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Architecture practice Feilden Clegg Bradley Studios has created a series of crescent-shaped student housing blocks with a CLT structure for King’s College at the University of Cambridge.

Called Stephen Taylor Court, the blocks contain 84 homes for King’s College’s graduate students and fellows that were designed to Passivhaus standards and to have as low a carbon impact as possible.

“Due to the considered material choice, prioritising low-embodied carbon materials, reuse of existing materials, local sourcing and targeting recycled content, and accounting for carbon sequestered in the cross-laminated timber, the project has negative embodied carbon on completion as more carbon has been sequestered in its production than emitted,” Feilden Clegg Bradley Studios partner Hugo Marrack told Dezeen.

Stephen Taylor Court by Feilden Clegg Bradley Studios — The project is made up of three crescent-shaped buildings

The architecture practice used its own carbon tool named FCBS Carbon at early design stages to help estimate and limit the whole-life carbon emissions of the scheme.

FCBS Carbon is a spreadsheet that is free to use by other architects and considers all the CO2 produced by a building, including the building material, construction and demolition.

Feilden Clegg Bradley Studios used Stephen Taylor Court as a “test case” for its tool and calculated its net carbon performance – both operational and embodied – to be less than zero for the first 10 to 15 years of the project’s life.

According to Marrack, the carbon calculations for the project did not consider furniture, fixtures and equipment (FF&E) or mechanical, electrical and plumbing (MEP).

Located within a conservation area in Cambridge, the apartments have a cross-laminated timber (CLT) structure clad in water-struck gault bricks that are similar in appearance to traditional Cambridge bricks.

The CLT structure was chosen for its lightweight property, airtightness of the structural envelope and the material’s low embodied carbon.

“The lightweight CLT structure of the buildings reduces foundation loads, allowing the use of a thin reinforced concrete raft foundation ‘floating’ on rigid insulation,” explained Smith and Wallwork structural engineer Tristan Wallwork.

“This not only reduces the amount of concrete used in the substructure but also provides a perfect Passivhaus foundation solution.”

“Detailing of any inherent thermal bridges, such as facade restraint ties, is also drastically simplified due to the robust and solid CLT structural envelope – providing complete flexibility on location of any fixings required,” continued Wallwork.

Feilden Clegg Bradley Studios plans to continue to work with the college in the future to help maintain net-zero carbon beyond the first 10 to 15 years after completion, by implementing renewable energy options such as photovoltaic panels.

The 4,300-square-metre scheme is located within a conservation area known for its arts and crafts houses, which influenced Feilden Clegg Bradley Studios’ design.

The housing at Stephen Taylor Court is made up of three brick crescents surrounding a garden courtyard with an adjacent red brick villa.

“The central triptych of three crescents creates an open and informal court which provides depth and breadth to views from the streetscape to the leafy context beyond,” said Hugo Marrack.

Steep-pitched roofs, dormer windows that punctuate the roofline and oriel windows on the gable ends of the apartments reference the arts and crafts buildings in the area.

“The sympathy with the arts and crafts approach is in celebrating the joy in each of these building details and the material’s properties, rather than ironing them out, as one might with a more minimal approach,” Marrack explained.

“This being said, the results aim towards a leaner, contemporary expression of its time, rather than forms of reproduction. In some respects, the outcomes are almost brutalist,” he continued.

Along with the newly built housing, Feilden Clegg Bradley Studios refurbished and extended an existing Victorian-era villa on the site to accommodate a common room, library and laundry room.

Stephen Taylor Court is the second graduate accommodation at the college to be built in recent years after the development at Cramner Road by British firm Allies and Morrison, which was also built to Passivhaus standards and was longlisted in the 2021 Dezeen Awards.

The photography is by James Newton.

