You are here

Below is the text version of the webinar Lazy Air Conditioning: HVAC and Humidity Control, presented in November 2016. Watch the presentation.

Alex Krowka:
... Ready Home technical training webinar series. We're excited that you can join us today for "Lazy Air Conditioning: HVAC and Humidity Control." Our presenter today is Ken Gehring, president emeritus of Therma-Stor LLC. Today's session is one in a continuing series of technical training webinars to support our partners in designing and building DOE Zero Energy Ready Homes. My name is Alex Krowka, and I provide support for the program. I'm just going to take a quick moment here to cover some general notes on webinar housekeeping. All attendees will be in listen-only mode, however, we do invite you to ask questions throughout the session in the questions section of the GoToWebinar program. We'll monitor these throughout the webinar, and we'll try and answer as many as we can during the presentation, and then after the presentation we'll also take some time to go over some of the submitted questions that weren't answered during the webinar. This session is being recorded and will be placed on the resources page of the Zero Energy Ready Home website. If you could just have a little patience -- it takes a couple of days to go through the process before the recording will be added to the web page. But we will do that. Also, after the webinar we'll send out an email with a PDF of the presentation. So that's it for me. I'm going to go ahead and hand it over to Sam Rashkin, chief architect of the Building Technologies Office and program manager for ZERH, to give an introduction to the program and introduce Mr. Gehring.

Sam Rashkin:
Hey, thank-you, Alex, and actually, we'll introduce Jamie to provide some context. I want to welcome everyone to the webinar and also set the stage for this presentation. We do Zero Energy Ready Home training all across the country, and we always get requests for a deeper dive into many of the technical subjects that we just don't have time to cover during our workshops. So these technical webinars are a chance for us to pull in experts from all different subject matter areas of interest and have them share with you some really important insights. And that's what this one is about, and essentially, as you know, when we talk about Zero Energy Ready Home, there are six key building blocks that are essential to deliver the total performance we're after. There's optimized thermal protection to make sure the home's future-ready. There's whole house water protection to make sure the home is moisture-ready. There's high-performance heating and cooling to make sure the house is comfort-ready. There are energy-efficient components to make sure the house is tech-ready. Comprehensive indoor air quality to make sure the house is health-ready. And solar-ready construction to make sure the house ultimately is zero-ready. So today we're focused on high-performance heating and cooling. And a system can't be high-performance if it also doesn't manage humidity. So we've invited Ken Gehring, an expert from Therma-Stor, to provide some really important insights on this subject. And I'm going to hand off to Jamie Lyons now to provide more context on how these webinars fit within the total Zero Energy Ready Home subject matter. So Jamie, off to you.

Jamie Lyons:
First slide of presentation:

Great; thanks, Sam, and thanks, everybody, for joining us with part of your day here. We hope it will be worthwhile and useful information for you. So this will be fairly quick, but we want to provide a little context, because RH control is certainly important. And it's especially important in high-performance DOE Zero Energy Ready Homes. Sam just a minute ago mentioned six key building blocks. And that's what you should see here on this slide. The optimized enclosure all the way over to the solar readiness. I like to think of these as the foundation really for the program. And they make possible really all the reasons that builders and consumers can leverage value from Zero Energy Ready Homes. So today we're going to look at the building blocks, with sort of a crossover between the optimized comfort system as well as complete indoor air quality -- good humidity management of the indoor environment really cascades across both of those.

Next slide:
So if we look at indoor air quality as a complete system, that's a really strong core value proposition for DOE Zero Energy Ready Homes. We're doing all the things that make sense to comprehensively look at indoor air quality and assure we're using the best practices out there. So we get that from really two main building blocks: One is the ENERGY STAR Homes program, which does a pretty good job in dealing with the envelope and HVAC design, some moisture control, some carbon monoxide provisions. And then we really round it out into a complete system by also incorporating the Indoor airPLUS program as part of every Zero Energy Ready Home. You can see the list here that sort of cascades down from radon down to enhanced moisture protection. So that's sort of where we're going to zero in on today.

Next slide:
As far as what our exact provisions require within the DOE Zero Energy Ready Home program, it's fairly simple at the surface here. A provision to install equipment that has enough latent capacity to maintain indoor RH at or below 60 percent. A few options to get there are additional dehumidification or perhaps central HVAC with additional controls to operate effectively in a dehumidification mode.

