway down, usually results in a lot of infiltration? If you want to do it right, here's how you do it! You want 300 square foot of opening for every 100 square foot floor area, and then we want you to put 40 percent of it at the top and we want you to put 60 percent of it at the bottom.

So that is much less than most. People have now, if you ask the best builders that money can buy, how did you calculate the area of the attic vents four inches and it goes all the way around. They have no idea. Nobody ever calculates it.

So joe stiebrook's been telling you for 20 years that it's supposed to be 300 total for every 100 square, foot and you're supposed to put 40 percent of the opening at the top and 60 of the bottom. In other words, basically, what he's doing is he's giving it just enough ventilation that convection could work if everything else is right, but he's not allowing wind and cross flow ventilation to just be moving molecules of moisture through that space he's not going to allow it. You can do the big crappy spaghetti duck, lay it all on the ceiling. Do whatever you want to do when you foam it you'll get away with it.

As a matter of fact, i have never seen a encapsulated space unless it had leaks in it with sweaty ducts. You can get away with really really bad ductwork, which is a good thing, because crappy ductwork is extremely popular. It's everywhere. We can't keep it on the shelf, it's everywhere now.

The problem with the crappy duct is. We have no idea where it came from, because i know contractors and i've asked them. Do you put in crappy duckworth? No, we put in the best. I have asked i've.

You know so it's a mystery. Nobody knows where the crappy duck systems came from. One theory is spontaneous fabrication all right. Let's talk about the uh, the exposure moving, these molecules still air is pretty harmless stuff.

So here we got an example. We got still air in the attic space at 12.7. Gallons, we've got still air in the interior. Part of the house at 18 gallons is 18 gallons of moisture in the air.

Is that uncomfortable well only if you're uncomfortable at 75 at 50, because that's what it is so, yes, there's moisture in the air, but my point: is it doesn't condense until it moves so here's what it does moving air adds, 110 cfm or each 110 cfm adds One gallon per hour of moisture exposure, so that's 24 gallons a day, uh, 168 gallons per week, 672 gallons per month for every 110 cfm. So that's why? If you want to have some fun with this use data loggers, do you use them for building science? Because what you do is you put your data logger in the attic space and you set it for a couple of days. You uh, let it run just the way. The attic is because every day in the summer is about the same conditions, you're going to measure about the same thing, so measure 24 hours of it and then go back and leave the data logger alone, but seal off the big goofy roof caps just put pieces Of fiberglass in them to stop all that wind that cross ventilation to stop all those molecules of moisture that are going across your duct seal it off.

Then you go to uh, true tech tools, and you do what i did. I bought seven hundred dollars worth of duck mask and somebody was saying: well man. You must be doing a lot of duck testing. No, i'm i'm sealing up the eaves, so i go through a lot of dust mast.

You know you guys know what i mean by duck mask it's the stuff you put on when you do a blower door test, you mask off the diffusers. Well, you can mask off the soffit outside the house with a data logger up there and seal the stupid roof caps and you can watch it get drier without doing anything else and you've recorded it as a matter of fact, you're anticipating, what's going to happen with The foam it that's how this started well, rick, you say i should foam this attic. Well, what's it going to be like do you want to see? Well, if i seal off - and i don't let any moisture through the big goofy roof cap - and i don't let any of it come through the it makes a world of difference and you can in florida. I don't know about other states, but in florida you can seal your attic by any means you want and put a dehumidifier in it and keep the insulation on the ceiling.

That's totally legit and it works. So, just like you put a crawl space uh. If you want to put a crawl, uh dehumidifier to crawl space up north, i'm assuming you seal the crawl space right, yeah you're, not gon na you're, not gon na put a dehumidifier in it. Unless it's sealed will be the same thing with an attic.

If you don't want to do the foam, but you want it dry, you can just seal it because the whole point is keep the moisture out. That's all you got to do. How do you keep the moisture out? Well, you seal the holes in the boat. That's what you do: okay, let's go to the next one here all right, so everything that uh that we just went over is more or less about conducting heat.

So it's all! It's all conduction we're going to look at radiant, because radiant can solve all kinds of things. When it comes to duck sweating, you can get away with a lot of stuff with a hot enough roof deck, because there's so much heat coming off that roof deck. You felt it if you've ever worked in an attic. You felt it that's enough heat to keep you above the dew point.

