HVAC Design Engineer

About Assystem

Assystem is an international engineering and project management company with over 8,000 Switchers worldwide, committed to accelerating the global energy transition. In the UK, we deliver complex infrastructure and nuclear programmes, supporting landmark projects such as Hinkley Point C, Sizewell C and emerging SMR developments. Our teams combine deep engineering heritage with digital capability, working across the full project lifecycle to deliver safe, efficient and sustainable solutions at scale. 

  Why Join the Community of Switchers?

Joining Assystem means becoming part of one of the three largest nuclear engineering companies in the world. Our UK teams operate at the heart of nationally significant infrastructure, shaping the future of clean energy delivery. You will work alongside experienced engineers in a collaborative environment where technical excellence, governance and safety drive every decision, while benefiting from structured development and exposure to major nuclear construction programmes. 

Our organization delivers engineering and project management services across a wide range of industrial, commercial, and infrastructure sectors. We develop efficient HVAC solutions that support safe, reliable, and sustainable building operations. Our teams work collaboratively to design, review, and deliver high‑quality engineering systems for complex, multi‑disciplinary projects.

Job Description

  Join the Fusion and Modular Nuclear Business Unit! Reporting to the Turbine Island Lead, the Senior Mechanical Engineer shall be responsible for various Turbine Island design development activities. The Senior Mechanical Engineer shall work closely with multidisciplined teams and the supply chain to help deliver the Turbine Island design. 

Your mission:

• Serve as the key liaison between HVAC design teams and construction/installation teams, ensuring seamless collaboration and delivery.
• Lead the development and review of HVAC designs , guaranteeing precision, quality, and alignment with detailed engineering specifications.
• ✅ Conduct thorough technical assessments to ensure full compliance with industry standards and project requirements.
• Evaluate and validate contractor deliverables , including drawings, method statements, and test plans, to uphold project excellence.
• ️ Drive the integration of HVAC systems within wider mechanical, electrical, and building services frameworks.
• Actively contribute to design coordination meetings and multi-disciplinary reviews, fostering alignment across all project stakeholders.
• ⚠️ Support risk assessments and safety evaluations , promoting a proactive and safety-first project environment.
• Assist in commissioning activities , ensuring HVAC systems perform efficiently and meet design intent.
• Provide expert input on change management , including design updates and configuration control processes.
• Maintain strong, consistent communication with project managers, quality teams, and cross-functional engineering disciplines.

Why Join the Community of Switchers?

• Over 55 years in nuclear engineering.
• Ranked among the top 3 largest nuclear engineering companies.
• Attractive social benefits, including an engaging Employee Committee and holiday bonuses.
• Ongoing training with numerous career opportunities.
• 70% of our managers are promoted internally!
• Hybrid work: 1-2 days remote per week.

Qualifications

Essential

• Degree-qualified in Mechanical Engineering, Building Services Engineering, or a related discipline.
• ️ Proven experience in HVAC design or building services engineering , with exposure to system integration in complex projects.
• Strong knowledge of HVAC codes and standards (e.g., ASHRAE, CIBSE, ISO, and relevant local regulations).
• Confident in interpreting technical drawings and specifications , with a keen eye for engineering detail.
• Experience collaborating with contractors and site teams , working effectively across multi-disciplinary environments.
• Excellent communication and teamwork skills , thriving in dynamic, project-driven settings.
• Experience in regulated industries or large-scale infrastructure projects is advantageous, but not essential.

Preferred Skills

• Proficiency in HVAC design software , including Revit, AutoCAD, BIM tools, and load calculation software.
• ️ Solid understanding of HVAC fundamentals , including ventilation, heat load calculations, duct sizing, equipment selection, and system performance analysis.
• Familiarity with commissioning processes and quality assurance practices , ensuring systems meet operational standards.
• Strong analytical and problem-solving skills , with exceptional attention to detail.

Additional Information

Due to the nature of work to be undertaken applicants will be required to meet certain residency criteria in order to attain a minimum level of UK security clearance if not already security cleared to a minimum SC level.

We are committed to equal treatment of candidates and promote, as well as foster all forms of diversity within our company. We believe that bringing together people with different backgrounds and perspectives is essential for creating innovative and impactful solutions. Skills, talent, and our people’s ability to dare are the only things that matter !. Bring your unique contributions and help us shape the future.