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36 minute read
Steve Rogers, head of The Energy Conservatory (TEC), leads one of the most influential companies in HVAC. TEC’s True Flow Grid has transformed how many Amply customers approach home analysis and system design—and in this episode, Steve explains why airflow and duct analysis are crucial for building efficient, high-performance heat pump systems.
Steve is an engineer’s engineer, the kind of person who creates detailed spreadsheets—just for fun—to balance every tradeoff in heat pump selection, from comfort to cost and efficiency. In this episode, he brings that same rigor to topics every HVAC pro needs to know, including:
- Air flow and heat pumps
- Duct placement and why leakage can double the load
- Envelope vs. duct leakage and their impact on performance
- Ducted vs. ductless systems and when each is optimal
- Best-case vs. worst-case scenarios for heat pump installs (and how to avoid costly mistakes)
Listening to Steve is like taking a masterclass from a professor who makes complex concepts easy to understand. If you’re ready to elevate your expertise in heat pump design, this episode is for you. Don’t miss it!
Show notes
- Steve's LinkedIn
- The Energy Conservatory
- The TrueFlow Grid on TruTech Tools
- The National Comfort Institute
- measureQuick
- Bryan Orr's HVAC School
- Kristof Irwin's Building Science Podcast
Transcript
[00:00:00] Steve Rogers: worst case scenario is somebody's trying to put in a four ton heat pump because that's going to cover, all the load at a cold design temperature, but the ductworks are really only suitable for two and a half tons. The fan is going to try to push enough airflow, but it probably can't.the static pressure is going to go way high. And the airflow is also going to be reduced. to the point where the system is locking out on the high head pressure limit, and In some cases It'll lock out permanently until the technician comes to reset it. And then the homeowner's operating on backup heat they realize maybe a month later they've been heating with the electric resistance for the last month.And in that worst case scenario, they don't understand why is my energy bill three times what it should be. they just blame it on the heat pump. this is what Russ King likes to refer to as the, the great heat pump revolt of 2025
[00:01:00] Ed Smith: Welcome to the heat pump podcast. Our goal is to ensure the transition to heat pumps goes well. For everyone, homeowners, contractors and the planet. Today, we welcome Steve Rogers. In addition to being Captain America, Steve is also CEO of The Energy Conservatory. The Energy Conservatory manufacturers precision diagnostic equipment and develops processes used to solve comfort, energy, durability and air quality the problems in buildings. You may know them. As makers of the True Flow Grid. Steve is an engineer's engineer and home comfort system design. is near and dear to his heart. We start by learning more about Steve. And The energy conservatory.
And then we dig deep into where our worlds intersect. Heat pumps and home comfort. We discuss. Air flow and heat pumps. Duct leakage and heat pumps. On envelope leakage. Heat pumps. Ducted versus ductless. And more. We. I get pretty darn nitty-gritty into heat pumps system design and the technicalities. So if nerding out on that is as exciting to you as it is to us. Join us for this episode.
[00:02:08] Ed Smith: Welcome to the Heat Pump Podcast, where we tell the stories of entrepreneurs who are fueling the transition to fully electrified homes. I'm Ed Smith.
[00:02:17] Eric Fitz: And I'm Eric Fitz. We are co founders of Amply Energy.
[00:02:21] Ed Smith: Today we are thrilled to welcome Steve Rogers, CEO of The Energy Conservatory. to the show. The Energy Conservatory is doing fascinating work. Steve, at the recent NCI Summit, it was a competition between TEC and MeasureQuick and you and Jim Bergman who got the most shoutouts. In every presentation.
We're really glad to have you. Would you tell us a little bit about what TEC is first? and then we want to learn more about you too.
[00:02:52] Steve Rogers: The Energy Conservatory is a manufacturer of equipment, that is used for, Testing energy efficiency and performance of buildings, of ductwork, and airflow in forced air systems. That's the measurements that we play in, and a lot of what we do is just driven by building codes, but more and more, we're finding out that. performance HVAC professionals and people who are interested in moving into heat pumps need to be more concerned about making sure that the equipment is operating optimally and that they know if there's risk In the building itself or in the duct work that could cause problems with,a new high performance install. we're a manufacturer based outside of Minneapolis, Minnesota, I've been in business for 30 plus years. It was, early eighties when our founder, Gary Nelson, started the company.
[00:03:50] Ed Smith: we'll come back to the Energy Conservatory. Tell us more about you though, and your career path and how you landed as leading the Energy Conservatory.
[00:03:59] Steve Rogers: Yeah. So I began with the Energy Conservatory in 2015, as a result of, some career changes that I'd, gone through. So I'm fairly new ish to, HVAC and home performance. what I did before that was actually quite closely related. I worked for an instrument manufacturer for almost 20 years, that manufactures equipment to measure pressure, temperature, level, and flow in more industrial settings. As opposed to, buildings and HVAC, it turns out that pressure is measuring pressure and measuring airflow is measuring airflow. And so,those 20 years I spent working in this instrument manufacturer are very directly applicable to what the Energy Conservatory does. I met with Gary for my first interview in 2015 and within 10 minutes, I felt oh, these people are speaking my language.
We start talking about flow conditioners and orifice plates and flow laboratories and why it's difficult to measure flow as opposed to water. Other things that are simpler to measure. I felt like I'd found my people and this was a home for me.So I started as engineering and operations manager energy conservatory in 2015 and then in 2017, I bought the company from Gary Nelson, its founder.
He was looking for a successor. then in 2019, I brought on Bill Graber as a partner in the company to focus on the sales and marketing side. We had a sales and marketing manager who was retiring. So Bill's been a great fit for that role.
[00:05:39] Ed Smith: I didn't realize you had purchased the company.
