This episode of the HVAC school podcast is made possible by our sponsors, who really do make this possible. I just want to say that again, like I do a lot of this stuff now, obviously I run a business, and this does take away from it a little bit, although of course our employees benefit from it. But to put this much work into it, we have to have some support and these sponsors are the ones who help support us and they provide us with content and ideas and feedback, and I really do appreciate them. So, let's dimension them carrier and carrier.

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By going to true tech tools, comm TR, you tech tools, comm use the offer code, get schooled for a great discount at check out and now your host, the guy, who checks the air filter of every single hotel room right when he walks in, but still can't Change his own filter when he's supposed to Brian - or this is the HVAC school podcast, the podcast that helps you remember some things you might have forgot along the way as well as helps you remember some things you forgot to know in the first place, and I'm Brian and today we're gon na be talking about ventilation. We've talked about ventilation in the past this or that the RV's HR ves ventilating dehumidifiers, but we have never talked about it soup to nuts, and today I have the guy who is just nuts enough to talk about it soup to nuts. That's John Cemil hack, a really good guy up in Virginia somebody who participates in the group, our HVAC school Facebook group and we're gon na go through it from start to finish talking through primarily the topics that are addressed in ASHRAE. Sixty two point, two that relate to outdoor air, but we're gon na talk, point ventilation and everything in between.

So here we go John Similac talking ventilation thanks for joining us, John thanks, Brian good, to be here great to have you a topic. I've been wanting to talk about for a long time is ventilation. We've touched on it here and there, but I haven't done the comprehensive podcast on ventilation and neelkant. Barreto, I think, is a friend of yours called me out and said: hey.

You need to do a podcast on ventilation. You need to have John on, so you appreciate you taking the time to do this and share your knowledge and ventilation. Yeah thanks Brian thanks Neil before we get into talking ventilation, I want to give you a chance to tell us a little bit about what you do. I know your businesses think little tell us about how that got started.

What that is and how you got into this business in the first place sure I started the company. I think little in 2008 we're a small home performance, consulting company, three people right now, based in central Virginia, and we do most of our work in the central Virginia market with a couple of exceptions. So we're in Charlottesville and that's most of our work - is in Charlottesville Richmond a little bit up in DC. I got into the field when my wife and I decided to try to build a house in the early 2000s and I didn't have kids at the time and a lot of time for research, both in the job that I had at the time and off the Job and just got into the world of residential energy efficiency, and the more I learned about it, the more interesting it became, and I found out about the world of home energy ratings and energy audits, and things like that and decided to you jump in and start A small business I've really been kind of in school.

Ever since I'm trying to constantly learn about all sorts of different topics, that's kind of where we are now. We work on a range of houses from single-family to multifamily. Everything is fairly high performance, extremely high performance houses. Most of our work is in new construction right now we do a little bit of existing home work and we hope to do more in existing homes in the future and where does most of that work come from? Is it from contractors you work with regularly? Is it homeowners who are seeking you out it's an interesting mix, so we work with home builders, architects, homeowners, multi-family property developers and as consultants.

Our job is to help them build better buildings and the things that we focus on our comfort, indoor, air quality, energy efficiency and durability of their buildings. Most of our clients come to us for energy efficiency and we help them get those other items. The comfort and indoor air quality and durability, while delivering really great energy performance, so when people really want energy efficiency, like I'm thinking of something like passive house, which I know you've done some work with, what is there? Why, generally I mean? Is it really to try to save money? Sometimes it's a little bit to save money. I think the main reason is because it's just a fantastic product, it's just a fantastic house, superior comfort or indoor air quality and energy.

So if some of it's definitely for environmental reasons, some of its for operating cost reasons, but in general it's just you're helping them get the superior product, no different than a superior car or computer or airplane. Or what have you it's? A combination of a lot of things, but in a lot of ways it's just looking for a premium result premium product. It's the same reason: you would buy a Porsche over a Volkswagen sort of thing, exactly yeah, we're talking about ventilation today and ventilation is one of those kind of hot-button topics. I had Jack rise on the podcast a couple times and he's a trainer and he's written a book for akka on manual D and manual J, so two books rekha on those two topics.

