PHA: How did you improve on your initial prototype to provide that kind of experience to people?
Romanin: After we learned those things, we kind of had the tech stack. We had the problem and the thesis. We had very small amounts of initial funding, but we knew we needed to make this exciting for people and we had this user pain point that we wanted to solve. We got connected through Matt Rogers to the former head of design at Nest, a guy named Rocky Jacob. He consulted for us, and he was the person who reminded us that nobody wants to look at their AC. They want to look out their window.
So, we built this saddlebag with a shelf on top. That shelf on top of the indoor unit is something that, in hindsight, seems so obvious. This is why you get a good industrial designer. And then we put a plant on it and took a picture, and we're like, “This is awesome, right?” The focus is the plant—not the actual HVAC. That image with the plant has done a better job of pitching the company than I ever could in words. It just becomes so obvious when you look at it.
So, we recognized that this concept works, but had to make sure that it's easy to install. We made the decision that anything that required a licensed technician was the big barrier that is going to add costs. There's workforce shortages in HVAC technicians and electricians and building contractors. So we said, “Let's make the installation cheap and fast, so there's no need for extra permits skilled labor with specific licenses. That was a big engineering effort.
But there's more that we want to do. We eventually want to get to gradient temperature. The level of air movement is really important, obviously, like the convective cooling of moving air changes your comfort. Long term, we want to get into air quality management, so you don't have to decide to bring in fresh air. The same thing with natural light control. Your system should know when you want natural light and when you don't from an energy perspective or a comfort perspective.
PHA: How much energy does a Gradient unit use in a year when compared to a conventional heat pump system or when compared to an older HVAC system?
Romanin: Our flagship model is well suited for moderate climates. Its rated cooling capacity is 8600 BTU/hr, and its heating capacity range is 3000 - 8000 BTU/hr. The big difference between our flagship model and our cold climate model, currently in development, is in heating mode. Our cold climate model offers very high performance in freezing temperatures and heating mode. It's also better performing in cooling, but it is really optimized to hit those cold New York winters. Specs for our flagship model are available on our website, and we'll be announcing the specs for our cold climate very soon.
PHA: Do Gradient units work better in a humid or a drier climate?
Romanin: They're certainly designed for both. From a thermal perspective, all HVAC units work better in dry climates because removing water is harder. Think of your window AC. It condenses the humidity out of the air into water, which is an intensive process. It is not very thermodynamically efficient. Ideally, you would want that humidity to just move as vapor at the same temperature outside, but instead you're spending energy to cool it and then you dump the cold water outside.
So, you should do a couple of things. You should re-evaporate it on the condenser outside when you can. Our system does that. We take that condensate and spray it over the outside part, and it kind of cools the outdoor hot part. The second thing you should do is you should only dehumidify as much as you need to make people comfortable. A lot of times people say they get sick when they run the air conditioner because the air gets really dry. The indoor heat exchanger gets very cold and pulls out too much humidity.
What you can do when your system has a variable speed drive, which ours does, is you can to a certain extent control how much humidity you're pulling out. Right now, if you buy a Gradient, you can't set a specific humidity level, but one day you'll be able to. Because this is another area of comfort, right? It's air temperature, humidity, and radiant temperature, which are the three things that result in how you perceive the temperature in the environment. I guess air movement, too.
PHA: What types of refrigerants do the Gradient units use?
Romanin: So I've got a really long soapbox on refrigerants that I sometimes get into. I kind of hinted at it already, right? We invented CFCs in the 1950s, and they created a hole in the ozone layer. We had the Montreal Protocol that phased them out, and the industry shifted to HFCs. The part of that story that's not often told is that DuPont at first resisted the ozone science, but eventually came around and funded the Montreal Protocol. They were one of the supporters of it because they had lower margins on CFCs because their patents were expiring, and they had already patented HFCs and thought they could get higher margins with this transition.
They repeated the same trick with the Kigali Amendment. The chemical companies that own these HFC refrigerants partially funded the amendment that would phase them out because they had patents for the next generation of refrigerants, HFOs [hydrofluoroolefins], which have no ozone depletion potential and no global warming potential, but plenty of other bad things. It's still a manufactured fluorinated chemical for which we have little understanding of what happens if we dump massive quantities of it into the atmosphere. One of the things that we do know is that it breaks down into TFA [trifluoroacetic acid], which is a forever chemical that appears to have lots of issues disrupting plants and animals.
If you tried to think of two environmental disasters that threatened global ecosystems, ecosystems on a global level, you'd come up with the hole in the ozone layer and global warming, both in no small part caused by refrigerants. Do we want to phase out HFCs and replace it with another chemical and run this experiment again on a global scale?
The class of refrigerants that I believe should be the future are called natural refrigerants. They're called natural because we don't manufacture them. They are substances that exist naturally that we use as refrigerants. The three most common are CO2 (R-744), propane (R-290), and butane (R-600). CO2 is a global warming gas, but it has a GWP of 1 compared to GWP of 2000 [like R-410a].
There is a fear-mongering campaign that we can't use propane or butane as a refrigerant because it is flammable, which is true, but it's in such small quantities and that vulnerability is very controllable. If you have a mini fridge, it's probably using butane. No mini fridges ever explode. We are using propane to replace an open natural gas line in many homes—an open line that runs kilograms of natural gas through it on a regular basis in front of a pilot light. The idea that we can't switch to these other refrigerants is insane.
The good news is that there seems to be a massive movement in the industry away from HFOs and toward natural refrigerants. Europe has passed some laws outlawing the byproducts of HFOs. They also passed laws encouraging the use of natural refrigerants. Europe seems to be leaning into R-290, which I think is great, right? If Europe does it, and then a couple other regions do it, it will be enough to pull the rest of the industry along. The US does not have as good of a track record. Europe is hopefully going to drag us along.
To answer your question, though, in the US today we use R-32. R-32 is a steppingstone refrigerant. It has a GWP that is 68% lower than R-410a, the other standard. Our system also uses less charge and is hermetically sealed in the factory, not in the field, which allows us to cut down on leakage by 87% when compared to split system heat pumps. And looking ahead—while R-32 is better than R-410a, we still hope to eventually move to natural refrigerants.