In today’s episode, Reuben, Tessa, and Pat discuss heat pumps and their use in heating and cooling homes. They discuss the different types of heat pumps, including air-to-air and air-to-water systems, and the advantages of using heat pumps, such as energy efficiency and reduced fossil fuel emissions. Overall, they highlight the increasing popularity of heat pumps and the potential for them to become the primary heating and cooling solution. Ground source heat pumps, also known as geothermal systems, are another option that provides efficient heating and cooling, but they come with a higher upfront cost. The future of HVAC lies in heat pumps and their ability to efficiently move heat from one place to another.
Takeaways
A heat pump is an air conditioner that can run in reverse, extracting heat from the outside air and transferring it indoors.
Heat pumps can be more energy efficient and environmentally friendly compared to traditional heating systems.
In cold climates, the capacity and efficiency of heat pumps may decrease, making backup systems or hybrid systems necessary.
Efficient homes are better suited for heat pumps, as they can maximize their effectiveness and reduce energy costs.
The HVAC industry is still catching up with the technology and delivery of heat pumps, which can affect their availability and affordability. Heat pumps are a viable option for heating homes in cold climates
The HVAC industry is lagging in terms of knowledge and installation expertise
Ground source heat pumps provide efficient heating and cooling but come with a higher upfront cost
Central air source heat pump systems offer better filtration, ventilation, and dehumidification
The future of HVAC lies in heat pumps and their ability to efficiently move heat
Chapters
00:00 Introduction and Teaser
02:05 Understanding Heat Pumps
06:21 Variable Capacity and Efficiency of Heat Pumps
12:36 Hybrid Systems and Backup Solutions
26:20 Challenges and Adoption of Heat Pumps
32:30 Using Internal Gains to Supplement Heat Pump Performance
34:21 Advancements in Heat Pump Technology
35:17 Determining the Suitability of Homes for Heat Pumps
37:59 The Potential of Ground Source Heat Pumps
39:47 Transitioning Older Homes to Heat Pumps
41:00 The Age of Homes and Heat Pump Compatibility
44:22 Exploring the History of Heat Pump Technology
45:20 The Advantages of Central Air Source Heat Pump Systems
47:35 The Importance of Proper Dehumidification in Air Conditioning
49:00 The Variable Capacity Advantage of Heat Pumps
50:01 Considerations for Elevating Outdoor Heat Pump Units
53:26 The Potential for Heat Pump Systems to Heat Water
56:40 Condensation and Defrosting in Heat Pump Systems
58:30 The Future of HVAC: Heat Pumps and Efficient Heat Transfer
TRANSCRIPTION
The following is a transcription from an audio recording. Although the transcription is largely accurate, in some cases it may be slightly incomplete or contain minor inaccuracies due to inaudible passages or transcription errors.
Reuben Saltzman: Welcome to my house. Welcome to the Structure Talk podcast, a production of Structure Tech Home Inspections. My name is Reuben Saltzman. I’m your host alongside building science geek, Tessa Murray. We help home inspectors up their game through education and we help homeowners to be better stewards of their houses. We’ve been keeping it real on this podcast since 2019 and we are also the number one home inspection podcast in the world, according to my mom. Welcome back to the show, Tessa, great to see you. I am excited that we’re finally getting around on this topic, I teased this a couple episodes ago. We said we’re gonna get somebody on to talk about heat pumps. Didn’t we kinda talk about it on the air? We kinda brainstormed, like we need to get an expert on about heat pumps?
Tessa Murray: Yes.
RS: I think we talked about Pat Heulman in the middle of our podcast, we said we gotta reach out to him and see if we could get him on a guest to talk about heat pumps ’cause I’m kinda incompetent when it comes to these things and Tessa…
TM: Same. Same.
RS: Who’d we get on?
TM: Everybody, happy to announce we have special guest Pat Heulman on today with us. Hi, Pat. Welcome.
Patrick Huelman: Hey, hi all. Yeah, glad to be back.
TM: Good to see you. Well, Pat, when we reached out to you, you’re initially like, “I’m not a heat pump expert.” But I have to tell you, sitting through some of the classes with you this past semester teaching building science at the U of M, you touched on heat pumps and you know way more than you give yourself credit for. You understand all the history, you understand the future, the big picture and you understand the minutia, like the mechanics of actually how the systems work too. So don’t sell yourself short. We are really happy to have you on and kinda pick your brain today about heat pumps.
PH: Yeah, yeah. Well, so it’s fun to be here. And like I said, I feel very comfortable at the high level, I can go pretty deep, but there’s a lot of things happening pretty fast and quick in the field and in the whole area of heat pumps. And so it’s a moving target for sure, but let’s kind of look at the big picture and what we have today and where it might be headed.
RS: Well, Pat, to start off, can you just explain to us what is a heat pump? My basic understanding is it’s an air conditioner that runs in reverse, but help me understand a little bit more about that.
PH: Exactly. Yeah, that’s irony is that we’ve had heat pumps around us for a long, long time. So let’s go way, way back here. So in nature, things always go from more to less, high energy to lower energy, from warm to cold, from water runs from high to low downhill. So let’s take water. So you have water and you would in the ground and you’d like to get it up to the surface or maybe into the water tower. What do you do? You use a pump.
RS: You pump it.
PH: So you have an impeller, you have a motor and some external energy that runs that motor, runs the impeller and is able to pump the water up against nature. So that’s what a heat pump’s doing. So remember, heat is always flowing from warm to cold. So how in the world does the… You take the heat out of your cold refrigerator and put it into your kitchen, it’s just warmer, right? The kitchen’s warmer than the refrigerator. How are you getting that heat out of the refrigerator, out of the food that you put in there and pass that off to the kitchen? You have to have a pump. In this case, it’s a heat pump. It’ll be an impeller, we’ll call it a compressor and then we add a refrigerant that can be compressed and condense and expand. And we gotta have external energy, in this case, electricity generally, to run that pump to pump from cold to warm. So what happens when you set an air conditioner? What’s happening with an air conditioner? We’re taking heat out of our house, we’ll call it 75 degrees or 72 degrees, and we’re putting it outdoors where it’s 90 degrees. How do you do that? That doesn’t… Nature doesn’t allow that to happen. Well, we use an air conditioner that uses a heat pump to pump heat from the warm to the warmer, [laughter] cold to warmer, right? Against nature.
