HVAC 2.0 – Home Comfort and Efficiency Isn’t Just Hot Air
Episode ID S1E13
December 15, 2021
To keep a house comfortable and the temperature stable, the key is to trickle in the right amount of heating or cooling, instead of blasting it – like a shower instead of a bucket of water. In this episode, CoBank’s Teri Viswanath and Tamra Reynolds speak with Nate Adams, author of "The Home Comfort Book," co-founder of HVAC 2.0, and a partner of Energy Smart Home Performance. Learn how HVAC equipment has improved in recent years, and the important role that energy from surfaces plays in determining comfort.
Teri Viswanath: Welcome to Power Plays, a CoBank Knowledge Exchange podcast series. An audio program where we connect you with top energy and environmental innovators and policymakers who share their insights, experience, and market observations. Hello. I'm Teri Viswanath, the lead economist for power, energy, and water at CoBank. I'm joined today by cohost and CoBank managing director, Tamra Reynolds. Hi, Tamra.
Tamra Reynolds: Hello, Teri. For our December winter podcast, we wanted to end the year on a seasonally appropriate note by talking about home heating. Heating and cooling typically accounts for 40% to 60% of consumer energy bills, depending, of course, on where you live and the home you live in, and this year in particular since Americans are expecting to pay a lot more to heat their homes this winter.
Teri: That's right. Beyond the home economics bottom line, there's also this really important issue of home comfort. Are the rooms in your house uncomfortable or unusable during the height of winter or during the blistering summer? Is your home drafty in the winter season or maybe it's too tropical in the summer.
Tamra: We sat down with Nate Adams, author of "The Home Comfort Book," co-founder of HVAC 2.0, and a partner of Energy Smart Home Performance. To better understand home heating equipment, here's our discussion with Nate.
Teri: Nate, thanks for joining our program to discuss energy-efficient homes.
Nate Adams: Thanks for having me.
Teri: We lifted your book title for our podcast because it appears you align the notion of home comfort with energy efficiency. Why was energy efficiency an important part of the story you wanted to discuss with your readers?
Nate: Well, the funny thing is, it's actually not as we have moved forward. What we have found is, in many pieces of our work, there are good goals and then there are natural outcomes, and those are two different things. If you do a good project, energy efficiency is a natural outcome, but if you make energy efficiency your upfront outcome--
Teri: Priority, right?
Nate: Yes. Typically the next question is, well, what's the payback?
Teri: Yes, that's right.
Nate: The only things that make any kind of sense are to go from incandescent light bulbs to LEDs or CFLs, and that's basically done at this point and to go from a resistance water heater to a heat pump water heater or something along those lines. Those are the only predictable--
Teri: Efficiency goals.
Nate: If you lead with energy efficiency and saving money, you're going to become a liar because fuel prices change. Now, if you can focus on solving problems that people care about--The easiest one is if there are any rooms in your house that are more than 2 or 3 degrees different from any other room and you don't want it to be, that's a problem that can be solved.
Now, what does that look like? I don't know. It varies from house to house. My book dives into a bunch of the details, but if you can solve for those comfort problems, A, you typically end up with a heat pump, and B, you almost always save energy. Selling heat pumps and energy efficiency, it's a really bad selling point, but it is a natural outcome of solving problems that people care enough to pay money for.
Tamra: Let's talk a little bit about the HVAC system and that aspect with consumers potentially purchasing the wrong one. You might be stuck with that decision for several years, 15 to 20 years or more. From an energy efficiency standpoint in the home, why should we be thinking about heating and cooling? What are some practical things that you could share with us from the home buyer perspective about how to approach that conundrum?
Nate: I'll just start with a simple number to begin. Heating and cooling is between 40% and 60% of your annual energy bill. It is the single largest piece of what you spend money on, at least with your utility bill in a house. There's that piece.
Now, there's a really important analogy moving to comfort, which is ultimately what we find sells projects. In what we do in the program that we build HVAC 2.0, which is instead of just looking at what's called the box in the house, the furnace, the air conditioner, the heat pump, whatever it might be, we zoom out and we look at the entire house at the same time, which you have to do to understand, and particularly if you're looking at heat pumps because heat pumps have lower outputs than furnaces. If you don't make it so the house is easier to heat or cool, a heat pump is oftentimes the wrong piece of equipment to do the job. It's like putting a four-cylinder in a pickup truck and asking it to tow a trailer. It's not going to be a good experience.
Now, you can make it work in almost any house so that that can be helpful. Taking a quick step back to looking at comfort. I'll give you two a choice. You need to take a shower or you need to get clean, and you have 10 gallons of hot water to do it. You have two options. You can have a bucket dumped over your head, or you can take a five-minute shower. Which one would you prefer?
