All right, so this is a kind of a test, video we're going to be doing one of these. Our SES, Nate prep videos, it's the first time, I'm using this new setup for doing these presentations with which hopefully will be a little easier. I'm doing it from my home studio, so new new experience, but this is the world we live in today, but I wanted to definitely take a chance to talk about something that I do care a lot about which is building construction, but specifically how that impacts comfort In the homes and buildings that we work on, so our SES has these great presentations you can find them on their web site, our SES dot org. You can also find out more about preparing for Nate at Nadex, plus an X on the end dot org.

So if you also would like to chat, feel free to do so, we're just gon na go through this real, quick and see if there's anything that that, hopefully you can get from it. So first thing is: building construction is changing. We are building houses, tighter or reducing air infiltration, and a good way of thinking about this, because we talk about convection, conduction and radiation as the three ways that heat moves and by sealing the envelope of a building you're controlling the convective forces. Convection is when you have molecules that are free to move specifically in liquids or fluids, including vapor and liquid form of matter, and so for us in a home or in a building.

That's generally gon na be air, and when air can move around, then that's convection, and so we don't really want air moving in and out of the structures without it being controlled, and the reason is is: if we can't control it, then we can't control all the Different factors that relate to it, I'm gon na check, chat here, real quick cuz. Some of you were already here. I just wanted to make sure that this works properly. Give me one.

Second, that's the thing with the being live. I want to be able to answer any of your questions, all right cool, so so anyway, we want to. We want to control all the different factors of what's coming in and out of the house now. This is a controversial topic by a lot of people who have done this a long time because they Batak about how a structure needs to breathe.

Well they'll say the house needs to breathe just like we need to breathe, and there was some truth to that in the past. So I grew up in Florida. My wife actually grew up with no air conditioning and in her home they had a whole house fan in the hallway and whenever it got really hot, her dad would turn the whole house fan on. The thing was super noisy and it was hard for us to talk over it and it would just pull air through the through the space.

He would open the front and back doors and it would just draw air through the building and that's not a bad way of doing that. Frankly, the downside to that whole house fan type of configuration is that it's bringing in a ton of unfiltered air, it's bringing in a ton of air where the humidity is not controlled, and I say humidity - you're not controlled, because in some spaces places that may be Humidity, that's too low, for example. Right now we know that, with this virus, that's going on, people want to actually keep their humidities up higher than usual and if you're, in a really cold dry climate, like a lot of people in the Midwest New York areas like that in the winter cold, air Is dry air because cold air can only hold so much humidity if you bring in more moisture or I'm sorry more outside air into the structure, then you're bringing in dry air, which can then dry the structure out. So it's one of the reasons why and cold climates we want to control how much airs going in and out and in climates like ours.

Like I said, her dad used to turn the whole house fan on well, what would happen you'd bring in all of that? Really humid air now the reason you could get away with it is that, even though it was very high humidity, you weren't attempting to cool it, and so we run into problems when we take a humid air mass and we attempt to cool that humid air mass, Because what happens is is that you actually increase the relative humidity when you cool an air mass, and so in order to really control what the humidity and cleanliness of indoor air is going to be. We need to make sure that we're controlling how much of it is going in and out of the building, which is why we're building tighter buildings, so you build tighter structures that results in more control. Now control is a two-edged sword if you're gon na control, if you're going to keep a building tighter. Well now you need to think about things like VOCs chemicals in our house.

You have to think more about things like CO and co2 inside the because those can concentrate inside the building and that can make us sick, and so, whenever we're talking about building buildings tighter. That is generally gon na be a good idea. But we now still have to think more about filtration and ventilation than we ever had to before, as well as humidity control all right. Another thing is building construction, makes a big difference so again we're talking about human comfort, we're talking about really.

This is building science, but it's more so building science for air-conditioning professionals, things that we have to think about in what we do, one somebody's saying that the volumes low. So let me check that, for you, real, quick, we're going to I'll just move with it mic a little bit closer to my mouth. That should help with that. You may want to check your own volume too, because on my end here, I'm not showing it being low.

So in order to impact human comfort, we have to think about the building itself and how the building is oriented. Now you don't design air-conditioning systems based on rules of thumb, like you know, like oh well, it's facing someone such in such a way, and so that's resulting in you know we need to add more air or whatever the case may be. It's not simple like that, and I see people do this a lot. So whenever I'm telling you the things that impact heat gain and heat loss from a building, I'm not telling you that you should try to compensate for that.

Just on the fly you do that through proper design, but understanding the different factors that can impact a building do help because, for example, in Manuel J, we designed for things like shading well, shading is based on a percentage. It's based on how the Sun moves across the horizon. It changed season the season and a lot of that modeling software like writes off, does it's good of a job if you're going to do, but the reality is one jet. One house varies from another house depending on you know the type of shade cover what type of tree it is all the sorts of factors matter, and so thinking about the way that a building is constructed in real life is something that an AC technician should be Able to assess good example of this is: is my my dad's building a house right now and I helped design the AC and he's built these really enormous porches, and so the porches helped to shade the building and when you have the rising and Setting Sun from Those solar gains, but in addition to that after we made the design he changed some of his tree cover, so he added some trees in some areas.