Next slide:
Where this provision is actually required by the Zero Ready program is sort of down here in climate zones 1A, 2A, and a portion of 3A, which falls below this white line. This is the IECC climate zones map, for those of you who might not have seen this before. That's where it's required to have those mechanical systems that can maintain RH below 60 percent. But from working really with hundreds of builders around the country, the question of good, reliable RH control comes up in other markets beyond just this lower southeast portion of the country. So for that reason we also recommend consideration of enhanced RH control, even as we get a bit further north, up into zones 3A and 4A. Really into some more of the mixed climate, where RH management can be equally important.

Next slide:
Before handing it over to Ken as our presenter today, I just want to take the pulse of the group here and get a bit of understanding about, for new home projects in which you're involved, what type of RH control strategy do you typically use?

Poll question:
So I'll launch that poll right now. And I'll give everybody here just a minute to click the appropriate selection there. And I'll share the results and hand it over to Ken. While you're completing the poll, let me go ahead and read Ken's bio so you know a little bit more about our presenter. Ken Gehring is the president of Therma-Stor, and he's been involved in innovation, design, and product management of ventilation and energy conservation devices for the last 38 years. During the last 11 years, he's really focused strongly on moisture and ventilation research and development for Ultra-Aire. His areas of interest include indoor air quality, energy conservation, and comfort in residential and light commercial structures. So we're happy to have Ken share some of his knowledge today. Let me close this poll. And I want to share the results so you, too, can get a sense of the group today.

Poll results:
So roughly half the group, when they're involved with new residential construction, the common approach is a typically sized central AC system. Maybe a quarter of the group leverages variable speed AC for greater latent removal. And then 15 percent, 16 percent, typically would go with a supplemental dehumidifier. So Ken, I'm sure you'll find that to be instructive as you prepare your remarks. So while you get ready, Ken, I'm going to hand over control of the presentation to you.

Ken Gehring:
OK, thank-you.

Next slide:
Lot of years lately with Electria, focusing on homes ventilating and starting out, and then going on to provide some part of conditioning, which would be the dehumidification, primarily, getting fresh air into them.

Next slide:
The plague is, or the wonderful thing about all this is, that we've got weather on earth, as you all have experienced. I don't have to explain it to you. Sometimes it's beautiful, very comfortable, ideal, and all the way to life-threatening. Because weather depends on massive systems moving around the earth, you may have weather typical of the last season we are exiting, the current season we're in, or the next season. Weather systems typically pass in 1 to 14 days. The ones that are easy to handle are the three-day systems. The systems that are longer, more extended, are the ones that provide the biggest opportunity or problem for us. (inaudible) for survival and comfort.

Next slide:
Outline of things that we're going to talk about today: Certainly the seasonal impact on the house as a system, current best practices of dealing with this, and then concerns we have, particularly with the air conditioner showing up and then we really have the ability to keep a house at lower temperature, which heightens the moisture concerns. And then the impact of -- we'll call it the lazy AC here, but let's just say the random kind of AC applied to homes by contractors. And then also what we see could be the gold standard, the way ideally to do this.

Next slide:
The four seasons of the year, and you talk about the zones of the map, -- we look at this more as being a green-grass climate. If there's enough rain to support grass outside your home, chances are you should have humidity concerns. It certainly needs to be observed. The four seasons of the year, winter and spring, summer and fall. And they're different in different parts of the country, of course, and in different zones. But the way that we're going to refer to it is looking at the dew points. Typically the winters that we're concerned about have dew points in the 10-degree area. And spring, it starts moving up. Summer, all the green-grass climates have dew points in the area of 75, 80 degrees. What do we want inside? We want 40 percent relative humidity in the coldest weather and then ideally 50 percent inside, and that's our target. The next issue is how much water do we have to add or remove to a home to obtain this condition? Looking at dehumidification, we have somewheres between 0 to 10 gallons of water to take out of a house in a day to maintain 50 percent RH. In the wintertime, we look at the other part of this. The humidification -- we may have to add 3, 4 gallons of water to a home a day to maintain 40 percent RH, depending on how much air is moving through the home.

Next slide:
The house as a system. Sort of considering this being, let's say, an optimum house, but certainly a typical house, damp air passes through the home, and the occupants add moisture, and the home gets damp. How much air goes through depends on mostly wind, and mechanicals in the home purports, but a 20-mile-an-hour wind is like a blower door at 50 Pascals. So you get an idea of, we have to be set up for some kind of air movement through the house. We're going to, for the sake of this presentation, talk about 0 to 200 cfm of air moving into a house. Assuming that it's damp, it might be 8 pounds of water an hour moving into the house compared to what we really would like. We've got occupants that add something in the area of 2 to 4 pounds of water an hour. And then we have equipment in there that we're told will keep it dry and cool and that's our air conditioner, which can remove anywheres from 0 to 15 pounds of water an hour, under ideal conditions, which should keep a house dry and comfortable and cool.

