Flex, duct works just fine when it's installed properly um neil compareto who's. One of my one of my buddies does a lot of testing on duct leakage and on delivered performance as far as cfm output and they install super high end installations. A lot of low static, ducted, ductless systems, ducted mini splits up in the virginia market, and they test them a lot. And what they find is is that when you extend flex duct fully so it doesn't, it's not compressed internally, meaning stretch tight you're, not making sharp 90s or really any bends or turns of any significance with the flex itself and you're sealing it properly.

It actually performs really well the objection to it being that it doesn't last as long and it's not as durable. That's still a perfectly fine objection, but you know get real we're in florida. Nothing lasts very long here. You know the houses are going to be destroyed by a giant wrecking ball every 15 years.

It's a new code. Did you know that? Yes, really termites yeah termites take care of it so anyway, when we're running a flex duct, if you can think of it in terms of like a pipe with water flowing through it. I think this is a really good uh analogy again credit where credits do michael housh always says this when you think about a pipe with water running through it. If you make turns or bends in the pipe, what's the water going to do inside the pipe? What's going to happen, it's going to have turbulence right, you're, just going to create turbulence.

So when you have fittings, when you have changes in size, when you have turns and curves you're going to get turbulence inside a pipe and both air and water are both a fluid and so they behave in the same way. They both behave according to the laws of fluid dynamics, so when you're running a duct, if you do anything weird with it or if you compress it so those ribs are impinging on the ductwork. It creates turbulence along the side and that turbulence creates resistance to airflow. So what we want to do when we're installing a duct system - and it doesn't matter what material we're using we want it to be as straight as possible.

We want to reduce turbulence when we make bends. We want them to be nice, gentle bends right, where possible, or at least at the very minimum, have minimal impingement on the bend. If you imagine a piece of flex and you take a piece of flex and you turn it on a 90 - that internal corner, there is very rough as those ribs kind of all come together, and so that creates a lot of turbulence. But even if you were going to be running, you know duck board or metal or whatever you wouldn't want, a bunch of turns and curves and that sort of thing.

So it's just common sense. And so when we design a duck system or when we're installing a duct, for example, if you take a you know a duct off of the side of a plenum, and you immediately curve it around in order to make it fit somewhere that radius that you just Made is going to create a lot of turbulence, so, let's start there, what could you do? Instead? Let's say you have a really tight supply plenum in an attic. You know it's coming right near the corner of the of the roof and you need to come out and make a quick 90.. What would be another way of making that connection other than taking flex, and attaching it to that? To that plenum you could extend the box.

That would be a way sure you could you could. You know radius around. Sometimes we've done that where you can actually get the get the actual plenum extended away. That's that's a good way.

What are some other things you could do yup? You could use a piece of snap lock 90., so you could take it now again. A snap lock 90 is still pretty tight radius you're going to still get a decent amount of resistance in that. But that's not a bad idea and in fact it may be easier to make that connection with that 90 in there get it transitioned away and then attach your flex, and what you can do with your flex is really easy, because it's going to be the same Diameter, what you do is cut back your insulation or cut back your inner liner. So you have excess insulation, make your attachment and then pull that that insulation over that 90.

so now you're not having to wrap that 90 or just using some excess external insulation. Off of the flex duct, that makes sense. So when you start to think about some of your alternatives, your alternative options, you can come up with pretty creative ways of reducing uh restrictions and in terms of where the restrictions matter most they matter most when they're closer to the system. So the closer the system closer to the system, the restriction is whether it's return or supply the closer to the system.

The turbulence is the more impact it's going to have on total system airflow, so getting that supply plenum right, making that return duct as big as you can using a really low static pressure drop filter is going to make a big difference. Those of you who have done installs recently we're doing more and more media filters, you're looking at static pressure numbers. Have you noticed a difference in using media with with kind of putting them in different locations than what we had before with one inch filters. Yeah makes a big difference now again, if the one inch filter you're using, is the factory hog hair filter.

Well, then, maybe not, but that's just a bad filter in the first place and besides the fact that you get bypass around that filter so anyway, one of our number one objectives is to reduce total system static. Now, again, some people will say well yeah. You could get static, that's too low. There are possibly cases on supply duct, where low air velocity could become an issue, but, like emmanuel d, says of the things to worry about, that is super low on the list.