He removed some trees in some areas and that's also going to impact the house and we can't design for all of those factors. Of course, over time the the Sun somebody just said: the Sun is a hoax, and so that made me laugh over time. Shading changes and that's also going to affect our comfort, so overhangs, trees, Hills, other buildings, screens orientation from an orientation standpoint. The southern exposure is going to tend to get the most overall heat and a lot of people will say well what about the north or south? But it has to do with the way that the Sun travels across the horizon.

The south side and the northern hemisphere still tends to get the most heat load and, of course, there can be some variation there. But in general, that's how that works and if you think about stories like the Underground Railroad, Harriet Tubman was a good example of this, where she, in order to try to find her way through the woods or in instructed people, you would feel for moss on the North side of trees, and that would help you know that you were headed north because the north side of trees, the north side of buildings, that's where you tend to get more mildew and more of moss and different types of fungus and growth. And the reason for that is is because the north side tends to have the lowest heat loads. So obviously, if you're, trying to heat a building, the north side is gon na, be the most challenging.

If you try to cool a building, the south side is gon na, be the most challenging, and then you also have to think about the way the Sun moves across the horizon. So again, all pretty obvious things, but all things that sometimes we miss when we're thinking about human comfort and building construction. Next one - and this is one of my favorite topics - is moisture control and that's one of my favorite topics, because in Florida, moisture is just a major problem. When you see that that ugly growth that shows up on your ducts, sometimes or a round event or whatever around a duct in an attic, we call that a moisture problem, because the reality is a lot of the fungal growth, especially which is a lot of what We see - I'm not gon na use the M word here, but that growth that we see is often caused by a moisture problem and how do we control moisture? Well, we control moisture.

You know we learned this. Obviously we're draining water outside the air. Conditioner has to be working properly, you don't want surfaces to get too cold, but we also want to control the moisture, that's generated inside the home, and we want to control the moisture that is coming in from the outside of the home. So a couple of these different things that you're looking at here is how we control moisture through things like.

If you look up here, you know vapor barriers and then also things that are added from the inside of the home, like humidifiers dishwashers, all that so having good vapor barriers having good windows and doors with proper seals. Those are all factors that will help control the humidity as it as it enters the space and then inside the home. Think about things like a dryer, for example, the dryer is a pretty significant source of moisture inside the home. If it's not vented properly, you see a lot of those the flexible dryer vents that people use and a lot of times they'll be leaking they're not connected properly and if that's allowed, to kind of spill into the laundry room.

That's a big factor, another big factor. If moisture added inside the home is bath fans, people aren't running their bath fans while they're taking showers and baths and then allowing them to run for quite a while afterwards in order to help vent that moisture, that's going to be a contributing factor. How often you run your kitchen exhaust kitchen exhaust is a really big one for a lot of factors. Some people, you know they'll, boil a pot of water and they won't run the kitchen exhaust because they think well, water doesn't smell.

You still have that moisture that that is leaving that that pot, obviously that's going into the space, so you want to have a good quality kitchen hood. My friend, Joel Becker was talking to me recently. It was actually right after the the Super Bowl I'm a 49ers fan, so don't hold that against me and Joel was trying to talk to me about hood capture efficiency, and I just was having a hard time focusing because of that sad loss. But what he was talking to me about, which is a really good point, is that having a larger hood that naturally captures the vapors as they leave the pot or you know condensate.

That sort of thing because of its size is helpful, because then you don't need to use as much wattage and move as much airflow. When you move less airflow now you put your home under less negative pressure. There's another thing to think about when controlling moisture is think about whenever we're exhausting air out of the space and it's good to do, for example, the showers and with your kitchen exhaust, because those are very high, moisture content points and with your dryer. But whenever we're taking air and we're blowing it out of the space, we have to bring in the same amount of air into the space in order to equalize those pressures.

And so the thought that we're exhausting out we're not bringing any in is false. And so we don't want to exhaust more than we need to exhaust. We want to exhaust the right amount in order to get the moisture out, but we don't want to exhaust more than we need to, and that's we're using larger Capture hoods with last CFM of airflow can be helpful to that end, and I thought that was just An interesting thing that he mentioned, and I thought I'd, bring it up here. So you know it talks about here.

You know vapor barriers, that's a big one and and a lot of people will say in the building science. Community they'll say it's a it's actually, a vapor retarder is a better phrase, so it slows down the movement of vapor into your house. Nothing is going to completely stop it, or maybe there would be things, but that would probably cause more problems. So you do still want the ability for moisture to move through, but you want to impede that motion of moisture and that's things that we use like tie.

That could be a common product. Nowadays, a lot of people are using zip system which is actually treated plywood. As their external sheathing, but things that just prevent that moisture from making it in make a lot of sense, we do want to control. It says this here we do want to control our relative humidity.