I listened to those yeah Jack is of the opinion and he's been very vocal about it. That the problem in his mind is that we're building houses too tight, and so the reason why we got to do all this ventilation stuff is because houses are just built to tighten. We should just go back to the good old days when they were built. Nice and loose I'm not putting words in his mouth.

That is really how he feels about it. So I want to just kind of address that right off the bat, because I know anytime, we talk about this. There's gon na be this cohort who's going to comment on it in that way. So what would be your thoughts on that a way of looking at ventilation? So we look at ventilation and air tightness of houses from a standpoint of control, so the tighter your house is and the better your ventilation system is the more control you have over the amount of outside air that you're bringing in the temperature of that outside air.

The quality of that outside air and the energy impact of that outside air, if you have a leaky, er house, all of those things are kind of random and you don't necessarily get the right amount of air at the right times at the right quality. And you pay extra for it so kind of the way we look at it. Is you build tight, you ventilate right and we take that to the full extent of those words. We try to eliminate in our new construction practices all of the air leaks, get down to passive house levels of air tightness so that we have full control over the outside air and the indoor air all right.

So real quick, let's define this word passive house because I'm sure there's a lot of text. You don't even know what that means. So what is that? All about passive house is a energy efficiency standard that was originally developed in Germany in part from some super insulation concept, buildings that were built in the Northeast and in Canada in the 1970s. One of the big parts of passive house is that it has very strict air tightness requirement.

So for those of you who are familiar with the blower door, air tightness, testing requirements that are in the current energy codes, the Passivhaus levels are very tightness, are around about five times tighter than the energy codes in that ballpark. It varies a little bit depending on your climate, so from an air tightness standpoint, that's kind of a metric that we shoot for on our very best new construction projects and I think, even for the regular homes so for most people, passive house isn't something that you're Gon na achieve your average homeowner, but one thing I like about the fact that it's going on is that so much has been learned about air tightness and how to handle things when you start to get into tighter situations and how to achieve really high energy efficiencies. Even for regular houses, I kind of almost look at passive houses as kind of like the NASA, where you have all these products and ideas that come out of it. It becomes almost like a think tank or a testing grounds for new products.

Yeah I'd agree with that. I think there's we'd like to think that there's a good bit of trickle-down of products and technologies and techniques from the Passivhaus world into other buildings. So let's dig into the specifics of ventilation and we're gon na talk about residential commercial. We've been working with ventilation and commercial forever.

I mean as long as I've been in the trade. That's been a consideration, but it's a newer thing for us to have to think about ventilation in a thoughtful manner on a residence. Let's really just start there and I'll. Let you kind of take the ball and run with it.

How should a a/c technician, AC contractor, be thinking about ventilation in a way that's different than just I put in math hands I put in a kitchen exhaust. What else is there? No, that's a good place to start, though, is with the local exhaust local exhaust requirements for bass, fans and kitchens, but going beyond that, there is a need, especially in the tighter construction. We have with new construction to provide whole house ventilation, which is really the goal there is to dilute indoor pollutants with presumably cleaner, outside air. We can get into how that's not always the case and what you do about it maybe later on.

But the idea is to bring in that outside air and to dilute pollutants and reduce the overall levels of different pollutants inside the house. And those pollutants might be things like fine particulate, odors, moisture, volatile organic compounds coming off of cooking or perfumes or all kinds of different things. All of your furnishings, for instance, and then kind of the next step, is really thinking about how you want to introduce that outside air into the house and think about the energy impact, the impact on the loads, the impact on air quality, the impact moisture levels in The house, depending on where you are in the country, and try to figure out, what's going to be the kind of optimal solution for a particular building or a particular client. So, let's talk about your design approach as it relates to the ventilation portion, say: you're, doing a design for a new home, new construction, home and you're, considering ventilation.