Next slide:
As previously talked about, many organizations have decided that less than 60 percent or equal to 60 percent is satisfactory. And I think that's where we're at. Ideally, we like to have it a little drier, but nobody gets concerned as long as we keep it below 60. The options are add additional dehumidification systems, which that's what I'm going to primarily talk about today. Or there are things you can do to an air conditioner to make it be better at controlling humidity. And one of the things that I don't want to leave out -- we're a humidifier company, don't sell air conditioning -- but you can buy air conditioners with reheating, commonly used commercially, that can keep a space dry if sized properly.

Next slide:
There's our map again, and like I say, green-grass climate, for me, the difference is that many times, Minnesota -- Minnesota in fact holds the record for the highest dew point in the nation. It's something like 74 degrees, hard to believe. There are truck periods of time when these climates are wetter than the places like Miami, which are surrounded by salt water. Salt water can only generate about 75, 80 percent relative humidity, typically just evaporating water out of the salt water into the air. Where places that have a lot of fresh water like Minnesota -- fresh water will quickly go to 100 percent. So you can see quite a difference. But the duration is much shorter than it would be in the zones that have been highlighted here.

Next slide:
Best practices. This is sort of the starting point. Most of us have had it drilled into us, and we agree with this. The first thing you've got to do is look at the design conditions, and then decide what it is that you want for an indoor humidity level. Identify these things. Look at the number of occupants and the amount of fresh air. That's the latent part of the equation. And then we calculate the load. Total Btu, an estimate of sensible, an estimate of latent.

Next slide:
Then we select equipment. This generally is something that they just look at total Btu and pick a piece of equipment that will give them the total Btu they need. I'm looking at it from the contractor's point of view. And they may add a small safety factor depending on the variables involved. A lot of emphasis today to not oversize the AC. And it does help maintain indoor relative humidity if the air conditioner is not grossly oversized.

Next slide:
So now an HVAC system is sized according to industry best practices. It's installed. Quite a feat, actually, in most cases. We collect the money. Some consider this done, right? Well, now it's done. If everything happens to work out, again, it's done. But the concern is that the system has been sized for peak load conditions, but the house sees mostly partial or no-load conditions.

Next slide:
Looking at a real load, a typical load condition throughout 24 hours, the sizing is done on the peak load, one hour or so. This is a typical day in a peak load. Looking at temperature, you can see that in the sensible load, it is from 90 percent to near 0 on most days. While the latent load is based on not the percent RH but the actual dew point in the air or the moisture content. We're going to use dew point here. The other method of citing it is grains of moisture per pound of air, but we're going to use dew point, trying to keep it simple. And that's pretty straight-line. That's constant load, peak of the day, including the evening. That's why there's water all over the grass. The car is wet. All those temperatures have come down to the dew point. And many times, mostly, the low outdoor temperature is determined by the dew point of the actual air. It keeps going down until condensation occurs, and that heat is put into the air, and that's what stops it from going lower.

Next slide:
Let's look at a new example, a Manual J. For our example here, we picked on a house that we had a lot information. This was a little bigger house in a warm climate and it was a little bit bigger. A 3,000-square-foot house in Texas, actually. So that house had a 45,000 Btu per hour sensible load with a 12,000 Btu latent load. Total 57,000 Btu cooling. So on a hot day, four hours per day, our heat was in 45,000 and then declined near 0 at night, while the latent load remained pretty steady at 12,000 Btu per day.

Next slide:
Best practice systems work at design load. Yea. So here's how that works. An example, back to our house. In the heat of the day, we've got 95-degree, 56 percent RH, it's a 77-degree dew point. Some infiltration rate. We put a -- use the example here of 200 cfm. We've got a family of four that typically on an average adds about 2 pounds of water. So that total load there is about 10 pounds. We've got an air conditioner -- a 5-pound air conditioner -- in there, which is during the peak of the day, remain almost nonstop. And it's removing some moisture and -- next trip there we'll see how -- there's its operating condition. I'm using typical here. This is pretending that the AC contractor installed and connected to the ductwork and he gets what he gets. He gets 10 pounds of dehumidification an hour. He has 57-degree air, 95 percent, with a 56-degree dew point going into the house. The house ends up 75 degrees, 59 percent RH, 60-degree dew point. It meets all the criteria that we're looking for. We've got 200 cfm of air passing through it. This meets our 60-percent RH criteria, right? So, should be no problem. And typically most people would be happy with that. I don't think elated would be a word, but satisfied. That's where it satisfied.