So that way, we make sure that furnishings wood trim, pianos things like that that are sensitive to relative humidity, aren't gon na have problems. We ran into this at a big custom home where they were having all sorts of issues with crown, molding cracking and coming apart, and all that, and it was because they were having big moisture fluctuations. And so, when you do something like you know, construct a house initially, you need to control the relative humidity in the space. Allow that wood to sit in the space and kind of acclimate and then assemble it if you assemble it, while the house still has high relative humidity, still has high moisture content in it, and then you dry it out a lot of times.

It's gon na pull back and it's gon na crack. It's gon na break the seams and all that sort of thing Eric, Mele, says or just don't, which I don't know exactly what that has to do with this. But thank you for your kind kind. Addition to the conversation Eric another thing that Neil mentioned is duct.

Leakage also leads to higher indoor relative humidity and that's one that maybe isn't always super intuitive. Now, if we think of a return leakage in an attic or in a crawlspace, that makes sense, because we imagine that air being drawn in to the to the return and into the equipment and into the house, because it's under negative pressure but actually supply side leakage. Also results in high relative humidity in the space, and the reason is, is that when we're leaking air outside of the envelope, so some of the air that we're blowing through our duct system is going outside of the envelope. That means that that means that your home is going under negative pressure or the structure is going under negative pressure, and so it's going to draw more in from the outside, so duct leakage outside of the envelope meaning into an attic into a crawlspace outside the home.

Those are all things you don't want, because it creates this pressure imbalance. We really don't want to see pressure imbalances unless we absolutely have to - and we talked about this already in the case of a kitchen exhaust, we're accepting that we have to exhaust in order to get those vapors out the VOCs from cooking and also the water vapor And all that we don't really have a choice there, but we just recognize. We don't want to move more air out of that space than we absolutely have to. Otherwise that will that will cause a problem.

Erik Mele says you can't have duct leakage. If you don't have ducts - and that is true - that is true - that is one of the arguments for vrf now, as you know Erik, if you listen to the podcast, he hates high wall ductless, and I and I can't say that I disagree on some of his Points so Erik has ceiling cassettes in his house, and that does you know it does make a lot of sense, because now you don't have a potential for air leakage outside of the envelope, and it does reduce some of these issues that we're talking about here, but Controlling relative humidity is a really important factor in comfort here, we're talking about controlling, moisture keeping it from entering the home. Now, let's talk about, let's say you're in a really dry climate, if you're in a really dry climate. Is that something that you just want to take showers and cook through all the time and not exhausted? I don't think so, because that's localized high levels of moisture you can still get fungal growth.

You can still have VOCs and things from your cooking, not something you. Maybe care as much about if you have a dry climate but the best way to control the moisture in the home when you have a dry climate is to use a proper, properly installed, properly maintained, dehumidifier and humidifier. Sorry, I always say dehumidifier because we're in Florida, but a humidifier and again we don't have humidifiers in our market. But everybody ice talked to about humidifiers talks about how critical it is to make sure they're appropriately installed in the first place and that they're continuously maintained.

So that way, you don't have leakage, you don't have problems, so those are things that that you want to take into account as it relates to moisture control in your home and you're in the occupy structures. All right air filtration - and this is one of my favorite topics right now - there's a lot of confusion about air filtration we've. We've gone to a lot of fancy technologies and all that, but I would like to see us not there's necessarily anything wrong with some of these technologies. But I would like to see us get back to the fundamentals of good quality air filtration.

And let's talk about that, obviously it cleans the air, that's the reason we do it and it is important. It says here as important as proper temperature and humidity, but I want to point out that cleaning your air with filtration is quite possible and is a lot easier to do than you may think, and so one of the one of the people who's tuned in here Is neelkant barreto? I talked about him and his partner John Cemil hack, all the time, because what they do with air filtration, I think, is really smart. They do very large filter, grills, so larger surface area, larger open area than you would normally have on your intakes, and then they use filter grills that accept two-inch filters or larger. They also make some media filters that can be accepted.

Sometimes you might have to make them custom, but by using bigger returns. What you do is. Is you decrease the velocity to face velocity across that filter, which a means that you have less restriction, so smaller filters, gon na be more restrictive? Bigger filters mean less restrictive, but also when you reduce the speed that the air moves over the filter, it's going to filter better and it's gon na be less likely that the dirt pulls around the edges. That's another thing with filtration that drives me crazy is people? Will put good quality filters in a filter, grille or inside the equipment, but there'll be all these little gaps and cracks around the edges.

Well, especially with a high velocity air stream that air is gon na, find its way around those gaps and cracks. So something that you always want to think about - and it really is a good technician - practice that brand new Tech's right out of school can practice or senior guys who have maybe never thought about it. Just do a better job of sealing around those gaps and cracks. You can use foam tape around the inside of the filter grille in order to make it fit tighter, that's a way or heck.