Where does that start and end, and how do you kind of think about that for any new construction project we're working on? It's not even a consideration? It's a standards, the default every house that we do gets ventilation system as part of the design. So where we start is with the ASHRAE standard for ventilation, which is a American standard for ventilation rates and, generally speaking, the ASHRAE standard is where the building code ventilation rates typically come from or in that ballpark. So we do a calculation, that's based on the number of bedrooms in the house, the floor area of the house and with the new ASHRAE standard, our expected air tightness that we confirm in the field later on and we get a whole house continuous air flow rate. So that might be in the ballpark of 90 or 100 CFM for let's say like a 3,000 square-foot, three or four bedroom house, so there will be a continuous airflow rate and then the next step that we do is we start to think about? Okay.

So what kind of equipment choices do we have to deliver that airflow? Are we going to deliver that airflow continuously so 100 CFM 24/7 365 days, or are we going to deliver that intermittently where we say deliver two hundred CFM for 30 minutes out of every hour, or maybe two hundred CFM for 12 hours out of every day or Something like that and that of course impacts the different equipment choices, because that gets you into different choices for fans and duct sizes and controls all right. So talk a little bit more about this idea of continuous ventilation versus timed ventilation. How do you go about deciding whether or not the continuous ventilation is the best solution, or whether or not you would only do it for certain times a day or during certain conditions? Continuous ventilation is, in my opinion, the easiest to set up because the system just runs and there's no real occupants input into the system. There's not a big amount of extra setup, that's required from the installers, but there's some situations.

Where I mean, I guess in terms of pollutants that are being introduced to the house, most of those are being generated indoors and many of those are being generated when people are in the house. So, there's a certain argument to be made for reducing ventilation flow rates when the house is unoccupied and increasing ventilation flow rates. When the house is occupied and that's something that you would see would be pretty typical on a commercial building and you can do that in a residential building, but it starts to get into more complex controls, more complex ventilation systems and in homes. We don't have like a facility manager, maintenance staff on hand to help set those things and make sure that they're running properly, so we tend to err on the side of continuous operation and simplicity in terms of the ventilation controls it makes sense in residential.

So we talked about treating outerwear, and you alluded to this a little bit earlier that sometimes our air may not be necessarily fresh-air me fee, warm or cold or high humidity. It may have different contaminants in it that we would rather not have in our space. What are some strategies that you use to mitigate that or deal with that? The filtration is, I guess we have filtration for particulates. We have for temperature there's a couple of different options: ye RVs and H.

Rvs are one option which are balanced ventilation systems that transfer heat or heat and moisture between the air flows without transferring air molecules. So that's another option for conditioning and then you can also bring in the outdoor air and mix it with return air. So that's another way of kind of tempering the indoor air by mixing it with murmur and then, of course, you can bring in the outdoor air and run it through something like a ventilating dehumidifier, that's going to take the moisture out of the air. So we like to kind of think of those from distinct silos.

I guess so from a filtration standpoint. We start, I think, that's in the ASHRAE standard. I think merv 8 is the minimum filtration level on the outdoor air, and we generally would like to see something higher than that in terms of the particular filtration, especially if you're working in a project in a fire prone area like just about everywhere in the Rockies Or west of the Rockies, that's a lot of houses. You'd want something more like a murse, 13 or higher, or maybe even have a level of filtration on the outdoor air so that you can actually ventilate.

Even when, from a particulate standpoint, the outdoor air might not be all that great. So there's cases where you might still want to ventilate for other things that are going on the house to get rid of indoor pollutants to get rid of carbon dioxide buildup in the house. But you have to take care of the particulate or the moisture or the temperature issues that are outside. You mentioned carbon dioxide, and I want to mention that quickly, because a lot of people will tout different new indoor air quality.

We used some of them ourselves. We use a couple products for air oasis from time to time and they're good products, but some people will tout that. Well, I don't mean outdoor air because I'm doing such a good job of filtrating but carbon dioxide is something you can't get away from. I mean that is the one thing that you really need: outdoor air for and as a perfect example.