That's very cool.
[00:05:42] Steve Rogers: the next question I want to ask Is the true flow grid your baby? Did that exist at TEC before you arrived?
Yes. many people don't realize that the TrueFlow grid is actually version two of the product.there's a version one of the TrueFlow, which has been around for more than 20 years.and it was the result of someand research that was done about 25 years ago.
TEC was the commercial, part of the research and it resulted in the original TrueFlow grid. So, no, that it's not my baby. But what I will say is my baby is the app. The original TrueFlow grid would give you the same accurate airflow. Measurement that the new one does, but there wasn't a lot of guidance about, where to measure the pressure, how to measure the pressure. It would just give you a number. You've got, 1, 237 CFM. And that left a lot of HVAC practitioners kind of scratching their heads and going, Is that good? because if we can't boil it down to CFM per ton, if we don't know what the capacity of the system is, we don't know where we're measuring pressures in the ductwork, we're not getting a complete picture and we're not really helping people. recognizing that we knew how to measure airflow, in a forced air system by replacing the filter with this TruFlo grid, we set out to make a version two, which was,Bluetooth enabled would talk to the app.the original TruFlo actually had tubes attached to it. So you had to like snake the tubes out through the filter slot. It was really, quite complicated. And then it had to be used with our really expensive blower door manometer.and so that made it expensive And not as useful because it wasn't helping you interpret the results. so we set out to make the grid cheaper, which it is substantially cheaper than the, original We released the DG 8 manometer as, you just need a simple basic single channel manometer, to go with it. And I think if you compare, the time of its release, The original TrueFlow to the new TrueFlow. The new TrueFlow is priced at 60 65 percent of the original device and that was intentional because we needed to get this into the hands of more people and make it more widely available.
Applicable. if you look at business trends, it's not often that version two of a product way cheaper than version one, we knew that was important that we knew that that was a part of the problem of getting this into more people's hands was making it cheaper and easier for them to use. and helping you to interpret the results.
[00:08:24] Eric Fitz: I've never used the old product, but just seeing the new product, man, it's magical.
When you can these accurate measurements, so quickly and easily. And then to your point, you're not left thinking, what does this even mean? You actually have. Context. Because a number by itself doesn't actually mean anything. It's the context around it that actually tells you, hey, I've got a problem or I don't have a problem, and then helps you figure out, okay, what are the potential solutions for if I do have a problem?
[00:08:54] Steve Rogers: Yeah, that was exactly the objective is to help people take that next step of, now what do I do with this number?
[00:09:00] Eric Fitz: Awesome. Tell me about, How airflow and heat pumps are related and maybe why, airflow measurements are particularly important for performance equipment like heat pumps
[00:09:10] Steve Rogers: heat pumps, in terms of efficiency, there's basically no airflow that's too high.but anybody who has been involved in installing heat pumps and working with customers knows that The problem with airflow being too high is that now the supply temperature can get really quite low and that can cause uncomfortable cold blow kinds of problems. if you want the most efficient heat pump ever, you might be pushing 500 CFM per ton, even 600 CFM per ton. might be causing some comfort problems too. So we want to aim for more around 400 CFM per ton. Now, if the airflow gets too low, you start to have a different problem. And that is that you're not taking heat away from that condenser coil fast enough. And now the refrigerant pressures start to rise and you can have problems with. locking out on high head pressure if your airflow a heat pump gets too low. And that's the challenge with heat pumps is you've got this Goldilocks zone around 400 CFM per ton that if you want it to,last and optimize comfort and efficiency, you need to it close to 400 CFM per ton.
[00:10:21] Ed Smith: Does that insight, Steve, differ for ductless versus ducted heat pumps?
[00:10:29] Steve Rogers: the reason it differs between ductless and ducted is because, with a ductless system. There's not really much you're doing to affect the airflow. The only thing that affects the airflow of a ductless system is whether it gets dirty, And of course the airflow goes down if the filters or the blower wheel start to get dirty. otherwise it's going to have the same airflow it would have in the factory. With the ducted system, you have this whole duct design that, it has been designed either correctly or incorrectly, or in many cases was already there before you tried to put the heat pump in. And so now you've got this air handling system that's trying to move the right amount of air. but the pressure loss of the duct work may be too high to do that, or it may be just fine. And so we're just. on the cusp of releasing an update to the app, which will allow you to forecast what static pressure you're going to have at the target airflow for a new system. So once you measure the existing equipment. You'll get some static pressure measurements at an airflow. And once we know what the static pressure through the supply ducts is at a particular airflow that we've measured, now we can easily calculate what that's going to be at any other airflow. And so that will allow us to help practitioners make sure that only have I picked the right heat pump capacity for the building, but that heat pump that fits the house going to be needing to move too much air for the ductwork that's in there? So we're going to measure the existing ductwork and then give you guidance on, how much airflow can that ductwork handle before the static pressure gets so high that it's going to cause noise problems and start to reduce the airflow.
[00:12:25] Ed Smith: Love that. And this has come up a few times. Eric and I just advised a friend who didn't totally listen to us, who went with a new heat pump, who the installer just walked in, sized it based on eyeballing the house and said it's going to work fine. And we're like, did he, did he measure the ducts? Did he do any?
No, didn't. Okay. So let's say that's the worst case scenario. I'd actually be curious, given your expertise, Worst case scenario, what can happen to the homeowner if that happens? And then maybe paint the other one of a best case scenario of what would an ideal process look like, if you take the ducts as fixed, basically, like you're not going to do a whole bunch of duct rework.
What would they do to figure out that they're putting the right system in for the home, given the ducts are what they are?