If you, if you need to tape it in place on the inside of the grille again we're not talking about something. People are gon na see anyway, so even using painters, tape or something like that in order to seal those gaps and cracks is gon na make a big difference underneath the unit a lot of times. Those factory filters are just not very well sealed, and so sometimes the only really good way of dealing with that is to go away from the factory filter and instead go to a nice 4 inch media and then make sure that that media is just fitting nice And snug all the way around so that way you fit that way. The air is forced through the filter, media and doesn't go around it, but one thing that I thought was really interesting and I would suggest that you take a look at this article.

There's an article from a company called smart air. Smart air is actually a it's a social good company, meaning that they do make profits, but the reason that they do what they do is to help people and they have all sorts of instructions on how to make do-it-yourself air cleaners and what they talk about. There is that good quality kind of HEPA level, air cleaners, so air cleaners that are up above that 13 Merv rating. They tend to be very restrictive, and so that's the reason why we don't like them generally in air conditioning unless we really oversize them, which is something we've got to start doing more of.

But one thing that he talked about is how filters at that level, where they have all these little fibers in there catch particles via diffusion and essentially what that means is. Is that it'll catch tiny, tiny, little particles that, based on our the way, we think about a filter like a net? We imagine a filter as a net and if the holes are too big, the small particles make it through, but schon study after study that those really high-quality filters can even catch particles down to around that point. Three microns level which cut to the chase means stuff. Like bacteria and viruses, the really nasty stuff that we want to get out of our air that we're facing today using heimer filters that kind of getting up into that HEPA range using those making them bigger so that we have a lower face velocity across them.

You can actually at least catch some, I'm not gon na give you a number of how many you're gon na catch, especially if you're creating kind of your own system here, but you will catch at least some of those very small particles, and it will make an Actual difference difference, so air filtration is a big thing. Think about using bigger surface area filters using filters that are thicker and think about using things like bigger return, grills and maybe big four-inch media filters. Those are all things that I would definitely. I would definitely suggest all right design tools for systems.

I get questions all the time about. How do you design an air conditioner? How do you size and air conditioner? I had a guy call me on a cell phone just the other day, to ask me how to size an air conditioner. The answer is: is that as of right now, these are the best tools that are out there. These are the ones that, generally, your local code, authorities are gon na recognize.

These are from the Air Conditioning Contractors of America. Acha manual j is for residential load calculation. That means calculating how much heat is going to enter or leave your space. It will also help you calculate latent load and latent load means how much moisture is gon na be generated.

That also needs to be either added or removed. So, in the case, when I say generated again, I'm always thinking of a humid climate. We want to remove it, but in some markets you need to add it, and this will help you calculate how much you need to add or remove, and so you have manual J, is residential load calculation manual and is commercial load. Calculation D is a residential duct design and Q is commercial duct design.

So when I hear people say I want to learn how to do a manual J on this commercial building. Well, that's not a manual J. That's a manual n all right! So, let's talk about what makes people comfortable temperature humidity those things - those two are pretty evident, pretty obvious. We could talk all day about just temperature and humidity, but this is an overview for the purposes of Nate testing.

So air movement is another really big one, and so we're gon na talk about some of the air movement guidelines you want to hit, but one of the number one rules for human comfort is don't blow air on people. Jack Rhys said that on a podcast - and I thought that was pretty smart - don't blow air on people. If you blow air on people, then you're not controlling their experience, because if they move to another space where air is not blowing on them, they're gon na either be uncomfortable or comfortable, depending on how they were before so. Controlling air movement is really big.

Even air movement within a space, though you may not be blowing air on people, but you may have air velocities moving across a space that are either too high or too low, and that can lead to discomfort. Air cleanliness is a really big factor and a lot of that is particles. So the majority of what we're measuring or looking at with air cleanliness is particles, but we also have some gases and the gases are tricky because you're not gon na catch. The gases.

In a typical filter, you can catch some gases and VOCs in things like activated carbon charcoal, which I'm a huge fan of by the way, I'm a massive charcoal and carbon fan. I think we need to use more and more of it. The challenges, sometimes the cost benefit, and also sometimes people will throw a little bit of carbon at a product to be able to say that it has carbon. But it's not a really effective amount of carbon.

Carbon generally needs to be removed and replaced, and so those are the factors when you're dealing with carbon, but I am a big fan of that in air purification and that's for the vapors and gases and then fresh air ventilation. Fresh air ventilation is really the only thing. That's gon na deal with one of the biggest things that we deal with, and that is co2. When I say it's one of the biggest things we deal with it's one of the biggest areas where we have elevated levels on the inside of the buildings, because in a lot of cases, the inside of a building may not be more contaminated from a particle standpoint Than the outside air, which is why, whenever you bring outside air inside, you need to filter it very well, and you need to control its humidity, so either add moisture or remove moisture in order to make it serviceable for the inside of the space.