Next slide:
Best practices -- OK, that's our best practice of systems. How does it work on a 70-degree day and it's rainy outside? So we have low or no sensible load with a fairly high dew point, a 70-degree dew point. We've got the 70-degree dew point infiltrating, not like a design load, quite, but certainly 200 cfm -- that would be 4 pounds of moisture. Our family still adding 2 pounds of moisture. But what's happening to our air conditioner? How much is it going to run at 69 degrees? I use this example just going through all the clutter and getting down to the point where there is no cooling load, whatever it is. Well, the inside dew point, relative humidity -- we know it isn't over 75 because the air conditioner isn't running. But assuming it's 75, there's 200 cfm of 68 dew point air passing through the home. The family is adding 2 pounds of water. When you mix that all up, pass that air through, we're going to end up with 75 degrees, 80 percent, of 68-degree dew point. How happy is that family going to be? Not going to quite cut it. A fix, though. Clearly you can see here, we could use reheat on an air conditioner. Want to get that. Which would mean running the air conditioner and taking the condenser heat and putting it into the house and operating to remove the water. Or we could add a dehumidifier. So if we add a dehumidifier that takes out 5 pounds of water an hour, we've got a new condition: Air conditioner isn't running, we're putting a little heat back into the dehumidifier, but we're ending up with 75 degrees, 50 percent, and we've got a happy condition for a family. Now that's a straightforward, simple solution. We know reheat would do it. We could tweak that air conditioner and get a little better control but all air conditioning requires cooling load. And if there's not enough cooling load, then we're forced into the reheat move and using an air conditioner if we're going to do the total job. That's happy, yea, right.

Next slide:
Let's go to the next condition. Best practices on a partial load. So we've got the same house. We have a humidifier in it. Our air conditioner could keep 60 percent. We have the dehumidifier in there, operational, and any time the humidity goes above let's say 50 percent and drops. OK. We've got 200 cfm air coming in. Our family is in there again, contributing their 2 points. Our air conditioner is sitting there running some. It's running enough to remove 6 pounds of moisture an hour. Doing that, we are going to end up with a 65 percent relative humidity. Let's not forget, we've got a dehumidifier on this house, of course, that has to exfiltrate. Now our dehumidifier is triggered and runs. The interesting thing that happens here, as that dehumidifier operates, and attempts to pull down the moisture level on the house, this air conditioner removes less water. And the overall effect is not much of an impact on humidity control in the house. That is a little bit of a shocking thing here, and the reason for this whole presentation is showing that interaction and its failure to control the house. And also how the air conditioner didn't quite do what we'd hoped for in the first scenario, where we've got the house down below 60 percent, but it didn't get it down to where it ought to be, more like 50 percent. So we have an unhappy family. Well, what do you do?

Next slide:
You call for your contractor and say, hey, this isn't working right. He says well, look, you don't have any cooling load; don't expect me to make this work. You've got a dehumidifier -- what else can I do? Well, that's what this is all going to all be about. It's really the heart of this talk.

Next slide:
Well, now, put yourself in a modern consumer's chair. And of course, what you're going to do, you're going to get on the Internet and you're going to dig into the solution, just like when you need a doctor or a dentist or anything, any kind of counseling. Get on the Internet; you do a search. Well, here's what the Internet offers you. There are several websites out there. One of them is called HVAC Talk. And it's one I do for my entertainment. I suppose you might say I'm a teddy bear on that, and here comes -- we're a group of contractors, guys like me, all different kinds of people with opinions or expertise in certain areas. And people come in and ask these questions. What about this? I have a house -- I can't read that on my slide here, but what that inquiry says on HVAC Talk is, I have a house, I have foam-insulated first-class job. I've got a 2-ton air conditioner. My house never gets below 65 percent. What can I do? So they come in and then we give them some kind of suggestions. Of course, I suggest get a dehumidifier. Why not, right? That's why I exist.

