Building electrification—the idea that global warming emissions can be effectively mitigated by either forcing or encouraging builders to install electric heat pumps instead of fossil fuel burning furnaces and water heaters—is catching on. Already, 30 cities in California have adopted codes that either restrict natural gas usage or outright require heat pumps in new construction, and many more are on the way, all over the country. In principle, encouraging electric heat pumps is a good idea for two reasons. First, burning fossil fuels (natural gas, propane, and oil) to heat buildings and water accounts for a tenth of total US carbon dioxide emissions. Second, heat pumps cut the amount of energy consumed by conventional electric equipment to heat space and water by at least one-half, or more. By combining their efficiency with their ability to tap into a low-carbon electric grid, heat pumps could dramatically reduce carbon dioxide emissions. There is a lurking unintended consequence, though, that has the potential to undo some of those gains.
With more heat pumps comes more of the refrigerants they are charged with, and inevitably, some of those refrigerants will leak into the atmosphere. The problem is that the hydrofluorocarbon (HFC) refrigerants we currently use are themselves potent greenhouse gases, able to trap thousands of times more atmospheric heat than carbon dioxide. The additional atmospheric warming due to more refrigerant leaking from more heat pumps is small compared to the potential gains from building electrification, but significant enough to alarm policymakers around the world. Indeed, the British government was sufficiently concerned that it appointed a team of researchers to study this problem. They concluded that it could be solved by charging heat pumps with a new generation of climate-friendly refrigerants.
Those new refrigerants foreseen by the British researchers are on the way. Not only are they more climate friendly than HFCs, but they are more efficient as well. Moreover, they will be used not just in heat pumps, but also in air conditioners, refrigerators, supermarkets, and cars. That’s the good news. The bad news is that the dawning of these new refrigerants, I call it “the refrigerant revolution,” is being delayed by numerous factors. Those factors include resistance at the highest levels of the US government, and obstacles at the state and local government level. For example, many of the new refrigerants are not yet approved for use by the vast majority of US building codes. Heat pump and air conditioner manufacturers are scrambling to bring new equipment charged with new climate-friendly refrigerants to market, but there’s only so much they can do in the face of so much regulatory uncertainty. It’s up to the rest of us to support the federal, state, and local policies it will take to bring the refrigerant revolution to fruition.
The search for climate-friendly refrigerants
About a decade ago, a team of researchers, led by scientists from the National Institute of Standards and Technology (NIST), set out to identify chemicals that could form the basis for a new generation of climate-friendly refrigerants. Atmospheric scientists express the contribution that refrigerants make to climate change with a metric named Global Warming Potential (GWP), which is the multiple of how much more atmospheric heat a given refrigerant traps than carbon dioxide. For example, the GWP of R-410A, the refrigerant most commonly found in recently installed heat pumps, is 1924. That means that if a pound of R-410A were to leak, it would trap nearly 2,000 times as much heat as a pound of carbon dioxide. The NIST researchers were determined to find new refrigerants for heat pumps and air conditioners that exhibited a GWP of less than 200.
After screening tens of millions of chemicals, the NIST researchers came to a disappointing realization. In the US, for nearly a century now, we’ve used nonflammable refrigerants in heat pumps and air conditioners. The NIST researchers found that they couldn’t identify a nonflammable refrigerant for that equipment that also met their low-GWP goal. They found that what makes a refrigerant exhibit low GWP is a molecular structure that decomposes rapidly when exposed to oxygen in the atmosphere. Furthermore, that very same ability to react with oxygen tends to make chemicals flammable. What lowered GWP also raised flammability. Something had to give.
Eventually, the NIST researchers came to accept that many of the refrigerants that made their final cut would be flammable, although not highly flammable. Many of their best candidates they described as “mildly flammable,” meaning that they can be ignited, but not easily: only in specific air concentrations, and only when they come in contact with an open flame or similar high-energy ignition source. Many, but not all, of these refrigerants came from a new family of chemicals that had never been used as refrigerants before: hydrofluoroolefins or HFOs for short. Like HFCs, HFOs are also composed of hydrogen, fluorine, and carbon, but unike HFCs, they feature a unique molecular structure that breaks down rapidly in the atmosphere.