But with fresh air, the one big advantage that fresh air has or outdoor air has, because it's not always fresh depending on where you live, is that generally it's going to have lower co2 levels and while co2 is not a poison, it's not a toxin. Elevated levels of co2 carbon dioxide can make us feel lethargic. It can definitely impact our cognitive ability. Studies have shown time and time again that even slightly mildly, elevated levels of co2, like a hundred part or sorry thousand parts per million, can cause us to feel drowsy.

Groggy and can impact our attention span, so those are reasons why you want to bring an outside air to help dilute it. Now, when it talks about air changes per hour, 0.3 0.3 to 0.5 air changes per hour recommended you have to be really clear about, and I don't necessarily make this recommendation. I think there's a lot of nuance to this, so I'm not telling you to ignore this. I'm just not gon na speak to it, because this is something you really need to design for when you're talking about air changes per hour, you have to know.

Are you talking about air changes frappe per hour within a space in a structure? So, are you saying I'm going to change the air in this room so many times per hour, or do you mean how many times you're going to change the air in an entire structure? So an entire structure from inside to outside and again that's gon na depend a lot on how clean is the outdoor air? What is the humidity like outside what type of filtration do you have inside? What are your co2 levels, and I would like to see a future where, rather than guessing at this stuff, we're more carefully looking at is the space occupied, because you only need to bring in outside air when the space is occupied. There's no reason to bring in outside air if there aren't people or pets living things inside the space. So that's that's the first factor and the next one is is what are those co2 levels and then you can even add in what are the vo sea levels? What are the chemicals in the air, those other gases and that could be affecting people's health? If you could monitor those three things occupancy co2 levels, vo sea levels, then you would do a much better job of bringing in the right amount of outdoor air without the need to bring in too much because, generally speaking, when you're bringing in outdoor air you're having To condition that air and that's costing you money and sometimes that outdoor air may have other things in it, that we don't want. So those are all things that all things to think about this here talks about an ERV and energy recovery, ventilator, an energy recovery ventilator.

Actually crosses air streams so that, as you discharge from air, you bring in the same amount or around the same amount and they can transfer energy to one another, both in moisture and in so both latent and sensible energy. It's a good way of maintaining a balanced indoor air pressure, our balanced ventilation. We call it where you're, bringing in the same amount that you're discharging in our market, especially, I prefer ventilating the humidifiers so markets where you primarily have to pull moisture out of the outer air. I prefer a ventilating dehumidifier to an ERV, because a ventilating dehumidifier is just gon na move a lot more moisture than any RV will.

But you can also use the two in conjunction with one another, and that may be a solution that works for you as well. Heat gentle generated for different physical activities, so you can generate anywhere from around 400 BTUs per hour all the way up to about about 1600, a little over 1600 BTUs per hour, depending on what you've got going on inside that space. What do you? What are you doing? Are you jogging? Are you exercising or you're doing really heavy work in a warehouse, or are you just sitting at a desk typing, and so those are all factors to consider and in things like residential applications, this becomes pretty important, because if a room is a if a room is A workout room, for example, it may look exactly the same as a room that will be an office. May look exactly the same as a room.

That's a bedroom! Well, those three rooms could be used very differently. An office may be used for a really long period of time, with somebody's just sitting there. During the day, a bedroom is generally only gon na be occupied for significant periods of time at night and a workout room is gon na, be occupied for short periods of time, but at really high intensity and all three of those are going to pose different problems. As it relates to indoor comfort and for us when we design systems initially, when we use do our manual J and then we do our manual D and we figure out what this you know, what we're gon na deliver as far as BTUs or what we're gon Na remove, as far as BTUs to each room, we're not always taking into account exactly how that room we lived in or how that house will be lived in, and so we have to be willing to adjust based on the way that customer lives in that house And understanding the differences in how heat is generated will help us do that all right, so people generate different heat at different rates depending on activity and depending on size.

I mean a little kid is gon na produce a lot less heat than then you know say, for example, Joe Shearer. I mean that guy is pushing about 400, so that guy is gon na generate a lot more heat. I'm just kidding, that's not true. If Joe, the next thing is people give up heat by radiation, convection and evaporation, so radiation is heat that can move through a vacuum through the air in between surfaces of different temperature.

And so, if you have say, for example, this wall, that's on the other side of me. If this wall is colder than my body, my body will give up heat to that cold wall via radiation without even the need to heat the room in between. But so I'm gon na give up heat to radiation. I'm gon na give up heat to convection.

That's when molecules are actually moving because air is always moving around us, so heat will move via convection and then I'm also going to move heat via evaporation. Now evaporation isn't one of the main three ways of moving Heat, but it is in human comfort, a really big factor, and that relates to relative humidities. So if I have a space that has lower relative humidities, my sweat is going to evaporate at a higher rate and it's gon na cool me more effectively. It's just you know.

We see this all the time people go to people go to Arizona and they'll use, swamp coolers, which are essentially evaporative, coolers, adiabatic, coolers and they'll use those little things around your neck with the gel that help evaporate and keep you cool and they'll say well, it's Hot but it's a dry heat. Well, you go to Florida. None of those things work because the relative humidity is so much higher. Your sweat just stays on you and drenches.