Tamra: Oh, the shower.
Teri: The bucket for me [chuckles].
Nate: What you want to do to achieve better comfort is to get the equivalent of that shower. You want to put a small amount of heat or cool into the house, whatever it takes to keep up with the conditions that it's seeing right now, and you want to trickle that heating or cooling in. What that ends up doing is it makes all the surfaces and the materials in the house about the same temperature. The dorky term for that is mean radiant temperature or MRT. Radiant energy, which is energy coming off of surfaces, is about 60% of human comfort.
Most people in the HVAC industry can't define mean radiant temperature, which means they're literally missing over half the equation. The best way to deliver good comfort is to put in right size equipment that can run at lots of different speeds. Basically, you get a throttle, the heating and cooling, versus an on-off switch. If you look at a typical furnace, if it's a 50-degree day, it's probably 10 times larger than it needs to be to do the job. It's going to turn on, it's going to put out heat like that bucket, and then it's going to turn off. Everything in the house is going to stay cold, even though the air is technically warm in the house. The couch can literally be cold.
If you can downsize the equipment and make it multiple speeds and trickle that heating or cooling out, just like a shower, all of a sudden the house gets much more comfortable. This naturally puts you in the heat pump territory because the smallest furnace that you can get that's modulating is 60,000 BTUs; 3 tons is 36,000, by the way. That modulating furnace will only come down to 20,000 BTUs at minimum output. If you get a 3-ton variable speed heat pump, it'll drop down to about 9,000 BTUs, which means it can match what that house needs most of the year. The house just naturally becomes more comfortable. Because heat pumps naturally have smaller outputs and can vary further down than furnaces can, heat pumps naturally provide better comfort.
Teri: I think that's a really good point because that feeling of being blasted by the furnace, and I think that's a common experience, but I'll tell you what Nate, when discussing this particular issue about heat pumps, there's so many of our electric co-ops that have had offering rebates and have had not a great experience because of the issue of comfort because they've said that it's a hard sell for consumers. Let's address that a little bit because I know you've talked about the technology change. Is it truly this level of comfort because we also have to overcome this sense that heat pumps are not going to be comfortable. They're basically blowing cool air and I'm not comfortable in that environment. I'd love to hear your thoughts on those concerns.
Nate: That's a really key concern, and this is basically why heat pumps have a bad rep in general. The technology has changed in basically the last decade in the US. Now we have something called the inverter, which it takes alternating current, it turns it into direct current, and then oddly enough, it turns it back into alternating current and feeds it into the motor. That allows, by varying the frequency, which is nerdy, sorry, but by varying the frequency, you can make that compressor run at sometimes between 25% of capacity and as high as 200% of full capacity. You can actually feed more power into it than it's used to taking.
This is a huge shift from what we used to have because heat pumps, until recently, and you can still buy lots of single-stage heat pumps, they just turn on or off. That's all they do. Most of them are set up so, in single-stage, so that they have a very high amount of airflow. The air coming out of the vents may be 90 or 95 degrees, sometimes even as low as in the 80s. Air moving quickly at those temperatures feels cold. People don't like that feeling. The inverter, you can run lower amounts of airflow which increases the temperature that's coming out. That's really only something that happens with the newer inverter heat pumps. That they started hitting the market about a decade ago, and the last three or four years, there's been a rush of new products coming out.
Their costs are coming down, which is good. There's fundamentally three different types of heat pumps. There's single stage, which is on or off. There's two-stage, which is a variation of single-stage where low stage is typically about two-thirds of full output. Then there's variable speed, which can run anywhere between 25 or 30% up to 100 or like I said, even 200%. It's called overclocking. That's how they can maintain a full output to low temperatures, 0 degrees Fahrenheit and below.
We used to have the cold air coming out, and now if you're running at lower speeds, so the air is not blasting and making the curtains flutter when the system turns on and you're not hearing the unit running. Between it being silent, not blowing as hard, and being warmer, the experience is very different than it was even just a few years ago.
Tamra: Can you talk a little bit about the different, what we would call categories? You hear a lot about ground source heat pumps, air-source heat pumps, what's the distinction is between those? Is there any difference in terms of how they work, the cost, where they work, maybe is probably a better way to approach it and maybe give some context on how you've guided conversations with people in the past about that aspect?
Nate: Sure. Fundamentally, there's two different types of heat pumps. There's ground source heat pumps which pull heat from the ground. You dig a well down and you have pipes that run either vertical or horizontal on the ground and then you pull heat from the ground through the winter and then, in the summertime, you actually feed heat back in. Air source is what it sounds like, an air source heat pump. It pulls heat from the air outside, or in air conditioning mode, technically, it's pulling heat from the air inside and ejecting it outdoors.