So this is the heat behavior yeah, that's good! That's it! Thank you! We're going to look at how heat behaves in this simple shape and things that affect it when you troubleshoot this one of the things that's different about it is this thing gains heat in the daytime, but it gives off heat at night and that's not like we're Used to generally in the summertime down in the house, you know the air-conditioned part of the building. You have a heat load heat gain at night, it's less, but you have it, but you think about it. Your attic, doesn't your attic is giving off heat just like. Why why does your your car windshield, when you get up in the morning and it's covered with dew? Why is it covered with dew, because it was emitting heat to the the vacuum of the sky? It was going from hotter to colder right into space, so that is also occurring in an attic and don't forget it because a lot of times well, almost all the time you're not there at night, when it's really getting wet you're, not you're, not seeing it.

So if you're taking measurements chances are that while you're there you're measuring you're, saying man that shouldn't be wet well, the reason is it's drying, it's just not dry, yet it got wet last night when the attic got down to 80.. Well, then, you get there and you take out the access and it's 80 degrees. No, it shouldn't sweat, it was already wet and then in some cases you have thousands of pounds of lumber which gives us thermal storage. So we can soak up a lot of heat during the daytime and then that heat battery that energy keeps it warm.

Now, if you have a drop ceiling in a building like this, you don't have that you don't have all that lumber to store all that solar energy to keep things warm on into the night. In a steel building, there's not any thermal storage at all. It's it's! The temperature changes rapidly so we're going to look at how the heat changes things when we change the reflective roof. One of the ways to make duct sweat is simply reflect.

The heat. Don't allow the heat to come into the space. To begin with and you'll have a cooler attic, which is more likely to have the sweaty ducts less transmitted, the same thing will occur if you use radiant barrier radiant barrier film is installed on the inside. It's the shiny stuff just expect the ducks to sweat in florida.

If you choose that, if you choose to put in a radiant barrier in florida, i'm going to say all the way up to jacksonville really, i don't know why you wouldn't expect the ducks to sweat. I'm i'm going to predict they're going to sweat because you're not going to have those nine you're, not gon na get that radiant heat that kept it from sweating, because the radiant barrier film is not gon na. Let it through so we're exchanging heat not only through the roof, but the lack of heat between the ceiling and the duct. Obviously, it's going to be a lot cooler down by the ceiling down by knee walls and the higher we get up in that space.

The less it's going to be: you only have radiation, conduction convection. So whatever diagnosis you go out and you give this - it has to fit within that because we don't get to make stuff up it. It's either going to be radiation, conduction or convection. You can write fusion if you think you can sell that, but probably you'll just get away with those three uh another thing to think about right.

There we've got a return air duct on top of a cold cabinet uh we're here we're looking at normal venting here. The correct venting is one square foot per 300 square foot of floor area, and we want 60 percent of the area of that soffit to be at the bottom. We want 40 at the top that path of moisture and outside air. That's venting that roof does it have any reason to come near the air handler? Not really, it's got a path set up and it's limited it's controlled, but that's not what we really build.

What do we really build? Big goofy roof caps and the big goofy roof caps are a way to convey hundreds of cfm of airborne, moisture and cross ventilation through the attic. So some people say well. Doesn't it make the attic cooler if you want to make the attic cooler anticipate the ducks are going to sweat? That's where we started right. What was the biggest difference? The biggest difference was the temperature of the air around the duct.

Remember that was, that makes a big deal. It only makes a little deal what the air is on the inside of the duct, so this is a bad situation. So what i recommend you do when you find this? How many times is the air handler light right? Next, to that thing right, the air handler is right in there there's the big goofy blow in cold air on this cold cabinet. Why wouldn't this sweat so anyway, put your data logger in that space, take some duct board seal these off go buy some dust masks! Seal these off and watch it stop sweating.

Simply because you took the moisture away, you dammed it up, you're, not letting the moisture get to the duct, all right, so uh we're going to look at what happens when you lay a duct on top of an air handler cabinet. This is a very common reasons that ducks would sweat if you lay a duct on top of an air handler cabinet, you're shading, it there's no radiant heat. The worst thing you can do is let it actually touch, but it would be better if you just didn't. Have any duct on top of it at all, and the other thing that's true is, if you put the supply air duct on the top, go back a minute.

