1 New Park Square, designed by Allford Hall Monaghan Morris (AHMM) at Edinburgh Park, is an eloquent example of the shift in thinking that business parks, and offices in general, have undergone since the park opened in 1995.
Masterplanned by US architect Richard Meier but never fully developed, the park was a largely car-dependent development of entirely commercial office space on the outskirts of Edinburgh. Sustainable design was yet to rise up the agenda. Fast-forward a generation, and it’s a very different story. Powered by renewable energy from the grid, this all-electric, concrete-framed building is low-carbon for operational energy use.
It is the first in a southern phase masterplanned by Dixon Jones which seeks to include 1,800 homes including affordable, for sale and rented housing, all now served by both a mainline station and a tram stop within the park. Conceived by developer Parabola as a mixed-use urban quarter, the extended park will have a new civic square, which 1 New Park Square overlooks.
The building provides 87,500 square feet of offices over four floors above conference and events space, restaurant and public facilities on the ground floor. According to AHMM associate Matthew Hart, concrete suited the ethos of the project. “The brief was for a relatively simple building made of robust material that would stand the test of time, together with being a marker for new office space within Edinburgh Park,” he explains. “Concrete enabled simplicity in terms of fire compartmentation and structural efficiencies, and significantly contributed to lowering operational energy. It’s also a self-finished material, which we enjoy aesthetically.”
The decision to use concrete was supported by the findings of an early-stage sustainability review. This analysed the design using the CIBSE TM52 overheating assessment methodology (for dynamic thermal modelling) to understand the performance for different options including buildings with openable windows, sealed buildings with air conditioning, buildings with exposed concrete, and those with a plasterboard ceiling finish.
The results suggested that summer cooling loads would be reduced by 88% by having opening rather than non-opening windows, and by a further 38% with exposed heavyweight concrete as opposed to lightweight plasterboard. This drove a strategy that included both exposed thermal mass and openable windows (with active systems to supplement the internal zones), along with 3.15m floor-to-ceiling heights to improve daylighting and thermal comfort, and deep window reveals to provide some passive solar shading. Hart notes that the more temperate Scottish climate also helped: “The peak summer temperature is lower than in southern England, which lowers the peak cooling load.”
AHMM’s design has a 9m x 9m grid with a reinforced concrete slab, just 325mm thick. The concrete columns and slabs were cast in-situ with an underfloor air displacement system enabling exposed soffits, while the external columns that form a colonnade on three sides of the building were faced with precast shells. The facade is made from hand-laid brickwork with precast concrete lintels and sills.
Two sets of prototypes for the super-structure elements were trialled on site, with 20% and 40% GGBS cement replacement. For each, concrete contractor Cidon poured a small circular column, a 1m-high wall and part of a soffit. One factor under consideration was the impact on the programme – more GGBS can increase curing times, which were already lengthened due to the cold Scottish winter climate. In the end, the 40% GGBS mix was used for the main structure.
“The decision was driven by both the client and ourselves, for environmental as well as aesthetic reasons,” explains Hart. “When we reviewed the test results, we noticed that increasing the GGBS content lightened the colour of the concrete – the local sources of concrete materials in Scotland naturally gives a browner tone.”
AHMM specified a consistent, uniform and matt appearance for the fair-face concrete, which was rubbed down and treated with a Keim dust suppressant. Peri’s Vario system was used for the formwork, with the design team working with the sub-contractor to achieve the optimum arrangement of 1.2 x 2.4m boards.
MDO plywood was specified for all exposed elements to give a very smooth surface, and was reused a maximum of five times to preserve the quality of the finish. Pouring was a challenge on such an exposed site, with the contractor taking care to ensure the internal formwork faces were free from moisture and debris to protect the final quality of finish. Precast concrete plugs were set into the vertical surfaces, while the circular internal columns were created using a Peri column formwork.
A different approach was taken for the 1m-diameter columns that form a colonnade on three sides of the building, with 5cm-deep fluting. These were precast by Border Concrete, which created bespoke moulds for two fluted halves. The pieces were then acid-etched and fitted together on site around an insulated in-situ concrete structural column, and given an external coating to protect against weathering and graffiti.
Designed for either one or two tenant companies per floor, the building achieved a BREEAM Excellent rating.