Project credits:

Architect: Feilden Clegg Bradley Studios
Landscape architect: Robert Myers Associates
Planning consultant: Turley
Structural engineer: Smith and Wallwork
MEP and sustainability engineer, acoustic engineer and Passivhaus consultant: Max Fordham
Principal designer, project manager and quantity surveyor: Faithful and Gould
Fire engineer: The Fire Surgery
Main contractor: Gilbert Ash

Reference

Energy savings achieved by insulating UK homes appear to be cancelled out within a few years by an increase in energy use, according to a study by the University of Cambridge.

The study, which analysed the gas-use patterns of more than 55,000 homes across England and Wales, found that the fall in gas consumption achieved by retrofitting wall insulation was voided within four years.

Retrofitting lofts proved half as effective, with any gains becoming “insignificant” after year two, the researchers said.

Further research is now needed into the causes of this “rebound effect”, which is preventing energy savings from continuing long-term.

But the study posits that it could be due to the simultaneous construction of home extensions, which can increase a household’s energy consumption by around 16 per cent.

“We found that energy efficiency retrofits are often combined with home improvements that actually increase consumption, such as extensions,” explained Cristina Peñasco, an associate professor in public policy at the University of Cambridge, who co-authored the study.

Home insulation “not a magic bullet”

Other possible causes include the fact that 18 per cent of English households have conservatories, which according to the study negate any energy savings within the first year, as well as the possibility that energy and cost savings could in turn encourage increased consumption.

To achieve a long-term reduction in gas use and the associated emission – in line with the UK’s mission to reach energy independence and net-zero emissions – the researchers argue that insulation thus needs to go hand-in-hand with the installation of heat pumps and regulations to change people’s behaviour.

“There are very real benefits to households from good insulation, not least in terms of health and comfort,” said co-author Laura Diaz Anadon, who is the director of the Cambridge Centre for Environment, Energy and Natural Resource Governance.

“However, home insulation alone is not a magic bullet,” she added. “In the long term, simply funding more of the same insulation roll-out to meet the UK’s carbon reduction and energy security targets may not move the dial as much as is hoped.”

Wall insulation causes seven per cent drop in gas use

Published in the Energy Economics journal, the study is the first to track the long-term effects of insulation in households across England and Wales, according to the researchers.

Their analysis is based on data collected by the UK’s Department of Energy and Climate Change, tracking households’ gas use for five years before and after insulation was installed.

Factoring in the age and size of the building, as well as the weather and gas prices at the time, the study found that cavity wall insulation was the most effective, leading to an average seven per cent drop in gas use in the first year.

In comparison, retrofitting loft insulation saw an initial fall of only four per cent.

“Insulating the lofts and cavity walls of existing UK housing stock only reduces gas consumption for the first year or two, with all energy savings vanishing by the fourth year after a retrofit,” the study concluded.

Retrofits must include heat pumps

In low-income households, these savings were even smaller – an average of three per cent during the first and second year post-retrofit – suggesting that any savings are immediately redirected into keeping the home warmer for longer.

This proves that insulation is effective in democratising access to heating and fighting fuel poverty, the researchers argue, especially in light of the current energy and cost-of-living crises.

But the study also shows that, to actually cut down on gas use and emissions, insulation retrofits must go along with energy reduction targets for households and waivers on energy bills for low-income households, the researchers argue.

In addition, they argue electric heat pumps should be installed alongside insulation to decarbonise residential heating, which is responsible for around 14 per cent of the UK’s carbon emissions.

The country’s housing stock is among the oldest and least energy efficient in Europe, which has long led industry groups including the Royal Institute of British Architects, the Construction Leadership Council and the Architects Climate Action Network to call for a comprehensive national retrofit strategy.

Alongside insulation, they argue a holistic approach would must include the addition of “low-carbon” heat pumps and triple-glazed windows at the same time.

The top photo is by Jupiter Images.

Reference

Cambridge

FCBS creates Passivhaus student accommodation crescents in Cambridge

Insulation’s energy savings “vanish” after four years Cambridge study finds

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