Hey thanks for watching this video. This is one class from the 2022 hvacr symposium in claremont florida. We have the symposium every year and so to find out more information, kind of upcoming go to hvacrschool.com symposium big thanks to our sponsors. For this event, which was accutools and truetech tools, they're the two title sponsors that made the event possible in this session generally garcia and sam meyer sam, is with retrotech and january.

Is a florida contractor south florida contractor talk about rtfm but wait. The home doesn't have a manual, so what do you do to diagnose the envelope of a home? What do you do to diagnose the issues inside a home in order to make sure you get great outcomes when every house is a little different? My name is sam myers. This is jenny, garcia um. As you see the title here rtfm, but wait.

This house has no manual. You know we came up with this concept of you know in the hvac field, building science field, the way that we look at equipment. The way we look at tools. The best way to do things is to read the manual houses.

Don't really come with those there's, a there's, a saying that uh you know with especially with custom-built homes. Every house is a prototype, so you really have just one one chance to get it right and figure it out, but um houses have a lot of moving parts. They're, not just stand-alone um, solid state objects, there's a lot going on there. Lots of different pressure changes, mechanical systems, uh winds and stack effects that play a role on all these things that are happening all at one time so uh.

So we came up with this concept like what, if houses had manuals, what how? What would it look like? What kind of things would they entail? What kind of things would be included? So, even though this is not a thing and likely never will be, we at least put some concepts together to show how we can at least have some practices to look at certain things that we can use in pretty much every home to make sure that it's Going to be comfortable and working as it should keeping the occupants happy. So my name's sam myers, i'm with retro tech. We make building science hvac diagnostic tools, things like blower doors, duct, testers, airflow measurement tools, high precision, manometers and things such as that. So i serve as our in-house trainer building science consultant.

Wear some other hats as well and generally, i think you're going to be the best person to introduce yourself here. My name is general garcia. I'm not much of a scientist, not unlike many of you guys. I get in my work van in the morning and work through the calls and rush home to make it.

So before my kids go to sleep at night, i have had a an incredible blessing in the sense that i have been exposed to some of the greatest minds in the industry. I feel and as a result of that and some resilience slash luck. I have been exposed to some really really tricky problems uh when it comes to problematic homes that didn't really have an ac problem or an hvac problem, so to speak, um from the standpoint of the equipment or the charge or the airflow, or anything like that, and That's what we're going to try to represent here that was very modest generally is a rock star pretty much. I remember when he first started using blower doors just a few years ago and he's just hit the ground running ever since, and it's been really fun to watch some of the things that he uncovers inside of houses.

So this is uh generally, and i wrote an article together that was published at hvac school just a few weeks ago, where we kind of touch on this subject and we're diving more a little bit into it today to show some real world scenarios and demonstrate how Some of these concepts work, and so when a the typical hvac contractor is looking at things as far as mechanicals go, you know, checking static pressure, looking uh looking at superheat and sub cooling yeah, that's great, but you're not really going to get the full scale of Comfort generally, what what would you add to this part here, because you you've done that right? So as an hvac person, we we are um, we're conditioned right. So we have this thing where we need to look at pressures and temperatures and superheats up cooling. All these things, air flow static pressure and somehow we're going to fix everything like that. This presentation is more about what happens with all those boxes checked out and still you know things don't add up.

People are not comfortable and they have. You know high humidity issues. Just complaints about indoor equality, etc house as a system as a concept, is just like the presentation that eric was having before us. It's just nature, seeking balance i have mentioned before in other platforms.

We we have grown accustomed to the fact that we are removing heat from inside a home with refrigerant at high pressure and high temperature before it hits the txv and we are rejecting heat outside through the through the coal gas and the suction line. That is running at 50 55 degrees and then just we're gon na get rid of that heat when it when it goes to the condenser coil in 90 degree weather, like those things, are counter-intuitive, but somehow it just makes perfect sense for us, like the refrigeration system. Even though it's not account it's not even though it's not self-intuitive, it just makes sense for us and we appreciate it and we fix it every day, right and uh. This stuff's easier a lot easier.

