3OU Holdings Leeds adds building physics capability as three-business group targets net zero design market

Leeds-based building services group 3OU Holdings Leeds has merged with Decarbonised Ltd, adding low-carbon building physics expertise to its existing commissioning and design consultancy businesses. The deal creates a three-business portfolio under the 3OU umbrella: Verisys (commissioning and validation), Kaizen Consulting Engineers (MEP design), and now Decarbonised (energy modelling, airflow analysis, daylighting, and thermal performance). The group, founded in 2022, has grown to a 35-strong team with combined turnover of £3 million across its existing operations.

What the Merger Adds

Decarbonised specialises in building physics, the modelling and analysis work that sits at the front end of construction projects, assessing how a building will perform in terms of energy use, temperature control, daylight, and ventilation before it is built. That capability plugs a specific gap in the 3OU Holdings Leeds offer. Kaizen designs the mechanical, electrical, and plumbing systems; Verisys validates and commissions them once installed. Decarbonised now provides the early-stage performance modelling that informs the design in the first place.

The group’s three founders Chris Tate, Leigh Farr, and Phil Riddeal, previously worked together at fellow Leeds engineering consultancy Silcock Leedham before launching Kaizen in 2020. The three businesses now operate from offices in Leeds and Warrington.

“Bringing Decarbonised into the group is a natural next step as its expertise in building physics and energy services is paramount to the success of any project in the built environment. Together, we are closing the loop on early building physics work and validating design for performance, which sets us apart and helps our clients achieve their ESG goals.”

— Phil Riddeal, Director, 3OU Holdings

Why It Matters in the Current Market

The merger reflects a broader trend in the construction and property sector: as net zero and ESG requirements become standard in commercial development, the demand for integrated building performance services is growing. Clients increasingly want a single group that can model energy performance, design the building systems, and then commission and validate them rather than working with three separate consultancies.

Why this matters for Leeds

Leeds has a growing cluster of building services and sustainability consultancies, and this merger is a good example of how smaller firms are combining to compete for larger, more complex contracts. As net zero requirements become standard in commercial development integrated groups that can handle building performance from design through to commissioning are better positioned to win work.