Radical efficiency can lead to better resource stewardship and productivity improvements

Better resource stewardship can drive productivity improvements, Peter Fisher from architectural firm Bennetts Associates told GIRI members as he shared lessons learned from the Timber Square project in Southwark, arguing that radical efficiency comes from eliminating unnecessary complexity in the design phase. 

Timber Square is a recently completed 380,000 sqft, £280 million commercial scheme in Southwark for Landsec that combined reuse and new build. “It used cross laminate timber (CLT) as its primary slab, and it is probably the biggest CLT building in the country by a factor of 10,” said Peter. An advantage of this, he explained, is lower upfront carbon. “The project came out at about 450 kg of CO2 per square metre against a brief of 900kg. When we started in 2019, 1,200kg was typical.” 

Using CLT had logistical advantages, said Peter, including halving the number of trucks required for site deliveries and a reduction in building weight by 25%. However, the project also experienced challenges, many of which were caused by the complexity and cost of the MEP (mechanical, electric and plumbing) system. 

He shared figures from the Building Cost Information Service showing the real-term cost increase of buildings in the UK in the last 30 years compared with the stagnation in sector productivity. The cost of MEP and finishes, he pointed out, has almost doubled in that time, and the time taken for MEP installation has substantially increased. “Inflation on the Timber Square project was about 25%. In MEP, it was 125%. One of the reasons buildings aren’t happening in central London right now is because they are simply not viable.” 

More with less 

In response, should the sector change the way it thinks about sustainability? “In the past, sustainable building was seen as costing more. And if you take business as usual and layer advanced technologies on top, then it will be more expensive. But if instead of ‘sustainability’ we look at it as resource stewardship – using the resources we have as efficiently as possible – then we can get to a place where we use fewer resources, and reduce cost, carbon and complexity." 

A lot of the ‘stuff’ that goes into buildings is there for contingency, said Peter, arguing that construction has increasingly focused on design for manufacture and assembly (DfMA) in the wrong areas. While structural systems and envelopes have become more efficient, services and finishes have become increasingly expensive and complex. 

"Our buildings are overspecified. What can we remove? What if the building becomes a kit of parts? We probably can’t do modular cores for the time being, but we can begin to modularise and standardise all those components inside the cores. Then, once the cores are simplified, the structure becomes relatively straightforward as long as the interfaces are managed.” 

He said that Bennetts Associates is working towards using standard components where possible. “This is about the unseen stuff. The problem with buildings that are heavily modular is that they can look like it, so we are working on the invisible details, the things that don’t really matter architecturally, and going forward from there.”  

The MEP challenge 

 “If we can’t simplify MEP, we don’t have a chance of simplifying buildings. So we've been looking at how we can modularise it.” 

Peter shared an example of a refurbishment and timber extension project on a 1990s steel-frame building in Manchester to demonstrate the advantages of mechanical ventilation with heat recovery (MVHR) - a system more commonly seen in schools than office buildings - instead of a centralised MEP. He explained that because centralised MEP systems are designed around a building’s maximum occupancy, rather than its actual day-to-day occupancy, and must be installed in their entirety on day one to satisfy the brief, they typically result in a 40% overspecification.  

“Average office buildings today are occupied at about 1: 15 sqm and many of them are occupied at about 1:20. We estimate that in commercial offices in London and Manchester, unused capacity is probably costing £20-30 per sqft.”  With a modular MVHR system, in contrast, you only instal what the building actually needs, saving on cost and wasted capacity.  

“At Bennetts, we’re progressively trying to move away from centralised systems towards decentralised ones, and eventually to buildings that have no mechanical systems in them at all, which to me as an architect is nirvana. The trade-off is that we spend twice as much on the envelope - which lasts much longer.” 

Eliminating the unnecessary 

Peter closed by sharing another project, Kett House in Cambridge, which is all about simplicity and reduction. “Austro-American artist Hans Hoffman said, ‘The ability to simplify means to eliminate the unnecessary, so that the necessary may speak’. And that’s what we’re trying to do on this project.” 

He explained that the project builds on the lessons learned from Timber Square but looking instead at stone facades. “That sounds very expensive, but if you look at how facades are supported, there’s more carbon in the steel supporting system behind a brick façade than in the brick itself. Stone has around 10% of the thermal expansion of clay brickwork, so you can get away with up to about nine stops with no bench angles. The material costs more, but there’s no supporting framework behind it. It's simply standing on the ground. So it is substantially cheaper than a standard façade because we’ve removed the unnecessary.” 

The result, he said, is richer buildings. “And the reason they are richer, and the reason we can afford to build them, is because of that elimination of the unnecessary behind the scenes. In a sense, that's what we mean by radical efficiency.” 

Further reading:

More With Less: Rethinking cost, carbon and complexity through a systems approach