Rab Bennetts from Bennetts Associates, together with AT Awards judges Lee Mallett, Farshid Moussavi and Asif Din, discuss the drivers behind the design of Wessex Water Operations Centre and the lessons learned from over 20 years of post-occupancy evaluation. Timothy Soar’s photographs capture the project as it is today.
Located on a steeply-sloping site in a designated Area of Outstanding Natural Beauty outside Bath, Wessex Water Operations Centre is a simple, robust building that incorporates a wide range of passive and active environmental technologies, including natural ventilation, low-embodied energy, lots of daylight, reduced transport, waste, and recycling, photovoltaics and enhanced biodiversity.
On completion, the building achieved the highest BREEAM rating for a commercial office, attaining standards comparable to low-carbon targets being set in 2023. It also trialled the Building Research Establishment’s new Envest software to minimise lifetime embodied carbon – the first UK building to do so on a large scale.
All the energy-saving strategies worked, as regular post-occupancy evaluations have since proved. The architect has retained an ongoing interest in the building, allowing it to share building performance data from more than 20 years of use.
Elevations composed of solar shading and local Bath stone sit comfortably within the rural setting. The landscape incorporates restored semi-natural habitats including wildflower grasslands.
Rab Bennetts, architect This was one of a series of four projects we were doing in the 1990s: PowerGen in Coventry, John Menzies and BT Scotland in Edinburgh, and Wessex Water in Bath. They were all owner-occupied buildings, they all wanted to radically improve their own workspace, and they were all able to introduce us to the users who we worked with during and after the project. Furthermore, they all had an interest in sustainability, or energy efficiency as we tended to call it at the time. And that was generally for the operation of the buildings, but as the series of buildings progressed we started looking at carbon in construction as well.
Farshid Moussavi This 20-year-old building is completely responsive to the environmental challenges of today. It’s aged well. It shows a level of care, both locally, in its clever siting and use of materials, and globally, with its strategies for low-carbon consumption and the circular economy.
Naturally ventilated workspaces are connected by an internal street and designed to give everybody access to views of the surrounding countryside.
Rab Bennetts We’d started to think quite hard about the amount of concrete we were using in buildings at that time because of the thermal mass. That led to a culture of measurement for everything we do. So we measured when we designed, we measured when we’d finished, and we’ve measured things ever since. Design is objective as well as subjective, and if you can prove the science behind what you do it’s a great vehicle for promoting good architectural ideas.
Asif Din It’s impressive to see a clear lineage in Bennetts Associates’ work, and a systematic culture of learning from previous projects.
Rab Bennetts The wellbeing in the workplace agenda that we know now really started here so, for the very first time, we were looking at things like comfort in the workspace, access to a view, opening windows, sociability – all the things that make a nice place to work, as opposed to the uniformity you were getting through the British Council for Offices specification and the air-conditioned norms of the time.
Elegant brises-soleils made from perforated aluminium are fixed along the south and west facades. The lightweight design protects views out and optimises internal daylight while reducing solar gain to levels that allow the natural ventilation strategy to work during summer.
Farshid Moussavi It is a best-case example of how all architects should have been thinking at the time, and in many ways, office design is still trying to catch up.
Rab Bennetts It was built into the brief that we should do three years of post-occupancy evaluation, so we accumulated a huge amount of information about how the building was performing. And it was slightly underperforming when it was finished, so we spent the first year refining it to get it back to the standards we had in the design brief and the specification.
Lee Mallett It’s also a good example a practice maintaining an interest in the project beyond formal post-occupancy evaluation. You can see how the learning has fed into subsequent Bennetts Associates’ projects. The fact that, in 2019, the whole practice revisited the project to see how it had performed and share results from nearly 20 years of occupation, demonstrates just how seriously it takes this role.
Rab Bennetts How has it fared 22 years on? It is low carbon in operation and reasonably low carbon in construction. If the gas boiler was changed to a heat pump it would be consistent with the current LETI/UKGBC targets. There’s minimal weathering, there’s been no internal redecoration at all. The company itself has been taken over twice, so the building has accommodated multiple changes in ownership and the occupancy has gone up about 30 per cent and yet it’s functioning pretty well.
Mature trees form an integral part of the solar shading strategy, which varies in form according to the orientation of each facade.
Project presentation
View Rab Bennetts from Bennetts Associates give a presentation on Wessex Water Operations Centre below
Additional Images