We just got ta expose ourselves to it and just understand it, and hopefully we can. We can show that here yeah, so there's going to be some things here that really piggyback on some of the things that eric was talking about. If you were in here when he was presenting um, but in the article that generally - and i wrote - i mean if you come out of here with one thing - just understand - that the the building envelope is a part of the hvac system and if you're really not Looking at how it's performing or how well it's matched up to the system that's installed or that you're planning to install there's a lot that can go overlooked there. So there's three key points that we put in here and uh.

We want to determine the amount of leakage, that's in the in the building envelope. We want to know how leaky it is. Is it a crazy high number? Can it be controlled um? Where are we? Where do we stand with that and then two is we wanted to see how that leakage is distributed? Is it evenly throughout? Is the whole house kind of unified and how it leaks? Is it all in one room uh? Is it all ceiling? Is it all floor? That's important to know too, if we're really going to try to reel this thing in and get it to perform like it should, and then we want to see. The third thing that we want to see is how the mechanical system interacts with the envelope cool.

So we've done the blower door at 50, pascals we've seen how that performs, we've seen where some of these problems are. So whenever we kick the hvac system on what happens to these rooms, they go up. Do they go down? Do they stay neutral? Are we pushing air out um? Are we sucking hot humid air in what's going on so we'll show you uh how we can uncover some of these things um? I know eric kind of said this verbatim. I stole this from joe madosh to be fair.

He left it where i could found it uh, where i could find it, but uh he might have used it today. I caught part of his presentation, but when you think about it, the building envelope is the container that holds the final product. You deliver to your client, it's that simple like. If our job is to carry water in a bucket, don't we want to know if that bucket's going to have a hole in it first, so the building envelope is it works? Similarly, um.

Does the mechanical system match the house? Can we fix it with more airflow? Is that going to do anything is throwing a bigger? Does throwing a bigger system in there make any sense? So we need to see if this kind of thing can be fixed and see where those problems are um. So this is uh. When we talk about the envelope, there's different terms, building envelope pressure, boundary air barrier, those are all the same thing and what basically, what we're talking about is that outer skin of the building that defines inside from outside and the materials constantly change as you go around So these are some some sectional drawings that we did. I used to work for an engineering firm in raleigh called advanced energy and we managed several different building performance programs, and so this is a checklist we put together to call out where different weak spots are that commonly occur in the air barrier.

So you know your common culprits of things to look for, basically, where one material meets another. That's not deliberately sealed. That's where we see things fail, so things like corners, especially when we're talking about walls, whether if they're exterior well, it really gets louder. When i put my mouth closer to it, doesn't it um? I guess that's how these things work, but when we have the most common one that we see here for addicts, especially if we have a ventilated attic, is where this drywall meets the top plate.

That right there, we see that as a pretty high leaky spot, that a lot of people don't think about you have this crack between the drywall and the top plate. That goes on both sides of an interior wall, and it adds up so that's air. That's connecting to uh to a hot, ventilated attic during the summer, but as you can see basically anywhere, we have a penetration going through the wall. Was it sealed? Well, are there any chases in there that are uncapped? There's there's a huge list of things where we could find problems, so i'm not going to dwell too much on this.

I mean for that number one point for testing. You have to do that with a blower door. That's how you get your number, whether if it's ach or cfm50, the cfm per square foot of envelope envelope area. However, you want to look at it at least just get some kind of number to see where it lies and if you've never seen this done or had any experience with it.

The way this works is we usually depressurize the house there's some cases where we don't want to do that. So if we have any ashes in a fireplace or if there's any mold, that's growing on the air barrier somewhere, we don't want to pull any mold spores in the house, but usually what we do is depressurize. So, like we're pulling bath, fan dampers kitchen exhaust dampers closer instead of blowing them open, but it's just exaggerating all of those leaks in the house and the way this this thing works is if we know fan pressure and we know the surface area of the hole We can calculate flow and that's exactly what this thing is doing. So that's how we get uh, that's how we determine how leaky the whole building envelope is and uh.