PH: So the same thing happens. I guess one other thing I missed here is everything has energy down to absolute zero. So the air has energy in it until it hits 460 some degrees below zero. And so even in the winter, there’s air out there with heat in it, not very much and we don’t know… It’s not comfortable, but we can extract heat out of that cold air with the heat pump and pump it into the warm space, now the house. And typically, you’re gonna pump it up to 100 degrees or something like this to send it down your ductwork to get to your room and be 75 or whatever it is you want for your space temperature in the heating mode. So that’s really what a pump is and it’s all around us. Like I said, it’s in your refrigerator, it’s in your freezer, it’s in your air conditioner, whether it’s a window air conditioner or a central unit. Same thing’s happening. There’s this compressor, it has a motor on it that uses external energy, electricity to pump between a condenser and evaporator. Those are terms that kind of represent the two sides, one’s taking the heat and one’s giving up the heat. And they can be switched. The air conditioner in a sense simply takes a reversing valve and we can take an air conditioner and reverse it and take heat from outdoors and put it into the indoors.
PH: So you think about an electric car, how’s an electric car getting heated? And it doesn’t have warm water in the radiator. It’s not taking heat off the electric motors like we would with a gas car, so it has to have a heat pump. And even our regular cars, gas powered cars have an air conditioner, same thing. There’s a motor running a compressor and it’s taking heat out of the car and pumping it outdoors. So it’s all around us. And heat pumps are just gonna be more and more prevalent in our lives in the future. There’s just no way around it, it’s a very clever system, very clever device to move heat against the kind of the natural laws or nature’s laws.
RS: And so if I’m doing a home inspection and I see your traditional air conditioner, split system air conditioner, half of the unit sits outside, it’s that big box on the outside of the house, the half of it. The other half of it sits on top of the furnace, that’s the evaporator coil, the part that grabs heat. If I’m looking at an air conditioner that is also a heat pump, it’ll work in reverse. How do I know I’m looking at it? What are the tell-tale signs, Pat?
PH: Yeah, well…
TM: That’s a million dollar question.
PH: Yeah, it’s gonna look very, very similar. So there’s gonna be a coil inside that looks very similar to air conditioning coil and there’s gonna be a box outside that has a fan in it that blows air over a coil. And it’s just with the reversing valve in the system and generally the compressor’s outdoors with the coil that’s outside. With this reversing valve, they simply are going to change the inside coil from an evaporator to a condenser coil. And you’re gonna change the outside, what used to be a condenser coil in air conditioning mode, to the evaporator coil. So it’s picking up heat from outdoors and it’s condensing and giving up its heat indoors, just the opposite of an air conditioner. As far as looking at it, yes, the outdoor unit probably looks a little different. The old traditional heat pump that was introduced probably in the ’70s when we started thinking about electrification of homes and whatever, the old, what we call the air source heat pump, and that’s really still what it is. When we classify heat pumps, we classify them by where did it get its energy and where is it giving… How is it giving up its energy? And so in the case of an air conditioner or a reverse of the air conditioner or a heat pump, it’s taking heat from the air and it’s giving it up to air.
PH: So it’s air-to-air heat pump. We can take heat out of water, we can put heat in the water so then we have air to water heat pumps and we can do water to water. So that kinda helps define the working medium, so it really is what it is. But the old air source heat pumps that we had back when forever, didn’t look that different from an air conditioner actually.
RS: Yeah.
PH: Pretty big unit for doors typically that had kind of same shape and whatever and these reversing valve, you don’t see, it’s kind of buried in the box. The new air source heat pumps and certainly now as we move into what’s called cold climate air source heat pumps, inverter-driven heat pumps, there’s all kinds of terms that get used and thrown around here. They do have a different look generally, they’re gonna be a more of a rectangle box and a different kind of front facing fan, that kind of thing. So that’s a pretty good giveaway. You have a heat pump, if you see something that doesn’t look like the traditional outdoor air conditioning unit.
RS: Okay.
PH: And that’s what I’m saying is it can look like an air conditioning unit, it’d still be a heat pump.
RS: Yeah, and I ask because they can look indistinguishable. I’ve got a property that you two have both been to our rental property, where you guys were using that for some training. And there was a time this… When was it? It was last fall, where it was like 40 degrees outside, I’m doing some yard work, raking leaves, and then the thing kicks on and it starts running. The AC starts running and I’m like, “What the heck? How is the AC running when it’s 40 degrees and it’s like 65 degrees? What the heck is this set to?” And I go inside and it’s set to heat. And I’m just scratching my head going, “What is going on right now?” And then the light bulb goes off over the top of my head, like holy cow, that’s probably a heat pump. And I go back out there and I look inside and like you described, Pat, when it’s a heat pump, there is a reversing valve inside there and you’re not gonna know what it is, I’m not gonna try to describe it. But if you go online and you google reversing valve, you can see what they look like, it’s an extra little thing that’s gonna be sitting inside of the air conditioner. And if you’ve looked inside enough of ’em, you know that this doesn’t quite belong. And sure enough, I’ve got a heat pump in my house, I had no idea.
RS: And then I go back inside and yeah, it’s blowing warm air. And I’ll tell you one other thing. The first time I came across one during a home inspection, I was like, “Oh, so this is a heat pump. I’ve read about these in books.” Okay, this is cool. So normally, you put your hand on the suction line on an air conditioner, it’s gonna be really cold, it’ll… It might even condense in the summertime. So I put my hand on there expecting it to be warm, it wasn’t warm. That was one of the worst burns I have ever gotten in my life, I think. When I put my hand on that, holy cow, that was hot.