Ground source, we're not very bullish on at all moving forward because it's so much more expensive. You always have to drill the well. The well cost is going to be $6,000 to $20,000, depending on a bunch of factors, and you can't get rid of that cost. In general, because the inverter has gotten so good with air source heat pumps, it used to be this huge performance difference between them, and now it's just a very small performance difference. For all but the very coldest places, air source is likely to be what we're going to see moving forward. I'd expect 99% of the solution to be air source moving forward, thanks to the inverter.
Teri: Let's talk a little bit about that because there is that upfront cost that I think is hard. Overall, I mean, how do you think about the cost consideration? The pure equipment purchase is going to be higher.
Nate: Absolutely. It doesn't have to be drastically higher. For instance, if you're buying an air conditioner, almost every air conditioner has an equivalent heat pump model. The wholesale cost difference isn't that large; it's typically somewhere between $400 and $600 or $700. When you're looking at a $10,000 purchase, it's not a massive spread.
Teri: There's that education too which happens because, when do you replace your air conditioner, your furnace, right? You replace it when you don't have a lot of time to make a considered choice on that equipment, right? Having some of the fareway defined is helpful.
Nate: Yes. Well, if you go to the supply house and your choices is a heat pump, a heat pump, or a heat pump, like Henry Ford said, you can have any color you want as long as it's black. If only heat pumps are available at the supply house and 85% of residential HVAC equipment is replaced on an emergency basis when it breaks. If the only thing you can buy as a heat pump, guess what gets installed? It's a small cost difference. Typically, you're not concerned about the quality of the heating or cooling; you're concerned about the presence of it. Does it work at all?
I mean, if it's 25 degrees out and your furnace is out and you're worried about your pipes freezing, you aren't thinking about, what's the ideal piece of equipment I can get? It's, who's the first person that can show up with the first piece of equipment that will keep my house from freezing? That's what you're looking at. That's the fundamental challenge that we have. If we don't solve that piece on the supply side, it's going to be really difficult to solve.
Tamra: Let's discuss the backup heating element for a moment. Somebody lives in Colorado, for extra cold days, supplemental heating is required. You mentioned in one of your videos that when done right, a house won't use a great deal of resistance heat. Can we talk a little bit about that and put that into context too?
Nate: If it is done well. A real struggle here is, there's the quality of the equipment and then there's the quality of the controls, how the equipment is turned on and off. Good equipment will have multiple-stage backup. The equipment that we usually use, Carrier and Bryant, it has three-stage backup resistance heat. It'll be 5,000 watts, 10,000 watts, 15,000 watts, or 5kW, 10kW, 15 kW. It will only use that as the system starts to fall behind in very cold temperatures. You don't have to use resistance heat as backup.
Technically, you could oversize the heat pump. The challenge is, when you get into colder climates, and particularly in humid ones, so the whole East Coast, east of the Mississippi, essentially, you have humidity problems. If you size the system too large, it doesn't run long enough to actually start to dehumidify and dry the house out, and then you can turn a house into a mold farm. That is more than a small risk. We're seeing all kinds of crazy stuff happening on the East Coast right now that we haven't seen before. This is going to be a major challenge, and we can actually make people sick if we aren't paying attention about this.
We typically size the heat pumps. I'm from Cleveland, I happen to be living in West Virginia now, but from Cleveland, which is a cold climate. It's very similar to Boulder and most of Colorado. We'll size in between heating and cooling load and make up the difference with a little bit of resistance, which tends to freak out most utilities, sorry. But we can solve for that with inexpensive batteries, which are-- they're coming. If you have 20 or 50-kilowatt hours of backup electricity, it serves all kinds of purposes.
I love seeing what Green Mountain Power does with that. They reserve half of it to use for themselves and then the other half goes to the homeowner, and the homeowner pays $25 a month or $40 a month, whatever it is, for having that privilege.
Teri: Nate, it's interesting. We had the CEO from Vermont Electric, and they have a residual battery program. Absolutely, you're spot on. That's exactly why.
Nate: It solves the problem for resistance because every morning, when it's a cold morning, even if they aren't using setback, if you think about how the heat of a house works, if it's a sunny day, the sun actually helps a great deal heating the house. The sun goes down, 6:00 PM or 7:00 PM, whatever it might be, and the air temperature goes down, and then it's dark. There's also another crazy thing called night sky radiation where the sky actually sucks heat out of the ground.
The key thing is, somewhere around dawn, everything in the house is cold. All the building materials have gone cold, the air temperature has gone cold. When people start waking up, the heat load starts going up, and that's by far your highest peak. If you're going to need some resistance heat, that's the time. If we had a bit of battery to pull from, we could drastically flatten that peak. That's, I think, going to be the ultimate solution because that has so many other benefits.