[00:13:11] Steve Rogers: you're rarely going to have the budget to replace the entire duct system. If you do, great. Replace the duct system, Follow manual D, but that's rarely the case. But what does make practical sense in many cases is to increase the size of the filter, or maybe, in the Midwestern and, Northeastern systems where you have the system in a basement and you've got a drop coming down from the trunks on the ceiling, down to the, furnace or air handler, on the floor, drop can often be increased, in size. When you replace the furnace or the air handler and that can increase the airflow. So let's assume you're going to make minor renovations or you're just going to replace the filter and the app will guide you through those cases. worst case scenario that you mentioned is somebody's trying to put in a four ton heat pump because that's going to cover, all the load at a cold design temperature, but the ductworks are really only suitable for two and a half tons. So what happens in that case is. The fan is going to try to push enough airflow, but it probably can't.the static pressure is going to go way high. That's hard on blower motors. And the airflow is also going to be reduced. to the point where the system is locking out on high limit. And, the high head pressure limit, and different manufacturers do different things with that limit. In some cases it'll be, one strike and you're out, it will hit that head pressure. It'll lock out permanently until the technician comes to reset it. And then the homeowner's operating on backup heat they realize maybe a month later because they got a huge energy bill they've been heating with the electric resistance for the last month.other manufacturers, it might reset each time it cycles. but in either case, if the compressor is getting locked out because of high head pressure, then the heat pump is not running nearly as much as it should be. and so rather than having this great four ton heat pump that covers almost all of the load, way down near your design temperature, You might be covering very little of it because it locks out every time you try to run it. So that's a worst case scenario. And in that worst case scenario, they don't understand why is my energy bill three times what it should be. they just blame it on the heat pump. this is what Russ King likes to refer to as the, the great heat pump revolt of 2025 that we're trying to avoid
[00:15:43] Ed Smith: Yep.
[00:15:44] Steve Rogers: by making sure things get designed correctly. whereas in a case where, say it's that same house, it has ductwork that's only suitable for two and a half tons of heat pump. and that means that. Either our electric resistance by design is going to run a little bit more, or maybe we've looked at the loads and we said, okay, this is a better candidate for a dual fuel system. in that case, we end up running the heat pump as much as possible, assuming we've got our control set up to run the heat pump as much as possible. And then when it gets too cold, it's either adding some electric resistance to maintain temperature, or it might switch over to a gas furnace on those coldest days. to pick up the load. so what the homeowner notices when the airflow is set correctly and we're sized correctly for both the load. and for that existing duct system, notice a fairly smooth transition from heat pump to whatever the backup source is. They're comfortable, and especially because heat pump is running more constantly, they're probably going to notice fewer fluctuations. It's more like you're getting a two or three stage system. even if you have a simple one or two stage heat pump, you might get two stages of heating and then it switches to your furnace and then that's like a three stage system.
And, I'll just say something here that people may not realize. When you do a heat load calculation, figure out how many BTUs does this house need at its design temperature.and a lot of people mistakenly think that if I can only get halfway down to that design temperature, Maybe I'm only covering of the annual heating load, but that's not the case because even in really cold climates, most of your hours get spent around freezing.
Even in Minneapolis, we spend way more hours between 20 and 40 than we do in the summer. Below zero and that's true of almost all, all cold climates that there's a lot of hours around freezing. And so even if you think you're only covering halfway down to the design temperature, you might be covering 70 percent of the annual hours and of the annual energy that's needed to eat that house.
[00:18:03] Eric Fitz: such important nuance, we got to get that word out to more people that it's not a, it's not a linear relationship between that design temperature and, actual performance of the equipment or energy consumption. the bin graph of how many hours are you spending in 5 degree increments for the year,Any location in general, it's a curve, like a bell curve and that the middle point of that curve is typically around the freezing point. and not way down in those cold temperatures. And Steve, the other thing I think you mentioned, it's. Important to clarify. So in this scenario where we've got, the ducts are fixed, we've got, we're capped out.
Let's say at 1200 CFM as all that, keeping static pressure is reasonable, that's the maximum flow that we can handle in this, duct system. The reason why that still works potentially, with a, a dual fuel system scenario where you've got the heat pump and you have a furnace as backup is that the furnace typically has a higher. Delta T. It's got a higher discharge temperature from the furnace, you can get more, BTUs delivered in that air, and you're able to, keep the house comfortable. the challenge is that with the heat pump, typically are slightly lower, Delta T. in order to deliver the same BTUs, you need to, you end up needing to have that higher flow rate. But if you're, if you're capped at flow rate, the only other option is to increase the delta T in some way to be able to stay at that same flow.
[00:19:31] Steve Rogers: yeah. And whether it's a furnace that's just putting out much warmer air or. Even when you run electric resistance as the backup, the electric resistance is actually also causing a higher, supplier
[00:19:43] Eric Fitz: Right.
[00:19:44] Steve Rogers: Either way, you're just packing more BTUs into the airflow because the air is hotter.
[00:19:48] Eric Fitz: I've heard anecdotally, there are more and more, particularly cold climate heat pumps that are, getting to higher, Delta T's. and interestingly, not all furnaces are equal as well. particularly if you get into, condensing really high efficiency furnaces, there are scenarios where those furnaces can actually have a lower Delta T than a typical high performance heat pump. it's, there's a lot of nuance, to, to keep track of.
[00:20:16] Steve Rogers: Yeah, and that's something that Jim Bergman brought to my attention. He said, look at the airflow on this. And this was not even a a high efficiency furnace. It was an 80 percent furnace, the Delta T range was like 25 to 45 degrees temperature rise. That's heat pump territory. HVAC practitioner needs to know, even if you're just doing furnace swaps, you might need a lot more air than you used to because that new furnace is designed to move a lot more air than the old one was.
Okay.