I did a some monitoring during Thanksgiving dinner this year and to see the rising carbon dioxide levels when everybody was in the house and we were doing cooking, we had some of the chafing dishes with the little candles underneath it so on and so forth, and our Carbon dioxide levels were really spiking too, not as a dangerous levels, but up to the point where you start to get headaches and things I mean so, the carbon dioxide is something that we've got to deal with, and I don't know of any strategy to deal with Carbon dioxide other than bringing in outdoor air right yeah, that's exactly the case, and so it's really coming up with solutions to allow you to ventilate. Even when the outside air isn't perfect. If the outside air was perfect, then you just open the windows, so yeah filtration is one thing from a moisture standpoint: that's going to be the moisture levels of the outdoor air are going to be the big concern everywhere kind of east of the Rockies not so Concerned about the forest fires, but moisture is a big deal, especially in the southeast. So how are you going to deal with the extra moisture that comes from the ventilation, air or in some cases it might not be that much extra moisture, but just kind of acknowledging that there is especially in the summertime more moisture in the outdoor air.

And how are you dealing with that making sure you're accounting for that in your load, calculations, making sure your heat pump or air conditioner can deal with it and or installing dedicated beautification equipment that can handle that extra moisture load? I think kind of our gold standard for installations would be to use an ERV that will reduce the amount of moisture that comes in from the ventilation air compared to just straight outside air and then have a dedicated dehumidification system. That's just recirculating air inside and, if moisture levels get too high, then the dedicated D who come to take care of that all right. This brings up one of my biggest questions and I asked a lot of people this and I honestly don't know what the best solution is. But if you're in a humid environment, we are in Florida, Gulf Coast, states very humid environments, if you're bringing in outdoor air - and you are dumping that outdoor air to where in order to prevent there from potentially being condensation.

When that outdoor air makes it into the conditioned space so you're either delivering that outdoor air directly to the rooms that are occupied or most likely to be occupied, such as the bedrooms where people are sleeping overnight or maybe in living rooms, dining room. Something like that. So that's one option and then the other option is you're, delivering that air to the existing HVAC duct work and it's mixing with the rest of that system and then it's getting deliver to whichever rooms are being conditioned by that system. So, in terms of, I guess, condensation risk if you're delivering it directly to rooms.

Then your surface temperatures in that room in relation to the dew point of that outdoor air are really critical right, which in general means that you've got to think about, because this is something we've run into several occasions. Is that you've really got to think about the occupied space temperature setpoint becomes kind of critical, because if you have in our marketplace a lot of times, contractors are just in fact most commonly they're, just bringing a duct in from the outdoors and they're just dumping. It straight into the returned generally not running it through any sort of ventilation, blower or anything they're, just demonstrating to their turn and, of course, that's not an adequate way of doing it. But what we see in a lot of cases is where that outside air hits that return air stream.

It condenses, and you can only imagine what else occurs there. Where we have moisture, do you have any thoughts or solutions? To that I mean. I know you probably weren't prepared to answer this question, but it is something that we run into and I don't necessarily have a great answer to that. Because one answer is yeah.

You need to make sure that the space temperature isn't below the dew point of the outdoor air, where it enters yeah, but that's impossible to do in your climate. So I mean you probably average mid 70 dew points in the summer with Peaks. Well over that. So that's not really an option, so I think what you in those situations in those high dew point high humidity outdoor areas, think you really have to do some type of preconditioning of that outdoor air before it hits the return, duct or return plenum or before it's Delivered to the space, so that's either going to be ventilating dehumidifier or that's going to be an ERV that can knock down the dew point enough that it gets below the surface temperatures and just to call out quickly because we've mentioned ERV and HRV.

Some text may not know what those are and essentially what you're doing in any RV or HRV is you're, exhausting the same amount of air that you're bringing in but you're crossing those air streams. So that the way there's a transfer of heat and sometimes even latent heat, so moisture and an ERV transfers, both sensible heat and latent heat, so you're gon na see a drop in dew point. It may be significant or it may be insignificant in some cases. In the case of an HRV, it's just transferring sensible heat so you're not going to see a change in the dew point right exactly so in the climates where you have high outdoor moisture levels, certainly in the commercial and residential world and the ERV is going to Be a more appropriate choice there compared to an HRV all right.

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Your customers will like it. That's for sure, because they don't have strong odors. They try to make their products as natural as possible. Safe for technicians is safe for customers to breathe.

