So i'm here with my good buddy sam meyers from retrotech all right, good job, yeah good to see you too buddy and uh. We're just gon na be talking a little bit about some of the stuff that we've written about recently on hvac school. We're here at international builder, show in orlando florida 2022 and it's always good to kind of see some hvac stuff represented. Here.

We were talking a little bit about how hvac equipment interacts with the envelope and some of the different ways of thinking about that, because i think a lot of technicians, they focus on the duct work they think about getting the ducts the right size they think about. You know maybe even total system airflow if they're really being thoughtful, but maybe they don't think about the envelope as a whole sure yeah when we're looking at the big picture of things i mean the building envelope is a part of the hvac system. It contains all of the conditioned air that we're working to get to a certain temperature, a certain humidity. So that's the container for all of that, so i mean it's it's it's hard to say that that's not a part of the hvac system, the hvac system, depending on how leaky certain ducts are, whether it's on the supply or return side.

It's going to push and pull on certain parts of that building envelope so say we have a bedroom, that's maybe being it's getting more air than it should and we shut the bedroom door and it's getting over pressurized and if that air doesn't really have a way To get back to the return that room is going to again over pressurize and then if it's leaky it's going to push that conditioned air out outside of the envelope. So it's going to amplify the leakage of that a little bit more yeah. So we want to have a way to balance that house out. We want that air to be able to return back to the back to the blower, so it'll keep all of those rooms at an even pressure so that the house isn't going to leak more than it would otherwise yeah.

Because again, we think so much about leaking ducts. Being this major problem, especially in certain climates. We're really focused on that keeping the ducts from leaking, and we know that, if you have say, for example, supply ducts that are leaking into the unconditioned space or outside the envelope, then that's going to result in negative pressure inside the structure. So we're keenly aware of that yeah or if there's return, ducts that are leaking in the attic, then that's going to cause.

You know negative pressure outside the structure, which is going to lead to positive, so you're going to have losses so we're keenly aware of those aspects of it. But what we don't think about sometimes is is, if you have a room that is getting too much air. Put into that room and then not enough into another meaning, there's imbalanced pressures, but that also results in a very similar, dynamic yeah. And it's such an easy thing to check.

I mean if you already have a blower door or a duct tester system or a high precision, manometer shut the door toss the tube underneath and just see what it's doing. Let the system run and then see what that pressure difference is yeah. With the equipment running with the equipment, running, shut the door, throw the tube underneath and just see. I think it's one of the most underrated tests that technicians really fail to do when they're.

Looking at you know what is that, what's the issue with comfort here, why do i have, for example, in our market? Why do i have this high humidity condition in this space? Well, if you have a room, that's going under negative pressure for whatever reason, because of imbalance or duct leakage or whatever, then that's going to result in air being drawn in often from outside the attic which is the worst of all in our market. I mean the attic is the absolute worst that we deal with right and that results in latent issues results in discomfort and all kinds of other problems right yeah and one example too. I mean i live in a human area. I live in wilmington north carolina and we had a house that we we tested last year that you know we did the blower door test.

We did a thermal scan. We saw that there was a corner here that was very leaky but uh. They were complaining about humidity in this room, and so we shut the door. We saw that it was way negative and then we learned at some point an hvac contractor along the way said: okay, i'll fix this, we'll put a big return in here, but it drew that room about five pascals negative and then they had a bath fan in The master bath that would kick on and then draw it down to eight right, so yeah we had to just all we had to do was damper down that return and bring it more, even and then those humidity issues exactly and that comes to that.

That concept, that a lot of people have that you can't oversize returns. People say that in fact, i think i've said that like 50 zillion times, if i counted it, but that means overall you can. You can't have too much overall return for the system, but you can have too much zonal return in a particular area, exactly that's drawing that down to negative pressure. When i first heard this, i was like okay, i've got a manometer on my truck and i use it for gas pressure and i use it for checking static pressure.

My air conditioner, so i'm going to take a tube, i'm going to throw it under the door. I'm going to see what i get, but i wasn't finding anything. So what was i doing wrong? Well, it's got to be a high resolution. Manometer, that's the key here, we're talking about a few pascals and there's roughly 250 pascals in one inch of water.

So we're talking about very small increments of pressure that have a big impact, yeah, yeah, yeah and again like even when we do something as extreme as a blower door test we're pulling it down to 50 pascals. That's still not even one inch of water column like this is a tiny amount of pressure, even with a super extreme test like a blower door, where you're pulling that entire space down to negative 50 pascals, and so in those cases, obviously we're going to see pretty Massive amounts of leakage, but in the case of you know just this test, it's going to even be less than that, so you have to have a really good manometer to do that absolutely, and it's got to be accurate. It's got to be that that high resolution to be able to pick that stuff up and be reliable yeah, so you guys did a great article uh on the hvc school website, which you can find just by searching your name, sam myers or jenny, garcia. That's an excellent article on this exact topic, you're going to be at the symposium talking about a lot of the similar stuff coming up here soon, which will be you know, live streamed out all over the place.

Absolutely generally, you know we'll be presenting on that topic. Together, we've got some examples from the field, so yeah excellent it'll be fine, talk quickly, uh, just before we wrap up here. What what instruments do you guys have that are going to help diagnose this problem? What are the actual tools and instruments that you need in order to do this yeah? So of course, the high resolution monometer that we were talking about and if you have a blower door or a duct tester kit, it's that same manometer. That comes with that.

The blower door itself is a great tool, especially when you combine it with a thermal imaging camera um the guys that hike micro over here they've got a really cool new camera coming out soon, that's in a really good price range that has a high resolution yeah. I just saw that really incredible tool, yeah. So really what that does is the blower door kind of serves as an amplifier for the camera, especially if you have a good delta t between indoors and out to be able to see where these points are failing. So if you use a blower door and a thermal camera, you got to have enough delta t to be able to see.

What's going on, the blower door serves as the amplifier for the camera, but until you really get in there and look i mean there might be some spots that are easy to fix. I mean a lot of the areas that we see in homes that are really leaky are at the bottom and the top right um, especially attics, if there's chases going through there. So sometimes those can be easy fixes, awesome, yeah, yeah, it's really nice. Talking to you man, it's always good to see.

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