Built on principles: White Collar Factory

It all started in 2008 with the property crash. While many construction projects stalled, property developer Derwent London decided to commission a research study into what the next generation of offices would be like and appointed three regular consultants – architect AHMM, and engineers Arup and AKT II – to do the work. The brief was simple: given an unconstrained site, what would be the ideal office building? What would it look like, how would it work and who would use it? It had to be sustainable, adaptable for changes in use, and inexpensive to build and operate.

Naturally enough, the team started with its previous experiences with Derwent in London. This had been almost exclusively in conversions of old factories, warehouses or office buildings that had reached the end of their lives, such as the Tea Building in Shoreditch (once, the Lipton Tea factory).

These conversions had to accommodate the buildings’ robust frames, usually concrete columns and concrete floors, with (by modern standards) close column spacing and often low ceiling heights. The solutions for these existing buildings included flexible open-plan offices, albeit with columns; exposed services with no false ceilings; exposed interior concrete to make use of thermal mass; and as much natural ventilation as possible. The market was initially sceptical, but soon a new breed of London tenant – often young creative or technological companies – came to embrace the new approach. They did not mind the close-spaced columns or the ‘unfinished’ ceilings, and they liked the natural, more sustainable, ventilation, especially, when offered, the ability to open the windows.

These young tenants were now expanding into substantial firms, and others were beginning to catch on. The team decided that this was the future London office market. So why not, for the first time ever, design a new office building that applied the lessons learnt on converting old warehouses and factories, but that was unconstrained by the limitations of building around what was there before? The concept of the White Collar Factory was born.

This meant challenging some of the principles that often governed the London property market, in particular, the belief that the environment inside the office should be specified by the required air temperature. Comfort depends on many more things than that, including the radiant temperature of surfaces, air movement and humidity, and the team believed that achieving ‘comfort’ could be done with much less air conditioning. It also meant keeping things simple: no frills, highly adaptive, inexpensive and easy to maintain.

Key criteria

After several months of study, the team had established five design principles for its office of the future: high ceilings, use of thermal mass, concrete core cooling, windows that open, and flexible occupation.

Generous ceiling heights (as in old warehouses and factories) make workers feel less hemmed in, increase the penetration of natural daylight from high windows deep into the building, and improve air circulation. They can also be created by simply omitting the large false ceilings of conventional offices and leaving the services fully exposed on the ceiling, so retaining the same number of floors in a given height of building (the team retained a shallow ‘false floor’ to contain power and data cabling).

Thermal mass is the ability of a material to store heat energy. High-density materials such as concrete have high thermal mass, which can be used to help retain warmth in winter and to keep the building cool in summer. This meant building a concrete structure with sufficient mass and, equally important, with as much of the concrete’s interior surface exposed as possible. This tied in nicely with the first principle, since the absence of false ceilings allowed the soffit (underside) of the concrete slabs to be exposed.

In a modern well-insulated office in a UK climate, providing summer cooling in an efficient and sustainable way is much more challenging than heating in winter. Conventional air conditioning is energy and carbon intensive, noisy and takes up a lot of space. The White Collar Factory approach is to use passive environmental controls where possible, and a method called concrete core cooling has been introduced: chilled water pipes embedded in the reinforced concrete slabs provide radiant cooling, enhancing the natural effect of the thermal mass, and chilled water at 15°C is passed through the pipes, cooling the slab to around 20°C. The technique is used widely in Germany and Holland but less so in the UK, and never before on a London office.

Another of the maxims that the team has overturned is the belief that, to be both comfortable and energy efficient, a building must be sealed. This limits occupants’ control over their environment and their connection with the outside world, and excludes the most basic method of natural ventilation – opening a window. Calculations showed that in London weather conditions, and in conjunction with thermal mass and chilled slabs, the mechanical system could be switched off for 50% of the year and comfort provided by natural ventilation with opened windows. A traffic light system provides guidance for occupants, turning red to advise people not to open the windows when the weather is too warm or too cold.

The principle of ‘flexible space’ is a response to changing office use. Tenants’ requirements are increasingly diverse, some for example requiring large open spaces and others more compartmentalised offices, and each tenant’s requirements can change over time. Large floor plates and high ceilings allow a variety of fit-outs, and quick subdivision of space if needed.