If that duct system is located outside of the envelope, the duct system is part of the envelope. It's part of the air barrier, so so all that uh leaky, duct leakage is counted there. Um there's a ton more on this. I've got videos on youtube, just search, retro tech, energy, and you can see uh how a blower door test is run, but we're not gon na dive too far into that today.

We can later, though, if you want so feel free to i'll, be here till saturday. So uh the point number two that we had in our article was locating those envelope leaks. Where are they um there's different ways to do that? One of my favorite ways to do it is to flip that blower door fan around and pressurize the house. You can shut doors, bedroom doors, whatever room you want to focus on and if you see smoke shooting up under that doorway, yeah, there's some leaks going on on the other side of that door in that room somewhere.

Basically, what that smoke is doing is making that air current visible, that's being exaggerated by the blower door fan, and so it's just leading you to it. This is quick and easy to do. This is great for encapsulated addicts to encapsulated addicts. If they actually did it right, you can pop the attic door open if smoke is going up in there immediately yeah.

It's not sealed. Well, so that's another great test. You can do there too, but that's just one example generally has a whole series of articles on zonal pressure diagnostics, how you can use a high resolution, manometer same type of monometer, that would come with the blower door system. How you can use that to uh to determine how a how a room is leaking, how a crawl space is leaking if it's encapsulated encapsulated attic, just different ways to look at that to see how that leakage is is occurring.

So we talk a lot about quit: equipment sizing too i mean this shoe has to fit. I'm sure if you've seen me comment on anything on the hvac school facebook group or any of the videos that we put out, i mean this is kind of step. One. You need to do a load calc, the rule of thumb thing has to go uh.

If we're really going to get things right. Um i live in wilmington north carolina. We have we love putting duck work flex up in the attic. That's just what we do there.

I don't know why, but that's that's how it is. The systems are always oversized, so we're always turning fan speeds down uh. We still have over pressurized rooms when we turn it down. We still have high humidity, so we put in a whole house dehumidifier to help resolve those issues, but it's kind of a stupid problem to have at this point, if we just actually measured it to see and calculated what size system that we need.

A lot of those problems would go away, but this is from wright, saw from a house that i had in raleigh infiltration made up about a quarter of the heating load here so um. But we had to run a blower door to us in order to see that yeah, like i said, the shoe has to fit um. The system has to match the house if we're really gon na dial this in, and do it right, big thanks to allison bells for making this image it's great. I use it all the time yeah.

Just like you wouldn't put an oversized. You know system in a house, you wouldn't go hike the appalachian trail and a pair of boots that are too small for you. I mean it's kind of the same thing. It has to be right.

Yeah, like i said it really does so, then we have to go and do things like this to make that installed system uh, actually work out for that house needs a little help to get uh that humidity out of there generally. Why don't you talk about uh? The old balance check for the house here all right so when we do a blower door test uh, which is incredibly helpful. But it doesn't tell us about mechanical driven infiltration. So we could have a house with x amount of leakage through a blower door test.

But when the ac runs and when we do a low calculation and we got, we do all these assessments and things based on that. But if we don't take a look at the mechanical driven infiltration when the ac runs, it can drive enough air in or out of the building in and out of the building, i should say to offset whatever value we accounted for in infiltration so uh. This happens through leaky dots, that's pretty much what it is, um the main reason also when we have unbalanced rooms. This is a test that is very, very easy to do.

The hardest part about this test is just spending money on the monomer. That's it and a piece of tubing that comes with the manometer, that's it so, essentially what we do is we run the we would run the hvac, and then we can go sneak that tubing under under a closed door on a unit on a space that is Conditioned and we see how that space is pressurized with relationship to the main body of the house or just the rest of of the main area that you're trying to check right so uh we don't. Normally we don't want that space to be um above or below. It's within three pascals is what you wanted to be.