PH: Yeah.
RS: Oh my goodness. Tip for…
PH: I guess it wasn’t the suction line, was it?
RS: No, that was the pressure line and that thing was hot. So don’t ever touch the big thick line when you’re running your heat pump on heat mode. Bad news. That’s all I got for you.
PH: Yeah. Well, it’s yeah. And like I said, it’s the heat pump split system, whole house heat pumps have been around. And now what you have experienced there is a hybrid. So indoors, there’s a furnace, looks like a furnace. When you have the heat on, it runs like a furnace, sometimes.
RS: Sometimes.
PH: There’s other times… Yeah, other times where it’s saying, hey, I think the conditions are really pretty reasonable here outdoors, I’m gonna take heat from outdoors with my heat pump and heat the house rather than using gas. And so that’s really the whole impetus of what this electric heat pump transition or movement is all about. Is can we move from heating with gas to heating with a heat pump or electricity, and you have what we call hybrid system. Yeah, okay, I’ve got both. So I’ve got a… Yeah. So anyway, go ahead.
RS: So help me understand, Pat, how does it know when to switch from heat pump to furnace or furnace to heat pump? How does it decide which one it’s gonna operate on?
PH: That’s where it gets a tricky and that’s where it gets kind of proprietary. So all the heat pump manufacturers have different algorithms and different setups. Some of them are gonna base it on outdoor temperature. And so you say, okay, I think my system will do fine down to this temperature and then I want the heat pump to quit and my furnace to take over. There’s some where they can work kinda in tandem, not generally, but they can, where the heat pump continues to do its work, do its work, do its work and the furnace comes on because the heat pump isn’t keeping up. So that’s a different control strategy, it’s saying, gosh, the heat pump’s working, but it’s kinda slipping or falling behind, I better kick in the gas to back it up. Traditionally, we had heat pumps that, again, run by electricity, people didn’t have gas available in some of these subdivisions or whatever that were built without gas, they were using heat pumps only. So you didn’t have the choice for a gas backup, you had electric resistance backup. And so right up within the indoor unit, set a set of electric coils, those are coils for lack of a better analogy, that would come on and boost the temperature when the heat pump’s falling behind.
PH: So, again, there’s lots of different combo and combinations here, and there’s a lot of different control strategies. Like I said, some of them, they’d simply shut off, it’s just an on off, and sometimes the homeowner can do it. They just hit a button and they move from heat pump mode to furnace only mode. Some the heat pump is gonna give the signal that I’m done here it’s… And like I said, there’s others where the heat pump continues to go and the furnace just slides in behind to back it up. That’s a little harder to set up because now you’ve got a furnace that’s kind of interacting with this coil that causes some confusion that the manufacturer may not like. So that, like I said, that’s where it gets kind of right down to a particular brand or a particular unit.
RS: Okay. Okay.
PH: But, yeah. The one thing to keep in mind, so with this conversation of the hybrid and/or the backup need, and when you only talk more about cold climates. But heat pumps in general that are trying to heat houses, as it gets colder and colder and colder, the heat loss of the house, the load from the home is getting bigger and bigger and bigger. The colder it gets, the greater the load.
RS: Yeah, yeah.
PH: A heat pump that’s outside trying to bring heat from outdoor air in, the colder it gets, the higher the lift, it’s like a taller water tower, you need a bigger pump. And if you have a fixed pump, it can only pump so high. And so as the outside air gets colder and colder and colder, house loads going up, the capacity of the heat pump’s going down.
RS: Sure.
PH: So they have this X where they cross and say, alright, now my load’s gotten bigger than what my heat pump can produce. And that’s kind of old school, and that’s where the backup heat came in. The heat pumps that are being produced today, they’re trying to manipulate things in a way that they can still get a lot of capacity even at colder temperatures. And you sacrifice efficiency and other things in doing so, but they can go colder and colder and colder and still try to meet the load. And the other piece that made this a little, getting a little far ahead or a little too technical is heat pumps can be highly variable, like a furnace on, off. Some people have two stage furnaces, on and on more, two levels. Well, heat pumps, especially the modern, what we call inverter-driven heat pumps and even the regular motor-driven heat pumps can be variable capacity. And so what people will do is they’ll oversize the heat pump a bit. But because it can go down much lower in capacity, when the load is low, it can still do a decent job of cooling and dehumidifying, which we haven’t got to yet. And yet when it gets really cold in the winter, it’s got enough capacity to kinda bump up and meet the load. In particular, I think for efficient homes.
PH: So that we can kinda go into, well, will the heat pumps fit and where do they fit well, or maybe not so well? But that’s just the fact of heat pumps, as the temperature gets colder, the heating load for the house goes up and the capacity of the heat pump goes down. And we’re all trying to see how we can manipulate that in the heat pump. Well, I’d say manipulate the house, get the house super efficient and then you don’t have to go to a huge… Yeah, you don’t have to go to a huge heat pump to get the job done, or you may be able to actually eliminate the need for backup heat.
TM: So going back a second, I feel like we haven’t seen a lot of heat pumps in Minnesota. At least when we’re inspecting houses, usually we run across a natural gas furnace or a boiler that does the heating. But occasionally, we run across these heat pumps, but we’re starting to see more and more of them. And I think we definitely have seen them in the capacity for cooling houses that don’t have ductwork systems that have boilers and they wanna add some sort of air conditioning, then they’ll add these mini splits or these heat pump systems to provide cooling to the house. So I feel like those are more common and becoming more common as we update houses. But would you say that we are going to be seeing more and more heat pumps used for just heating too in houses moving forward in cold climates? Is that going to be the most efficient way to heat houses you think?
PH: Well, efficiency’s a big word. When we provide the heat we need in houses in Minnesota with the heat pump, yes. With what we call today’s cold climate air source heat pump, absolutely. Now, you introduced another piece of this in terms of kinds of units. There are heat pumps that are more like the traditional split unit where there’s outdoor unit and then an indoor air handler that looks maybe like a furnace and it’s providing a whole central heat and cool for the whole house. And then we call these mini splits where they’re typically smaller units that have an outdoor unit and then an indoor head that’s sitting in a particular room. And so that’s another advantage, if you will, of these, is that you don’t have to have a ductwork system necessarily to move to a heat pump.
