A close up of an aerosol can

+ Not all refrigerants are created equal

Cooling is becoming an increasingly hot topic. As countries develop, more people demand air conditioning. That means rising demand for refrigerants. We need to act now to make sure those refrigerants are as green as possible.

Making refrigerants is a complicated business best left to chemists and refrigerant engineers. But which ones we use is a question that we should all be thinking about – because our choices can have a big impact on the environment.

There are lots of types of refrigerant because different ones are best for different target temperatures (you want the refrigerant’s boiling point to be a bit below your target temperature). If possible, refrigerants also need to be non-toxic, chemically unreactive and non-flammable.

Unfortunately almost all of the known chemicals that meet these criteria are really bad for the environment. They cause ozone depletion (an issue most people associate with now widely banned CFCs) and they cause global warming.

The popular refrigerants used today are generally good on ozone and bad on global warming. The most common one used in cars and to cool buildings – R134a – is chosen because it has zero ozone depletion potential (ODP). However it has a massive global warming potential (GWP) of 1430 (carbon dioxide has a GWP of one). It simply has to be replaced.

The people at BRE (UK) have updated their BREEAM sustainable building rating system to include points for refrigerants with a global warming potential (GWP) of less than ten. This strict, but appropriate, limit cuts out most refrigerants.

Using the BRE standard leaves just a handful of options and only three that tick most boxes: ammonia (R717), carbon dioxide (R744) and the rather difficult to pronounce hydrofluoroolefins (HFOs), known collectively as R1234.

Almost all the other discovered refrigerants that have a GWP lower than ten with a zero ODP are flammable concoctions derived from propane, pentane, butane, propylene, ethane or isopropane. So if you’re a non-chemist like me, it’s actually quite simple; we have just three refrigerants to get excited about.

Ammonia (R717) is a fantastic refrigerant that is very efficient at useful temperatures. But because it’s poisonous at high concentrations, it is mainly used in large-scale applications – where it’s actually quite common. From an environmental perspective you can’t do better; it has zero ODP and zero GWP.

Carbon dioxide (R744) isn’t as efficient as ammonia, partly because it has to be operated at very high pressures to be useful. But it’s much safer, making it a great choice for small-scale heat pumps in a garden environment. It also has zero ODP and a GWP of just one.

HFO (R1234) is a new refrigerant developed by Dupont and Honeywell over the last decade. It has a very low flammability and is nearly a “drop-in replacement” for the very popular R134a, while only having a GWP of six and zero ODP.

The automotive industry is in the process of adopting R744 & R1234 and we in the construction industry could do a lot to tackle climate change by following their example. Because let’s face it, the pace at which these clean refrigerants are adopted in the built environment is not just up to the chemists, refrigerant engineers and environmental legislators, it’s up to all of us.