There are some extreme cases where you would want it to be as low as two based on the you know, the pressure and the duct uh that that's bringing the air into the space when we have an unbalanced room. We have an unbalanced house. So if we close two doors in a house and that causes - i don't know - 50 cfm each of infiltration - that 100 cfm of infiltration to come in the house on a count of four driven infiltration. This is an intermittent problem that is extremely hard to diagnose.

Unless you know where to look right, diagnostic itself is not hard, like, i said it's just pressure, trying to balance itself right, nature doing its job. You just got to know where to look right. So when you close a bedroom, a bedroom door, you want that pressure to be within three pascals of with the relationship to the rest of the house. There is a caveat there.

The pressure in the room could be balanced, but you might not have enough supply air coming into the room so before before we go any further here, you know, there's got to be a way of assess the flow, the supply flow into the space. Where you know it's adequate, or at least adequate enough to keep the space cool, because you can have a room that is under condition that is perfectly balanced and the room will still be uncomfortable right. There are others uh, there's at least one more scenario where the room could look balanced and actually not be that we're gon na discuss a little bit ahead, but uh. This is basically the the base of it once you fm in once, once you fm out once you have it right, we just went through this in the previous presentation you have to you know every room: has you got to have enough return air path for every Cfm of supply air that makes it into the bedroom to make it back out to the a-track.

Otherwise, that's going to offset the balance of the house and then we're going to have problems. This is uh an example of the house with all the doors and windows closed. We have supply predominantly supplier leakage and the house is pulling down to minus two pascals. If we have air leaving the supplier side in the dock, where it's outside the envelope, then you're losing air to the outside, essentially to a vented attic to a you know, open call for an open crawl.

Uh software garage depends on what it is right to offset that balance right um. This is an example of leaky ducts. Those are not very rare to come by. As you you all know, um sometimes they're hard to find spaces are tight but they're out there.

This is a predominantly leaky returner side. This means that we are bringing in more out more outside air, more air through the return that we are delivering through the supply right. We're pulling air from the attic along with through the return vents right here and then we are getting it's getting delivered to the supply right, so we are pulling more we're pushing more air through the supply duct side. I should have said that we are getting in through the returner event and that's because we're making up the balance through leakage on the on the return side of the duck we're running through the air-conditioned space.

Yeah. Sorry, there's a guy named robert, barely uh that had an article in this old house magazine where this exact thing happened, and i think there were four or five uh members of the household there. I think four out of five had asthma and then uh. They went in and fixed this problem and got some other things sealed up on the attic plane as well and uh.

I think half of the household got off of their asthma medication, just from fixing the house that way and we've had similar things happen too. In eastern north carolina where in greenville north carolina, their utilities, municipal utilities actually has a couple of guys that goes out and does this and actually does a good job with it and uh. We have also with ducks and addicts. We have a lot of ducks and vented crawl spaces too and uh.

This lady had asthma and uh very leaky, return, duct and uh, and a molly crossblade in a moldy crawl space. So you can imagine uh the stuff that was getting pumped into that house. So once that was sealed up and fixed, you know her asthma symptoms were cut in half so big ieq penalty. Here, whenever this kind of thing happens, um you know a leak that commonly gets missed whenever air sealing is occurring.

Is that gap between the return box and the and the drywall that counts as a duct leak? And that's that's a sealing return. If you stick your head halfway in there um but yeah, especially if you have several returns throughout the house, that adds up same for supplies, um for the return or the supply uh boots too. So that's an area you want to seal with caulk or mastic. So uh yeah this is uh.

This is a gem that generally found here. So this is a predominantly returner side leakage. So you see this unit is in the attic and the pressure in the house was 20 pascals positive with relationship to outside. This is an extreme case, which is you know, fair, that it's not very uh common, but that is there for a reason.

