In a recent heat pump video I covered how air source heat pumps are getting so much better in the cold, but in my new house I decided not to go with one. Instead I went with the more expensive option: a geothermal heat pump. Why did I decide it was a better option to drill into the earth 400 hundred feet at more cost for my new home? I’ll run through that, but there’s also a few other things I kind of went a little nuts on in my house that are worth touching on too, like smart electric panels, a crazy home network, and more. Let’s get into the current state of my net zero energy home.
So it’s been a while since my last update on my home build. If you haven’t seen the last video where I showed the process of assembling my factory built home on my property, you should check that out.
But to catch everyone up really quick, I’m building a new, super energy efficient home with the goal of being net zero energy … meaning that my home will generate as much energy as it uses over the course of the year. To hit that goal the first step was to build something that’s going to be super energy efficient. During the time period since the last video a lot of things have been happening at once: from my geothermal system, getting the metal roof on, roughing in the electrical and plumbing, and by the time this video goes out, the drywall will be done.
My wife and I have gone a little nuts with what we’re putting into the house. Who am I kidding … a lot of this is me pushing this stuff (not my wife). I keep joking with her that I feel like John Hammond building out Jurassic Park. “We spared no expense.” I just hope I don’t come to regret those decisions like John Hammond did. One of the big updates I wanted to run through was my geothermal system and why I decided to go that route.
It shouldn’t be a surprise that I’m all in on heat pumps. I’ve put out quite a few videos on why we should heat pump all the things, and my house is no different. I’m going to go into a lot more detail in a future video breaking down the costs and analysis of the system I installed, but the TLDR of why we went geothermal vs. an air source heat pump system (or even a mini-split system) came down to efficiency and longevity (not just cost). Getting a geothermal system is typically a lot more expensive than a typical air source heat pump, but there are incentives that bring that cost more in line … it’s still more expensive up front though. However, the geothermal system is more efficient, can be tied into my hot water generation, and that combo will save money and energy long term. This is our forever home, so we’re looking at living here for 20-30 years, which means we’ll get our money and quality of life improvements out of the slightly higher upfront cost.
It was an interesting experience getting the system designed and seeing it installed. We hired an independent mechanical engineer to design a system that would meet our goals. We walked through some different options, like air source heat pumps, but ultimately we landed on a geothermal system. And yes, this is going to be tied into the smart electrical system, which I’ll get to a bit later. In the end we went with the brand WaterFurnace … and for full transparency, I do have an arrangement with WaterFurnace where they’re helping me out with some of the HVAC system, but they have no say over the videos … and they’ve never asked to. In any case, the independent designer we hired calculated that we’d probably need about 25,000 btu/hour for heating on the coldest days (around -10F / -23C) and 15,000 btu/hour for cooling in summer on the hotter days (around 90F / 32C). Ideally we’d have something around a 2-ton system, but since we ended up going with the Waterfurance Series 7, the smallest size available is a 3-ton system. The fact it’s a little oversized shouldn’t be an issue since it’s variable speed and can easily run partial-load demands. In fact it might actually help us since it’ll be running at lower percentages most of the time, which should make for even quieter operation. I’ll have to live with it to actually find out though, so more to come on that down the road.
But it’s the geothermal well I was crazy interested to see built out.
There are two typical options for the ground loop: 1) a horizontal loop, or 2) a vertical loop. The more affordable horizontal loop is where they dig down, ideally 6-10 feet, over a large area of your yard. Then they put a single run of tubing in small loops that feed back to the house and cover it up. Given the size of my yard and its location a horizontal loop wasn’t the best option for us, so we had to go the more expensive route with a vertical loop. Drilling a vertical well isn’t that different from drilling a well for water, but as someone who’s never seen that in person, I was fascinated by this process.
The drilling truck was backed into my backyard and then the crew had to dig down about 5 or six feet with a backhoe before they could start. I live in New England and the weather wasn’t cooperating the day or two before. We had a cold snap, which froze the ground, so they had to dig out some of the frozen dirt by hand with the help of a jackhammer. Once they got past that they were able to get the drill set up.
They dug a little trench system that they filled with water and added a material, which is usually something like a bentonite additive, to create the drilling mud. The mud is essential for drilling because it forms a thin film on the walls of the borehole to seal it and prevent water loss while drilling. It also supports the borehole wall to keep it from caving in. During the drilling process a drill bit is attached to a long steel pipe that they keep adding onto as it goes. After the hole is completed they feed a closed loop polyethylene pipe into the hole and then fill the hole with grout. The grout is extremely important because it helps to transfer the heat from the surrounding rock and dirt into the tubing and ultimately the fluid inside.
In my case they drilled down about 400 feet and only needed to drill one well to support the heating and cooling demands of my HVAC system. Someone else’s home may need a couple of wells. Once you get down to about 6-10 feet below the surface, the earth becomes a consistent 50F / 10C. That’s critical for the efficiency of the heat pump system. No matter what time of year it is, we can always count on having that 50F to pull heat from in the winter or move heat into during the summer. The exterior air temperature is less of a concern. Again, I’ll refer you back to my previous videos on how heat pumps work, but by using a compressor they can boost that heat from 50F up to comfortable temperatures for your home.
And if you’re curious about the liquid that’s going to be pressurized in the tube, it’s going to be Environol, which is an alcohol-based antifreeze to make sure it doesn’t freeze up in the middle of winter. That tubing was run towards the house where it was connected up to tubing that had been pre installed in the foundation and up into my mechanical room.
