Rather than demolish, Architect Howarth Tompkins opted to refurbish a 1970s teaching block, introducing sustainability measures, which earned the building a BREEAM Outstanding rating.
Tucked in between a network of narrow streets and the Hogsmill River, a tributary of the Thames, Kingston School of Art’s Knight Park campus has been a feature of the area since its founding in 1939.
The campus site started as a single three-storey building that was gradually expanded along the river. Extensions and buildings were added over the following decades, including a formal 1930s quadrangle, a 1960s tower and the 1970s Mill Street Building, which now dominates .
At a glance
Client : Kingston University
Architect: Haworth Tompkins
Main Contractor: Overbury
Structural Engineer: MLM
Start: July 2016
Completion: November 2019
Gross Internal Area: 10,000 m2
Construction Cost: £20,000,000
BREEAM Rating: Outstanding
The 10,000sqm Mill Street building, which was built specifically for teaching, had suffered from ad-hoc modifications leading to underutilised spaces. It also had poor environmental performance, with high energy use, poor insulation, large expanses of south-facing single glazing and poor ventilation.
Nevertheless, the brick, steel and concrete shell remained in good condition, so rather than demolition, the architect Howarth Tompkins decided to upgrade and adapt the building in incremental measures that demonstrate how a robust but unloved building can be transformed.
Retaining and reusing elements would also help to keep the equivalent of around 1.5 million KG of embodied carbon locked up, compared with rebuilding.
Howarth Tompkins carried out early building modelling to understand the building’s most significant energy uses and assess the range of options available to reduce energy use, reduce solar gain and improve the building fabric. Overheating and cooling were found to be critical issues, therefore a solar shading design was developed for the South façade, which resulted in a 60% reduction in solar gain.
Mechanical cooling demands were also minimised through the careful consideration of thermal mass, fenestration design, maximising passive shading opportunities, internal gains, night time purge and ventilation as much as possible.
Air handling units incorporate adiabatic cooling systems as a low energy alternative to cool the building. Mechanical cooling provided was then only to areas of high ICT use, lecture theatres or where thermal modelling demonstrates that overheating could not be prevented by any other viable means.
A full lifecycle assessment was carried out at RIBA Stage 2, which gave the design team a quantifiable baseline from which to consider design modifications that would reduce embodied carbon and environment impact.
As a result, a number of internal partitions were replaced by timber frame, resulting in a reduction of carbon by 1600 kgCO2e. A portion of the concrete slab was wall also retained, which also resulted in a substantial 6000 kgCO2e of carbon saving by not using new concrete for construction.
Howarth Tompkins calculates that overall, there will be a reduction of 7E3 kgCO2e over the lifespan because of design optimisation.
The existing brick, steel and concrete shell and core, which account for almost half the building’s total material volume, were re-utilised and repaired. Retaining these reduced the embodied carbon added by the project by around 200 kgCO2eq/m2 when compared to building an equivalent new structure.
A 800sqm green roof was introduced to support biodiversity, which also helps to attenuate rainwater run-off, avoiding the need for introducing additional rainwater outlets. The green roof features 20 species of plug plants and required careful design to ensure the existing structural capacity of the roof was not exceeded.
The building is located in a high flood-risk area, with peak river flows through the adjacent Hogsmill River predicted to increase by 35% by 2080 according to climate change modelling.
Resilience measures were therefore considered in the early design stages, with the ground floor workshops incorporate resilient design measures, such as high-level services and flood-resistant materials, including the use of masonry instead of plasterboard. The footprint of the building was also reduced slightly, helping to reduce water displacement on the functional floodplain.
Re-use of existing brick and concrete structure
Replacement of all glazing
Insulation to external wall linings and roof deck, and increased airtightness
98% of waste diverted from landfill
Solar shading structures to the south of the building
800sqm of biodiverse green roof
Flexible services infrastructure to and furniture to allow spaces to be adapted
Before refurbishment, the Mill Street Building was one of the worst performing of Kingston University’s estate. It is now among the highest performing and has delivered 52% savings in energy consumption and running costs.