In this quick video, my friend henry garcia, who is really an expert on the building performance side, as well as the technical side of hvac talks about a common mistake that people make in explaining something called zonal pressure, diagnostics and the ways in which maybe it can Create a misconception with customers and with practitioners i think you'll enjoy it. It's a little bit. Technical, maybe doesn't apply to everyday stuff, but especially if you ever dabble in the building performance side of things, this is going to be really helpful for you to see. So i'm gon na set up the video that you're gon na watch really quick.

It's about zonal pressure, diagnostics or zbd. It's really. The purpose is the purpose of it is to show how how much it lacks in in legitimacy. The readings that we get of zpd on intel on interior rooms when we are using a blower door and trying to diagnose leakage from internal rooms in a nutshell, zvd, it's just a ratio of two openings right.

It's a ratio of the one opening from the zone or the room in this case and the rest of the house and or with relationship to the opening between that zone and the outside right example. If you get a 25 pascal cbd rating, then that tells you that the room, the you know, the collective opening size of the of the hole between the room and the inside is the same dimensions of the collective hole size between the room and the outside. It doesn't tell you exactly the size of the hole, doesn't tell you how much, how many cfm50 that room is leaking. You know it could be a three foot wide or three foot diameter hole or it could be a one inch diameter hole, and you know if it's the same.

It's going to read 25 pascal so and the same goes for the rest of the pressure readings. Just at the ratios, the ratio changes with each value, so it doesn't. You know to say that something is that same rule, for example, to say that that room is 50 connected to outside, because you're reading 25 pascals. Without you really knowing how much you know what size somebody you're dealing with, or how many cfm50 or anything like that, you know it doesn't really hold any any value from a technical standpoint.

What it does do, and probably the reason why it has hung on so long this practice is it aids in presenting the client with um. I don't know proof right. It's just one more thing that you can present the client to establish that there's leakage to that ring. You don't know how much leakage, but there is a legitimate room with which honestly shouldn't be any, but well there is.

Is that wrong should? Should people stop doing that? No, no, i mean not really i've done it. If it helps you sell the job and that's you know, that's why you need to close a uh a cell to help ultimately, the client really because i mean we get paid for these things. But you know the real benefit comes uh to the side of the consumers, the people paying the the utility bills right, the people now being comfortable in their bedrooms and such that's one thing that it helps you with the sale and it helps you to present your Case to a consumer, but i mean to to say that you know a room is x amount percent connected to outside you're just playing yourself. Maybe it helps you with the cell, like i said, but in reality from a technical standpoint, if you've begun to believe that you're just playing yourself, because that's not how it works at all.

In this video you're gon na see that how just by changing one opening uh one of the two openings, that pressure is going to change and how much it changes all at once. Just one remark on the video there's a there's, a part where i mentioned that that the pressure reading means that you know there's supposed to be a lot of there's supposed to be a lot of holes between that. So between that room and the outside, what i meant to say there is that there's a lot of leakage, not holes. It's just the wrong word for that here.

It is, i hope you like it, the use of the blower door. We have the space that minus 50 pascal, so this room, it's a negative 50 pascals with relationship to outside. In the other side of this wall, there is a laundry room that laundry room is internal. It means that it has a supply vent.

It means it has. A return path right this here is the return path for that laundry room. We took out the room we removed the vent for to show the example and show the example that we're going to get into. So it is believed that if you run the blower door and the house has a minor 50 relationship to outside, if you get a pressure pressure reading from an adjacent room, internal room, then you can say that that room is x, amount uh connected to outside we're Gon na show why that's wrong so, based on that principle, this room for that room is say: 84 86 connected to outside, which means the room is very leaky.

That implies that there's a lot of holes between that room and the outside right. That's what it's one! It's being uh meant to believe and look look. What we're gon na do all we're gon na do is change the size of the hole between this room and the inside. We're not gon na do anything to the hole between that room and the outside.

Look at that we opened the dog mask covering the whole about, i don't know a couple of inches, but what happened to the pressure? He went down 27 pascal. So when you know now you could say that this room is fine 54 connected to outside. It. Isn't the holes between that room and the outside didn't change? We didn't know anything to affect that.

All we did was affect the opening between that room and this one. By doing this, remember what the pressure was before in the high 40s or mid 40s. Look when we put the dark mask back, it goes right back to where it was. This shows.

You know the fallacy. Why we're doing this wrong when it comes to some pressure, big thanks to general for doing this. As always, we appreciate the contributors who come on and help bring clarity to some of the maybe more confusing parts of our trade by showing real field experiences. Much appreciated thanks for watching our video.

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