Next slide:
Let's look at a Texas home where this happened. A person was going into HVAC Talk, reading all the posts, responding -- actually went ahead and put in a dehumidifier, all on his own without ever posting. But anyway, came back after that and said, hey, my house -- I have a dehumidifier -- my house is wet. And I can't get it down to 50 percent, and that's what I want. So we put some data logging on that house and took a look at what's really happening. On the left is the outdoor conditions, where you can see this weather. We're monitoring this. It's only 63-degree dew point outside, not extreme at all. And the temperature, what is it, a little over 80 degrees. So here's what his AC looked like -- the effect of the AC on the home inside. And as you can see, he can cool the house down, but he just couldn't get the humidity down appreciably. So we're going to do some things here to show the problem. Let's go to the next slide.

Next slide:
We had a moderate DP of -- dew point inside that was very similar to outside. But the AC in incapable of lowering the indoor humidity.

Next slide:
So let's focus on that data. That's a good start if you have a problem home and you want to know what's going on. If you -- you can inexpensively put data logging on these homes and track them. And we took a look at the details of when that thing did run, and had a condition here where -- by gosh, my pointer's working. I wonder if it's working for everybody. But anyway, this air conditioner ran for 81 minutes in its longest cycle. I cooled it down quite a bit, but it never lowered the indoor dew point at all. In fact, it went up a little, which you'd expect in that when you lower the inside temperature, every degree you lower that temperature, you're going to raise the indoor humidity 2 and a half percent if you don't remove water. So the AC was removing some water but not adequate. And then to make problems even worse yet, this guy had 150-pint dehumidifier on this 2,000-square-foot house. And it just couldn't handle his humidity.

Next slide:
What's going on? Well, this takes some serious thought, right? Enters the lazy AC. Now, I'm saying enters the lazy AC -- we've got an air conditioner not working. We could have gross air infiltration. All kinds of things like that could be happening. But assuming, and they didn't have the contractor out there to check that AC that was working to the best of his knowledge, the charges hit and all that. So here we look at, the condition inside the house is roughly about 70 degrees and 60 percent. And at that condition, that air conditioner was removing about 30 pounds of water -- 10 pounds of water an hour. So 10 pounds of water an hour is what it was removing. Now, if you look at that, that means that it was taking out 10 pounds, that means that between the fresh air coming in and the occupants, they were adding 10 pounds. And this sort of balances out to be at this 75, 60 percent relative humidity. Now if it was dry outside, or if the family went away, and that load declined -- let's say it declined 2 pounds -- now you'd get a new inside relative humidity with that air conditioner working. It'd be lower. And all the way down to here is his objective, 75 degrees and 50 percent. Well, if he could get it down to a 4-pound load or a 5-pound load, this house would be 50 percent. But it just all balances out and it sort of -- you're adding water with people, you're adding water with fresh air at a variable dew point, and you've got a device over here that's taking out water. And you get something on the level of that moisture in the air as it passes through the house.

Next slide:
Now, here we come along, we have a dehumidifier added in here, and we still can't do it. The dehumidifier has an effect, and that's what I was talking about before. It has an effect on what the air conditioner does.

Next slide:
And next slide here we'll see what -- see how running that dehumidifier in that home and trying to pull that house down actually decreases the amount of water taken out by the air conditioner. A little bit more is removed but not much. Not the full impact. So if the air conditioner responds to the humidity level, and as you keep lowering the indoor dew point, the AC takes out less moisture. So the two must be compatible, or else you don't get the benefit.

Next slide:
Now, we're going to fix this thing. And I'm going to jump right to the fix. I'm not going to tell you why, how or what. But what we're going to do is optimize this AC. And we're going to fix this AC so it takes out the amount of water it ought to. Up here at our previous condition, this AC would take out 27 pounds of water an hour at this high humidity condition. When we're running at our 75 / 50, where he wants to be in the first place, we fix that air conditioner so it takes out 15 pounds of water an hour. Well, wonderful. So what's that all about? More explanation needed, right?

Next slide:
This shows the interaction of the dehumidifier with an optimized AC. First I'm showing you just adding the dehumidifier. The adding the dehumidifier also takes away a little something from the optimized AC; it reduces its water output. But now we can take out something in the area of 20 pounds of water an hour running both of them, and we can get that house down to 50 percent, which, running the lazy AC with the dehumidifier, we had very little effect on that house.

Next slide:
So how do we fix it? What's that all about? Well, the key to that is, that it's all about the air flow flowing through the evaporator coil. We have a compressor outside the house that's going to give it capacity. And it does so much cooling.