You can use it for voltage regulation, just all sorts of different things that that battery can be used for where if we just have an oversized piece of HVAC, it only has one purpose, which is for a few hours a year. That has a lot of other comfort drawbacks or health drawbacks. If we're talking about dehumidification, there's a lot of risk that comes with it. To me, like what I'm really hoping for is a 20-kilowatt-hour battery installed for $5,000 as that can just replace a generator, done. If you're talking a few-hour outage, not a big deal.
Teri: That's right. As we think about the electric vehicle programs that our co-ops are developing as well, we now have a mobile source of battery that offers that connectivity. One part and an important part of our electric co-ops happens to be their member education and program. As we think about this particular element of education, would love to hear if you were designing an HVAC education program, the highlights or the toolkit you might actually put out for members, what would be in it?
Nate: Well, it's funny. I wrote The Home Comfort Book, and the first chapter, everyone ignores, which is basically here's the physics as how your house works. The second chapter of it is called HVAC 101. What it does is it takes what everyone intuitively understands, which is the HVAC system in your car. You can put out variable amounts of heating or cooling, depending on how red or blue you're going for. It's got different fan speeds. You can bring in fresh air or not, the recirculate feature, and dehumidification looks distinctly like the air conditioner button.
When people start to understand what an HVAC system should be able to do and then you show them that, while most cars can do five of the six functions of HVAC as we call them, most homes can't do any, but if you make a different equipment choice, which is going to cost marginally more money to imagine that. You want better stuff, it costs more, shock. [laughs] That's just how it works. Once people at least understand that, they become open to better pieces of equipment. When they do that, all of a sudden heat pumps hit the table where, before, they were just thinking about an air conditioner.
Teri: Super helpful. Nate, did we miss anything in our conversation when we're thinking about a comfortable home in HVAC, anything that we missed discussing?
Nate: There's one piece that we should at least touch on, which is the building shell, which means insulation and air ceiling. The easiest analogy for this is, imagine that I'm just a really mean jerk. I take you out to appear on a very cold windy day. It's 20 degrees out. There's a 30 mile an hour wind, and you're out there on the pier. The waves are crashing, you're getting wet, and all you have on is a t-shirt and jeans. You are freezing. Now, I give you the option of one of two garments. You can either get a very loose-knit sweater, or you can get a windbreaker. Which one do you want?
Teri: Back to your bucket challenge, I'm going to go for the shower and I'm going to go for the windbreaker. Those are my choices.
Nate: Good job. The windbreaker will at least keep the wind off of you where a loose knit sweater, it's just going to blow right through. Insulation is like that loose-knit sweater. Now, it's still important because a windbreaker without insulation inside is not a coat. You want both, but given the choice between one or the other, you want to make sure that you have the windbreaker. The windbreaker is air sealing on a house. It's sealing up a bunch of cracks. All of the traditional tips are actually horrific. You don't caulk your freaking windows. It doesn't matter. [laughs] It just doesn't.
All of the big leaks in your house are in the unmentionable places, the crawlspace, the basement, the attic. It's all the places that no one wants to be. That's where almost all of the big leaks are. If you can get a house tighter by sealing it up, you give it that windbreaker so that the loose-knit sweater of the insulation can do its job. In doing that, you reduce how much it takes to heat or cool that house. In doing that, if you lower it enough, you get it to where a heat pump can do the job because, remember, heat pumps have lower outputs than furnaces. It depends on the house.
Teri: That makes perfect sense. Nate, thank you so much. This has been a really helpful conversation, especially as we're getting into the winter season. We appreciate you joining us this morning.
Nate: It was my pleasure. Have a wonderful day.
Teri: Great. Thanks.
Teri: Nate makes this really interesting observation of how important it is to look beyond what he calls "the box in the house" at your furnace or an air conditioner, heat pump, whatever it might be, to look at the entire house for home comfort.
Tamra: Nate discusses how important it is to introduce the right amount of heating or cooling into the house to keep the conditions stable and comfortable, kind of Goldilocks. He compared this to taking a shower or having a bucket dumped over your head, mentioning that trickling in heating or cooling to keep the surfaces and the materials in the house about the same temperature or keeping the mean radiant temperature stable. He also mentioned that radiant energy, which is energy coming off of surfaces is about 60% of human comfort. My dog would agree with that too. He changes sleeping positions when the sun moves.
Teri: Absolutely. I really enjoyed this discussion with Nate, Tamra, and I hope our audience has as well. I'm looking forward to embarking on our second year of podcasting where our guests will walk us through how cryptocurrency might pose the next big threat to our electricity grid.
Tamra: Yes, me too. That's going to be an interesting discussion for sure. Hope you join us then.