PH: And then it has advantage of course, of providing cooling, and then you can kick it in and provide heating. So we’ll see people doing that where they might have rooms that have typically been cold, one of pets, pet peeves or rooms over garages. And they’re just notorious for heat loss and they’re notoriously bad for getting enough heat out to them. And so somebody will spot one of these in there. Now they have air conditioning more comfortable in the summer and they’ve got ability to pop some heat in there in the winter. So yeah. So those units have been moving into apartments, other application for some time. And now, like I said, they’re being retrofitted into houses where people either don’t have the central duct system and want to get air conditioning and can at the same time take advantage of them for a little bit of heat.
TM: I think we’re gonna see some of these now come into central systems like Ruben describing with this, that house of his. But now to your kinda your question, why would somebody do this? So I look at it in three ways. Am I trying to save energy? And that’s a very difficult question because you have to decide how you’re gonna count energy. And so for most people, the energy in the outside air we’re gonna say is free. We don’t count that. [laughter] It is energy and we are borrowing it, if you will, or stealing it and putting it in the house. We’re not gonna count that. We’ll just count the energy in the pump, the heat pump if it’s needed to move that energy to the house. And in doing so, you get what we call coefficients of performance that are greater than one. You buy one unit of electricity and you might get one and a half in really cold weather units of heat, you might get two. Or if it’s really 40 degrees outside, like the Ruben’s example, you might get three or four units of heat for the one unit of electricity that you used.
PH: So that’s coefficient of performance. And that’s one reason people look at these is, you think you’re getting something for free, but in a way, you’re paying for it. The second part is people say, well, I wanna save money, and I’ll come back to that one. Another reason people would do it is they’re concerned about fossil fuel emissions. And that’s really probably the primary driver right now of the transition from gas forced air to potentially…
TM: Electrification.
PH: Yeah. Electrification, air source heat pump, central air source heat pump. And so yes, if the grid is relatively green or maybe you’re using your own solar power and a few other things, you can look at this system from a very high level kind of house and equipment and electric generation grid and say, I think I used… I produced less CO2 in the atmosphere for my one unit of energy than I would’ve had I burned natural gas. So that’s probably the… At the very high level, the climate change and fossil fuel emissions level and policy level changes is trying to promote and encourage electrification and one way to electrify or not kind of de-gasification is what it is, is a way that we can heat and cool our houses. And by the way, we can also heat our hot water this way too. So that’s the move. The thing is right now, in cold climates, even with the superior technology that we’re seeing today, and what we call an inverter-driven, that’s really just a fancy word for the motor something, is acting slightly different and it has this variable capacity, easily variable capacity thing that we talked about earlier that they can be quite efficient and they can change their load characteristics and things to try to match up the house in different ways.
TM: It can be modulated.
PH: Modulated, et cetera. Yeah. They just become a viable candidate. The problem is even with that equipment, in a really cold climate when it gets cold and there’s not as much energy outside here or you have to lift it further, it’s gonna cost you more. Current prices, it’s just simply gonna cost more. And then that kinda wraps. So people say, am I helping the environment? Most likely, yes. Unless you’re using a very dirty grid. Now, am I saving energy? Well, energy’s a very hard question, but yes, you probably are saving energy at, we’ll call it at the house meter level. And then, am I saving money? Well, when it’s working really well, yes. And when it’s struggling a bit, probably not. And that really brings us back to this idea of the hybrid is, so people… When it gets cold and its capacity goes down and its efficiency goes down, its output, its capacity is down, what it means is it’s sending less energy to the house. The air coming out of the vents is gonna feel cooler. It isn’t gonna keep up perhaps depending again, on all the sizing issues.
PH: And so that’s the kind of the downside, if you will, is, ah, darn it’s not doing the job now when I really need it. And so that comes back to, well, should we be looking… And then people say, well, I’ll put in an electric stripe. Well, that’s COP of one. One unit electricity, you get one unit of energy. And a power plant, when they use, when they send a unit of energy, I keep kind of doing this not from a true technical physics level, but they send you one unit of energy, they burn three.
RS: Cool.
PH: So think about this. The power plant burned three, sent you one, you put one in your heat pump. If you don’t get a COP of three, you went backwards.
RS: Okay.
PH: And so some of that three might have been wind or solar, and there’s some other things going on if we wanted to get down, really try to compare emissions to emissions. But I’m just saying that you always gotta remember what’s behind the electricity that’s feeding that motor. And there’s a whole set of downstream things happening there that most people don’t understand or appreciate or look into very deeply. It’s just yeah. Here’s my meter, here’s what it read, and here’s what I’m paying for electricity. So anyway, I was saying this system has another system behind it. Gas does too. You have to pump it out of the ground and pump it through pipes to wherever it’s going. And the car, there’s an efficiency loss. You can’t burn it 100% efficient.
PH: So yeah, both have their issues, if you will. But I think that’s why we’re struggling with this idea of, well, geez, how does the heat pump fit? And back to hybrid, if the heat pump’s hitting COP of three or better, you’re doing well on energy and emissions, and you’re probably doing fine on cost or what’s it costing you? But when you slide down colder, you lose that. You say, well, gosh, should I have a backup? And then I don’t think the backups, you don’t want it to be electricity. And so that’s when gas starts to look better, and that’s where the hybrid starts to look better. And then you go, well, that’s kind of silly. I just bought two systems. I got a furnace and I got a heat pump. Yeah. And there’s this great argument kind of what people, the climate policy and climate advocates are saying we need a revolution. And I’m gonna say, I think we need an evolution. [laughter] I think we need to move from what we have to where we’d like to be and maybe a little more step like fashion, and I think the hybrid does that. Here’s the irony of the whole conversation about hybrids and moving that way. I simply don’t understand why anybody is putting in an air conditioner today.