Next slide:
And the more air we put over the coil inside, the less dehumidification we get. This specification is for a typical 5-ton heat pump, in fact, it's the one for the one that was in this house. First we're going to look at total capacity. We needed something like 57,000 Btu. This is total capacity. I hope you can read those numbers. But 5-ton will take out 57,000 Btu to 60,000 Btu, depending on the flow. And then the flow. Here's our cfm -- cubic feet per minute of air flow over that coil. And as we decrease that flow, the coil gets colder. A greater percentage of moisture is taken, of heat is removed in the form of latent water condensation on the coil, and less sensible. We're going to blow that up a little bit. Just focus on this part we're concerned about instead of all these ... A good design engineer would look at this, but many contractors -- this is a very difficult chart to read and determine what you want to do. They typically fire these things off then deal with the problems. They've usually got one guy in the organization that will follow the install and try to do a setup. Sometimes he understands these problems; sometimes he doesn't. But let's take a look here at the difference. That original AC was running up in the area of about 2,100 cfm flowing over that coil, at a 50-degree coil temperature. It was taking out about 10 pounds of water an hour. But by slowing that down to 1,750, we were able to increase that dehumidification capacity 50 percent, of that same AC. It also had the effect of slowing down the sensible cooling, which gave us longer runs. So we had two benefits. Longer cooling runs and much more moisture removed. Next slide.

Next slide:
So you see air flow. It's all about air flow after you get the install. How do we verify that we've achieved the desired effect? Or if you were an installer or the guy that sets it up, what would you do to make sure this thing was really working right in the first place? Well, the easiest thing for an installer or a service tech is to measure the suction pressure. Next slide.

Next slide:
And there's a chart right on the gauges that will tell you what the given refrigerant (next slide)

Next slide:
... what the given refrigerant, will tell you what the coil temperature is. So that's the professional way of doing this. So you look at the chart. You slow the air flow down until you get the coil temperature you're after. We're looking for 45 degrees, with typical outdoor conditions. And now we've got an AC that's working at least at setup. Trained AC techs know how to do this. Change air flow through the cooling coil to get the desired coil temperature.

Next slide:
Now, another way you can do this. You can measure the temperature and relative humidity of the air coming into the house at the closest register to the air handler. And if you look at the temperature, you look at the percent RH, you can quickly get down to what is the dew point of that air. Well, that dew point of that air is going to be a few degrees above the coil temperature. Possibly as much as 4 degrees or 5 degrees above the coil temperature. So you're looking, if you want 75 and 50 percent, that's a 55-degree dew point, you want about a 48-degree, 49-degree supply dew point to the home.

Next slide:
The other thing you do is measure the amount of water taken out from that chart -- those latent Btu, 1,050 Btu is a pound of water. So you can measure how much water is coming out of an air conditioner, if you measure for 15 minutes, and score that's how much of water -- how much water is coming out in an hour. Now, one of the things you want to remember when you look at this part of it: It takes 30 minutes for an air conditioner to load up the coil in the pan before it starts dripping to the drain. So you've got to wait 15 minutes or a half-hour until it's dripping, and now you can start measuring. You can measure for a given amount of time, equated to an hour, and you're in business. The goal is, you'd like to see 3 pounds of condensate per hour per ton under normal load conditions. This tells you that you've got an air conditioner that's working quite well.

Next slide:
What does it really look like at the air conditioner? Well, we've got 75-degree air going in through a fan. We've got a cooling coil of some temperature, depending on this flow. We end up with a coil temperature. We end up with a dew point air coming off of it. We end up with pounds of water removed. First of all, what does it require? We have to have functioning components. And like I said earlier, when you have a house that's not being controlled properly, the first thing to mistrust is the system, the mechanical system. The correct amount of refrigerant, unrestricted air flowing through clean-outs, outdoor condensing coil, obvious things. Again, the technician, they know what to do. The quantity of air flow through the inside cooling coil determines the sensible and latent removed. That's simple enough. Looking at the air conditioners, we've been talking about the lazy ones, they typically, less than 3,000 Btu per ton, 2,000, 1,000, sometimes not. You can imagine what that's like. Two pounds of water of dehumidification, the first pound of condensate to get the coil wet. Lazy flat-ton AC might remove something in the area of only 10 pounds, where it's capable of at least 15 or even more. Some contractors are very aggressive with this, and they'll set that coil temperature down even to 43 degrees. Now, as you go colder on your coil, you've got to keep in mind, you're going to be prone to having more condensation problems on your grills and your ductwork. So you can't get crazy with this concept.

