Already established as one of Ireland’s premier mechanical engineering contractors – specialising in HVAC, steam, water, air and heating systems – Dominic O’Connor Ltd. is also delivering decarbonisation through deep retrofit projects that cut carbon and improve BER. Building Ireland spoke to commercial director David Twomey to find out more.
Energy upgrade projects – many of these delivered under the Schools Energy Pathfinder Programme – have become a big part of the extensive service offering at Dominic O’Connor Ltd.
The eponymous founder of this progressive and innovative Galway-headquartered, industry-leading mechanical contracting company took the lead in embracing the energy evolution many years ago and is now reaping the rewards of that vision.
As commercial director David Twomey confirms: “We’ve been doing the energy upgrades since 2020. Dominic was ahead of his time and was always interested in going down this road. He initially took on a couple of schools jobs, delivering deep energy retrofits under the SEAI and Energy Pathfinder schemes., and that has taken off in a big way for us.”
Today, alongside their core engineering capabilities, Dominic O’Connor Ltd. plays a key role in building retrofitting and decarbonisation, supporting the transition to more sustainable and energy-efficient buildings. Their team delivers tailored upgrade solutions across existing infrastructure, incorporating advanced technologies and modern mechanical systems to improve performance and reduce environmental impact.
This critical, value-added, building futureproofing work includes energy retrofits in sectors such as healthcare, education and commercial buildings, where careful planning and coordination are essential to minimise disruption. By integrating innovative approaches with practical onsite experience, the company enhances building efficiency, extends asset life and contributes to national sustainability goals.
With a strong focus on quality, innovation and continuous improvement, Dominic O’Connor Ltd. is helping shape a more sustainable built environment across Ireland.
To successfully deliver these deep energy retrofit programmes, invariably working in live setting for key clients such as the Department of Education and the HSE as well as enjoying strong collaborations with a who’s who of Tier One main contractors, Dominic O’Connor Ltd. have developed an in-house decarbonisation department / team, headed up by a dedicated senior project manager. “It’s an area that has taken on a life of its own really and probably accounts for up to 30 per cent of our turnover over the past two years,” David continues.
“We’re currently looking at a large bundle of tenders for retrofits schemes with works including air source heat pumps, biomass and ground source heat pumps. Because of the Government’s 2040 and 2050 sustainability targets, this is an area of the construction industry that’s growing.
“We take the projects on as the main contractor. Because 50–70 per cent of the work is mechanical and electrical upgrades, we can obviously self-deliver the mechanical element, then bring in proven subcontractors to look after everything else.
“As Main Contractor we self-deliver all mechanical installations while working alongside a carefully selected network of specialist supply chain partners across the civil, electrical and building trades. We place huge importance on developing long-term relationships with trusted subcontractors while continually expanding our supply chain to ensure we have the right expertise and capacity for every project.”
Dominic O’Connor Ltd. is a progressive mechanical building services contractor headquartered in Loughrea, County Galway and with a second office in Cork. Operating in various sectors including healthcare, education, residential, leisure, commercial and mixed use developments, the company has experienced significant growth since its establishment in 1999.
Dominic O’Connor Ltd. provides a comprehensive range of mechanical building services, including HVAC, plumbing and public health systems, heating, ventilation, building management systems (BMS), process pipework and renewable energy solutions. With extensive experience across public and private sector projects, the company delivers complex mechanical installations, specialist engineering systems and large-scale decarbonisation and energy retrofit programmes for clients across the public and private sectors. The company’s continued growth and industry reputation were recognised this year when it was shortlisted in three categories at the Irish Build & Design Awards.
Boasting a strong track record in delivering complex commercial, healthcare, industrial and education projects across Ireland and with extensive experience in both design and installation, the company provides a complete service from initial planning through to project completion. Their expertise spans high-spec mechanical systems including HVAC, pipework, heating and specialist laboratory and process installations.
Known for quality workmanship and dependable delivery, Dominic O’Connor Ltd. has built a reputation for successfully managing technically demanding projects, particularly within live environments such as hospitals, pharmaceutical facilities and largescale educational developments. By combining skilled in-house teams with modern construction methods such as BIM, offsite fabrication and Lean principles, Dominic O’Connor Ltd. ensures precision, efficiency and consistently high standards across every project.
“We’re very busy at the moment between live projects and jobs currently being tendered,” says David. “The success and growth we’ve experienced is down to the quality and commitment of our people. We now directly employ around 180 staff across the business, reflecting the significant investment we’ve made in building a highly skilled in-house team. When I joined the company in 2020, we employed between 80 and 100 people, so that gives a good indication of the scale of growth we’ve achieved over the past six years.
“Having a large directly employed workforce that self-delivers our mechanical installations is one of our greatest strengths. It gives us greater control over quality, programme delivery and health and safety while ensuring consistency across all our projects. We’re equally committed to developing the next generation of skilled tradespeople, maintaining a strong balance of experienced personnel and apprentices as the business continues to grow.
“We’re particularly proud that many of the apprentices who joined the business over recent years have progressed into site supervision and foreman roles. Investing in our people and creating long-term career opportunities has been central to the company’s continued growth, and we’re fortunate to have many employees who have built their careers with us.
“Office staff is probably the area where we’re finding it hardest at present. We got lucky during Covid when people couldn’t really travel or go anywhere but we have lost a couple of QS’s, for example, and it’s difficult to replace them. Don’t get me wrong, we have an exceptional team currently and couldn’t be in a stronger position, but you need to find more skilled people if you want to grow the business in a sustainable manner.”
Dominic O’Connor Ltd. has a strong presence nationwide, with recent and ongoing energy upgrade packages being delivered from Wexford town to Galway, Ennis, Leixlip and Athy.
On the mechanical front, they are delivering full mechanical installation on the new STEM building at Letterkenny IT (now Donegal ATU) for BAM, having delivered a similar project at GMIT (ATU Galway city) as well as at the colleges of further education in Athlone and Tralee last year. They are working on surgical services hubs in Cork, Limerick and Waterford for JJ Rhatigan as well as a series of schools projects nationwide, including in Kilbride in Wicklow and Rathcoole in Dublin.
“We’ve built strong, long-term relationships with many of Ireland’s leading Tier 1 contractors, public sector clients and design teams, and we’re proud that so much of our work comes from repeat business. We believe those relationships are built on trust, quality and consistently delivering successful projects, and they’re something we never take for granted.”
Dominic O’Connor Ltd.,
Eastpoint Business Park,
Greeneenagh,
Loughrea,
County Galway.
Tel: 091 880340
Email: [email protected]
Web: doconnor.ie
This article was published in Building Ireland Magazine, October 2026, Vol 12 No 11