[00:20:45] Ed Smith: So there's a lot of discussion in general in the industry about. addressing the envelope of the building, particularly when you're thinking about heat pumps. what your thoughts are around, doing weatherization, with a heat pump system or not.
[00:21:00] Steve Rogers: I'm going to go at this a little bit backwards and start by saying, yes, improving the building envelope is a good idea when you're evaluating a home for a heat pump. If there's that's outside of conditioned space, that's potentially a much bigger problem and should be a higher priority than working on the envelope. And let me explain why that is. There's something that we call duct leakage to outside. this happens anytime you have ductwork in an attic or a crawl space, which is vented to outside. if your attic is sealed, that's a different situation. If your crawl space is sealed, that's a different situation. when that ductwork leaks, there's two different things that happen, and they compound the problem. going to take an example of a problem that we were helping an HVAC technician with in Miami, I'm going to adapt the numbers to be heating since we're talking about heat pumps, because it's exactly the same phenomenon that happens.let's say you've got ductwork in the attic, And it's leaky. the technician was taking a complaint that the system's not keeping up. we'll adapt this to heating and say that, homeowner sets the thermostat to 72 degrees and on cold nights, it's getting down to 65. The HVAC technician does a load calc and determines that. On that design night, there, the heating required should be four tons of heating. That's what the house needs and this is a four ton system. So why is it not keeping up? we've done our manual J, we've done our load calc, took our static pressures, that's not the problem, but it's not keeping up.
It's not keeping the house warm. what this technician discovered is that there was significant duct leakage to the outside. In this case, it was leaking about 300 CFM.out of 1200, that's 25 percent of the conditioned air that just goes out the vents in the attic.
It just went outside.and Now we've got a four ton heat pump that's only really putting three tons of heat back in the house. 25 percent or one ton of the heat just blew out the holes in the attic. So that's fairly easy to understand. the thing that's a little trickier to understand is the second part and why this is not just a problem, but it's actually a double whammy problem. The second part of the problem happens if the Air handler is sucking 1200 out of the house and it's only putting, 900 CFM back into the house. Where does the other 300 CFM come from?
[00:23:48] Ed Smith: Yeah, it's coming from outside.
yeah.
[00:23:49] Steve Rogers: So we, we know that it does come from somewhere because if the air doesn't get made up, then the house would implode. Okay. But that's, that's not a phenomenon that we observe when there's an imbalance, right?
[00:24:04] Ed Smith: Yep.
[00:24:06] Steve Rogers: If you're constantly taking 1200 CFM out and putting 900 CFM back into the house, and you observe that the house did not implode, you can safely assume that there's 300 CFM coming back into the house from somewhere, And the place that that comes from is from outside.The house gets depressurized because you're taking more air out than you're putting back in.
So it lowers the pressure in the house until it can suck those 300 CFM that it lost back into the house. what does that do to the load? if you're drawing an extra 300 CFM of outdoor air
[00:24:43] Ed Smith: Hmm.
[00:24:44] Steve Rogers: that wasn't in your load calc, What's the real load of the house?
[00:24:50] Eric Fitz: Yeah, it's,
[00:24:50] Steve Rogers: case, instead of trying to heat a 4 ton load with a 4 ton heat pump, now we're trying to heat a 5 ton load with only 3 tons of capacity that didn't blow out the attic. this is potentially a really big problem when people retrofit to heat pumps because furnaces are typically oversized by approximately a factor of 2. You have a lot of bandwidth to make up for that problem. If you have leaky ductwork in an attic, and you're running a furnace, it's usually not a problem. But now we convert that house to a heat pump, and even if we've done a good job with our load calc, we tested the ducts to make sure we know how much airflow it will support.
We've got the correct airflow, we've got the correct load calc, andwe've set the air flow correctly at 400 CFM per ton when we set up the system. You can still have a problem because the leaky ductwork is causing this double whammy where not only do you lose capacity, but you actually artificially increase the load on the house as well. the only solution really is to seal the ducts. If you put in a bigger heat pump, now your static pressure goes up and guess what happens? You leak more.
[00:26:13] Ed Smith: Hmm.
[00:26:14] Steve Rogers: instead of leaking 300 CFM, now you might be leaking 400 CFM. so you end up chasing your tail and you can't make up very much ground by doing that. The only solution really is to find the leaks and seal the ductwork.
[00:26:29] Ed Smith: Exceptionally well explained. I feel like I'm getting a personal tutoring session from a college professor. I feel like you didn't answer the question that's on everyone's minds though, Steve, which is what percentage of homes in the U. S. implode every year and how worried should we be about that?
[00:26:48] Eric Fitz: I think the, the impact you provided is fantastic. I'm thinking about all of a sudden you've got five tons of load, but only three tons of capacity.thinking about that, that CFM number, 300 CFM, so a typical engineered ventilation system, whether it's a HRV, ERV, or just an outside air damper. you're typically targeting like 50 CFM, maybe 100 CFM. if you're doing 300 CFM, that's like having your kitchen exhaust fan just going full bore 24 seven, even beyond that, it's a massive amount of air. And if you do a blower door test, pressurize the house to 50 Pascals. is way higher than natural pressure. let's say it's a relatively small home, let's imagine about 2, 000 square feet. you might get a, a blower door measurement of 1, 500 CFM. And that's when you're, intentionally really pressurizing the house. so just 300 CFM, that is a lot. It's a lot of air to lose. It's a, that's a big problem.
[00:27:55] Steve Rogers: it is a lot and it's surprisingly common. research that was done in, leaky duct systems,the type that are all across the south in attics, found that, It was not uncommon to have anywhere between 20 and 30 percent of the total airflow leaking out of the duct system and now that would be supply plus return. But depending on the design of the system, in a lot of setups, your leakage is almost exclusively on the supply side. if the return is in the attic, then you might have, leakage on the supply side and the return side. But we could do a similar exercise with return leakage, and I'll just give you the spoiler.
