The UK's first "air rights" building – constructed on top of an existing structure – 1 Embankment Place was built over Charing Cross Station in the early 1990s.
This 40,000 sq ft (3,716 sq m) floor space has since been occupied by PwC, whose office is on the ground floor below the busy station and floors one to nine above.
After receiving the UK's first BREEAM Outstanding award for its new-build riverside offices near Tower Bridge, the company had a decision to make: with just four years to run on the lease, should it replace its leaky old building further upstream with a more sustainable new-build?
In fact the company opted to refurbish the structure into a world-first for energy efficiency and low carbon technology. In 2013, 1 Embankment Place achieved the highest BREEAM Outstanding rating recorded worldwide. The company believes the experience proves the business case for re-use of an old building as well as the associated benefits for employees and the local community.
Tackling the impact of old building stock is one of the major challenges in a transition to a low carbon economy. PwC engaged an energy-modelling specialist to develop options that would achieve a minimum BREEAM rating of Excellent, while aspiring to Outstanding status.
Workshops were held with staff, locals and businesses to ensure the plan worked for everyone, including issues of noise and timely delivery.
First, the building was stripped back while part-occupied by 2,000 staff. With floors five to nine completed, staff shifted to enable refitting of the remainder.
New technologies include a tri-generation combined cooling, heat and power system. This is fuelled by recycled waste vegetable oil that is collected and refined locally to a new efficiency standard by Uptown Oil and South Bank University.
Chiller beams replace air conditioning and low-power lift braking has been installed, along with eco-friendly carpet tiles and electrical charging points. Open plan spaces and airy atria provide natural light; roof gardens and green walls contribute to the building's ecology; and waterless urinals and low flush toilets reduce water use.
During the work, 95% of materials were sourced responsibly and 96% of construction waste was diverted from landfill.
The result is a building with Environmental Performance Certificate A and a BREEAM score of 96.31% – surpassing all others internationally. Today the building emits 40% less carbon than one typical of its size; and 20% of heat and 60% of its energy needs are produced on-site.
Estimates suggest a utility bill saving of £250,000 a year, but PwC forecasts more: electricity (-221%); gas (-11%); and water (-33%).
The refurbishment is expected to pay for itself in less than four years and the company says the transformation will help it achieve PwC's 2017 targets to reduce carbon emissions by 50% and energy use by 25%.
The result? A leaky old building has become the most sustainable in the world.
Lynn Beavis is part of the wordworks network
The Guardian Sustainable Business Sustainability Case Studies contain articles on all the initiatives that met the criteria for the GSB Awards.
