The owners of the landmark 70,000 square foot Omnibus Reigate office block have future-proofed the building by installing Mitsubishi Electric renewable heat pump technology and air handling units.
The recent project saw gas-fired boilers and air-to-water cooling systems replaced with heat pumps, which will simultaneously heat and cool the three-story building to keep occupants comfortable while reducing environmental impact.
When major components of the building’s existing systems were nearing the end of their operational life, the owners, Skelton Group Investments LTD, wanted to explore a new low carbon solution which would replace the gas boilers with a more sustainable system.
Decarbonisation specialists Internal Environments LTD worked closely with the building owners to identify how the old system could be replaced with a fully electric system. They opted for two Climaveneta air source heat pumps, which offer simultaneous heating and cooling, and three Climaveneta water source heat pumps, all from Mitsubishi Electric. The building also benefits from WizardX-G07 E-OU air handing units (AHUs), which are fed heating or cooling from six Mr Slim air conditioning systems.
Chris Roy, Sales Director for Internal Environments, comments: “We evaluated various systems and determined that a 4-pipe heat pump providing simultaneous heat and cooling would be the optimal solutions to achieve our client’s need for a low-carbon, low energy system.”
In doing so, the building has shifted away from reliance on natural gas and driven up energy performance and carbon reduction – factors which are increasingly important for the office’s tenants.
Mitsubishi low-carbon systems in action
The 4-pipe heat pump chillers now supply heated water at a 45°C flow temperature and chilled water at a 6°C flow temperature. The team from Internal Environments worked closely with Mitsubishi Electric to carry out thermal modelling to show that a temperature of 45°C will heat the offices using the existing fan coil ceiling units when the ambient temperature is around 6-7°C and above.
To supply heating on colder days, the EW/HT water-to-water heat pumps boost the water temperature from 45°C to 75°C when necessary.
The team also prioritised refurbishment over replacing technology where possible, as Chris Roy explains.
“We thoroughly evaluated the existing fan coil units, and given that they were in good condition, decided that a refurbishment would be more environmentally friendly than a replacement. This minimised the work needed around the building and helped ensure the retrofit project was as low carbon as possible,” he says.
Reducing disruption for occupants was a key factor in the retrofit, as Daniel Chapman, Managing Director of the building owners, Skelton Group Investments LTD explains.
“The refurbished heating, cooling and ventilation system strikes a brilliant balance between efficiency, capital costs, and the preservation of embodied carbon. The work was undertaken in an occupied building with minimal disruption to tenants, and delivers a fully decarbonised, future-proof system while maintaining the comfort of current and future occupants and delivering an EPC of A,” he says.
In its recent Sustainability Index 2025 Report, global investment firm, CBRE, found that there is a ‘green premium’ for efficient, sustainable office space, and an increasing appetite for energy efficiency from both investors and tenants.
This project has strengthened Omnibus Reigate’s position in the highly competitive office market, where demonstrable energy efficiency and sustainability features extend beyond financial value to owner and tenant reputation.
As natural gas becomes less viable, this project ensures that Omnibus Reigate is fit for the future and will remain a proud landmark building in the heart of Surrey.
To explore the range of products from Mitsubishi Electric UK for cooling, heating, ventilation and controls and to find out how to order spare parts, download CAD files and request a callback via the company’s website.
