Goldsmith Street in Norwich by Mikhail Riches with Cathy Hawley sets a new benchmark for sustainable housing design, says Clare Murray

Words
Clare Murray
Photos
Tim Crocker

Few architects can claim that they combine high-quality design and sustainability so effortlessly as is found at the new Goldsmith Street housing development in Norwich, but architects Mikhail Riches and Cathy Hawley have set a precedent with the seemingly impossible: a beautiful scheme that meets the technical requirements of Passivhaus.

Courtesy of Norwich City Council’s (NCC) aspirations as a client, and the architects’ determination and attention to detail, it demonstrates that both high-quality design and exemplary sustainability are possible. This was within budget too, at a remarkable £1,875/m2, about 10 per cent above the cost of a basic Building Regulations-compliant home.

The site accommodates 93 one- to four-bedroom social rent homes, set near the city’s highest-value area, known as the Golden Triangle, but ironically adjacent to some of its lowest environmentally performing existing affordable housing stock. Another 12 homes have been designed to the same standard and have received planning approval on smaller adjacent sites. When complete, this will bring the total to 105 Passivhaus homes – the largest scheme of its kind in the UK to date.

The project began with a 2008 competition brief to design a low-carbon solar scheme. Mikhail Riches’ submission caught the client’s eye with its low-rise, fine grained, contextual approach inspired by the neighbouring streets.

The 14-metre-wide solar informed street patterns and roof profiles formed part of this approach to allow all homes to receive sun in summer and winter. The brief later developed into a requirement to achieve Passivhaus – primarily driven by NCC’s desire to reduce fuel poverty, which in turn is hoped to support a reduction in rent arrears and tenant turnover.

The technical requirements of Passivhaus and good housing design are often seen as competing forces. However, at Goldsmith Street, the architects approached Passivhaus as an opportunity to extend their design concept, from the solar-inspired orientations developed at competition stage through to the execution of each construction detail.

The design of the scheme has much to offer: densely packed but generous homes that are 10 to 20 per cent above space standards and feature vaulted ceilings; shared gardens to encourage play and social interaction; and the elimination of problematic shared entrance cores, giving all apartments their own front door. Much of the design finesse is also in the things you don’t see, such as bin stores, utility meter cupboards and mechanical service penetrations in the facade, all carefully and elegantly concealed and easy to use.

Determining where Passivhaus may have influenced the design is where the real magic happens, with many environmental design features seamlessly integrated”

Determining where Passivhaus may have influenced the design is where the real magic happens, with many environmental design features seamlessly integrated. Thick, brick-faced walls create generous window sills for residents and a U-value of 0.11 W/m²K. The 600mm-deep walls are constructed from 400mm-thick Cygnum timber frames built offsite and fully filled with cellulose fibre insulation made from recycled newspaper, retaining the home’s heat in winter and delaying heat entering in summer. Roofs and floors are also highly insulated with U-values of 0.10 and 0.12 W/m²K respectively.

Coffered window reveals with rendered panels set back by 100mm from the face of the brickwork, and windows set back a further 100mm from the render, not only increases the perceived window size – which can often appear ungenerous in Passivhaus homes – but also places the window at the optimum depth for thermal bridging while providing some shading.

Woven aluminium blinkers over south-facing windows provide additional shading from the summer sun. This moderates excessive heat gains which would otherwise be problematic to a Passivhaus that seeks to carefully balance heat gains and losses.

Incredible levels of air-tightness and thermal bridging hidden under the shell of the fabric would have been meticulously detailed by the architect and slaved over by the contractor”

Incredible levels of air-tightness and thermal bridging are hidden under the shell of the fabric. These would have been meticulously detailed by the architect and slaved over by the contractor to ensure that such extreme energy-efficiency could be achieved.

With a scheme working this hard to meet design and sustainability goals it is inevitable that some value engineering was required pre-construction. The client allowed the architect to take the lead on the VE process and Mikhail Riches addressed it with a real sense of ownership, quite unlike the cost-cutting exercises so often driven by quantity surveyors or contractors. This approach ensured that quality prevailed, important design features were retained, and significant amounts of money were saved.

One such change was the replacement of standing-seam zinc roofs with beautiful and distinctive black-glazed pantiles from Nelskamp – a substitution that would leave most architects in awe that a VE item could possibly turn out to be better than the original.

Changing the brick supplier to Nelissen (a manufacturing partner of the tile-maker) also saved a significant sum, and secured a fantastic brick for a fraction of the price.

The use of render on the rear facade instead of brick is a similar approach to that taken by the architects of nearby Victorian housing, with its decorative front facades and cheaper fletton brick on the rear elevations.

Another cost-saving measure was the use of non-Passivhaus-certified triple-glazed windows. It’s a myth that the windows of Passivhaus buildings need to be certified, as long as their performance is taken into account. It is also a myth that a Passivhaus can’t have openable windows. The Goldsmith Street homes have mixed-mode mechanical ventilation with heat recovery, supplying energy-efficient background ventilation, and openable windows for purge ventilation.

Interestingly, some of the items salvaged from the VE process wouldn’t have saved much money, but make a significant impact in terms of finish. These include the brushed-steel house numerals, and external wall-mounted light fittings which could have been swapped to Victorian-style lanterns for a micro-saving, but with a complete change in look and feel.

The ‘ginnel’ between the backs of houses has a wavy landscaped path down the centre to avoid giving the impression of a linear back alley.

All of the above has been made achievable through the use of a traditional contract – selected primarily to manage the build-quality required by the technical aspects of Passivhaus, including periodic airtightness tests. Acting as contract administrators, the architects could ensure that all architectural details would be executed as drawn. The rigour of this contractual approach has undoubtedly safeguarded the design quality and technical performance of the dwellings while also contributing to a reduction in the performance gap between design intent and the completed scheme. As a result, the client is intending to carry out post-occupancy monitoring of the homes, including analysis of fuel bills to determine the effectiveness of these measures.

Landscaped central space.

This project demonstrates that it is possible to challenge the status quo in which ‘design’ and ‘sustainability’ make competing claims, by using one to strengthen the other. But this could only have been possible with a client with an unshakable vision and commitment to sustainable social housing, who appointed, supported and trusted the architect to deliver on their passion for beautiful design, and who selected a traditional procurement route to safeguard and enhance the quality of the housing for the residents.

So, is Goldsmith Street destined to remain an outlier ­– a rare example of things done right? We have no more excuses: there is a climate emergency and this project has just set a precedent for all sustainable homes of the future.

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