This is the opposite side of the spectrum. This is the supply of you know. Let's call it plenum for whatever it's worth and uh literally, the lid blew open pressure of the house, negative 60 pascals for reference, a blower door will, you know, will pull the house normally to minus 50 pascals. That's how we do and that's how we accounted account for leakage and this house with that much got as low as -60.

That's a very extreme case. Those two previous slides were extreme cases. These are cases that are not that extreme. Also because you see a negative number on the gauge, assuming that you put the tubing in the right place, because you see a negative number in the gauge, it doesn't mean that the all of the leakage is on the supply side.

It means that it's predominantly leaking on the supply side right. You could have the return side leakage, it's just that you have more on the supply than you have on the return. That's what that means right, um. There are also some cases where you don't you actually do this and you don't see a uh, a pressure difference.

The pressure of the house looks quote-unquote balance that dog might be tight or you might have the same amount of leakage in the return that you have in the supply. That's what that means right. The velocity of the of the uh, the velocity of the air moving through the duct, also makes a difference. We have through the supply we're moving air at higher velocities right, 6.

7. 800 900 feet per minute through the return, we're moving air much much slower. So a same size, let's call it hole if the same size opening on the return is not going to equal to the same amount of leakage through the same size hole on the supply right. So that's those that's another nuance to look at there.

So if, if you don't, if you do this, put it through this way, so if you, if you know, if you go, take a look at that, go, take a look at the return side or just whatever it's easy for you to find, and you see that The ducts looks like it's leaking like there's a there's, an opening, a gap that the the dogs is leaking through, either through the supply or through the return, and you do this test and the house pressure is zero. Then that means you have enough leakage on the opposite side of the other handler to go along with what you saw right. Does that make sense everybody? So that's that's essentially what we're trying to get at here right. This is, and i cannot stress how time-consuming can it be? You know trying to diagnose these things without this taking three minutes to do this.

It's extremely extremely helpful. Also, if you don't have enough return, airpath from a close from a bedroom with a closed door back into the space, then that room it's going to be. The house is going to be on balance before by. However much you're not getting back from that room right, there are cases where you have.

There are rooms that are perfect perfectly balanced. Let's say you have a room with you know two pascals right positive: two pascals you have enough supply airflow coming out of the vents and the room. Still, the room's still uncomfortable right, assuming the premise of enough insulation, because that's not what we're talking about here right, but assuming the premise of enough insulation. If you have enough supply airs, you know air supply air supply.

Conditioner is what i'm trying to say. Then you have to you have to look at the leakage of that room. So if you are pressurizing, a room and the room is leaking you're getting some of that air back through the return air path and you're getting some of that you're losing some of that air too out the outside the way to diagnose this. Is you close the door to that bedroom and then you go look at the pressure of the house? If you, if you close the bedroom door and the blue and the room looks looks to be, you know perfectly balanced or at least balanced enough and the room is not comfortable with enough air supply, then the house is going to be negative, because that means you're Losing air from that room to the outside, so therefore the house, it's pulling up it's pulling down and trying to make up that difference, make sense right, so it's not only about dog leakage! Think about it! If, if you have a passive, if you have a passive, if you have an overhead and over the door, return air vent right air path.

So what's what's your return, doc there, the room! You know what i mean, so the the the flow of the return back into the back out of the room is a sole function of the pressurization factor of the supply flow, pressurized in that room. That's how that works right. So there are other cases where the over there, if it's a, if that is with a passive return, if it's an active return, meaning a doctor return, then these things can happen. This is a room that is negative.

It's actually opposite to anything. That's been discussed. This room is actually negative with relationship to the rest of the house, so infiltration is, being you know, forced into this room through every crack on crevice. This is a an infrared shot of that room and how that that we had that corner there in the wall.

That show infiltration so this this was a house in wilmington we were. We were called over to see why the master bedroom suite was having high humidity and, as we shut the door. This is the number we got almost negative five um and it also had a connecting bathroom that had a bath fan that ran intermittently. So whenever that fan kicked on, it would go from negative five to negative seven and what we realized was there's a pretty pretty leaky corner here on this wall.