You evaporative coolers, don't cool the air that much because you don't have as much of that. Evaporative effect, the one form of moving heat that this doesn't talk about is conduction, because as humans, we don't move that much heat via conduction. That's the heat, that's move when you're touching something so one case where we do move heat, but I can action would be a case if we have a cooled seat in a car or a heated seat in a car. That's a case where we're directly in contact with a surface and were able to transfer heat to and from that surface all right.

So this kind of shows you some different ways that that heat is loss or gain, and this is just a. This is just kind of a round numbers guess, but for somebody who's in a room that 70 degrees Fahrenheit with a relative humidity between 30 and 60 %. It's showing here that evaporative loss are about a hundred BTUs an hour. Radiant loss is about a hundred and fifty BTUs per hour.

Convective loss is about 150 BTUs per hour, so this is a person just sitting there producing 400 BTUs per hour, which would be an adult. I'm sitting still doing office work a normal-sized adult. Let's see here the thermal envelope, this is fancy building science talk and building science. They talk about the envelope all the time, and that means the shell that separates the occupied space from the unoccupied space.

So if you have an attic or something like that or a crawlspace that is outside of the envelope, if it's an unconditioned attic or an unconditioned scrawls crawl space, if it is a conditioned attic, then that would be what we would call inside the envelope. So the envelope involves everything, that's conditioned. Everything outside of the envelope are the areas that are not conditioned in controlling that thermal envelope is a really big part of controlling comfort, says the insulation can reduce radiant heat loss and radiant heat gain either way, and so that would mean that as an example here In Florida, if we insulate the Attic - that's above me and that attic is 130 degrees up there, but we insulate it so it keeps the surface temperature of this ceiling. Above me, at a lower temperature, I'm going to gain less heat from radiant heat transfer, because radiant transfers through an air gap based on temperature difference in proximity.

So, by keeping that surface cooler, that's going to keep me more comfortable, also says wall surface temperatures are just important as important as room air temperature to occupant comfort and you've. All seen this you've seen cases if you're in a climate like ours, where somebody who works in in office all day and they sit near that window and they say they're uncomfortable, even though it's 74 degrees inside that space all day or 72 degrees. It's the same. Temperatures the rest of the house in many cases, but they feel uncomfortable because they're exposed to a hot wall and potentially a window.

Those are those radiant gains that are impacting their comfort and those are really really big factors. It says that vertical temperature difference from 4 inches to 67 inches off the ground should not exceed 5 degrees Fahrenheit, and that's talking about thermal stack effect. You don't want to have cases where there's not enough air mixing that you have significant difference in temperature in strata. In the room you want to keep between 4 inches and 67 inches.

If you were to take a thermometer and measure through there, that's what we call the occupied zone, you shouldn't have more than a 5 degree difference in that area, so humidity impacts human comfort by impacting the rate of evaporation. We already talked about that. You have lower relative humidity, your body is going to be able to give up more heat via sweat, and it's not just sweat like standing, sweat on your arm. I think often, when we think of sweat, we think I've got to be sweating but we're constantly giving up heat via evaporation.

Even if you don't see sweat on your body, as some people have said, we are very moist beings. We humans, that's a that's. A gross word. Humidity, also affects the body's health.

Another way static. Electricity is a problem at very low humidity, so people are uncomfortable. They start getting shocked when relative humidity gets too low flu viruses flourish and low humidity and coronaviruses also flourish in low humidity. So we want to control and keep that relative humidity in a in a good zone and that good zone generally for dry climates in the winter is around 30 %, maybe a little bit higher in some cases and in cooling, climates, humid climates.

We want to keep it below 55 %. Some people will say 60 to 30, but it really depends on your particular situation in the winter and a dry climate you're, not gon na get it much above 30 without running the risk of creating other moisture problems. In your walls - and things like that, so 30 is kind of your target and in hot humid climates 50s, pretty much your target. I would love to see.

Homes and commercial buildings had just set right at 50 percent relative humidity all the time, and then you can just control your more sensible temperature. You know somewhere between 75 and 72. You know in that spot 78. I guess would maybe even be better but 78 to 72 in there and just keep that relative humidity, around 50 % dust mites flourish at higher humidity and molds grow and higher humidity.

So you tend to see more dust mites, more more fungus and often bacteria as well. There are some so joe says I would think flow virus flu virus likes moisture. No, it's not what you think. Viruses aren't, how you think they are and that's all it cuts.

All I'll say about that. I've been doing a lot of research. We often get viruses confused with bacteria and fungus. Fungus is the one that really likes moisture.

So what we see growing in most cases is fungus. Sometimes it's bacteria, for example, that elephant snot that we see we call it elephant snot, sorry, it's kind of a gross term, but that we see in drain pans and coming off of evaporator coils that are aluminum. That appears to be bacterial. Some people have said they think it's fungal, but based on some tests it appears to be bacterial, and so we see those two things: you're not gon na see viral growth and flu and corona are both viruses, they're, not bacteria or fungus, and so we have to Get our head around that they they operate differently and then also dust mites, pollens VOCs.