If you put the supply air duct on the top, which is the one you're worried about sweating, you can't obstruct the heat from the roof. If you put the return air duct over the top of the supply air duct, it can shade the radiant heat. So now, you're and or if you put any duct across the top of the air handler you're shading, the air handler so radiant heat works just like shade. So, there's a lot of merit for hanging ducts, very high hanging air handlers on threaded rod, trapeze hangers, getting them up off the cold deck and putting the warmer duct now.

The other thing about this does a duck gain by heating up the supply air duct. Does that hurt the performance and comfort? No that's reheat baby! That's a reheat duct gain is great. What about return? Air duct gain ooh. Now we have a penalty, because when you warm up the air going into an evaporator things, don't go the same way.

So if we're going to get it duct hot, we always want it to be the supply. You know we don't want it to be the return. So this is the one that we'd say: okay, go ahead and bury this one we'll let you bury that one in the fluffy stuff we're not worried about it. Let's keep our coldest duct up on top and hung high for the best chance of success.

This is the worst spot in the mcmansions down in naples. There's lots of these knee walls and the knee walls block the radiant heat. You don't have radiant heat coming from multiple directions. The way you do when it's uh, just a big, open attic, and so you end up with very cold spaces, and usually they got the the big goofy roof cap.

They got it right there right next to the air handler just uh just to make you angry and look what else happens, what happens to convection on a cold wall in an attic it's going down. That's a cold wall. It's not going up! It's going up! The other wall - it's going down this one, so be aware that convection, you know it's disrupted by this, so this theory about how we're going to vent the attic. It only works if everything goes up by convection.

So just remember: when you have a knee wall, you've disrupted the the convection, so pull the air handler away from it, and the air handler and the duct will both be warmer. So what you don't want to do now? Here's something the service technician we talked about. All he's got is well i'll speed up the fan. That's all he's got right.

What else is he going to do? Somebody at your company has the authority to say where the air handler goes. So if you don't want the ducks to sweat, get that person to keep these things in mind that if you have a choice, could we please not put the air handler right up against the cold knee wall service tech, it's too late? Whatever they did, they did, you know and he's got a he's, got to make a call out of this, in my opinion, uh, if, if you really want to solve the customer's problem - and they have sweaty ducks, it's probably not a service call, if you want to Start it out that way and have a technician, go. Look at the lay of the land, but if you're thinking well i'll, send a tech out there and he'll fix it. What's he gon na, do you see the nature of this stuff? This is not service.

Call stuff: this is stuff. You need to plan for all right. What do we got here? Uh? Hang. The units up high, the.

If you look in thermal imaging cameras, you'll notice that the plywood, when it's down on the deck is also cold. So you want to get everything up. You want to get as much separation between the cold surfaces as you can unconditioned garages do not insulate the ceiling. The code doesn't require it if you're not going to insulate if you're not going to air condition the garage there's.

No reason to insulate the garage ceiling if you're going to have the air handler out there, it's much more likely that it's going to sweat. If you insulate that ceiling, we would rather that you just let the sun heat that garage sealing up, because it's it's not. It's not a space, that's using energy anyway, and we could use the heat so when the homeowner asks like. Oh, should i insulate my garage ceiling with the vented attic above it? Well, the ducts might start sweating.

It's not going to help you for energy, because you're, not air, conditioning your garage anyway, so uh, the one that you'll have the most trouble with, though you got ta, really build some stuff for this one unconditioned garage with a cold space. Above that's the worst. That's the worst is a garage where the guy leaves the garage door open and it's got an air-conditioned room above it. So there's no radiant heat.

You know we got nothing. It's sheltered! It's sheltered by a a radiant barrier. You know: radiant barrier is sometimes that that uh foil stuff that reflects solar energy. Sometimes what reflects solar energy is just the living space above so, for example, the worst ones we have to deal with are in high-rise.

Condominiums. You go down to the parking garage underneath this thing and it's underneath cold concrete because they keep the ballroom like 70 degrees. So the concrete floor is very cold. We go down underneath it in the parking garage and it's just damp.

You touch the concrete.