It's not any better. If the leakage is on the return side, you end up pressurizing the house, but you're sucking in air directly from the attic or from the crawl, which is unconditioned.
[00:28:40] Eric Fitz: So, bad news bears both directions. my follow up question to this is you went into this home, you measured static pressure, you measured airflow in the duct system. And then at some point later, you installed the equipment.
At some point later you discover, oh my gosh, I've got really, Leaky ducts. I've got this issue. go in and I dress the ductwork. I've now sealed the ducts. Do I need to rerun my calcs, remeasure static pressures? how does this impact the performance beyond the leakage piece of the ductwork?
[00:29:13] Steve Rogers: yeah. duct leakage will affect your static pressure. and I don't have. A lot of, information about how much. I can tell you that I had an aero seal done on my 1958 single story,ranch style house in outside Minneapolis. And my leakage was sealed from about 175 CFM of leakage down to about 25.and my static pressure, hardly changed at all. It was like I did a True Flow before and a true flow after and the static pressure was the same. could it be a problem? I think the answer is yes, but I think the leakage area, even if you have really leaky ducts, is going to be significantly smaller than the area of all your supply registers added up. it can be a problem. I don't have a lot of evidence one way or another that tells me. How often it's a problem.
[00:30:11] Eric Fitz: That makes sense. I think the anecdote that I've across is,when you're installing a new system, you gotta get up and inspect the duct work. Make sure there's not a giant hole that a raccoon could fit through in the duct system. As long as you're not dealing with that kind of scenario, yeah, there shouldn't be a massive impact on static pressures.
So that's why I say that duct leakage to outside a much bigger deal than having a leaky building envelope. if you have ducts outside of conditioned space, would prioritize that very highly. If I'm doing heat pump retrofits, that could really sabotage the whole project,
AeroSeal, it's a great product. What does that typically cost? How much does that add to a given project? for like your example for your house.
[00:31:00] Steve Rogers: Yeah. Typical, a couple thousand square foot house. I've heard prices anywhere from a thousand to 2, 000. The thing to recognize about AeroSeal on ducts, like you said, it's a great product. It works very well, but there's a limit to how big the hole can be that they can seal. AeroSeal. And it's about three quarters of an inch. if your ductwork is bad enough that you have several holes bigger than that, AeroSeal is not going to be able to seal them.so those have to get found and sealed manually before the AeroSeal process can start.
[00:31:36] Eric Fitz: Makes sense. But gosh,spending a couple thousand dollars to dramatically improve the probability of a good outcome for the homeowner. avoid those callbacks, and have the system actually perform, the way it's supposed to. a, it's a small amount to consider.
[00:31:52] Steve Rogers: there's ways to do a full duct test and duct screening. There's different ways that it can be done, but at least some sort of a screening to know if you've got a problem seems very prudent. if you're doing a heat pump retrofit.
[00:32:04] Ed Smith: Alright so Steve, what We covered duct leakage, and I like that, you put the one that's more often overlooked, but potentially a bigger issue. How about envelope leakage in heat pumps, people talk about permanently reducing the load. what are your thoughts on that?
[00:32:24] Steve Rogers: opportunity to look at, a permanent load reduction on the home. that's important for similar reasons to what we've been talking about. If you're heating with furnace or a gas boiler and a hydronic system, typically you have way more capacity than you're ever going to need. What that means is that If the house is drafty and leaky and poorly insulated and has been for years, you might find that when you want to do a heat pump retrofit, you now have much more trouble keeping up and that backup heat, whatever it is, needs to run a lot more than you expected it to. let's do a blower door test. Let's do an insulation inspection. Do we have, four inches of insulation in that attic? Or do we have 40 inches of insulation in that attic? Because that will make a big difference. And, looking at windows as well, if we've got old single pane windows,that was an opportunity to look at that. because it, it just increases the odds of success, typical for a furnace is 000 BTUs, but really the biggest residential heat pump that you can get only five tons or 60, 000 BTUs. And that's when it's reasonably warm out.there's just, way less bandwidth to deal with, a house that's got a much bigger load than you anticipate when you're dealing with heat pumps. And so it's not going to be the case that every homeowner has the budget to be doing air sealing or insulation or windows at the time that they do a heat pump retrofit.but. If it's, I think, advisable to talk to the homeowner through that journey and say, you might want to delay the heat pump until you've improved the house and maybe your journey is to work on the building envelope first then, next year or the year after that, then we'll do the heat pump because you'll be much more successful and there's no sense in replacing the system with, an replacement.
80, 000 or 100, 000 BTU furnace as your backup when once you do your building envelope improvements, you're only going to need 60k furnace as your backup and the heat pump is going to be able to cover much more of that load. every practitioner is going to have their own business model.
I think some are going to be much more,aggressive or maybe encouraging about. Envelope improvements. but regardless of which way, your business is going to steer people, it's wise to say if you don't have the budget to do any envelope improvements, maybe you're a better candidate for a dual fuel system because we're in a cold climate than if you're,if you really want to completely get rid of the gas and go electric resistance, maybe you should wait to do that. Until you've made the building envelope improvements. I think there's a relationship between what's your backup, and are you gonna do building, envelope improvements?
[00:35:26] Eric Fitz: With envelope improvements, the basic things like sealing, around the sill, thing in the attic, maybe adding a few more inches of, insulation in the attic as well. A lot can be done for a little money. a few thousand dollars of, of air sealing, can have a huge, huge impact, reduce those infiltration loads.