This picture was taken when the blower door was running at about negative 25 pascals to really exaggerate that leak, and i mean i didn't really need a fancy camera to get this, i mean this was just a clear one to take that i mean these. Are you know, as far as thermal cameras go, these are pretty inexpensive but uh they work well enough to be able to capture that. So what was happening was the we asked the homeowners. You sleep with the door closed at night yeah.

We do so with the door shut and with it pulling negative, it was pulling in air from that leak. From that massive return somewhere down down the line, an hvac contractor came in and put a huge return in the bedroom. So once we dampered that thing down and got it to balance out, they were fine. That's an exterior wall yep.

So nate's question is: how low can the pressure does the pressure have to be for you to know that the room is not problematic, assuming proper supply flow, normally within three pascals? What's what you are probably referring to it's if you really have uh, really awesome dots, if you redid all the duct work and the pressure on the dock was slow enough to deliver the same amount of the same amount of flow, then you need the room. The pressure in the room to be even lower than the standard and three pascal so i'll put it to you this way as slow as you can get it if you know being zero zero. It's not realistic without that! That's what we're after here right so or like, like you know like it's been mentioned right. So if you have three pascals and the room is not it and you have enough, if you have proper flow out of the out of the supply vent and the room's still not comfortable, then that means you need more return right, there's also new ways to account For the return airflow i mean, if you, if you use a power, fluid hood, you can it's very easy to measure the flow coming into the coming into the room and the flow coming out of the room right.

If those two numbers don't collide with one one with the other, then we have a problem. Another factor that gets lost here so the blower door number matters. Can we go back to a pressure to uh one of the house? So, let's, let's just say that this is the picture that we're working with. We got to a house, we measured the pressure and then and the in the house with relationship to outside and the the house is pulling down to minus 3.9 right.

That number and let's, let's just say that we have - i don't know uh 200 cfm of supply, predominantly supplier leakage that that's what it took to get this house down to minus 3.9, that number that readout for a given supply air value. It's going to vary with the lower door number of the house. What does that mean? If the house is very leaky, this number is going to go down. If the house is very very tight, this number is going to go up.

So while this is a a good, almost uh cheat cheat cheat approach. Let's just say a cheat approach to get to have an understanding of. What's going on in the house, we need to leave. We need to have at least a blower door number to have any idea of what's going on here and why we're getting that pressure.

That just goes back to that three-step thing that we put in that article. We want to know how leaky it is. We want to know how the leakage is distributed, and then we want to see how the hvac system interacts with it to go back to nate's question about how low do you have to go. I mean there's not really a universal answer to that.

It depends on the house. So what? If you have a room and you have the door shut and you're only getting two or three pascal's difference? What, if that room, is crazy, leaky still pumping air outside of that house and so you're still going to have comfort problems, but you're not going to get there with just looking at that balance check with a manometer? That's when it really helps to go back and see what you can see with a blower door and a thermal camera see what you can do with smoke. Zonal pressure diagnostics on that room. That's what's going to help narrow that, in you want to start getting a few tests in there to use together to where you can really dial in of.

What's going on so so joe's asking how we have the house set up when we do our blower door test yeah, we'll have all the doors open. We want access to that entire building envelope um if we're using a thermal camera and depressurizing right. Yeah jen recovered that earlier yeah, just yeah close the door and see what changes, and you know you can there's other ways to do it too. Going back and using the smoke, you can flip the fan around and pressurize the house, and then you can shut doors and see if that smoke shoots up under that uh that door undercut or not.

I mean that. Can that can tell you too there's more than one way to skin a cat? I mean, depending on the day, sometimes you don't have good weather for thermal smoke. Usually, works really well zone, usually works really well, but just kind of depends on which way you want to go, but just uh going back to this leak. Here we were actually able to go outside and measure this leak from the outside as well on that exterior corner.