Those are the Viper cleaners they make you the original Viper cleaner in a spray can which I was skeptical of at first I'll, be frank. I thought man. This seems like that's, not very much product in that little can, but man does it come in handy. It makes this really nice little pin spray and when you're working in tight areas, especially like maybe a refrigeration, condenser or a refrigeration, evaporator or something or maybe a clean in place on an evaporator coil, there's just really really nice little cans to have on the truck.

So it's one of many products if you haven't tried my log yet I'm definitely gon na suggest you do that everybody who tries it loves it haven't. Had anybody yet who's tried my log and said they. I don't care about that stuff. It's great for your vacuum! Hoses to make sure you get a nice tight seal, it's great for all your refrigeration connections, because it's not going to contaminate the system so find out more.

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But if you can't find anywhere locally, then go to true tech tools, comm and buy it there. If you want to get one of your local distributors set up with solder web products, if you've been around me for any amount of time, you know how much I talk about them, because they're great go-to products by proz.com products by pros comm and give them information There about who you buy from and who you want to have bring it in, and then they can use that information to try to get Schneider weld to adult supply house near you all right back to John yes, so from the standpoint of balance ventilation. So we're talking about ERV and HRV we're talking about balance ventilation, which is keeping the pressure in the house. In general I mean you still have your single point, exhaust and so yeah the home is gon na tend to be, even if you balance your other whole home intake versus exhaust, then your house is still gon na, tend to be a little bit on the positive Pressure side, but in a balance, ventilation system through the whole home you're, putting out the same amount that you're bringing in, and so why would that be a good idea versus going with a pressurized type of design? This is something I've heard a lot of debate about.

So again, it depends on where you are, if you're pressurizing, the house like in your climate and the hot humid climate, there's not a big risk in terms of the building enclosure. You're, pushing out conditioned air through your walls through your ceiling or what-have-you in colder climates, though in the wintertime, when you're pushing out warm humid air out through your walls or out through your ceiling, you can have situations where that warm moist air. The moisture starts to accumulate, especially in the exterior sheathing of the house, especially and next year your roof sheathing. If it's a cathedral ceiling or something like that, and you just start to get huge amounts of moisture accumulation and potential rot or mildew or mold buildup.

On those surfaces, so that's kind of really the big danger in your climate. The danger would perhaps be more if you were using exhaust ventilation systems for your whole house ventilation, and this is pretty common in colder climates in the Northeast, for instance, where you'll see a lot of times kind of the low end ventilation solution is having automatic controls On the bass fan on one or more bath fans or having one dedicated bath fan that runs constantly at whatever flow rate you need, and so your outside air isn't coming in through a dedicated source. That's just coming in through all of the different holes and cracks in the building and in a cold climate that from a building durability, standpoint that can be OK from a control of the ventilation system. That's really pretty poor! You don't have any control over exactly where the air is coming from or where you're delivering the air.

So that's a system that we don't really like to see. So when you say it's not ideal from a control standpoint, because you don't know where it's gon na come from, I'm thinking yeah, I mean it's gon na come around just windows and under doors and through wall cavities and all that and that doesn't seem ideal for A lot of reasons, but one of them, of course, being that a lot of those spaces that air is going to be pulling across or can be fairly dirty and so you're gon na be getting very unfiltered, potentially quite dirty air coming into the space through those Gaps and cracks right, you don't really know the quality of the air that you're going to get through those means, and you don't have control over how much air you're delivering to the different spaces. If you have a big hole somewhere in the house, all of your outdoor air will might be coming through that big hole into a random closet in the downstairs rec room that nobody uses anymore. Instead of having good control over the ventilation and being able to deliver it to where the people are, does 62 0.2 ASHRAE 62 point? Does it have any requirement for testing to make sure that the ventilation system that's have been installed is actually meeting the design requirements? I think that's presumed.

We don't really have to look into the standard for sure I can't say off the top of my head. I think the standard presumes that someone is actually measuring the air flow to confirm that the ventilation system is doing what it's supposed to do, and not just as a number on paper, and we do. We see a really big range of performance of ventilation systems going from the page or the screen to real life. So speaking of that I mean, since you've been around the block for a while.