Relax, it’s only mildly flammable
When industry researchers discovered that low-GWP refrigerants would be mildly flammable, they went to work figuring out how to use them safely. It turned out that it wasn’t easy to ignite them. For example, a small pinhole leak in a refrigerant pipe was unlikely to cause a fire. The leaking refrigerant would quickly diffuse into the surrounding air and become too diluted to ignite. Indeed, they found even much larger leaks could be prevented from igniting by using fans to mix the leaked refrigerant with room air. For the classic North American ducted central heating and air conditioning system, these researchers determined that those units would come standard with a factory installed refrigerant detector. If the detector ever sensed there was a refrigerant leak approaching the ignitable air-refrigerant concentration, the detector would turn on a fan to dilute the refrigerant with indoor air. For small room-size air conditioners, they decided that even less stringent measures would be sufficient. These safety measures, and others, were compiled into national standards governed by Underwriters Laboratories and the American Society of Heating, Refrigerating, and Air Conditioning Engineers.
There are good reasons to expect that these new generation refrigerants, if used in accordance with the new national standards, would not compromise public safety. In Asia and Europe, over 70 million installed air conditioners contain mildly flammable refrigerants. According to Julius Ballanco, P.E., an engineer who consults for equipment manufacturers, “To date, no accidents or incidents with loss of life or limb have been reported.” Furthermore, most new cars sold in the US currently contain mildly flammable refrigerants in their air conditioning systems.
The refrigerant revolution will not be televised
Probably, no one will ever make you replace the refrigerant in your existing heat pump or air conditioner with a new generation refrigerant. For one thing, most of the new generation refrigerants require specialized equipment designs. There would be problems if they were simply injected into older equipment. For another, policymakers know that, eventually, older equipment will be replaced when it’s worn out. As a result, the air conditioning industry and policymakers are focusing on refrigerants for new equipment. Even so, heat pumps and air conditioners containing the new low-GWP refrigerants won’t be available in the US for at least two-years, and maybe as long as five. What’s holding them back are the manufacturers’ new product development processes, regulatory uncertainty, and building codes.
Air conditioning manufacturers typically take at least three years to bring new equipment to market. It just takes that long to design, test, certify, train contractors, mass-produce, and ship new products to wholesalers. One thing that’s slowing them down, and they’ve been objecting to repeatedly in recent years, is the high level of regulatory uncertainty. Currently, there is no comprehensive national plan to mitigate climate change in general, let alone eliminate the use of high-GWP refrigerants. So far, five states passed legislation banning the use of old-generation HFC refrigerants in a variety of equipment types, like refrigerators and high-rise building cooling systems. Of those states, only California is considering regulations that would affect heat pumps and air conditioners, and the outcome of that effort is far from certain. If manufacturers knew there was a certain date on which they had to provide new generation equipment nationwide, that would enable them to focus their efforts and expedite those product development processes.
Arguably, the most intractable obstacle is building codes. There are few building codes in the United States that accept mildly flammable refrigerants. Yes, there are national standards that prescribe the safe use of these refrigerants, but they have hardly been incorporated into any codes. So far, only Washington State amended those standards to its codes. For the vast majority of states, cities, counties, and other building code jurisdictions, those standards won’t be incorporated into their codes for another six years, at the earliest. Given that there are thousands of building code jurisdictions in the US, encouraging them to expedite their standard code upgrade processes would be an enormous undertaking. Passing national refrigerant regulations would help here as well.
Public policymakers and wonks, if you want to support the refrigerant revolution, your best bet is to support regulations that eliminate the old high-GWP refrigerants at both the federal and state level. If you want to get even more deeply involved, support amending local building codes with the national standards that govern the safe use of mildly flammable refrigerants. For those of us who are neither policymakers nor wonks, there’s an election coming up. Support candidates who support comprehensive climate change mitigation. Some will explicitly support refrigerant regulation, but even if they don’t, candidates who support returning to the Paris agreement will also likely support eliminating the use of the old-generation, climate change-contributing, refrigerants.
Thanks for reading this post. If you’ve gotten this far, you’ll probably enjoy my previous post on this topic: US Push to Phase Down Global Warming Inducing Refrigerants Blocked by Trump Administration, Moves to the States