All those things do better when we control our relative humidity. So controlling relative humidity is huge and we have to be careful when we fix one problem we might be causing another. Like we talked about, if you're bringing in more outdoor air, it's more likely you're going to lose control of your humidity or lose control of your filtration. So you have to do that in a smart way.

You can't just take outdoor air and just dump it into the return and expect that it's all gon na work now it may, depending on your climate, but I would not expect that in most cases you have to do a really good job filtering that air, and You also have to think about whether or not you need to remove moisture from it in a lot of cases. Air movement - I like this little chart because this isn't something I think about a lot but controlling air velocity within a space within the space itself. So we talked a lot about duct velocity and face velocity, but within the space itself we won't really want to see kind of controlling in between that 15 feet per minute and that 65 feet per minute. You get above 65 paper blows off of a desk.

You get 160, that's when you're really moving a little too much for people to feel comfortable. Natural convection occurs just from you know: cold air sinking in warmer air and warm air floating in cooler air. One of my favorite questions, just to be kind of a jerk to people is to ask them: does he tries no heat, does not rise. Hot air or one hot substance, is buoyant in the same substance of a cooler temperature which that just is a really nerdy jerky way of answering that question, but just think of it.

This way a hot air balloon rises, because the air inside of it is lighter than the air around it. So the hotter air is floating in the cooler air and in the same way, cooler air is sinking in warmer air. For some reason, my camera decided to stop focusing there. There we go so that's it cold air sinks and warm air.

Warm air floats and out here it's its buoyancy that we're dealing with with convection mechanical equipment creates force convection. Well, we kind of know that air movement within the occupied zone of a room should be maintained at an average velocity of 30 feet per minute in winter and 60 feet per minute and summer and frankly this is one I never remember, but it is a good Guideline, it kind of gives you sort of edges that you want to see it's. We want our velocity to be lower in the winter, because in the winter we naturally are gon na feel colder, and so by keeping the velocities lower. It's gon na help us feel more comfortable and fifty feet per minute.

In the summer again, we already talked about the occupied zone as far as height in the occupied zone, but the occupied zone of room extends from the floor up to six feet above the floor and to within two feet of the rooms walls. So if you get within two feet of the rooms, walls you're not expecting to control the temperature as well within two feet, because that's not generally, where people gon na be they're generally not going to they're, generally not going to be within two feet of the wall. When they're occupying the space, somebody just noticed that my hats defective that it says HVAC backwards. Yes, it is a mirrored display.

So that way I can be on this side showing you doing it this way, which is much more comfortable for me. So this is all about me. It's all about me and my comfort with my hat being reading backwards, and I am a CV - see AVH technician. Alright, the adjusted wet bulb temperature within this zone should range from 67 to 73 in the winter and from 73 to 79 did I say, wet bulb, I'm gon na say: dry bulb 60 73 to 69 in the summer, and that's pretty typical, typically where people will Be comfortable sometimes in summer they nowadays seems like people like to keep it cooler than that.

Another thing you can do is you can increase the ventilation, air and industrial applications and adjust the temperature, so you can actually run a little warmer if you increase your air velocity. So that's why, in industrial applications, sometimes they're gon na run a little bit more airflow and you can get away with it being a little warmer Joe asks. Brian. Is it an old myth to have grills blowing at windows and across ceilings? No, not necessarily so when you cool an exterior wall, you're also decreasing that radiant effect.

So you do want to keep your exterior surfaces from getting too warm or too cool, and that's sort of the that's why you had old radiators on the exterior walls and blowing across the ceiling is useful because you get more throw because of the Conda effect Uncle Wanda, however, you say that, but the air travels across the ceiling, it actually creates a negative pressure area above the high pressure air, and so it allows the air to throw further across the room. So I don't think anybody's saying that that's a that's a myth. It's just that sometimes it may not make as big of a difference as people want to believe it does, and it's like a lot of things I would say there are. There are things that are good practices, but sometimes not worth it.

It's not worth the other costs to apply it, especially as we get to lower and lower velocity Airstream, so as we're running less and less air around buildings, we're gon na get less and less of that sort of effect. Okay, let's see here, the exchange of outside air is required to provide oxygen and remove contaminants. By far it has to be pretty bad before oxygen levels are gon na decrease in a space, it's more likely that you're gon na build up carbon dioxide. That is more likely.

Obviously, you wouldn't want oxygen levels to decrease, but it's generally that kind of carbon dioxide marker is what we want to watch and we definitely want to keep it below a thousand parts per million inside spaces when it starts to go above that, that's a problem, I Think in general, outside air is between 300 and 400 parts per million. Something like that. May I could be wrong. Don't quote me on that? Maybe somebody can tell me in chat what the what it is outside, but when we start to get those increased levels of co2 carbon dioxide, that's what is a that's.