Taking these five principles further, the team established a standard column spacing of nine metres, which hit a ‘sweet spot’: any greater and the regular 300 millimetre thickness of floor slabs would have to be compromised by beams; any smaller and the columns would become intrusive and reduce flexibility. A similar compromise was reached on the façade. Conventional wisdom has it that a sustainable building requires high insulation including triple glazing, plus shading to reduce solar gain – measures that can both be costly and take up space, which reduces the office area. However, most of the benefits can be achieved with relatively simple façades by carefully balancing glazing with shade and varying the proportions depending on the orientation of the sun.

All this work was translated into a ‘standard’ office design, five storeys high with a 45x45 metre floor plate, a four metre floor-to-floor height and a central services core. This was costed at a remarkably inexpensive £165 per square foot. Everything looked promising, but two major questions remained: would it work in practice, and could a conservative property market be persuaded? Derwent’s solution was simple: build a prototype that could be both a technical test-bed and a marketing suite.

In 2012, Derwent happened to be planning a development on a corner of Old Street roundabout, London’s ‘silicon roundabout’. It was decided that a small 18x18 metre section of one ‘standard’ floor would be built on the site, squeezed between the old existing buildings and perched three storeys up in the air to provide realistic exposure to sunlight. Further, a contractor (Brookfield, now Multiplex) was charged with building the prototype as if it was the ‘real thing’, providing a test of construction techniques. This also allowed for refinement of the ingredients and workmanship for achieving high-quality fair-faced concrete finishes, a notoriously difficult challenge.

The tests, running through the particularly hot summer of 2013 and the following winter, showed that the technology worked, with close correlation between computer modelling and measurements, and allowed the design and mode of operation to be refined. The initially sceptical letting agents for the property market were gradually won over. Arup’s SoundLab, a virtual listening environment that allows clients and designers to hear the sound of existing spaces and test the sound of designs, was also used to help people understand the impact of opening windows over a noisy roundabout (see box). Meanwhile, Derwent decided to go ahead with its Old Street project, a mixeduse development including some renovated old buildings, with the White Collar Factory presiding over the northern edge, and a research project was suddenly transformed into a live design-and-construction site.

Inevitably, the ‘standard’ design had to be modified to fit the site – 16 storeys with an asymmetrical floor plan and a large basement – but all of the design principles were retained. The façade is made up of three alternating elements: full-height double-glazing, solid insulated panels, and perforated panels, which the openable windows are behind at three-metre intervals along the façade and the proportion of each element varies with orientation to the sun.

Outside air (when the windows are closed) is provided by low-pressure central air-handling units with heat recovery at roof level. Supplementary air conditioning is available to tenants to ‘top up’ the cooling on very hot days or for specific requirements. The relatively little heating required comes from conventional trench heating – simple underfloor convector units fed from gas-fired boilers by a low temperature hot-water circuit. The tower’s roof is divided between amenity space for tenants, including a running track around the perimeter, and solar thermal panels that generate electricity from solar energy, which (with the heat recovery units) fuels the hot water, including that used for the showers accompanying the 276-space cycle park in the basement.

During the design stages, a case study was submitted to the government’s Technology Strategy Board (now Innovate UK) testing the building’s resilience to climate change, particularly to rising temperatures over the next 50 to 100 years. Energy and thermal comfort models were run through different scenarios, and the scope for future adaptations was tested. The results showed that with its in-built passive design measures, the building was well placed to cope. The study was turned into a Technology Strategy Board paper on best-practice design for future-proofing buildings.

Due to complete in December 2016, White Collar Factory is achieving BREEAM Outstanding and LEED (Leadership in Energy and Environmental Design) Platinum, the highest possible world standards for sustainability of buildings, while the cost of construction, and the fit-out and operating costs for tenants, are substantially below the norm. The fourth and fifth floors of the building will become the new headquarters of AKT II, a mark of the company’s confidence in what it has helped create, as well as an aid to monitoring the longer-term performance of the White Collar Factory concept.

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This article has been adapted from "Built on principles: White Collar Factory", which originally appeared in the print edition of Ingenia 69 (December 2016).