So that's where that foundation wall uh starts to meet uh the bottom plate there or i'm sorry over the crawl space. So we could kind of see where that leakage is coming in uh from the outside, as well, so just able to measure it there from a couple of different points to zero in yeah. That wall is leaky enough. That room is under enough negative pressure to cause that to happen.

If we zero it out, it'll stop amplifying that leakage looks like it's demo time, all right so um. So what we're going to do here? We're going to simulate well we'll have to pass the hat around what we have here. This is a duct simulator. We're going to use that we're going to say this is a bedroom and we're going to simulate that this is our hallway door and the way we do these, these pressure checks is that we can toss a tube under, and then we have our our high res Manometer, that's going to be reading pressure in that room, so we'll say that's the door shut and so we're going to use this duct tester fan just to kind of simulate the hvac system.

What would happen in this bedroom if we have a house or if we have a room? That's just too much. That's too positive so to simulate that we'll just run, and i've already done this before so i already know what pressure i need to go to and what fan speed. I need to go to so we'll just hit we'll say we'll run it at 20 and tell it to go the flow on channel b doesn't really matter. I mean this is a tiny little box, so yeah we're not going to be giving it too much to get to pressure, but i'm using about 10 pascals positive here, because that's a number that i see a lot um, 10, 12, sometimes 15 - that we see in Certain rooms, if you just shut the door with a tube under it, so that room is too positive.

Now, of course, if we open the door, that pressure is going to go down to zero doors open it's even we shut it back again, we pressurize again. So that's when we need to have some kind of way to get that air back to the return. So in a lot of cases we have a main return. We may not have one in their bedrooms, but when we have a door shut, there may not be enough undercut under there to allow that air to get back.

So if we can put a dedicated return of a correct size or a jumper duct or a transfer grill or one of those cool, tamarack transfer grills through a door if we find that sweet spot to get us in and open that up, we can watch that Start to drop to where we can get it close to a more manageable number down to three or whatever um, to go back to what uh nate was talking about like how do you know that that right, number um, let's say we flip things around uh? Let's say this is: let's say this is an attic or an exterior wall, or some space that connects to the outside. I'm not changing the fan, speed at all, it's maintaining the same speed, we're at nine and a half now, but what if i make the room? Leakier we're adding some leakage. We got a big chase in the uh in that wall somewhere now we're about even and at first glance. That's gon na look pretty good right, we're under that we're under that three pascal range, but we've got a really leaky room, so that alone isn't going to tell us the source of that comfort problem or if balancing is an issue, if we were to go in And fix whatever that, whatever that leak is and maintain the same, the same flow yeah, that pressure would crank back up.

So that's that's when it's worth taking a couple of different looks at it not only just doing that that balance check, but also looking at the room itself with the blower door to see what's actually happening there. How leaky is it? Where is it? How severe is it and how is it interacting with the hvac system, so on that same point, uh about nate's question, so let's say just bear with me here. So let's just say that you have 100 cfm, which is through a low calculation. It's enough to keep a room cool right and for whatever the reason.

Let's say you had a six inch duct going in there and for whatever the reason you replace it with an eight inch or even a nine inch, and you threw it through adjusting dampers. You get to the same 100 cfm moving through the same duct is the pressure gon na be the same in the duct. You guys pressure's gon na be lower right. So if the pressure in the duct that is bringing the air into the room, it's lower, then the pressure balance of the room needs to be lower below the the below the three pascal's threshold that i just gave you do you guys follow.

So if the pressure of the path that is delivering the flow into a room, drops then so does the pressure in the room has to drop to allow the flow of this of this air into the room? So that's that's where that came from everybody understand how this worked. I mean that's essentially, what's going on in our houses when we open and close doors things change and not all rooms are equal, some are leakier than others and we don't really know until we test it and we look at it. That's how we're going to narrow that down. So i guess the biggest takeaway is that you know whenever you guys leave just if you're not looking at the building envelope you're missing about half of the equation.

