Refrigerants are critical to decarbonizing the building sector. Heat pumps and chillers, the superstars of efficient heating & cooling rely on refrigerants to function. But not all refrigerants are created equal.

You may remember in a past life, the news was full of panic about a growing hole in Earth’s ozone layer, the atmospheric shield that protects us from being cooked by the sun’s powerful radiation. This was determined to be caused by Ozone Depleting Substances (ODS) which float to Earth’s upper atmosphere and create an ozone destroying chemical reaction. Some of the most common ODS were the CFCs and HCFCs used as refrigerants in appliances and air conditioning. Amazingly, in 1987 the World agreed to the Montreal Protocol and enacted a 10-year phaseout of ODS.

Now, decades later, we are faced with a different challenge: the prospect of unmitigated global warming and catastrophic climate change.

This is driven by a build-up of greenhouse gases in our atmosphere, including refrigerants. In fact, one group of ODS replacements, HFCs including refrigerants like the R410a commonly specified in our VRF and chiller plants, have a GWP (global warming potential) over 2,000x more impactful than CO2.

So in 2016, the world made a new agreement, the Kigali Amendment to the Montreal Protocol. Here, signatories agreed to a phased elimination of high-GWP HFC refrigerants, an effort that is expected to cut up to 0.5 degrees C from the anticipated global warming.

The Kigali Amendment is being implemented by different countries through various legislative mechanisms.

In 2020, the United States passed the American Innovation and Manufacturing, or AIM Act which mandates phased reduction of HFCs in alignment to the Kigali amendment. Starting in 2025, certain refrigerants will no longer be available.

The AIM Act is phasing out the most environmentally harmful refrigerants first.

The AIM Act sets specific targets for phasing out high-GWP refrigerants in both production and installation. The law requires percentage reductions from a CO2eq emissions baseline by certain years. To achieve these thresholds, the EPA set maximum GWP values for refrigerants that can be produced and sold. Starting in 2024, these thresholds will be reduced to GWP 700 for air conditioning equipment using R-410a (with a GWP of +2,000).

If current phasedown thresholds are maintained R410a will no longer be available for purchase in new systems on January 1, 2025 and will no longer be allowed to be installed in new applications by January 1, 2026. This means starting NOW, architects and engineers are required to consider lower-GWP alternatives. The systems being used will not change, but certain performance characteristics like cooling capacity, and most importantly, flammability, will.

Why care? New refrigerants will change coordination of VRF, and other systems.

Moving to low-GWP refrigerants is a great step toward achieving our climate goals. In fact, Project Drawdown identifies it as one of the highest impact actions available with today’s technology. This change will impact building design because almost all cooling systems use some kind of refrigerant.

The most common class of low-GWP refrigerants are A2L. These are very effective and have GWPs below 700, still problematic but a huge step down from a GWP of 2000. However, A2L refrigerants do have a big caveat, they are (somewhat) flammable.

So, how is that going to impact our designs?

Well, if you are in NYC, that remains to be seen. NYC uses the 2015 version of the International Mechanical Code (IMC) which did not include specific rules for A2L refrigerants. However, in the most recent 2021 IMC section 1109, there is language that will have the following impacts:

1. Refrigerant risers will have to be equipped with a leak detection system.
2. Refrigerant risers will be required to housed in a 2-hour rated ventilated shaft. Ventilation is only activated during a leak, similar to PFSP.
3. We will be able to have less refrigerant in a given riser

We should expect the greatest impact to be on VRF systems which require long runs of refrigerant travelling many floors through a building.

Changes to packaged systems with short, compartmentalized refrigerant loops (heat pumps, PTHPs, chillers) are unlikely to have an architectural impact.

There is still a lot of uncertainty here…

Code impacts are still being clarified by several AHJs, and timelines for phasing could change. Manufacturers are pushing for more leeway, the recent Supreme Court decision overturning the Chevron doctrine opens up many regulations including the AIM Act’s administration by the EPA to lawsuits, and we have a pivotal climate election in 2024. Should a Trump administration begin in 2025, they are expected to repeal or defang the AIM Act in accordance with Project 2025.

For the sake of progress toward mitigating the worst effect of climate change, we hope the phasedown will remain as scheduled so we can rapidly reduce high-GWP refrigerants.