RS: Go on.
PH: It makes absolutely no sense. It’s the same equipment. You’ve got a compressor, you’ve got two coils. You’ve got, oh, I added the reversing valve and you added some complexity. I’m not gonna try to overstate this. Now, people suggest that it’s probably a few $100 more. Now, if you go out in the market, they’re probably gonna charge you a few thousand more for the same size air conditioner versus heat pump, which is just, the market’s not there yet. And that’s a whole other conversation in terms of HVAC contracting base and the delivery market to deliver heat pumps to the customer. But in my mind of like… And that’s what happened in my house. So when we’re back to kind of personal experience, my air conditioner went out. It was like, oh, this is silliness. I’m not gonna put an air conditioner back in. This is when to make the transition to a heat pump. And my house is a little different. I was heating a little differently with what’s called a combi. I was using hot water coil, fan coil to heat the home, and I can put my air conditioner on top of that. I can put the heat pump on top of that. So that was the time to make the transition. And think about how many air conditioners have gone in the last, well, this summer or the last few years. And there really is no reason why they couldn’t have all been heat pumps like what Ruben had and the house that he purchased.
RS: Huh! You’re saying this now and I just replaced my air conditioner and furnace at my primary residence here a few years ago. And I’m thinking, why didn’t I do a heat pump? I don’t even know. It wasn’t even on my radar. I wasn’t even thinking about it. But now, after this conversation, I’m thinking, I feel like I’m kicking myself. Like, why didn’t I price that out and talk to a bunch of different contractors?
RS: Yeah.
PH: Yeah. If you priced it out, you probably wouldn’t want same decision. Unfortunately, like I said, it’s just not… It’s not as close as it should be yet. There’s hesitancy on the HVAC contractor trades on heat pumps. Like I said, they’ve been around forever. They’ve put them in some of the early ones, air source heat pumps I call the originals. We’re going into houses in central US and further south where there’s primarily air conditioner and a little bit of heat. They all worked fine, but as it got colder and colder, there were some poor experiences and contractors kinda got nipped a little and they’re a little nervous or a little afraid of the technology. So the contractors aren’t quite there. And then they’ve gotta figure out how to upsale somebody probably at a point in time where the furnace just went out on them and they’re anxious to get heat back, or the air conditioner went out and they want air conditioning quick.
PH: The whole HVAC delivery system is very unique and different in that not very proactive, it’s almost always reactive. And we’ve lost a lot of skilled trades in the HVAC industry. They are trailing behind in a lot, a lot of ways. So it’s just, like I said, it’s not just an equipment conversation, it’s also is this the right fit for your house and your set of circumstances? And even if you got the right equipment and the right house and the right circumstances, do I have a trade base that can provide the product in a reasonable way and with some confidence and with the reason, cost effective or affordable manner?
RS: Yeah.
PH: So there’s a lot of pieces that have to come together.
TM: So Pat, kinda what I hear you saying is that technology’s improved, so now that… So cold climates like Minnesota can use heat pumps for heating and cooling, and that’s effective and you don’t have to have a backup system installed at the same time?
PH: You don’t have to have a backup installed if you have an efficient home.
TM: Okay.
TM: Where the load just doesn’t go crazy on you when it gets cold. If you have an old leaky house and the wind’s blowing and it’s just losing heat right and left, the poor heat pump’s just gonna struggle.
TM: Sure. Okay.
TM: You just get a bigger and bigger and bigger heat pump, but you’re not gonna be happy, whether it’s the cost of the heat pump. Equipment’s gonna be twice as much. The operational cost is gonna be higher. So that’s back where I talked about kind of the right fit. But if you have an efficient home, yes, we can get heat pumps. There’s several of us who have run entirely on heat pumps in relatively efficient homes, myself, Gary Nelson, others, others. There’s a number of places around Minnesota where they have satisfactorily heated their house with a heat pump. Here’s the other little piece of it’s kind of a little back secretive. Is if you’re running your heat pump and you had your temperature set at 72 or something, and it starts to slide to 71 or 70, or you’re getting down to 68 or ‘9 and you’re not happy, just turn on some lights.
TM: [chuckle] We can’t use the incandescence anymore. We only have LEDs.
PH: Yeah, I know.
TM: Turn all your computers and your TV…
PH: Your computers and your TV and your…
TM: Your oven. Yeah.
PH: A little electric heater. Now that is electric resistance heat. Of course, it’s one to one, but I’m saying you can take that edge off of that…
TM: With internal. Internal gains.
PH: With internal gains.
TM: Yeah.
PH: And so you may end up doing that for a few hours a year. Whereas in the past, when we were doing backup heat in air source heat pumps, they were quitting it. They were designed to shut off at 20 degrees.
TM: Yeah. That’s what I remember. Yeah.
PH: You were on backup all the way down to minus 15 or whatever.
TM: That’s what I associate heat pumps with still. So that’s why it’s interesting to hear you say that they’ve come a long ways, that the technology’s advanced so that if you have an efficient home, you can heat it with just a heat pump, you don’t need a backup. But there’s a lot of old homes here in Minnesota that are not to that level and they would need a backup heat system.
PH: Yeah. So our current heat pumps are going down to zero. The cold climate, air source heat pumps should be able to operate down to zero pretty effectively. And many of them will go below zero and continue to run and continue to be above one COP, probably one and a half, one point whatever.
RS: Depending on the efficiency of the house. And you talk about having a newer, more modern, energy efficient home, do you feel like there’s an age of home where we kinda cross that threshold where you might say pretty much any house built after 1994 will probably be efficient enough? Is there an age of home where just a cookie cutter new construction built to the current energy code at that time would be enough where you could put in a heat pump without additional modifications to the home?
PH: Yeah, I’d say there were certainly houses built in the ’90s under the 91, 94 in Minnesota under those 1990 codes that were built above code and are tighter than what code would’ve have allowed at that time.