What can start to affect us see? Oh, carbon monoxide is always a bad thing and will make you sick it quite low levels and is something we definitely need to be measuring for if you're burning any fossil fuels, older buildings use natural ventilation. You know just open a window and there's nothing wrong with opening a window. I mean that's a that's a good old-fashioned way of doing it. You just have to know that when you do it that ventilation, air is gon na, be localized, and if that air is dirty, if that air is high or low relative humidity, that's going to affect the house.

Caleb says between 400 and 800 parts per million co2. Thank You Caleb. That's that's! Typically what you're gon na see outside and you don't want to really see. I mean frankly, if you can keep it, keep your indoor air from going above 800 parts per million inside then that's a good thing to do.

A quick, quick question in chant Oscar says: what's up with the new aluminum coils building up that clear, sediment elephants not faster than usual, is that correlated with the humidity? No, probably not because most coils are gon na get below dew points and most coils are going to have moisture on them. Obviously, if you're in any more you in climate, it's probably more likely that you would have more of it because you have more condensate, but no. The elephant snot is clearly associated with the fact that aluminum does not have nearly the antifungal and antibacterial and antiviral properties. That copper has copper, is a known, copper and brass are known to produce ions that attack and kill fungus, bacteria and viruses, and so when we went to all aluminum aluminum doesn't have the same properties, and so it's not attacking that stuff in its building up quicker.

It's kind of an unintended consequence of going to aluminum and it is, it is a real problem. Now what we do and when we have problems with it, is we'll take pieces of copper pound it flat and then stick some pieces of copper in the drain. Pan and it's not a full solution because it doesn't solve it at the coil level, but it can help deal with that. Some people have said pennies.

Pennies have zinc are mostly made of zinc nowadays, which can have some, I think, is. I think, zinc has some antibacterial properties as well, but copper is well known. You can also use a little bit of 15 % rod a little bit of that silver silver is also antibacterial, so those are some things to try. Newer buildings use mechanical ventilation.

That means we're bringing air in on purpose, exhausting it and bringing it in on purpose and like we talked about, that's can be a really good idea, but it requires design thinking in order to do it properly, so that you don't overdo it, because you can overdo It you have to be able to control the filtration and the humidity control, as well as even the temperature of that air. If you lose control of that and it results in occupant discomfort. Because of those other reasons, then you haven't done yourself any good by bringing in more outdoor air, Oh Joe says, modern pennies aren't, copper, and that is true. Modern pennies are made of, I believe, mostly zinc.

Pretty soon the probably made of plastic equipment selection will just rip through this part real quick. This has been pretty long, so I'm not gon na go too much further, but I mean some of this stuff has changed recently, but these are still good. General rules, equipment selection, equipment selected should match the calculated heat gain or loss as close as possible. So that means that don't want to oversized or undersized equipment, generally you're gon na oversize just a little bit in order to make sure that you're not under sized.

But you don't want to oversize significantly, so cooling equipment shouldn't be should not be oversize more than 15 % greater than the sensible heat gain. So that's just the heat that changes temperature. It's the heat. We can measure on a thermometer.

That's what sensible means where latent means moisture so we're talking about humidity when we talk about latent heat pumps, of up to 25 %, larger heat pumps up to 25 % over sizing when you have larger heating loads. So, in the case that you're here sizing a heat pump larger, so that way you can deal with the heating loads. They allow a little more over sizing on cooling again, just be very careful when you're doing this and cooling equipment equal to or greater than the latent heat load, and, I would add, in at design conditions. The problem is, is that a HRI design conditions are at a higher indoor temperature than what we generally are gon na really operate the equipment at so we adjust our design conditions so that way, it's based on a 75 degree, indoor temperature, instead of an 80 degree Indoor temperature, which also adjusts our wet, bulb temperature slightly.

I mean that's just to make sure that we're going to get all that moisture out. That needs to be gotten out, so we don't run into humidity problems. Equipment selection, heat pump, plus auxilary heat should not exceed 15 %. Of the total load means you don't want to oversize more than 15 %, with the heat pump, plus auxilary heat and fossil fuel equipment should be the next size larger than the load.

So you do. The load you pick the next size, bigger furnace or whatever you're, using pretty straightforward on that lots of factors for calculating system capacity. I think we're gon na stop. Here, we've been going pretty far.

You can find the rest of this slide and all the slides from our SES by going to our SES org one thing, so one of the comments here from Caleb is or undersized a little and make envelope improvements. Yes, that's actually is what I would prefer that you do when you find a space or your clothes, but you don't want to have to go up to the next size, find ways to improve the envelope, find ways to your your latent and sensible loads. So that way, you don't need such a large unit and that's a big value to the customer, because a lot of times smaller tonnage units are more efficient and obviously you run the the benefit of this equipment running longer. We want equipment to run longer in order to D humidify and to provide better mixing and better temperature control, there's just a lot of benefits to having equipment that runs longer and is not oversized so there you go, that's it for today, thanks for watching - and hopefully You learned a little bit of something about the factors that affect our comfort inside a space.

Ok, John, the next one.