Our client, a leading entity in the construction sector, is seeking a highly experienced and driven Principal Mechanical Building Services Design Engineer to join their team. This permanent role requires you to lead complex mechanical design packages and mentor a team of engineers. You will play a strategic role in delivering technically sound, regulation-compliant, and sustainable mechanical systems for new build and refurbishment projects across the UK and Ireland. Key Responsibilities: Lead mechanical design from concept through detailed design, tender, construction, and commissioning stages Develop designs for HVAC systems, Domestic Hot&Cold Water Services, LTHW and CHW, renewable and low-carbon energy systems, steam and compressed air systems, and Building Management Systems Manage and mentor design teams, ensuring adherence to project timelines, quality standards, and technical accuracy Produce and review detailed mechanical calculations for pipe and duct sizing, pump and fan selection, heat loss/gain, and system pressure drops Coordinate mechanical designs with other disciplines including electrical, public health, architectural, structural, and sustainability Provide technical input at all project stages including feasibility, value engineering, and commissioning reviews Attend and lead client meetings, site inspections, and technical workshops Ensure compliance with current UK and Irish regulations, energy targets, and best practices Support development and implementation of BIM Level 2 and ISO 19650 design workflows Job Requirements: High proficiency in Hevacomp, IES VE, MagiCAD for AutoCAD/Revit, Autodesk Revit (MEP), AutoCAD 2D, and BMS tools Proficient with Microsoft Excel for custom engineering calculations and performance schedules Degree in Mechanical Engineering or Building Services Engineering (BEng/BSc minimum; MEng preferred) Chartered Engineer (CEng) status with CIBSE or IMechE (or actively working towards) Significant experience in mechanical building services design within the UK, with leadership responsibilities Experience leading mechanical design on large-scale or complex projects Strong understanding of UK BIM standards (BS EN ISO 19650) and multidisciplinary coordination practices Excellent verbal and written communication skills Desirable Attributes: Experience in decarbonisation and whole-life carbon design strategies Knowledge of embodied carbon tools (e.g., CIBSE TM65) Experience working across both UK and Irish regulatory environments Sector-specific experience in healthcare, education, or data centres Experience supporting bid writing, fee proposals, and project planning If you are a seasoned design engineer with a blend of technical expertise, leadership qualities, and regulatory knowledge, we would love to hear from you. Apply now to contribute to our client's innovative and dynamic projects across the UK and Ireland.