RS: Okay.
PH: They’re certainly candidates. There’s some houses built in the ’90s that still were pretty leaky, maybe really didn’t hit the mark on all the installation levels or extravagantly large, or have lots of exterior surface area and a bonus room over the garage and whatnot, that you still kind of say, well, can we really? And you can. You could replace the central unit and it’s just sizing. It’s just a sizing issue. But yeah, you’re looking for a newer home, an older home that’s small and has been weatherized to be relatively tight might be a candidate too. And certainly, those are good candidates for the hybrid because they have an existing furnace or they are gonna need some backup or whatever.
PH: So I think in my mind, I guess that’s back to this kind of evolution approach as you kinda start sliding those houses to more and more efficient shells, and then that sets ’em up to be a good candidate for a heat pump. And then of course, watching their equipment cycle, the furnace goes bad. If somebody’s furnace goes out, somebody’s probably gonna try talking ’em into an air conditioner coil ’cause they gotta pull it all out anyway, whatever because the furnace cabinet’s gonna be a different size and all these things. And so then they’re throwing in the outside unit. Well now they should have a furnace and a heat pump instead of a furnace and air conditioner. So there’s a pretty easy, logical evolution transition there, even in our older homes. It just doesn’t make sense.
PH: In the old days when I first started this business, I was heavily into solar energy, passive solar, active solar energy. And I said, we always tell people it makes no sense to try to solar heat a corn crib, a barn. It just makes no sense at all. Conservation is so much more efficient, so much more controlled, so much more cost effective. You bring the load down and then you implement. And that’s really what this is about here is long term thinking about bringing the building shell back into better control and better compliance to kinda modern standards and then sliding the equipment towards the new generation of heat pumps.
TM: So Pat, how long would you say that kind of this newer technology of heat pump that can heat cold climate house when it gets to zero degrees outside has been around for? Is this like the last five years? The last 10 years, 20 years?
PH: So the mini split was kind of the introduction of the new version of heat pumps and that was being used for retrofitting older homes to get air conditioning into certain rooms and whatever. And then they said, oh, by the way, we could heat that room too. So those are 15, 20 years old in apartments. So the other thing is I was talking about examples earlier, almost every hotel room you’ve ever been in is a heat pump. And they go back 40, 50, 60 years. That’s what’s called a PTAC, Packaged Terminal Unit. Packaged terminal AC unit that would sit under the window and rattle all night and provide air conditioning. [laughter] And then they might have electric resistance if they needed some heat, or they might have had a baseboard maybe back then or whatever. But pretty soon, again, somebody said, hey, what if I just put a reversing valve in here and then heat with that? And so any hotel room that’s going back probably 20, 30 years has a heat pump in it, provide heating and cooling.
RS: Okay.
TM: So I’m just trying to catch up. It seems like you said our industry is lagging behind, a lot of the HVAC contractors were, like you said, kind of had those challenges before with the older systems that maybe couldn’t keep up. And they’re afraid to work with the newer systems and to try this newer technology, even though “new” is 20, 30 years old. [laughter]
PH: No. Yeah. And the cold… The very high-end cold climate inverter-driven heat pump, it’s more 10 years plus 10, 15 in the market. So it’s slightly newer than say the PTAC unit I was just talking about. And again, it was kind of a specialty thing. And so again, there’s contractors that used them on a spot here, a spot there. It certainly wasn’t a market transition. And now the equipment options are such that there could be a pretty general transition here and over the next decade.
TM: Okay. So I wanna ask you… So in your opinion it makes sense for people to be thinking about using this type of technology, but in reality it might be difficult to find a contractor [laughter] who can install this, but it’s available. And if you live in a cold climate, even you can have a heat… Use a heat pump and take advantage of that.
PH: Absolutely.
TM: Backing up though, I just wanna ask you, what do you think about ground source heat pumps? And we’ve been talking about air-to-air heat pumps, but what about water-to-air heat pumps or like geothermal system? Do those systems still make sense? Are they a smart investment?
PH: Two different questions there. [laughter] They make a ton of sense. So again, when you think about trying to strip heat out of 15 below air, it’s kind of a challenge.
TM: Yeah.
PH: And if you’re down in the ground and fluid that you’re circulating out to the ground loop is running even 25, 30 degrees, it’s gonna be a water glycol mixture, antifreeze mixture. It’s got twice as much available energy as the air outside does. So they’re remarkably efficient. Energy-wise, they don’t lose their capacity the same way. The ground’s not getting… It’s getting colder as you’re using heat from it, but it gets replenished and to a certain extent. And so it maintains its capacity pretty well, well all winter long. And then if you think about this in the summer, you’re pushing heat out there to heat up the ground that you’re gonna turn around and take out next fall in winter, it’s a remarkably efficient system. And there’s another advantage to it in that the equipment that’s in the water mode, it’s easy to get hot water off this with what’s called a desuperheater and heat your hot water. So now you’ve got really efficient heating, you’re heating your hot water, your air conditioning is practically free ’cause you’re dumping heat from a 75-degree house into a 50-degree ground or whatever. It’s just remarkably efficient. So air conditioning’s very, very high performance, but it’s just the cost. So that’s where is it cost effective? The fact that you have to put in this ground loop, you have to have the area, you have to have the expense of going vertical loops with a drill, well drilling equipment or…
TM: 100 feet down usually.
PH: Yeah. Probably 250, 300, something like that. Yeah. You can probably stop at 150, but the further you go down, the higher the efficiency and the less wells you need and so to maintain your capacity or you go with a horizontal system and there’s lots of different versions of that. Now, the trick here is now we’ve got inside equipment has to get married up with the outside field. It’s not just air blowing around, it’s a very intentional heat sink, heat source that your building and that has to marry up to your house. So there’s another contractor involved and we’ve seen where that’s been issues of the ground loop just simply wasn’t done properly. They typically undersized it ’cause it costs so much. And now we have undersized outside ground loop and then we lost some more efficiency, et cetera, et cetera.