So what that means is when we are field fabricating a duct system. Think in terms of the least back pressure, we can provide that system start with the return near the system start with the filter, those those areas and then move into the supply. The main plenum and then the trunks - it's not to say the runouts, don't matter, but they don't matter nearly as much to the system as the main supply plenum and the ducts that are really close to the system in terms of the actual delivered cfm to a Particular zone, that's where the the runouts matter more, but even then what we've you know. What we prefer to do is it's: okay, to oversize a little bit use a balancing damper and then just make sure you use the correct register.

Grille register diffuser right. You use the correct diffuser grill register diffuser, you deliver the right, airflow you're, going to get the right velocity coming out of that vent makes sense because again you have to throw air out of the supply, and so you have to have proper air velocity. That's where sizing of that of that register matters, so that's the basics with flex duct make sure it's fully extended, don't always assume that you just have to well in order to get it to fit. I got to jam it around this corner.

Look at your other options: can you extend the duct? Can you move it? Can you move the system in some cases that may be necessary in order to be able to get the ductwork on the piece of equipment, or can you use a piece of snap lock? 90, you know and if it doesn't have to be a 90, that's the nice thing about snap lock. You can adjust it to whatever angle. You need now make sure if you are using any hard fittings in addition to flex, because you can do that, but make sure you're supporting it, because a hard fitting has a little more weight to it right and it's going to be likely to pull out of The duct, so when you're, attaching that to a tab collar, you still have to make sure you seal it. You have to make sure it's really nicely mechanically fastened, and then you have to make sure that it's strapped underneath that heavier fitting okay, everybody, everybody with me on that all right next thing is strapping: go ahead: travis yeah travis said sometimes the snap lock 90s will Leak when you're dealing with snap lock and not spiral, i mean again spiral is a whole different animal.

But when you're dealing with you know your typical kind of inexpensive single wall, snap lock that we use with those adjustable 90s, they tend to leak so yeah. Once you get them set, how you want them, then go ahead and seal them when it comes to strapping of ductwork. This is an area that we don't think enough about it when we are doing changeouts. I don't know if you all know this, but we are required by code to inspect every existing duct system.

Leakage strapping are the two biggest things that we need to be inspecting. If you have ducts that are being supported across the ceiling joists across the trusses they're kind of doing this, that's not acceptable strapping. They have to be strapped so that way, there's tension on the duct a lot of times. You know 10 years ago they were doing explosion in the duct factory style, duct systems.

You just take your 25 foot of flex. You just throw it. If it's 10 feet, it's still 25 feet right. You see that sometimes, and in those cases it's going to be good to reduce the length of that duct and make it so that it's nice and it's nice and tight - i mean again, you don't want it banjo string tight.

So it's wanting to pull off the fitting, but you want it to be fully extended so that way that internal accordion is expanded and you don't get that additional turbulence because it does make a difference. You can test it sometime if you're measuring cfm, you just have somebody with a hood and just take a piece of flex, and just you know, put some bends in it. You'll notice that it does affect the amount of airflow that that duct uh produces because of the back pressure. That's produced so in terms of strapping every four feet is the standard.

So four inch i mean every four foot centers. Whenever you are strapping flex duct, you want to use an inch and a half wide or wider strap. That's pretty much true of everything that we do so that way it has more surface area, but keep in mind that the more surface area that we get, the less likely you are to collapse, the duct, and so that's why it has to be done regularly. So that way, you don't have any one support bearing too much weight, because that's when you get that sag there's a lot in the um.

What is it called? The uh, the duct council, flexible duct, council fdc, i think, is what it is um. They have a guide there that you can look at. That's got a lot of really good specific information, but again i know most of you aren't going to be thinking about the radius bend and how much is too much and all that, which is why i would much rather you just visualize it as water and think How do i reduce the turbulence in this duct system and especially when we're going out to do a new install? Our goal is not only to put in a nice new piece of equipment, but wherever possible to improve that duct system, and these are some really low pieces of low hanging fruit. In addition to improving your return, improving your filtration those things close to the system.

Look at that entire distributed duct system in terms of sealing ducts, so you go into an existing house that has a bunch of flex and board in it like pretty much. Every house has in florida. What are you looking for when it comes to saying all right? This needs to be sealed. What is your, what are your visual cues sweating discoloration? Another thing that a lot of people look for is: does it have mastic on the outside, but truthfully the whole mastic on the outside thing is really just a shortcut way that inspectors in our state have come to view duct sealing.

It really isn't a standard. In fact, if you look at the flexdot councils, two ways of attaching flex duct, neither of them include mastic on the outside. Now am i telling you not to use mastic on the outside? No because i don't want to fail inspections right, but mastic on the outside of the duct is not how you seal a flex duct. So i just want to get that so we're all clear on that.