Now, what are some of the things that you typically see as some of the challenges between what you design or what you want to see happen and then what actually happens in reality? I guess the most common ventilation system that we see in house is we don't design, but something that we're inspecting. You're testing is what's called a fan, cycler system. So that's a outdoor air duct, that's attached to a returned plenum of a furnace or a heat pump and it has a motorized damper on it and the control timer that tells the damper to open and tells the air handler or the furnace to turn on and Circulate air and that pulls some air from the outside and what we see in those systems. Of course, one of the big problems that we see is a lot of poorly installed flex duct, the outside air duct.

We see a lot of flex duct because it is important, especially in colder climates, to insulate the outside air ducts, to prevent condensation, because that outside air and the wintertime is cold. So the duct is cold. So you do want to insulate that duct to prevent condensation. But the of course inexpensive ways to do that is with a pre insulated flex duct that often gets poorly installed, and so we see poor air flows.

Because of that, the other thing that we see is we often see relatively good duct installations from a return side. Static pressure standpoint and these fan cycler outside air systems, rely on the pressure-relief nature of that duct in order to pull the outside air in. So if your return side is already really really low pressure and that outside air damper opens up, it's not a big pressure. Relief, so you don't get a lot of flow through that duct and then building on top of that.

If you're dealing with a variable, speed, air handler or a multi speed EC motor, usually there's a fan only setting that's set up by the Installer at maybe twenty-five percent or thirty, five percent of the maximum and so you're just you have an even lower return sight Pressure situation, so you get even less air flow than you think. So, in order to get a hundred CFM out of those kinds of systems, you either need a really big outside air duct or you need a powerful fan motor combined with kind of a more restrictive return side, duct system, all of which are not all it desirable. From an energy efficiency standpoint right and that's what strikes me that the thing that sometimes is missing in these standards that are maybe very well-meaning, is the sort of test out nature of what has to be done in order to prove that these designs are really working Because, for example, if you designed a particular duct size, so you're running in a six inch, outdoor docked and snap lock around snap-loc or something and you had very, very low - returned static pressure because the returned static pressure isn't always going to be high. Let's say you have a direct return and it's very large size.

You may have a nice low, static pressure and that's desirable for the system. But like you mentioned, it's not gon na bring in much in the way of outdoor air or on the other hand, and what we see, because we see the exact same thing in new construction. I went to a house and again I don't say the M word, but we had a UH same moisture, moisture source to say, but they use one of these systems and it just dumps outside air right into the return box underneath this unit. That's it very, very cold and of short-term vacation rental community.

So a lot of these guests are setting the things to 69 70 degrees, and you can only imagine what's happening when that outdoor air is hitting. That return, especially adding kind of insult to injury. Now you're cycling, the blower and so in running the blower. That's going to reoccur, it's going to increase your indoor relative humidity, and so now you've got nasty growth on top of high relative humidity on top of low indoor temperatures, and it just creates this essentially a petri dish underneath - and this is all created by a standard That was designed to make air more healthy, and the result is that now we have this duct board and of course that's the other thing in Florida.

We have duct board everywhere. So now we've got this duct board, petri dish, underneath this air handler and me as a servicing contractor I'm kind of at a loss. It's so like yeah. I don't want to cause trouble for anybody, but this is the standard.

This is how most of these systems are installed. Even our market today - and all I can do is thank God that I don't do residential new construction, so you have any thoughts on that like how that can be approached, because this is a real problem in the entire southeast yeah. The standard doesn't really tell you how to do it. The standard tells you what the air flow needs to be and what the filtration requirements are, and things like that, but the standard doesn't tell you how to do it.

The standard doesn't tell you what the implications are going to be for your particular building and your particular climate, and so that's really where the practitioners have to figure that stuff out and think about the house as a system. Instead of just checking a box, the code, compliance form or checking a box on that you're meeting, the airflow requirements for a particular standard, yeah and so in different climates, are going to have different issues that you have to deal with in the southeast. Definitely the outdoor air moisture and summertime is going to be the primary one and in starting from scratch in new construction. I think the answer is definitely you have to have some kind of pre conditioning system.

