Sustainability editor Hattie Hartman take a look at the environmental credentials of the buildings on this year’s Stirling Prize shortlist
Some argue that there are many routes to sustainability. Others, such as Seattle-based Living Building Challenge (LBC) founder Jason MacLennan who gave his inaugural UK lecture this week, are uncompromising. LBC-certified buildings are net positive in energy, water and waste, with energy metrics based on a full year of actual performance. Seen against this ambitious backdrop, the Stirling Prize shortlist – and the wider industry – have a long way to go.
Nevertheless, hopeful green signs emerge from close scrutiny of this year’s finalists. In terms of sustainability, all six buildings deserve their place on the shortlist, unlike last year where Zaha Hadid’s Aquatics Centre was a questionable contender. RIBA award winners’ overall approach to sustainability has improved considerably in recent years and the RIBA would do well in future to eliminate from the shortlist any building that does not meet basic sustainability criteria.
The Stirling Prize shortlist reveals several routes to sustainable design
Unpicking the environmental approaches of this year’s list reveals several ‘routes’ to sustainable design. MUMA’s Whitworth and Heneghan Peng’s Stockwell Building at the University of Greenwich employ holistic passive design to shape the buildings on their respective sites, and each elevation’s degree of transparency responds to its solar orientation. Top marks to both these projects for thoughtful embedded passive design. In these two well-considered projects, sustainability is a major determinant of building form, yet both sit comfortably in their contexts – one in a World Heritage site and the other an extension to a late Victorian structure. Neither reeks of – or overtly speaks of - sustainability.
At Burntwood, AHMM has also employed a holistic approach. Its regeneration of an urban secondary school, fashioning a series of inviting landscaped spaces from what were previously empty stretches of tarmac, creates a sense of place on the campus. This is reinforced by an effective rebranding of the buildings using a clever system of prefabricated concrete panels, which also upgrades the thermal performance. Careful attention has been paid to cement substitutes in the concrete and minimisation of waste through prefabrication as well as improved airtightness, facilitated by the precision of offsite construction.
Darbishire Place and Maggie’s Lanarkshire have opted for simplicity, an appropriate strategy for both a social housing provider and a charity with limited resources. When it comes to sustainability, the value of keeping it simple is that it minimises the chances for things going wrong. Blinds and linen curtains provide solar shading to the floor-to-ceiling glazing of Maggie’s west elevation. As Malcolm Tait of the centre’s M&E consultant KJ Tait Engineers observed, ‘the only moving parts in the building are two toilet fans and the air source heat pump, so nothing can go wrong and maintenance is minimal.’ While not pioneering, this approach is wise.
NEO Bankside adopts the technological fix approach: an extensive and expensive ground source heat pump built into the foundations as energy piles. Effective at creating light-filled apartments with spectacular views of St Paul’s and the Thames on a tight urban sight, the vast quantities of unshaded floor-to-ceiling glazing at NEO Bankside are difficult to justify in sustainabilty terms. This is not an argument for small windows facing the river, but rather for an envelope with a glazing ratio closer to 40 per cent, incorporating self-shading where appropriate.
All six shortlisted projects have majored on landscape design, be it on the roofs in Greenwich or opening a previously blind facade to Whitworth Park at the Manchester gallery. Landscape lies at the heart of Maggie’s Lanarkshire with the building sited to preserve existing trees and create external garden courts. At Darbishire Place, a specimen tree has been located along the pedestrian route into the centre of the block, while both Burntwood and NEO Bankside incorporate extensive landscaping on the site (though the NEO Bankside gardens are open only to residents after hours).
The strong concept design of Heneghan Peng’s Greenwich building is commendable. However, as is so often the case in buildings with high sustainability aspirations, value engineering meant that openable windows on to the internal courtyards – critical for natural ventilation via a stack effect – were omitted. This means that even if staff and students open the remaining doors into the courtyards, mechanical ventilation continues to operate, undermining this aspect of the building’s original design intent. This knocks it out of the running for the top prize.
MUMA’s Whitworth has my vote for the Stirling Prize
Of the six excellent schemes, MUMA’s Whitworth has my vote for the Stirling Prize this year. In addition to its rigorous and sensitive pursuit of passive design, the gallery is pioneering a bold approach to conditioning exhibition spaces – without air conditioning. Temperature fluctuation is used to control humidity, so you may have to keep your coat on in winter or strip down to a T-shirt in summer. This strategy should be widely emulated. Simple passive solutions such as earth ducts should also be employed more frequently when site conditions permit.
Treading lightly on the planet and enhancing community benefits are not the sole drivers of a project, but some design teams embrace these challenges more seriously than others. At the Whitworth, MUMA has masterfully navigated the competing priorities of sustainable design to great effect.