It's not that it's pointless, because anything that helps you pass inspections is still has a point right, but that's not what results in a flex duct leaking. Where does the flex duct leak leak from it leaks from the connection where the internal liner attaches to the collar? That's one place and also where the collar attaches in to the duct board. So what do we do to seal the collar to the duct board when you cut the hole you paint around the hole with mastic and when you set the collar in that, does a really good job, because then, when you, when you tab over that collar, you Get a really nice seal that collar edge, because again those those tabs are providing that that holding force for the mastic to dry. So that's a good one.

The most controversial part of the process is the next part, which is that internal liner to the tab collar? How do you make that connection? Travis says mastic. Anyone else, you didn't say mastic, i said, grant, grant your name, isn't travis. You look like a travis, though you know wow oh wow, that was this is getting dark in here. Quick grant, says mastic.

What does travis say? Okay, mastana pandu is strapping the underliner, any other suggestions, tape and a panduit on the inner liner. Okay, i was waiting for that one. Any other suggestions, panduit on the inner liner heyo, do the mastic first on the tape on the wet mastic. It works great.

Well, no, you get the mastic on the inner liner, you pull the inner liner over it, and then you tape the inner liner onto your collar and all the mastic is inside if okay, instead of on the collar inside the flex, instead of on the collar okay, I buy that one. Okay. Is this a way that people are doing this a lot, because this isn't a new one that i've? Okay, all right cool? I don't even do it the other way. Okay, thank you, kyle! Thank you, kyle, okay, so the flex duck council again i keep, i think, it's the air, duct council and it's the flex duct guide.

Maybe that's what i think it's air duct council, so they give you two alternate ways. One is to use tape on the collar with a drawband or panduit, strap or large, zip tie whatever you want to call it. Panduit straps just a brand name and some of them they actually show using like a giant uh hose clamp, which seems like kind of a cool way really a little excessive. Maybe but you know: okay, yeah ain't coming off um, so all of the both of their methods show the pan to it.

So let's just agree: we're going to use the panduit. Okay, all right so panduit on the inside that one's good, mastic or tape is allowable. Now the downside, of course, with mastic, is that mastic has to dry. That's the downside with mastic and if you're going to be doing a job where you're going to be running cold air through this thing really soon.

That's where mastic becomes more of a problem, because now you're pressurizing it it's more likely that it's going to blow out around the wet mastic you're going to get condensation. That's more of the challenge. So i am an advocate of the mastic method, especially when you are in a situation where you can allow it to drive new construction. You know big project come back the next day.

I like that way, and ideally, when you're using mastic on the inside again, i'm just telling you ideally so we're talking in a perfect world here. You would have that outer liner pulled back so that way it could be allowed to air dry before you pull the outer liner over. That would be an ideal circumstance: okay, but to kyle's point cleaning. The fittings with alcohol is really helpful if you are going to use any type of tape.

In fact, it's helpful even with mastic, because a lot of these fittings, because some of you will say well yeah, but if i don't get it wet, i don't sweat on it. Well, that's not really it. These fittings have an oil on them from the factory. So taking some rubbing alcohol on a rag - probably you better put it in a spritz bottle, actually sell them that way at the drugstore you can buy isopropyl alcohol.

Some people say denatured, alcohol. I don't care what kind of alcohol you use other than it's, not the drinking kind, because that's not allowed to be in your truck. Okay go ahead and try that one, you spritz it around, then just wipe it down. That will help the attachment of all types of methods that you use, but especially with the tape method.

Tape, that is the ul 181 fx, is specifically designed for flex. That's what the fx means, and so this stuff that you some of you, are complaining about. With this. You know beautiful type of uh.

You know a little bit more of a mastic tape type. It's not! This isn't technically a mastic tape, but it has that butyl type of um adhesive on it. I think it works well, but again, i'm not going to dictate to you specifically what tape you use for a job so long as you're, making sure that it is fully attached and you're squeegeeing it in place. So in terms of the things that i would really like to see, if you're using grant's method, where you put mastic on the inside of the flex and maybe not bringing it all the way to the edge, so it doesn't, you know squeeze out on you.

I think that's a really good method in addition to alcohol and tape and panduit that to me is beautiful and then, if you want to get even more extreme put some some mastic on top of that and let it dry there, you go bob's your uncle, but Again, the point isn't to be: what did he say you guys are so specific. So the point is to create a leak-free connection. That's not going to come apart. All right! That's really the point now.