It's not always the hvac system. The building envelope is a part of that hvac system. It's containing all of that condition there you guys are working so hard to create so we'll go to set speed again, we'll put it at that same pressure, but this time you know this is where the smoke can really help out. But for this aid we can just show where it's going to come to sit it right here.

So we'll fill this up, so we can actually see the air leaks. Yeah we'll pass it around. So if we crank it up again and if you ever do this, don't run smoke through your fan, please don't do that. Yeah do do as i say, not as i do so.

That's what's happening when we're pressurizing rooms we're just sending that air outside of the envelope as hard as we can so that's yeah allison bells had an article that said well, the blower door number doesn't tell us everything. So when we shut doors, we can actually have the hvac system exaggerate the leaks in certain parts of the house even harder, and this is what he's talking about when we shut doors and we're not balanced off that air's got to go somewhere when you're pressurizing it. It's going to follow the path of least resistance, which is going to be the leaks in that room and uh, and this is what this is the result. This is what we get well, it's up to the clients i mean you can you can show you can propose options, but at the end, it's up to the client um, at which point i'll tell you what? If, if you can establish that the house, it's which climate zone are you in, so so it's hot right, so it is if, if it is in a southern climate or a big concern, i'm in miami, so our concern is humidity right, um, when it's human, like That and the house is out of control.

They have to do something about the house, otherwise you're not going to extract your way out of that the blower door. It is incredibly incredibly helpful right because, even in climates like ours, we don't have a big delta. We don't have to worry about the heating loads it at least it shows the client right that the house is not a it's a basket case, so they don't have. They can't blame you for their shortcomings.

You know what i mean so his question is, you know my old unit worked fine right. Essentially, okay, so did your unit had a pse motor right? So now you have an ecm motor, that's going to move more air. So if you remember how i was talking about the leakage is going to be proportional to the speed of the air for a given hole right. So if you have a hole of one inch and you have air moving at 500 feet per minute, the leak is going to be.

The leakage is going to be less than if you have the same hole. And now the air is moving at 900 feet per minute. So when you increase the flow you're increasing the velocity you're, also forcing more air out of out of the space and that's why increasing the tarnish when you have leaky docker, increasing the tonnage of the equipment? I mean you're shooting yourself on the foot just creating more leakage, and maybe you put a dent on a dent on a little bit, but it's not going to be enough to keep it comfortable. I mean if you need all right, so i guess people gon na be mad.

Um i'll! Put it to you this way. If you need to use a five ton, there's something else wrong right, right, right: the amount of duct work to move. You know five tons worth of airflow through a space, especially for their return airside. The actual requirements to move such a volume of air efficiently and adequately are seldom possible and seldom they're, not i mean they're not really necessary, so yeah.

If, if the client's trying to you know suggest that you throw a larger system at it, i mean that's just where the blower door test helps. It helps you to make that division of okay. Is this an hvac system problem or is this a house problem? Is throwing more is throwing more at it actually going to help, or is it just going to be a waste of money? So it's just a good way to just kind of divide and conquer there. It's an alarm going off.

It must be noon january and i will be here through saturday um we're happy to take questions, i'm with retro tech. We have a booth out there um. I also have a ton of videos on our youtube channel. My dog and i put one on every tuesday.

We have a series called technical tuesdays where we just kind of spend five minutes covering different topics and uh he's the reason half the people show up and watch but um, but that's uh. That's gon na wrap us up here and we appreciate you guys joining us. Thanks for watching this video again to find out everything we have going on, you can download the free hvac school app on android or on iphone or go to hvacrschool.com and then, specifically up in the top you'll, see events to find out more about upcoming symposiums hope To see you there, thanks for watching our video, if you enjoyed it and got something out of it, if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click, the notifications bell to be notified when new videos come out, Hvac school is far more than a youtube channel. You can find out more by going to hvacrschool.com, which is our website and hub for all of our content, including tech tips, videos, podcasts and so much more.

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