HVAC refrigerants explained: A complete guide

Refrigerants are right at the centre of HVAC systems and without them the entire process would be impossible. This is because refrigerants do the hard work of absorbing heat from indoor spaces and then releasing it elsewhere – usually outdoors. This results in comfortable indoor temperatures for occupants in residential, commercial as well as industrial spaces. 

But it’s about more than just comfort. The choice of refrigerant actually affects the efficiency of the system as well as how safe it is and its impact on the environment. These days regulations globally are becoming more strict due to environmental concerns so making sure you fully understand HVAC refrigerants has never been more important. 

So this guide explains what HVAC refrigerants are, how they work, as well as the most common types used today. We will also look at the environmental impact of refrigerants and how to choose the right one for your system.

Complete guide to HVAC refrigerants

An HVAC refrigerant is a chemical used within a closed-loop system to transfer heat. In other words, when it is cooling, the refrigerant absorbs heat from indoor air as it evaporates at low pressure. It is then compressed which raises its temperature and releases the heat outdoors as it condenses back into a liquid. Meanwhile, in heat pump systems, the same process is reversed to provide heating.

Choosing the right refrigerant is vital because each is unique in terms of its properties, operating pressure, and safety classifications. If you get the wrong refrigerant it can reduce the efficiency of the system and, at its worst, cause equipment failure. Something to be avoided at all costs.

Common types of HVAC refrigerants

HVAC refrigerants have changed a lot over the years. Let’s look at the main options today:

• R-22: R-22 used to be the most widely used refrigerant in residential and commercial HVAC systems. It offers good heat transfer properties and it’s reliable but it has a high ozone depletion potential (ODP). Because it’s not environmentally friendly, it has been phased out in many countries and new production has been banned.

• R-410A: R-410A replaced R-22 in many modern systems because it has zero ODP and also works more efficiently and has a better cooling capacity. However, R-410A operates at much higher pressures so has a relatively high GWP so it is now considered a transitional solution rather than a long-term option.

• R-32: R-32 is increasingly used in modern HVAC equipment across the world. It has zero ODP and a significantly lower GWP. It’s also efficient and requires a smaller refrigerant charge which reduces environmental impact even more. However, because it is mildly flammable, systems must be specifically designed to use it.

Low-GWP alternatives

As we have seen, the industry is moving towards a broader range of low-GWP refrigerants. These include HFO-based blends and natural refrigerants such as CO₂ (R-744) and propane (R-290). These options can reduce climate impact but often require specialised systems, updated safety standards as well as trained technicians. So there is considerable investment required.

Environmental impact and regulations

The environmental impact of HVAC refrigerants is measured primarily through ozone depletion potential (ODP) and global warming potential (GWP). Let’s look at exactly how these terms are defined:

• ODP measures how much damage a substance can cause to the ozone layer compared to a reference compound. Older refrigerants have high ODP, which led to the global adoption of the Montreal Protocol that phased them out.

• GWP measures how much heat a greenhouse gas traps in the atmosphere compared to carbon dioxide over a specific time period. Many modern refrigerants have zero ODP but still contribute significantly to climate change due to high GWP values.

International agreements such as the Kigali Amendment to the Montreal Protocol now target high-GWP refrigerants, driving a global move towards low-GWP alternatives. Often regional regulations (including in Europe, North America and parts of Asia) impose strict limits on refrigerant use, leak management and end-of-life recovery.

Choosing the right refrigerant for your HVAC system

Selecting the correct refrigerant involves balancing a number of different considerations. The first is compatibility with your system. Because HVAC systems are engineered for specific refrigerants, retrofitting an existing one to a different refrigerant is often complicated and may require major modifications.

Energy efficiency should also be a priority, choosing refrigerants that have better performance and reduce the amount of electricity you use.

Climate is another consideration, as some refrigerants perform better in high ambient temperatures so they are more suitable for hot climates and heavy cooling loads.

Of course, safety is paramount. This includes flammability and toxicity classifications. While many low-GWP refrigerants are mildly flammable, modern system designs and standards mitigate these risks when properly applied.

Choosing a refrigerant that is already restricted or scheduled for phase-down is not recommended and can lead to higher costs. The best approach focuses on refrigerants that meet current regulations while aligning with long-term sustainability goals.

FAQs about HVAC refrigerants

What refrigerant is used in modern HVAC systems?

Most modern systems use R-410A or R-32.

Why is R-22 being phased out?

R-22 damages the ozone layer and is not environmentally friendly. International agreements have mandated that it be phased out, making it unsuitable for new systems.

Can refrigerants affect energy efficiency?

Yes. Refrigerants directly influence heat transfer efficiency. Advanced refrigerants can improve system performance and reduce energy consumption.

Is it possible to change the refrigerant in an existing HVAC system?

In some cases, limited retrofits are possible, but most systems are designed for a specific refrigerant. Full replacement is often more practical and reliable.

About Daikin

Daikin is a global leader in HVAC innovation and a pioneer in sustainable refrigerants. We have played a central role in advancing low-GWP refrigerants such as R-32 and designing systems that maximise efficiency while minimising environmental impact. 

Daikin delivers HVAC solutions that balance performance and sustainability and our next-generation systems demonstrate how refrigerant innovation can support both climate goals and long-term operational efficiency.