The problem is: is that we're not testing every duck connection that we make, and so this is why i have a lot of respect for the process that neil uses, which is what we put on instagram, because he does test his duck connections and he does use A ton of flex like a lot of flex over long runs and a lot of connections. So his method is what we showed, which is cleaning it using um, using tape using maskic using a panduit strap and on the outside of the duct, where you attach it. This is where, when you attach that outer liner, i don't really care how you do it so long as the insulation is fully butted up in an ideal world and an ideal world silver tape well cleaned with alcohol, and they call it uh. My my old boss at deller and evan wortenberger, used to call this the diaper method.

I don't know why he called it this. I guess because you use a lot of tape, i'm not sure, but you just take pieces of tape and you and you take that entire outside and you diaper it to the duck board, and so it's all a silver silver on silver. It does reduce condensation. It does reduce growth and you can ensure that you get that insulation all the way up and around.

If i had my choice in my own house, an inspector wasn't going to gripe about not seeing any mastic. That would be my favorite way of attaching that outer that outer jacket. The same thing is true in the villages where we can get away with not using mastic, and instead we just use silver tape who likes that way. As long as you get tight, fitment everything is tightly fitted.

Do you really need a bunch of glop on it? The answer is, no, you really don't. Everything has to be fit tight, it has to be nice and clean. You use a squeegee, you get a nice connection. You know nice overlap the biggest problem that i see with a lot of the duct systems that you know where, where they don't do this right, is they don't get enough tape, overlap and they're, not really squeeging it to a nice clean surface, so it peels off And then it starts to leak but mastic or duck sealant or pookie, as some people call it in the west, which i forbid you from calling it pookie.

That is not what it actually is a brand. There is there's actually a brand of duck. Sealant called pookie, which is where that comes from, i think, but it's just terrible anyway. The point is is to get tight, duct, fitment and good seal, and it's the inner of a piece of flex that you are sealing the outer it's about getting a solid vapor barrier.

So can you take here's a question for you? Can you take the outside of a flex duct, pull it up to the duck board, just put a zip tie, zip strap on it can do it whatever you want to call it draw band and leave it. Is that good enough? Why not because there's a gap, so it's not so much because again, if you seal the inner it's not going to leak air shouldn't, it's the inner sealed but you'd have you don't have that continuous vapor barrier and it's that continuous vapor barrier that prevents high dew Point air from getting in there and creating condensation around that edge. So what did i say between the two correct, correct if you, if air can get in from that outer into the inner where it attaches, you know where those two fit together, then it can create condensation in there, regardless of whether or not there's an air seal. You don't need an air leak to have condensation.

We all know this. You could just have poor insulation, poor vapor barrier, and so we need to have insulation intact, all the way to the duct board, where the flex attaches to the duct board. We need to have insulation intact and we need to have that outer vapor barrier intact now we're using mastic to fill in that gap right. But mastic really isn't the ideal answer, because you could have this gap that you glop mastic in, but you actually don't have the insulation pushed all the way up against.

So again, in my perfect world you wouldn't even be using a panduit on the outside. The problem is with our method, without using tape, if you don't put a pan to it, on the outside, you've got nothing holding that outer jacket, and while that mastic is drying, it will just pull away right. So, given our process, where you don't use tape on the outer, you don't really have a choice but to use that outer pan to it, but an outer pan do it has a problem and what is the problem with the outer pan to it? It squeezes the insulation correct, which is why the flex duct council does not show that as an option. When you compress insulation, it ceases to be insulation.

It would be just like. Oh i'm blown r30 in the house and then you just go and stomp it all down, because you don't like how it looks right it doesn't. It doesn't work right right. You need to have air in insulation in order for it to insulate, and so when you smash down that outer insulation of flex duct, you reduce its r value and when you do that, you can create sweating, especially in our market, where even regular old ducks just Running through the attic want to sweat because of how higher dew points are so again, i'm not the installation manager.

So i'm not going to tell you the specifics of how everything has to be done, but i would rather see i would rather see duck board and fittings cleaned and that outer jacket attached to the duct board using tape and then in order to pass inspection slap. Some mastic on it on the outside, rather than using a zip tie, panduit drawband, whatever you want to call it on that outer on the inner. Yes, so in the inner use, a zip tie for sure and use mastic for sure i would also, i think i like grant's method best, or i think you said the same thing travis you have some mastic on the inside then put it pull it over. Zip tie or first first tape.

I would still like to see you use tape and then a zip tie and then you're outer taped and then sealed just so that way the inspectors don't gripe at you. The village is done. In fact, the villagers doesn't want to see it right right, which is weird, but again it's not weird, because again they're going off of what the manufacturer's specifications say. So you.