Next slide:
Let's review how the AC operates. Well, I think the main message here is that when an AC comes to the end of its cooling cycle, this water, this kind of took the water on that coil so it started draining down to the drain. That water at the end of the cooling cycle -- whatever amount it took is going to come back into the house, re-evaporate, rehumidify. So there's a message in this.

Next slide:
One thing is we want to stay on the fan auto mode as opposed to being fan on all the time, which re-evaporates that water quite quickly. Green-grass climate: Adjust the AC coil to get our 45-degree coil. Under typical conditions it creates the thermostat dead band to increase the length of the cooling cycle. Anything above that at all. But thermostats, these new digitals, are capable of a half-degree turn-on, turn-off. We'd like to see something at the 1 to 3 degrees difference between turn-on, turn-off. That's the dead band. That will dramatically lengthen the cooling cycle, which increases the amount of water down the drain. Always auto mode when you're struggling in a house. Fan is going to be on only when the compressor is on. This is similar to the ideal home setup. Five ton removes 15 pounds of water an hour. Nothing wrong with that.

Next slide:
Cold coil specs: I'm going to go back here and -- I showed you what Lennox's specs look like. This is what happens under a given load condition to a system when it runs. First of all, we've got 55, 50 percent air going into an air handler. And the amount of it is about 363 cubic feet per ton. The air leaving is 52 degree dried-out and the 90 percent relative humidity. That'll take on about 14 pounds, 15 pounds of water per hour to the drain. So that's how that looks.

Next slide:
The lower the flow of air, the more water removed. Here's the gold standard. Going back to the house, we went right back to the house that had the dehumidifier, that had the system that was the lazy AC. Now it's got an optimized AC in it. It's got our same load conditions, part load conditions, our same family. They've upped their moisture output a little bit. They maxed it up to 4 pounds, kicked it up a notch. We're able to hold 75 percent, 50 percent with our Ultra-Aire and our air conditioner. They're not fighting each other. They're getting along. That air conditioner is removing much more water. Now we're going to go one step farther. We're going to do the other part of indoor air quality. We had our air flow infiltration rate 0 to 200 cfm. Well, if the wind isn't blowing and it's a calm day, how much air gets in that home? If the clothes dryer, bath fan, or kitchen hood is not running it may be near 0. So what's a person to do? You really ought to have some minimal amount of fresh air on that home. So whenever this house is occupied, that fresh air is being brought into that home. And fear strikes the heart of any contractor when you talk about bringing in fresh air, because he knows that it means more load, more difficulty. How can you bring in outside dew point air, 72 degrees, and keep the house dry? Well, here's how you do it, and you don't have to be afraid of it. Another thing about infiltrating air or powered-in fresh air: It slows down infiltration. When you're bringing 100 cfm of air mechanically, you don't have a 200 cfm of infiltration. If the wind was strong, that would drop to 125. That much of a penalty to pay to have fresh air when occupied. Voila. Fresh air reduces infiltration. AC, dehumidifier, and air conditioner keeps up with the part load condition. We looked at what worked with a no-load condition. The gold cup, huh? The ultimate result of what we're looking for.

Next slide:
Proof of analysis? Well, we finally fixed that home in Texas. Worked well. If you look at the relative humidity on it, it's almost a straight line. It is quite impressive. And even in no-load or low-load, if the equipment is sized right, set up right, this is what you can expect.

Next slide:
Well, Ben Franklin. We had support from yesteryear. A statement I came across by Ben Franklin. I say he was ahead of his time, unbelievable. Here's what he said: "I considered fresh air an enemy and closed with extreme care every crevice in the room I inhabited. Experience has convinced me of my error. I am persuaded that no common air from without is so unwholesome as the air within a closed room that has been breathed and not changed." So that's quite an impressive statement of yesteryear. Sounds like my forefather, huh? Well, here's another little plug. I'm going to go back a slide here. Another little plug for if you do have any interest in this HVAC dilemma and you need a little advice, I suppose anonymously, you might look at the HVAC Talk. I'm one of the moderators on there. And we've got a lot of people that know what they're doing, a few that don't. But they all seem to catch on. You know, if we can't convince our brethren of the error of their ways, our thinking may not be sound. But you'll enjoy that. It's an opportunity to ask some questions and to get some opinions.

