Silbury House in Milton Keynes has achieved a 5 Star NABERS UK Energy for Offices Whole Building rating following the refurbishment of the 1998 office building, with the assessment based on measured operational energy performance rather than design-stage predictions.
Owner RO Group says Silbury House is currently the only building in the UK holding a 5 Star NABERS UK Whole Building rating and is the third highest-rated Whole Building certified in the country. The distinction relates specifically to the Whole Building assessment, covering energy performance once the office is operating.
The result follows an extensive refurbishment intended to improve the performance of the existing property without demolishing and replacing the building. The approach retained the existing asset while upgrading its energy systems, building controls and internal specification.
Refurbished lounge area at Silbury House in Milton Keynes. Image: RO Group.
Operational Energy Upgrades at Silbury House
The refurbishment included 116 rooftop solar panels with a combined capacity of 41 kWp. According to RO Group, the installation can generate up to 20% of the building's energy demand. Heating and cooling are provided through a hybrid Variable Refrigerant Flow system incorporating heat recovery, supported by LED lighting and upgraded controls intended to reduce energy consumption. The building has also achieved an EPC A+ rating, according to the owner.
These measures are relevant because NABERS UK Energy for Offices assesses operational performance using metered energy data. This moves the assessment beyond a theoretical design target and provides evidence of how the completed building is performing in use. NABERS UK was launched in 2020 and is administered by CIBSE Certification. Office buildings can be assessed at Base Building, Tenancy or Whole Building level, with the latter taking account of energy used by office tenancies as well as base-building services serving lettable and common areas.
Retrofit Rather Than Demolition
Silbury House was originally constructed in 1998. RO Group chose to refurbish the existing building rather than demolish and redevelop the site, retaining and repurposing materials where possible. Recovered raised access flooring was reused during the works, while the specified carpet tiles contain 75% recycled content. RO Group also reports that no waste generated by the refurbishment was sent to landfill.
Ana Bajri, Group Head of Sustainability at RO Group, said the value of the NABERS assessment lies in its use of operational data.
“What is particularly important about NABERS is that it measures actual operational performance. This rating provides independent evidence that the work undertaken at Silbury House is delivering lower energy consumption and greater efficiency for our occupiers.”
Fitwel and Indoor Air Quality Certification
The energy rating forms part of a wider set of building-performance measures at Silbury House. The property has secured a 3 Star Fitwel certification for health and wellbeing, which RO Group says makes it the only building in Milton Keynes currently holding that accreditation. The building also holds RESET Air Certification, with indoor air quality continuously monitored and independently verified. RO Group says Silbury House is the only building in the region to achieve and maintain the certification.
Silbury House now provides Grade A office accommodation in central Milton Keynes, with smart-building technology, fitted office suites and upgraded occupier amenities forming part of the refurbishment. The NABERS result provides an in-use measure of the refurbishment rather than relying solely on the specifications installed during the works. RO Group has not disclosed the overall refurbishment cost in the information supplied to London Construction Magazine.
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