That's gon na ring out some of the moisture, if not all, of the moisture from that air in terms of going back and fixing those systems, that's, of course, more difficult to do depending on how much access you have how big the mechanical closet is, and things Like that yeah, but it sounds like ventilating, the humidification is probably one of the best options in our market, especially given that using a positive pressurization method for ventilation isn't necessarily a bad thing where we are exactly yeah. That's sort of the conclusion that I've come to and again thank heavens, we don't have to deal with it too much because we don't do new construction when we do add on a replacement, we sometimes offer ventilating the humidification, but that's essentially is what I come to As being our only really good solution, because in most cases, any RV still isn't going to temper the air enough from a moisture standpoint to make it safe to stick it in the return anyway, and really there's nothing safe as long as you're. And so this is kind of the point I want technicians to hear. Dewpoint is so critical and John's done a lot of really great stuff on dew point.

But dew point is so critical if you take air that has a dew point over the indoor temperature and you bring it inside it's going to draw moisture out of it and that's going to result in problems. I can't see how I'm missing anything there, but am I missing anything there? Is there any caveat to that? No, I think, that's pretty straightforward, and maybe the only thing I would quibble with just a little bit is whether or not the ERV can wring out enough moisture. But that's there's a lot of variables that go into that, including the performance of that particular RV and the actual air flow rate. And whether or not the indoor air is drying to begin with, because the ERV doesn't work unless the indoor air is dry or at the moisture transfer rate, it's not a fixed property of the ERV Corps.

It's you have a test rating. That's done at a particular test conditions, but if, when the indoor air is more moist, you're going to transfer less moisture, so if you're, starting off with a very low temperature high humidity situation in like you might have in a rental property, that's where the guests have Just arrived, but they've been running the system for a few hours, then the ERV isn't going to transfer a lot of moisture, necessarily yeah. That's a really really good point that has to be considered, and this is sort of what I was talking about before, with fee running the fan in the on position and just in bringing it in on a timed basis from the outdoors for the whole home in Florida, that's a double whammy of nastiness from a humidity standpoint, because we know that when you have all of that moisture that you've condensed on the evaporator coil and immediately as soon as it's cycles off you're now really in the on cycle. Then you add in outdoor air now you're making that worse as well and in our marketplace, we're just working so hard to try to get to that 50 percent.

Relative humidity mark, in many cases we're losing the battle and we're slipping over 60 and like you're, saying here, if you're already losing that battle and that's the air you're exhausting, then you're not going to remove as much air or as much humidity from that moist air. That's coming in from the outside as well! So that's a very good point and you got to think about all those things when you're choosing a design. So what else do we need to cover here to make sure that we don't miss anything in the ventilation conversation? You, of course, have a humid bias, but I think in colder places in tight homes, the ventilation system is actually what is drying out the house in the wintertime or in tighter construction. It's keeping it dry enough to avoid problems in the wintertime, so you can have situations and cold climates where your relative humidity is too high, even though that's not kind of the common conception for anyone.

Who's lived in a leaky drafty house in a cold climate. Those houses, of course, are extremely dry, but in newer construction and tighter construction that ventilation system is often what is keeping the house dry enough in the winter time. So that's another reason to have good control over your outdoor air. The other things that we like to think about just from a general ventilation standpoint, are thinking about the interactions between local exhaust, whether it be really kitchen exhaust, I guess, would be.

The big concern is thinking about kitchen exhaust and any natural draft combustion appliances, whether their furnaces or water, eaters or fireplaces, or wood stoves, or things like that. So we often will see in our new construction work custom homes, where the client wants a large capacity range hood to go with their large capacity cooktop, but they also want a natural draft open, fireplace at the same time and a tight house or the Builder just They build tight houses, they've built so many tight houses. They don't know how to build a leaky house, and so we get into kind of health and even potential life-and-death situations in those kinds of scenarios, and we start to have to think about dedicated makeup air. For the range hoods in those situations, if we can't talk the client out of the fireplace which were historically unsuccessful, I'm doing talking people out of things that they want is a tricky business yeah.