PH: So I love ground source heat pumps in theory and if I had the money, that’s what I would use because again, it’s just a marvelous application for a heat pump. It’s just… It’s really just a… It’s a cost and then having proper area to do what you need to do. And with vertical wells, it doesn’t take material at all. And again, good installers is really critical for the overall efficiency and performance of the system. Yeah. Love it. So it’s jus… Now, here was the challenge, flip side is, people thinking about ground source heat pumps for people building new houses. And if you build a super efficient house, how much can you afford to spend on heating it or cooling it? So that’s kind of a reverse…
TM: The roads are so small, then why would you spend 50 grand on a geothermal system?
PH: Yeah, exactly.
TM: You’ll never see the payback.
PH: Yeah. And so that’s why they kind of started to slip a bit.
TM: Okay.
PH: And the air source heat pump technology was coming on and it looked a lot cheaper and easier, maybe less issues with installation. Maybe, I’d say qualify it maybe, they just kind of took over and the ground source heat pump slipped a little. So that’s back to my original point was heat pumps are our future. It just makes sense to take heat from someplace that has excess and put it in your house. So whether you’re using solar energy in some way, using ground energy, the air, that’s kind of the last resort but it’s an easy resort. You can think of buildings all over the place where one side, the sun’s beating on it and it’s super hot, and the other side’s getting a cold northwest wind and it’s cold. Well, heat pump just moves the heat from here over there. Bingo. Done. Super efficient, super easy. So they’re here to stay. It’s just we need to work with our trade base and we need obviously some consumer education as to what it is, how it works, and before we see any kind of mass transition.
TM: Well, and would you say the majority of people in the south are using heat pumps already? Or would you say that they’re using just your standard air conditioning system ’cause they don’t really need heating?
PH: Well, they’re making the transition much faster. You’ll still see furnaces, central air system, central forced air in the South and they’ll use gas ’cause it’s cheap. It’s probably even cheaper in the south. But again, the heat pump makes such sense for them ’cause it’s gonna work way efficient in the heating mode. And then of course you need air conditioning, so you’ll be there for air conditioning. You’re gonna have a higher air conditioning load than heating load presumably. So you have to have a bigger unit, which means it can do the heating load very efficient ’cause there’s a lot of coil on both sides, the right compressor or whatever. So it should be almost automatic in the south. It’s not there yet, but it’ll clearly transition much quicker there. We’ll see a little slower…
TM: And they’re great for everywhere in-between the south and the big north.
PH: Oh yeah. In the, what we call the rust belt or the rot belt, the in-between.
TM: Yeah.
PH: Yeah. It’s a great fit. And really, the whole thing that’s gonna make this work is the fact that they are so variable or they can modulate so well ’cause here’s one last little piece that’s really important with heat pumps and air conditioning. Traditional air conditioning oversize led to houses that were cold and clammy. They had high efficiency, they could cool the house instantly, but they didn’t ring out the moisture. So to ring moisture out of the air, and a lot of people say it’s not the heat, it’s humidity and there’s some truth to that. To ring moisture out of the air for comfort in a home takes a lot of energy actually. And it takes a very long cooling cycle so that lots of air can move over that coil and can condense. Now you can slow the air down and slow down too much, coil freezes up, that’s not good. So what typically has happened is to get the efficiency of the air conditioner up, they move far more air across the coil end up with a far warmer delivery temperature. And that gets you maximum efficiency and minimum condensation, minimum moisture control. So that’s been a game of trying to show higher and higher seasonal energy efficiency ratios from an energy standpoint and compromising and sacrificing moisture control for big time, big time.
RS: Sure.
PH: And everybody was oversizing air conditioners anyway. And now they oversize a very high efficiency air conditioner and you just get zero moisture control. So we’ve been trying to tell people, downsize, downsize, downsize, or go to a two speed or a variable capacity air conditioner so that you can in fact wring the water out when you wanna wring the water out. But what’d we say about the heat pump? One of its prime advantages, highly modulating, highly variable capacity. And they’ve got all kinds of brains inside the system, sometimes they outsmart themselves, but they got the brains in there to be able to say, oh, let’s slide into a dry mode here and I’m gonna slow things down, get the coil a little colder and strip more moisture out on its way by and provide less what we call sensible cooling or let… The temperature of the air is not gonna be as cold or and there won’t be as much of it ’cause I slowed it down to meet the load, the sensible load of the house.
PH: And so there’s just this huge advantage, again, of good equipment and good installs where you can actually get better humidity control out of this heat pump because you can oversize it to meet the heat load without compromising the summer comfort. Again, if somebody’s smart and they’re playing the right rules and doing the right calcs, doing their load calcs and they’re system sizing properly, you don’t compromise that summer comfort as much if you happen to oversize a little bit to cover heating. So down south, that’s the opposite. It’s got more cooling, less heating, they’re in great shape. Up here we might size a little large for the heating best we don’t have a backup and that could compromise the cooling, but if it’s a smart system, it shouldn’t. So that’s one of my pet peeves is air conditioning oversizing and poor dehumidification of summer. It’s a far bigger problem than anybody realizes in terms of comfort. It’s a far bigger problem than anybody realizes in terms of mold growth and indoor air quality. And so again, with some fingers crossed and some positive thoughts, I think if the trades will pay attention here, we can move into where we use heat pumps and actually get better air conditioning, better dehumidification. And so that’s another plus.
TM: Yeah, that’s a huge benefit that you… We don’t have the same problem with oversizing ACs and having humidity issues with heat pumps, you can have a modular system that gets the humidity out, but still meets the demands.
PH: Yeah.
TM: That’s great.
PH: And the other transition that I’m sensing here is we’re gonna slide away from the mini split, which is kind of… Somebody’s not gonna be happy here, but kind of a bandaid approach to introducing heat pumps into certain marketplace, rental units and hotels and whatever. Hotels probably will stay there, but I like central forced air. I’m just a huge fan of central forced air in buildings to provide better…
TM: For filtration purposes?