[00:35:46] Steve Rogers: Lemme make a plug for finding the people in your, community that know how to do this. So all across the United States, there are people involved in what is called the low income weatherization program. And this is a federally funded program and they're often state grants that go along with it to help people at the lower end of the socioeconomic spectrum with their heating bills and then consequently, since the government is helping with the heating bills, the government can also help with improving the building envelope. significantly reduce the heating load. there's a whole, community, a whole network of people across the country, because I think there's federal money goes to every single county in the United States. And within that community are people who building shell improvements for a living. And because It's funded by government money. They're actually very good at knowing what's the most economical way to do air sealing. a lot of us know about spray foam and the magic that it can do in air sealing an attic, for example. but weatherization doesn't use a lot of spray foam because it's expensive. And so what you'll find is that there's a lot of people who can get it just as airtight. With caulk and one part foam using a little bit of foam and then filling it with adequate cellulose can get just as good a result as somebody who does a spray foam job for a lot more money find out who's doing weatherization in your area because a lot of times they're willing to Work with,privately funded jobs as well.
There may be, weatherization incentives in your area, and they are likely to know about that, but that's a group of people that has a lot of expertise, and can help get the best bang for your buck on those building improvements.
[00:37:44] Ed Smith: That's a great plug.
[00:37:47] Eric Fitz: Steve. The debate on everyone's mind, ducted or ductless. and we know it's not one or the other, but it's been interesting to talk to so many of our customers and hear very strong perspectives on both sides. And I know you've spent more time doing analysis on heat pumps than almost anyone we know.
[00:38:07] Ed Smith: what are your thoughts on this one?
[00:38:09] Steve Rogers: I think ductless is a great solution if there are no ducts, but I've heard people talking about abandoning a duct system, to put in ductless, and that doesn't make a lot of sense to me. So ductless has its advantages. You don't need to worry about airflow, really, with a ductless design.
You just need to make sure it gets cleaned regularly and you'll have adequate airflow. So that's one less thing to worry about. Okay, but there's some disadvantages that don't often get discussed. Such as, how are you going to do filtration if you're ductless? little screens that catch the big dust, that's like a MERV, not even two, filter. So you're not getting significant filtration through ductless heads.if you're concerned about particulates, you got to have another solution for filtering the air. And if we're talking about making building improvements, it often becomes necessary, as you make an older home tighter, to be thinking about mechanical ventilation. So if we're adding an ERV for ventilation, even if we're adding,other devices for ventilation, are we going to distribute that ventilation air? our heating and cooling is ductless. So now you're talking about potentially putting in a duct system, just so you can get the fresh air to the living room and to the bedrooms.if you think about distributing fresh air and filtration, both of which are important for indoor air quality. I think it starts to look attractive to see, can we repair that old duct system? If it's leaky, if it's bad, if it's got damage to it, repairing that duct system might be a better option than abandoning it because now you're set up. To do filtration and you're set up to do, ventilation and distribute that ventilation air well. I think twice before I abandon a duct system, even if it needs work. Because if you've got air going to all the rooms already, the other thing, that's important about ductless systems is, how do you heat and cool? a bathroom that's got a window or a walk in closet that's big enough to need a little bit of heating or cooling. it's hard to do that with ductless heads. You're not putting a ductless head in a bathroom or a closet very often. And now you're talking about, do we need to use,some ductless systems and a ducted unit to Serve those small spaces that are too small for an individual head,and those might not be a big deal in climates, but in the you know in the Northeast in the Midwest where it gets pretty cold know I don't want to use a bathroom on a cold night if there's a window in there and there's no heat source
[00:41:02] Ed Smith: It strikes me that the theme that like runs through all of your answers is know the problem. And use the right solution. And a lot of times it's hard to identify that problem with tools like the TrueFlow grid. You can, but it takes the time to understand, what are you doing? Because if you just have a hammer and the world looks like a nail, you're going to do things in people's homes that are not going to lead to the outcomes that they're looking for.
And there's a bunch of technology that's been released. That can help folks like understand the problem and pick the right solution for it so that you actually lead to the outcomes the homeowner is interested in. Which I think is just a super powerful point.
[00:41:44] Steve Rogers: And that's one thing that both you guys and us at TEC are doing is we're trying to leverage technology You to help people make those better decisions. if you can understand the load calc better, which you guys are just making it easier and easier, and we're trying to make the airflow side easier and easier. Leveraging technology can help us make it easier to understand those problems and apply the right solutions rather than relying on, some traditional wisdom or whatever your HVAC mentor taught you before they retired.
[00:42:15] Eric Fitz: Totally. what are some of the pros, for ductless units you typically
[00:42:19] Steve Rogers: Oh So first of all, if you're So in a that's heated with, hydronic heating system,you don't have to install ductwork to put in ductless. that's a big benefit. the other thing is, we've talked about if you have a duct system, you have to make sure that you're not putting in too much heat pump capacity for the existing ductwork. That's also not a problem if you're going ductless. So with a ductless system, it's almost always going to be possible to meet the entire heating load. With heat pump, they're willing to put in enough heads and enough units to do that, so that's a big advantage of ductless,and,cost will be lower than putting in a duct system.
I think in many cases, I guess I'm not certain, but I'm assuming that putting in some ductless units is going to be cheaper than a larger ducted unit and adding duct work to a house that didn't have it.yeah, there's some advantages there. for ductless. but like I said, my big, head scratcher is why would you abandon a duct system if it's already there?