It's funny because my brother just built a house and he's a really smart guy and he put in a ventilating dehumidifier and all this, but he does he's, got the big get the big range hood and he has a fireplace and, of course, we're from Florida. So we don't know anything about fireplaces like we really don't. I mean we never have him it's sort of a novelty and that's why you want one in your house because it's like hey it's cool, we fire so around Thanksgiving. He was having a bunch of family.

His wife side of the family over and I knew they were gon na - have a fire in the fireplace because they just moved in the house. All this, and so I sent him a text message and I said: hey, I'm gon na be really interested to see. If you can actually get a draft up that chimney - and I guess he didn't read my text or maybe who knows maybe he'd been drinking or whatnot and so a day, late or two days later, whatever it is, he sends me a text and he says yeah. I was wondering why that wasn't working so yeah we're idiots in Florida, but yeah.

It's a perfect example, and actually somebody brought that up the other day. I don't know who's talking about. If you have a fireplace it's actually drafting from the space, I mean it is essentially sucking on the entire house. It was Jack Rhys who was talking about it.

It is actually drawing on the entire house. There's a significant amount of air. That's going up that chimney and in some cases you may be radiantly heating that one room which are essentially cooling the whole rest of the house. If you have a fairly leaky structure - yeah, that's I mean the fireplace is with a good fire and it is going to be, I think, in the 300 to 400 CFM range for an open, fireplace, so it's exhausting 300 to 400 CFM out of the house and Then that's going to be that amount of outdoor air is going to be coming in, where I can, when you get into the big range.

Hoods, though, is if you're having that big party and you're doing a bunch of cooking at the same time in the kitchen and your range hood fan is going to be more powerful than the fireplace. Perhaps then, the draft of the fireplace. If you have a tight enough house and you can start to backdraft the fireplace start to get some smoke roll out and things like that which, if people are around everyone's gon na notice, that and hopefully someone will turn the fan off or put up the fire. But it gets to potentially be a really dangerous situation at the end of the night.

If somebody has left a fan running, an exhaust fan running and the fire is smoldering and dwindling, but is kind of back drafting unbeknownst to everybody else in the house. And then you get into a potential carbon monoxide situation which can of course be deadly yeah. And then also water heaters too. So if you have a gas water heater and then that can start to backdraft and you can have a carbon monoxide there as well.

So lots of reasons why you don't want a house that has combustion appliances being under negative pressure when the men are really what you're burning it's, not something you want to have significant negative pressure right anything else. I think we covered all the big points that I had on my note sheet here, good, so anybody who likes what they hear from you. Maybe he wants to reach out or wants to find out more about what you're doing what are some ways that they might be able to do that they can certainly email us or visit our website. We're also now and then commenters on the HVAC school Facebook group and on Twitter as well yep, and so that is think little that's John's company and if you're in that central Virginia area, a beautiful part of the country, I think it was three or four years Ago we went to visit, Monticello and Charlottesville and really really beautiful place.

I think Monticello is probably in need of a little bit of performance updates. I would guess all kinds of updates, but definitely home performance as well. Yeah. That's just up the hill from my house.

Very cool, very cool, all right, John well! Thank you so much for taking the time to discuss this and I'm sure we'll find opportunities to talk again sometime soon, great thanks, Bryan, it's been fun all right, thanks to John thanks to Neil can't Brett! Oh, actually is the one who sent me up on this podcast with John Niall is a longtime contributor to HVAC school and all of its different iterations he's a very good encouragement to me. He's one of those people who will call me out. If I get a little out of hand - and I do sometimes actually kind of an emotional guy - a lot of you may not know that. But I do sort of wear my emotion on my sleeve in a lot of cases and I'm very public with my thoughts and sometimes I get a little carried away and we all need people to rein.

Us in and Neal is one of those people who I trust to do that for me. So, thank you, Neal for all you do for HVAC school, for myself and for the industry and there's many others, many others like Neal, and that I can name and it's a long list. So we won't do that right now, but you know who you are anybody who's made, the industry better who's participated in the Facebook groups, who's commented who shared who's corrected me. When I make a mistake, I appreciate you and keep up the good work.

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