Exhibitor News

We recently spoke to Aimee Holloran, Business Development Manager for Heating at Samsung Climate Solutions, about a factor she believes is often overlooked in heat pump design: humidity.

While discussions around heat pumps tend to focus on outdoor temperatures, Aimee argues that the UK's increasingly humid climate presents a different challenge altogether. Drawing on data modelling, installer feedback and her own research, she explains why humidity should become a greater consideration for installers as the market continues to mature.

Aimee, when people talk about heat pump performance, the focus is usually on temperature. Why do you think humidity deserves more attention?
One of the biggest misconceptions around heat pumps is that cold weather is the main challenge. When, in reality, heat pumps often perform extremely well in colder countries because the air is much drier. If you look at Scandinavia, for example, temperatures are lower than the UK, but humidity levels are significantly reduced.

The issue we face in Britain is that we're an island nation, which means we're naturally very humid. As our climate continues to change, we're also seeing higher rainfall levels, warmer temperatures, and increasing humidity as a result. That can have a direct impact on how a heat pump operates, yet it's something that isn't discussed nearly as often as temperature.

Understanding the differences in climates is fundamental for heat pump design as it enables installers to understand how a heat pump will behave in real-world conditions, allowing them to make informed design decisions and optimise system performance.

What impact can humidity have on a heat pump system?

Heat pumps extract energy from the air around them, so the environmental conditions they're operating in play a critical role in both how a system should be designed and how it will perform in practice.

Higher humidity levels can affect system behaviour and, in some conditions, increase defrost activity. While defrosting is a normal part of heat pump operation, more moisture in the air can lead to more frequent defrost cycles. Each time this happens, the system must temporarily divert energy away from heating the property to remove ice build-up from the evaporator, impacting comfort and perceived performance.  

Design flow temperature can also influence defrost performance. While lower flow temperatures can improve seasonal efficiency, they provide less available energy during defrost cycles, which can increase defrost duration and extend the time the system spends temporarily diverting energy away from heating the property.

Are installers talking about humidity enough?
I think we all need to talk about it more.

When we look at heat pump system design, conversations almost always centre around system sizing, heat loss calculations and outdoor temperature. Those factors are obviously important, but they don't tell the whole story. Humidity is certainly one of the areas that I think deserves more attention because it has the potential to influence system behaviour in ways that many installers may not have considered before.

But it’s also important that installers understand how modern heat pumps respond to different operating conditions. Today's systems incorporate built-in control logic for functions such as compressor protection, defrost assistance and backup heating, all designed to maintain performance and protect the system. 

Therefore, understanding both the environmental conditions a heat pump is operating in and how the unit is designed to respond to them will help installers to make more informed decisions around design, commissioning and troubleshooting.

Are there installation factors that can make humidity-related issues worse?
Good design is, as always, fundamental. For example, airflow around an outdoor unit is critical. If a heat pump is enclosed, positioned incorrectly or installed without sufficient clearance, installers can inadvertently create a microclimate around the unit.

This can mean that the heat pump is effectively operating in conditions similar to a refrigerator, where moisture and cold air become trapped around the appliance. As a result, this can affect how efficiently the system operates, which is why following manufacturer guidance on positioning and clearances remains so important.

Ultimately, the better the airflow, the better the conditions for the heat pump to do its job.

Do you think current design standards fully account for humidity?

It's an area I'd certainly like to see explored further. Heat loss calculations have traditionally focused on temperature but in the UK’s unique environments, and as our climate changes, humidity must play a larger role in design methodologies.

MCS is currently reviewing MIS 3005, and I think this presents an important opportunity for the industry to have wider conversations about how we design and optimise systems for real-world conditions to ensure they perform correctly, for the long-term. 

Heat pumps don't struggle because it's cold. As I say, they often even thrive in colder climates. The challenge in the UK is that cold weather frequently arrives alongside high humidity and understanding that relationship is becoming increasingly important.

And as heat pump uptake increases across the UK, incorporating regional differences into design practices will be fundamental to ensure comfort and performance - and even protect the reputation of the technology itself. 

What is the key takeaway for installers?
The biggest takeaway is that good design remains fundamental to heat pump performance.

Heat pumps are incredibly capable technologies, but like any heating system, they perform best when they're designed and installed correctly.

For me, this is really about education. It's about giving installers the knowledge they need to make informed decisions about system design, commissioning and operation. The more we understand factors such as humidity and how local environmental conditions influence performance, the better equipped we are to deliver efficient, reliable systems for occupants.

Because, ultimately, successful heat pump installations rely on understanding both the technology itself and the environment it will operate in.