The only thing that we've seen, from customers who are, are doing that, Is in the scenario that the ductwork is at least part of it is so bad that it'd be so expensive to address. and it's typically not like abandoning the entire system. It's hey, I've got, I've got a relatively small house I've got a, equipment is in the basement and I've got ductwork that's serving the 1st story and the 2nd story of the building. Whatever was done with the 2nd story ductwork, it was just terrible. going to abandon just that second story ductwork. Dramatically drops the static pressure for that first story portion of the system. We can still use,air handler and unit in the basement to serve the first story. And now we're going to use ductwork. Duckless, only in the second story, like that.a scenario where you're really, you're really not abandoning the system. You're abandoning part of it.
[00:44:25] Eric Fitz: yeah.
[00:44:27] Steve Rogers: and you've now got a solution that's a combination of ducted and ductless. And that makes sense. The, one scenario you, you mentioned though, is.in one and a half story houses and in bonus rooms, where we've got that upper story that's never been comfortable.I'll mention another solution that people may not be aware of the reason there's something that one and a half story houses and bonus rooms over garages. in common structurally. Do you guys know what they have in common?
like to call them a frog, the frozen room over the garage. they have, they have an extra surface potentially that's exposed to the outdoors. that's one of them. The other thing they have in common is knee walls.
[00:45:16] Eric Fitz: Hmm.
[00:45:16] Ed Smith: Mm.
[00:45:17] Steve Rogers: And,one and a half story homes andfinished rooms over garages or frozen rooms over garages. I love, love the frozen spin on that.
[00:45:26] Ed Smith: Hmm.
[00:45:31] Steve Rogers: to air seal them properly. And the reason for that is the knee wall comes down, from the sloped ceiling,part way down and often they're, four feet high and down to the floor. think about what's underneath the floor where that knee wall hits the floor.in between the floor joists. It's wide open.
[00:45:54] Eric Fitz: might be some loose fill insulation in there, but there's probably a couple inches gap above the loose fill insulation that basically connects that triangular attic behind the knee wall, which might even be ventilated to outside. the bonus room or to that half story upstairs.
Yep.
[00:46:16] Steve Rogers: the reason that those are uncomfortable and we've been retrofitting those rooms with ductless systems is often because they're super leaky by virtue of how they're constructed. And so if you get, weatherization people involved, they'll look at that. They know exactly how to fix that. They do it. All the time, and they can make that frozen room over a garage into a comfortable room over a garage many times. Now, it might also be the case that the duct work was not adequate. to get enough air to that room. So it's not always the case, but very often half stories and bonus rooms are uncomfortable because they're extra leaky. And also, Eric, you alluded to the fact that that bonus room, if it's over a garage, it might have five sides of the cube. exterior walls, and that's not the case in any other room in the house. And so a lot of times the load calc was just incorrect.
[00:47:19] Eric Fitz: Yep.
[00:47:19] Steve Rogers: didn't realize that for the same floor area, that bonus room. needs twice as much conditioning as a similarly sized bedroom that's in the main part of the house. so it can be a supply problem, as well. but very often it's a building envelope and leakage problem, you might do a blower door number on your house and, and find out that, yeah, in Eric's example, it was leaking 1500 CFM. Yeah, but 600 of the 1500 are coming from just the bonus room. No.
and so that's why that room is uncomfortable.
[00:47:53] Eric Fitz: Totally.oh, this is great.
just around ductless versus ducted,there are a few other trade offs that we come across.
often, putting in a ducted system, if you've got good duct work, apples to apples, that ends up can be a cheaper install. In general, you have fewer pieces of equipment, can end up if you're not doing major modifications to the ductwork, you've got relatively, low labor. so it can be a lower cost, system. One of the key benefits of ductless relative to ducted is that you can often get. really good zoning control. So you've got these multi zone or single zone ductless units, where you can have, granular control on a room by room basis, is one of the, one of the key benefits. but certainly, yeah, the downside is around those, the air filtration, places like Maine and Vermont, New Hampshire, Northern New York, where you don't have any ductwork, people are really happy even though they only have an equivalent of one, two, or three with those. small filters that are on a ductless unit. we're nowhere near like a MERV 13 that you might be able to do with a, central system. but if you've never had any air filtration at all, you're pretty happy to have something for the first time. So it's a big benefit for those types of homes.
[00:49:10] Steve Rogers: yeah.
[00:49:10] Eric Fitz: And so the need for zoning control is often another symptom of an envelope that's leaky.and and the other thing about, infinite control, my understanding is there's a difference between multi heads, And, one to one mini splits in this regard, and that you need to be sure that you understand, I've heard manufacturers, talking to technicians and saying, I've got three heads on a single outdoor unit, There's a minimum number of BTUs that those heads can deliver if one zone is calling, and so you might be delivering heat to zones 2 and 3 if only zone 1 is calling for heat, because there's a minimum number of BTUs that the outdoor unit produce. And so that's where one to one would give you like a perfect amount of zoning, down, down to zero, but multiheads sometimes have limitations that. technicians need to be aware of.
yeah, that's true. going to multi zone ductless, you don't have to worry about the ducts, but there's some other design considerations you need to think about. don't exist for having a, with a ducted system. it's a great point.
[00:50:22] Ed Smith: So then, the question ultimately is, what is the right system? What is, is there a better heat pump, for a home? how do we provide guidance of how do you get to the right solution?
[00:50:33] Steve Rogers: it's a really complicated thing and I'm concerned that we don't have the tools to make it easy for people to answer that question. If I want to compare of three different heat pumps that I might want to put in my home, are big differences between manufacturers in, how much capacity and what COP, or coefficient of performance, they're capable of putting out. It's really simple with a furnace because, if it's an 80, 000 BTU furnace and it's got 95 percent efficiency, you get the same output at all temperatures, and you get the same efficiency at all temperatures. Okay, but heat pumps don't have that benefit.They're all rated per AHRI at 47 degrees and at 17 degrees. you'll get a COP and capacity at both of those temperatures. But a lot of times you need more than just those two points to really understand how they perform. especially with cold climate heat pumps, because they go flat.
in terms of capacity, and then only at a much colder temperature do they drop off. whereas a standard heat pump has a more or less linear drop off in capacity as temperature gets colder.and so what that means is to find out which one is best, actually have to do what Eric was suggesting.
