When major components of the Omnibus Reigate office block’s existing systems were nearing the end of their operational life, the owners, Skelton Group Investments, wanted to explore a new low carbon solution. Decarbonisation specialists Internal Environments 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.
“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,” said Chris Roy, Sales Director for Internal Environments.
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.
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 explained: “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.”
Reducing disruption for occupants was a key factor in the retrofit, as Daniel Chapman, Managing Director of the building owners, Skelton Group Investments LTD explained: “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.”
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.
Learn more: https://gb.mitsubishielectric.com/en/
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