PH: Filtration, circulation, bit more uniformity, more comfort. It just has so many advantages for providing overall comfort in that house. And you can get fancy and put more heat or cooler here or there, wherever you need it. There’s all kinds of things you can do with that system and provide a way to distribute your ventilation air to all the rooms, your bedroom where you spend all your time.
TM: Shall be easy where RVs can tie into it. Yeah.
PH: So I like central systems, central forced air systems, and now there’s no reason why we can’t have a central air source heat pump system that provides air conditioning, of course, heating and dehumidification properly done. So that all starts to package up. And then I’ll just kinda take the next step out is, well, what if we had an air source heat pump that could heat water or heat or chill water? So I got two tanks in your house, a hot water tank and a cold water tank and heat pump that can move heat from outside into the heating tank or from the cooling tank to the heating tank, from the cooling tank to outside. And now we’re managing the system for the maximum efficiency, and then you move that hot water or cold water to a coil and a air handler, and now you can heat and cool and dehumidify and have hot water with a single heat pump.
TM: It’s like your pumping system that you used to have in your house, but with a heat pump instead.
PH: Yep. Absolutely.
TM: Yeah. So that doesn’t exist yet?
PH: It does. There’s a lot of people looking at it. There’s some compromises that have to be made when you’re trying to cool, chill water and heat water. What refrigerant do we use? And there’s so many issues.
TM: Yeah.
PH: But I’m just saying back to this idea, heat pumps are our future and I don’t think we’ve even thought about yet how clever…
TM: All the applications.
PH: How the applications and how clever we could be to be super efficient in moving heat around with a heat pump. And it comes with complexity and controls and so there’s always challenges there.
TM: Our HVAC industry has a long ways to go I think. [laughter] You two have to teach them that they can install ’em in a cold climate to heat their house.
PH: That’s true. We better start… I could step back… Baby steps. Yeah. Let’s start there.
TM: Baby steps, man. Well, Pat, we covered a lot of ground today and you answered a lot of our questions and I think my key takeaways is that heat pumps do work in cold climates. The technology is there, it’s the HVAC industry, it’s kind of trailing behind and so it’s harder to find installers who are confident and competent installing them and that they’re priced affordably, so it makes sense. But the technology is there and depending on the size and kind of efficiency of your house, it could be a system that you could look into in the future when you’re thinking about upgrading. And so that…
PH: Absolutely.
TM: Yeah, I think that’s the key takeaway for me. And it’s something that we as home inspectors and for me doing the house coaching, I come across a lot of people that have systems that are kind of near approaching the end of their life expectancy and they’re like okay, what should I do? And it’s like, well, let’s think about does a heat pump make sense?
PH: Yeah. Now one other thing we had on the list was, do you need to elevate the outside unit? And Absolutely in cold climates, you don’t want the unit sitting down in the snow.
TM: Okay.
PH: And so, yeah, they all should be sitting on a stand to get good air flow. Air conditioners as well need good air flow and keep your bushes away and things like that. This thing is trying to transfer here heat from outside in or in the summer inside out, it needs airflow around that unit, outdoor unit. So always have good airflow around that unit. And in the winter, you’re gonna try to steal heat and if there’s snow on the ground, you wanna be up above it. The one other little piece of that that I’ll just mention is people might be surprised is in the winter, you may see condensation and water running off your outdoor unit. Well, if you think about what it’s doing, it’s chilling that outside coil down below the temperature of the outside air. That’s how heat moves from warm to cold to the cold fluid. And that cold fluid picks up the heat and we’ll be moving it in through the heat pump. And so the coils get colder than outside air. And when that happens, you can have condensation or dew and if it’s above freezing, if it’s below freezing, it’ll be frost. And so these outside units do go through a defrost in the winter to clear the frost off the coils if it that condition exists. And you’ll see water dripping off or you’ll have ice underneath of it or whatever. Another reason, again, to have it elevated.
RS: Sure, sure.
TM: Those are some more helpful clues for home inspectors or homeowners trying to identify what type of system they have.
RS: Yeah. If the outside unit is sitting on stilts, it’s such a product guarantee you’ve got a heat pump.
PH: Yep, absolutely.
TM: And if it’s not, it should be apparently.
PH: Yeah. Totally. Yeah. Yeah, it’s just… It depends on location, if it’s protected from snow drift and drifting and there’s some advantages of having it on the south side if you’re thinking about, you’re really trying to push its heating capacity a little bit, it’s not much that hurts the cooling side a little, but not much.
TM: Yeah.
PH: So there’s some things about where you put that unit too, and again, that’s kind of back to installation and sizing and proper finishing.
TM: How many contractors actually understand that and do that?
PH: Or homeowners, contractors, as you know, it’d be better he, and the homeowner says, no, I don’t want it there. I want it over here on the north side. So yeah, that’s a whole nother conversation about building design and [laughter] maximizing your equipment efficiency or whatever regardless what system you’re using.
TM: Yeah. Well, thanks for coming on Pat and myth busting for us a lot of things about heat pumps that I guess some things that I didn’t understand or know about them as well today. So I appreciate you sharing all of your wisdom and knowledge with us today.
RS: Yeah. Thank you so much for coming on, Pat. Always a treat to have you on.
PH: Yeah, I enjoyed it. Yeah, I appreciate it. And good luck. I hope folks can kind of start to learn more about it as well as our contractors and make this transition as easy as possible.
RS: Yeah. Love it.
TM: Agreed. Agreed.
RS: And for our listeners, if you’ve got any questions, Tessa and I surely will not be able to answer them, but you’re welcome to email us any way or any thoughts. We love your emails, you can send them to podcast@structuretech.com. And if you wanna get ahold of Tessa directly, I have a link to her website and all that contact info in the show notes as well. So Pat, thanks again for coming on. Always a pleasure. And we will catch you guys next time. Thanks for tuning in.
TM: Thanks.
RS: Take care everybody.
PH: Thank you.