You have to start looking at bin data or How many hours does my climate spend 35 degrees and 30 degrees and 25 degrees and on down the line until you get down to that design temperature where, you don't have enough hours to worry about and when you do that, find out that, there can be fairly significant differences and, the cold climate model Get you more capacity at colder temperatures, which you need, but maybe it's coefficient of performance or its efficiency is not as good at the warmer temperatures where you spend more of your time. I've done simulations on a spreadsheet where you actually do this at every single temperature. I look at the climate and how much, how many hours does Minneapolis spend at all the different temperatures and what's the efficiency or COP of the heat pump. And then, what is, the, capacity of the unit at that same temperature? And then I have to start looking at, okay, if the heat pump can't keep up, is my backup going to be electric resistance? Or is my backup going to be a gas furnace? Or, in other places, maybe it's a propane furnace. Or even an oil furnace. And then what are my prices of gas and electricity in my city? and it ends up being very, very complicated.
And like I said, I don't think we have good tools to do this. I'm, geek out on it just because I like to know the answers. but it's not easy to find all this information. the answer can change from year to year because last year gas was cheap and electricity was expensive. And this year. Gas is more expensive, electricity is a little cheaper. looking at a dual fuel system like that, the answer can change.the only way that I know of to answer those complicated questions. is to start looking at how many hours you spend at each temperature, to map out the performance of the equipment at all those temperatures, and add it all up for a year's worth of heating, and even a year's worth of cooling if you want to do that side as well. That's the only way I know how to do it, and it's really complicated.
[00:54:12] Ed Smith: So well articulated, and I think we talked about this in NCI, but that's exactly what we hope to build. We just think it's far too complicated, and heat pumps are the future of HVAC, but darn, are they a lot more complicated to design and do right. And so we just want to make sure that
It's easy to do fast and accurately. And it's the sort of thing that like software seems perfectly suited to fix and to solve, but we need the data. This is one of the things we kept coming back to, which, you talked about, the temperature points that we need and we need more than that, layer on latent.
And cause you got to think about what you're doing in the summertime. and it gets really complicated fast.
[00:54:53] Steve Rogers: and to add on top of what all that stuff that I just said, there's another layer here that we were talking about before. And then the last one that we talked about earlier, which is the manufacturer's published performance and the AHRI data. There's new research out that that, It's not reflective of real world conditions. I think, you and I have seen a presentation by Bruce Harley at the,Building Science Symposium. I saw the same data presented by Christopher Diamond, and, this is showing that when they compare the AHRI ratings To the real world performance, they installed heat pumps in a bunch of different houses, I think, in Canada, and then looked at their performance, over a season, the results were that there is not a good correlation between which ones are more efficient and using more energy. And which ones have better AHRI ratings. And that's very disconcerting because we want to know what the real world performance is going to be, not which one, was at or able to better game the AHRI test, to get, A better number.
[00:56:05] Eric Fitz: And this is a whole other topic to delve into for another, another podcast, but, there's definitely some good work being done on this. Like you mentioned, Bruce Harley is working with a number of different organizations to actually develop a new test that will hopefully result in laboratory tests that are actually predictive of real world performance, but there's definitely a lot of work to be done there still.and we're, we're keeping a close eye on it for sure.
[00:56:30] Steve Rogers: Yeah, that's the upshot is I think they've got the ear of people at AHRI talking about we need to make sure that the test that you're running, can more accurately reflect real world conditions and hopefully resolve this issue of, real world tests giving a very different answer from AHRI tests.
[00:56:47] Ed Smith: Steve, thank you. So well articulated, and what a skill you have in taking complicated stuff and boiling it down to its essence and just communicating it clearly. I learned a ton.
you've already shared so much knowledge. If you were going to point folks To recommendations, books, podcasts, organizations, events, whatever, that they can keep learning about some of the topics that we've, discussed.
What would you point people towards?
[00:57:18] Steve Rogers: Everything. Um, you know, so we were at the AHRI summit, or sorry, the, NCI summit a couple of weeks ago. That's a great organization that teaches practical testing, how to make sure that you've got the air side of the system working properly. so they're great. in terms of education, they train tons of people every year, and they're good at it. I would direct you to NCI for, formal training. Their training is outstanding. Their trainers are outstanding. you want something more informal, then follow Brian Orr and HVAC School. his stuff is excellent. of course, follow, Jim Bergman and Measure Quick. looking at the refrigerant side and making sure you're getting that side of things done, correctly. Christoph Irwin, has a podcast. If you want to dig deep into the building science and HVAC design, he goes pretty deep. It's really pretty nerdy, but I like that one.
his company is called Positive Energy, I think the podcast is just called the Building Science Podcast.
[00:58:16] Ed Smith: Great recommendations. Thank you so much, Steve Rogers. We really appreciate you being on.
[00:58:22] Steve Rogers: Happy to be here. It's been great.
[00:58:24] Eric Fitz: Thanks, Steve. Take care.
[00:58:27] Eric Fitz: Thanks for listening to The Heat Pump Podcast. It is a production of Amply Energy. And just a reminder that the opinions voiced, were those of our guests or us, depending on who was talking. If you like what you've heard and haven't subscribed, please subscribe in your favorite podcast platform. We'd love to hear from you.
So feel free to reach out. You can reach us once again at hello@amply.Energy. No .com, just .energy. Thanks a lot.
