Sean McMahon, Design Engineer, PMEP Consulting /Treasurer CIBSE YEN Ireland
– Careers in Engineering
SEAN MCMAHON, Design Engineer at PMEP Consulting, Treasurer, CIBSE YEN Ireland, and CIBSE YEN Ireland Mechanical Award winner, answers some questions about what he values about being an engineer.
What is your current job and with what company?
I am a Mechanical Design Engineer with PMEP Consulting.
What drew you to engineering, more specifically building services, and what was your path to becoming an engineer and developing your earlier career?
My interest in building services engineering started from a young age. My dad is a building services engineer and owns a HVAC supply company. I grew up around large plant, like chillers and heat pumps. At the time, I didn’t really understand what any of it did. I just thought they were big, impressive machines.
As a child, when I would be out in the car with my dad, he would point out buildings and say, “We did the heating and cooling in that one”, and he would always say that’s what allowed us to go on holidays and do things as a family.
One memory that stands out as I got older is from when I was 15. I wanted money for a concert, so my dad brought me out to work on a job servicing a chiller over a couple of days. At the time, I thought it would be the most boring way to earn money. But during the job, he found a refrigerant leak and used dye and UV glasses to trace it. Seeing that this process is something you couldn’t spot with the naked eye was the first time I realised how technical and interesting the work actually was.
I started helping out in the business from around that age, going on-site with service engineers and getting exposure to sales and marketing as well. That gave me an early understanding of the industry’s different aspects, including working with contractors, consultants, and suppliers.
School itself was something I struggled to engage with. I knew I wanted to go into engineering, so I focused on engineering-related classes, and I found it difficult to connect with subjects that didn’t feel relevant.
When I started studying Building Services Engineering at TU Dublin, Bolton Street, everything clicked into place. I remember a lecture on air conditioning where we were shown how using the wrong psychrometric data for a climate could lead to a complete system failure. That was the moment I began to think like an engineer, realising how many variables are involved and how critical the decisions that we make are.
From then on, I was fascinated by how systems work together, how they impact people’s comfort, and how they can be designed more efficiently.
Among your various responsibilities, what would you say is your favourite part of the job?
In my current role as a Mechanical Design Engineer, I’m responsible for designing complete mechanical systems for new and existing buildings and conducting site visits to ensure installations align with the design intent.
The part of the job I enjoy most is starting with a fresh set of drawings and building up a complete system from scratch. One project that stands out was a large hotel retrofit, where we had to completely rethink the heating, cooling, and ventilation systems within an existing building.
The challenge wasn’t just designing new systems; it was understanding what was already there, identifying what could be reused, and figuring out how to integrate everything together. Initially, we looked at fully electrifying the heating system, but the available electrical capacity couldn’t support it. That forced us back to the drawing board to rethink our approach.
And this is what I enjoy most about the job, the problem-solving side. You can have a design in mind, but real-world constraints like power, space, and existing infrastructure mean you constantly have to adapt. It keeps the job interesting and ensures you’re always learning.
What stand out as career highlights to date?
A key highlight for me has been winning the CIBSE YEN Ireland Mechanical Award for my paper on integrating heat pumps into retrofit projects. I found out while I was in work. I got a phone call telling me I’d won, and it genuinely came as a shock. I assumed there would be others with more experience or stronger submissions.
It was the first time my work had been recognised at an industry level, which made it particularly meaningful.
Another highlight has been working on deep energy retrofit projects in schools. Seeing the real-life impact of these projects is incredibly rewarding. In some cases, improved ventilation with heat-recovery systems made a noticeable difference for students, particularly those with asthma, helping to create a healthier and more comfortable learning environment.
It’s the moments when you see the outcome beyond just drawings and calculations that really stand out to me.
Looking ahead, what aspects of your work or the broader engineering landscape genuinely excite you for the future?
What excites me most is how the push to reduce carbon emissions is actively changing the way building services engineers design buildings. It’s not just about swapping out old systems for new ones; it’s forcing a complete rethink of how buildings operate.
One area I’m particularly interested in is heat pumps in retrofit projects. There’s a common misconception in the general public that you can simply replace a boiler with a heat pump and everything will work the same, but in reality, it requires a completely different approach. The physics involved is different, and systems need to be designed accordingly.
That challenge in educating clients and designing systems that actually perform as intended is something I find really engaging. It’s not just about applying technology; it’s about understanding it properly and making it work in real buildings.
Who or what are your primary sources of support, both professionally and personally (networks), as you navigate your engineering career?
My main support network comes from my dad, my colleagues and the wider group of industry contacts I’ve built over time. Having grown up around building services, my dad has always been someone I can go to for practical advice, particularly for real-world applications.
I’m also part of the ASHRAE Young Engineers in ASHRAE (YEA) programme, where I’ve been paired with a senior mentor. Having someone experienced to bounce ideas off and challenge my thinking has been really valuable in developing my technical and professional skills.
What bodies are you a member of, and how important is this to you?
I am currently the Treasurer of CIBSE YEN Ireland and also part of the ASHRAE YEA mentorship programme.
Being involved in these organisations has been very important for networking and development. Through CIBSE YEN, I’ve helped organise events such as karting and social meetups, which bring young engineers together in informal settings.
I’ve also had the opportunity to give a guest lecture in TU Dublin, Bolton Street, speaking to students about entering the industry. That was something I found particularly rewarding, being able to share my experience with people in the same position I was in not too long ago.
If you could offer one piece of advice to a younger person starting out in engineering, what would it be?
My main advice would be to always ask questions. Early in my career, I sometimes avoided asking questions because I didn’t want to come across as inexperienced or not worth my salary. Looking back, that was completely the wrong approach.
The more questions you ask, the more you learn, and it’s far better to clarify something early than to make mistakes or assumptions.
I would also encourage young engineers to take risks. Put forward ideas, get involved, and don’t be afraid to step outside your comfort zone. Early in your career is the best time to do this, as it helps you build confidence and develop your own way of thinking.
To have your career journey to date considered for a “Careers in Engineering” feature, email the editor at robbie@buildingsevicesengineering.ie