A sustainable prize winner? Goldsmith Street | Brussels Blog

A sustainable prize winner? Goldsmith Street

posted by on 25th Oct 2019
25th,Oct

“There is a theme running through all this: sustainability.
What’s the best way to be gentle on the planet?”

David Sillito, BBC Newsnight, reporting on the
2019 Stirling Prize from the Royal Institute of British Architects.

The winning entry of the 2019 Stirling Prize is a council housing development in Norwich, Goldsmith Street. The site is a mile from the centre of Norwich.

It compromises 60 flats, mostly one bedroomed, and 45 houses, mostly two bedroomed. The density of the site is 83 dwellings per hectare, compared to an average density for new buildings on previously developed sites of 51 dph.

Social success promised

The Goldsmith Street housing, in looks and layout, looks like the Victorian terraces built 150 years ago, except that the development has more flats than actual houses.

The architects for Goldsmith Street, Mikhail Riches and Cathy Hawley, rejected the blocks of flats that had become ‘the’ solution for much council housing in the second half of the 20th century. Blocks of flats were seen as a good way of making the most of limited space. Architects Riches and Hawley wanted to prove that developments based on houses could be high density and have a higher social value for the residents.

In the Newsnight report, Mikhail Riches said

I think we’ve got a real problem of lack of social connectedness and this housing is thinking about how we can encourage social connections. People meeting each other.

Cathy Hawley, emphasised the benefits to children

I think there is also ideas about how to encourage children to play out doors. How to get to play areas without crossing roads and make that safe.

A resident agreed saying

My little girl loves the garden. She’s got the passageway out the back. she’s made so many friends.

Goldsmith Street promises to be a success as a socially pleasant family orientated, place to live. Just like some existing Victorian streets today.

Remaining carbon budget: 47 tonnes CO2e

A remaining carbon budget is the quantity of greenhouse gases that can be emitted before a given rise in Earth’s temperature occurs. Raising the Earth’s surface temperature by 1.5°C above pre-industrial is regarded as very dangerous. The remaining carbon budget to keep below 1.5°C is 47 tonnes of CO2e per person.

This means that, if everyone in the world caused 47 tonnes CO2e of emissions, many more climate disasters would happen.

Home energy use

Goldsmith Street houses were designed to be low energy to the PassivHaus standard. They have very thick insulated walls. They have no letters boxes in their doors in case they let out some heat.

They are orientated and designed to get the benefit of the sun – even at the darkest day of winter – the winter equinox. One resident that was interviewed said that the heating had been turned on only twice in a year.

In reducing home energy use, Goldsmith Street is a success, probably more than five times better than the average household in the UK. [Note 1]

Embodied carbon

Construction at Goldsmith Street is described as “Passivhaus specification with insulated and air-tight timber frame and brick cladding”. The other main materials are bricks, cement, glass and aluminium:

Buff brick with Cemex ‘Braintree Light’ mortar for the walls and black clay pantiles to roofs with ppc aluminium detailing to verges and standing seam system to flat roofs. Render cladding to dormers. Triple glazed aluminium frame windows.

Estimating the emissions of greenhouse gasses for wood used in construction (its embodied carbon) is controversial: There are widely different views. However, it is generally accepted that wooden framed buildings have significantly lower embodied carbon than buildings with other structural elements like steel and concrete. The wooden frames in Goldsmith Street seem to be a good choice for lower embodied carbon.

However, making the bricks and mortar will have caused large emissions of greenhouse gasses but the cement specified, Cemex, does create lower than average emissions in its manufacture, due mostly to the use of fly ash, a by-product of at coal-fired power plants.

There is no estimate of the greenhouse gas emissions from the construction of Goldsmith Street, its embodied carbon.

The embodied carbon in Goldsmith Street is probably about 20 tonnes per resident, over 40% of the important personal remaining carbon budget for 1.5C. [Note 2]

Car ownership and carbon footprints

There were 86 car parking spaces including 1 car club space and an electric car charging point specified for Goldsmith Street. That’s 82% car provision per household.

The residents of the “affordable and sustainable” development at Derwenthorpe, York, were estimated to have carbon footprints of 14.52 tonnes of CO2e. That’s less than 4 years of a personal carbon budget of 47 tonnes CO2e. In the range of Derwenthorpe footprints, by far the lowest one was for the one household that did not have a car.

The residents of Derwenthorpe will probably be more affluent than residents at Goldsmith Street so Goldsmith Street residents will likely have lower annual carbon footprints because emissions increase with wealth.

However, for residents in households with a motor car in Goldman Street it is unlikely that the yearly emissions will be less than 10 tonnes CO2e. [Note 3]

That exhausts the remaining carbon budget in less than five years. Less, if the emissions from building Goldsmith Street development are counted.

Summary

Despite saving on home energy use, residents of Goldsmith Street are unlikely to have carbon emissions less than 10 tonnes CO2e per year and will have been responsible for 20 tonnes as their share of the building process.

Compared to a remaining carbon budget of 47 tonnes CO2e Goldsmith Street is a disaster for the climate – but just a bit less of a disaster than other housing schemes.

Note 1: Home energy

Figures from the Energy Savings Trust suggest that for a typical household non-heating electricity use is 3,638 Kwh per year and BEIS figures suggest 200 gm CO2 per Kwh of electricity generation is typical. This makes 0.727 tonnes CO2 per household per year.

The PassivHaus standard in Goldsmith Street almost eliminates electricity directly used for heating, so a reasonable yearly estimate of emissions from home energy use is 0.75 tonnes CO2 per household. The Committee on Climate Change have estimated an average of 4 tonnes CO2e per household. for home enegy use.

Goldsmith Street households creates less than a fifth of the greenhouse gas emissions from home energy than the average UK household.

Note 2: Embodied carbon

The famous sustainable development, The Beddington Zero Energy Development (BedZED), had emissions from construction measured at 675 Kgs CO2 per metre of floor space.

Goldsmith Street is probably better than this because of its wooden frame construction, but the embodied carbon is unlikely to be less than 500 Kgs CO2e per square metre of floor space. The Goldsmith Street scheme has 8007 m2 of internal floor space shared among about 200 residents.

This meas that the embodied carbon in Goldsmith Street is probably about 20 tonnes CO2 per resident, over 40% of the personal remaining carbon budget of 47 tonnes CO2e.

Note 3: Car provision

The carbon footprints of the residents of Goldsmith Street will be lower than those at the “affordable and sustainable” development at Derwenthorpe, York, because Derwenthorpe residents are more affluent However, the Stockholm Environment Institute has measured carbon footprints at Derwenthorpe, so there may be a useful comparison.

The Passivhaus standard at Goldsmith Street means home energy use per resident is about half that of the residents of Derwenthorpe. Table 1 is an extract from the report on Derwenthorpe.

‘Other’ is standard across the UK and is based on the individual share of emissions associated with government spending on hospitals, roads etc.

Of the sample of 40 residents measured at Derwenthorpe, the lowest was in the household without a car.

Making comparisons with Derwenthorpe, the carbon footprints of residents of car-owning households in in Goldsmith Street is very unlikely to be less than 10 tonnes CO2e per year.

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