It’s in there that you’ll find the WaterFurnace system and all the ductwork that feeds the forced air throughout the house. And yes, we went with forced-air over something like radiant heat. You can think that was a bad call on my part all you want, but we wanted a system that could both heat and cool. And our home is going to have somewhere around R-60 insulation in the attic space and R-35 in the walls, as well as triple paned windows, so it was a little bit of overkill for radiant heating. In fact, our mechanical engineer said we might run into a problem with the house getting too warm because of the low and slow way radiant systems heat homes. The system would shut off when you get close to your ideal temperature, but it continues to go beyond that because of the nature of the radiant system.
In the mechanical room you can see the Series 7 is set up. All of the ductwork runs throughout the house, and over here you can see the Renewaire ERV system. This is probably one of the most critical components of the entire house because of how air tight it is. Homes need to breathe, otherwise CO2 levels would become dangerous. In typical, draftier homes this is partially taken care of by air just naturally forcing its way through all the cracks and holes around the house. With an air tight house and ERV system you control how the air enters and exits the house, which gives you some huge advantages. One is that you can recover the heat of the air as it exits the house and exchange that with the cooler air coming into the house to warm it up. The second benefit is for someone like me with pretty bad allergies. I’m controlling how things like pollen work their way into my home and can filter that air before it’s mixed into the rest of the house. I’m also working with someone to help design an add-on to my Renewaire ERV to give it smarts for my smart home. It’ll allow me to set up some more sophisticated automations for how the system ramps up and down, and I’ll be able link it into the smart electrical system in new ways … again … I’ll get to the electrical system in a bit.
The ERV is tied into the same HVAC ductwork to provide that fresh air through that system. However, there are dedicated ERV air intakes for exhausting stale air outside the house in a few key locations. For instance, there’s an ERV intake vent in both bathrooms, in the kitchen near where the stove will be, and near the laundry room. It’ll help to pull out excess moisture from the bathrooms and laundry area, as well as cooking fumes near the kitchen. Meanwhile, fresh air will be fed through all of the heating and cooling vents throughout the house.
One last note on the geothermal system in the mechanical room is that there will be a desuperheater that will take excess heat from the geothermal system and hold it as warmed water that feeds into a heat pump water heater from Rheem. Not only is a heat pump water heater one of the more energy efficient ways to create hot water, but it’ll be even more efficient with the pre-warmed water coming from the geothermal system. It’s pretty cool … oh … uh … hot.
And that leads me to the electrical needs of the house. Since I’m going all electric for everything, and won’t even have a natural gas line run to the house, we’re trying to optimize our energy usage. The geothermal system, desuperheater, and heat pump water heater are the big ticket items helping with that, but there’s also what I’m doing with the electrical system itself.
If you haven’t seen my video on the Span smart electric panel, I actually have one of those in my current house and absolutely love it. I looked into a few other options for smart panel setups for my new house, but ultimately decided to stay the course and go with Span again. Full transparency again, Span has sponsored previous videos on my channel and they provided the smart panels for my new home. But just like with Waterfurance, they have no say over anything I say in my videos … my opinions are my own … and I wanted to go with Span again because I love the product. For me though it was a no brainer because I’ve also been playing around with integrating my current Span smart panel into the rest of my smart home setup using Home Assistant, so it all works locally and in my control. It’s pretty slick. I may get into more on that in a future video if anyone is interested, but for my new house this is going to be the brain of my electrical system. It’ll help regulate how my solar panel and battery system works in conjunction with all of the devices in my house. I’ll be able to optimize how and when my EVs charge based on excess solar production, or what happens if the grid goes down to extend the length of time my batteries can provide power. There’s a lot I’ll be able to do.
Which leads to my, “I think Matt may have lost his mind” territory that some of you will call out. Since I’m all in on smart homes and having devices being able to communicate and optimize my home’s energy, I’m installing an extensive home network. Partially for that and partially for my business. There’s a hall closet that I’ve dubbed my networking closet that has … I actually can’t remember how many ethernet cables run to it … 60? My electrician was teasing me that I’ve won the crown for most ethernet lines he’s run in a single house.
I also had low voltage lines run to each window to support powered smart shades. I’m going with Lutron for those, but there’s other options too. Necessary? No, but I’m really excited about it. One of the automations I’m looking forward to experimenting with is automatically dropping the shades depending on time of day, and how bright/warm it’s making a room, to help control how much energy the HVAC system uses. In theory, that should help with cooling costs over the summer and heating costs over the winter. Probably not enough to make it financially worth it, but the convenience and comfort factor is high with this. I’ll be doing some experiments and sharing what I find.
I’m also going to have Lutron smart switches throughout the house. I’ve got Lutron switches throughout my current house and they’re the most rock solid smart home tech I’ve ever used. Never had a problem, so it was another no brainer for me with the new house. Again, ticks the box of convenience and the ability to automate lights to save on energy, but I’ll be sharing more details on that later too.
And there’s going to be wired security cameras I’m installing around the house, which will record locally. The plan right now is to have Ubiquti power not only my home network, but also the security camera setup.
There’s even more I could go into like the sound proofing insulation that’s throughout the house, what I’m doing with my home studio, why I went with a metal roof, the EV charging setup, the garage, and my solar and home battery. That’s going to be Enphase by the way. Let me know what you’d like to hear more about, but I am planning dedicated videos on my solar and home battery setup, the Span setup, the HVAC system once it’s up and running and I’ve had some experience with it … there’s so much to share.