Next slide:
In summary, to cover all your bases. Size the HVAC according to Manual J and Manual S. Also, ductwork: Make sure it's designed -- somebody should be checking the ductwork to make sure that it can handle the flow. We are in a situation, like in southern Florida; a lot of ACs are working well because they have such lousy ductwork systems. They're so choked that the air handlers are pushing as hard as they can. And they just can't get enough air through there to get the coil temperature up to 50 degrees. So they get up to 45 degrees, 43 degrees. We end up with air conditioners that remove a lot of water. Set up the HVAC properly, optimize it as opposed to lazy or random. Have someone look at it who knows what they're doing. Install a whole house dehumidifier to handle low- / no-load, partial conditions. You can consider other things. You can tweak an air conditioner to improve its performance. You can add reheat to make it do the job. When you look at all those ways, they are a little more energy-intensive to solve the problem. Under certain conditions, if you have very occasional high latent, you might consider them and it might be valid. ... Oh, you don't have that last slide. OK. It has sort of my email and everything. I think you'll have to add that before she sends this out to you. I'm open to questions.

Jamie Lyons:
Great. Thank-you very much, Ken. Let me queue a few up for you. Let me start with a general one, then I'll offer up a specific one. A few slides ago, one of the recommendations was adjust the thermostat dead band. Can you comment on how that would be done?

Ken Gehring:
Most modern thermostats have got an actual dead band cycle setting, or they have how many cycles an hour. And you can tweak that to extend the dead band of -- you may have to contact somebody technical at the manufacturer of the thermostat. And they also can tell you how to extend that.

Jamie Lyons:
OK. But it is a configurable setting on a thermostat?

Ken Gehring:
On most of them it is, yes. On most of them it is.

Jamie Lyons:
OK. Here's a more detailed question; I'll try to summarize the key points. So it's a zero-energy home in upstate New York. So, probably a climate zone 5, maybe 6. It's very tight construction. There's a minisplit with a capacity of 9,000 Btu for heating and cooling. And then there's a small HRV -- it's a LUNOS system, which is a small, high-efficiency, HRV ventilation component. On occasion -- there's an apartment as well as a main home -- on occasion the indoor humidity gets up over 60 percent. The occupancy is two people and a yellow lab. So given all that, the minisplit, the HRV, are there any other strategies that they can incorporate? They do use increased back ventilation fans to exhaust moisture out that way. Any other options to lower the RH?

Ken Gehring:
Technically, you should look -- have someone look at the minifan to make sure that that unit has got as slow a fan as possible. Another problem with some brands is that the fan wants to run all the time. And of course that wipes the moisture off the coil quickly back into the space during the off-cycle. So that's another little problem. But adding dehumidification is certainly a solution to it, after you have made sure that you've got the minisplit optimized from the standpoint of the coil temperature. Things like filters. You know, a dirty filter slows air flow, makes a colder coil, removes moisture. A thicker filter reduces air flow, lowers coil temperature, removes more moisture. A freestanding dehumidifier in a small space that's located out of the way, sitting over a drain in a laundry room or whatever, you know, that's another way of helping this whole thing. Occasionally over 60 percent, not all bad. Might be personal preference to want it drier. Consider putting the lab up for adoption. Ah, that's a joke.

Jamie Lyons:
Thank-you. OK, let's wrap up with one closing question here, and then rest assured, everybody, the slides will be sent out to you, as well as the recording of this session will be made available on the DOE Zero Energy Ready Home website. Thank-you, also, for your patience in sticking with us through the technical holdup earlier. So Ken, a final question. There's a couple in this area. What's the best way to control the air flow through an older, existing, constant-volume air handler? Are there options to be able to modify that?

Ken Gehring:
Yes, there are. You know, all these air handler fan blowers have got taps on them that usually have variable speeds. So you pick -- you keep lowering the tap speed until you get down to what you want. If you can't get there, if you can't get low enough where there's no in-between, you might look at the quality of the filter. Improving the quality of the filter. Increasing the restrictiveness on it, like, you know, adding some kind of coarse cloth or running a little dirtier filter. All these things influence air flow. Worst case scenario, you can add a damper to your system, on the supplier return of the air handler, to induce some restriction. It doesn't have to be much. And it'll accomplish the mission to optimize the amount of moisture removed by the AC.

Jamie Lyons:
Fantastic. Thank-you, Ken, and thanks, everybody, for joining us and sticking with us through the session. Again, look for an email with follow-up. We'll include Ken's contact information in there, as well as the slides from today's session. Thanks again for your time, and you guys have a great afternoon.

Ken Gehring:
Thanks for the opportunity again.