Nottingham Energiesprong has seen the retrofit of 136 occupied council properties along West Walk, Keswick Street and Camden Close. The homes have been renovated and insulated to create low maintenance near net zero operational energy homes, after the local authority won £5m from the EU’s European Regional Development Fund. The retrofit of each of the 1960s homes was completed in 12 days, with the retrofits designed to extend the useful life of the housing by 60 years.

Who is on the project team? (designer, consultants, etc)

Architect: Studio Partington

Client: Nottingham City Homes

Solution Provider (Contractor): Melius Homes

Helping Hand/Guardian: Energiesprong UK 

Describe the context of this project, its neighbourhood and people.

Nottingham City Homes has pioneered Energiesprong revolutionary whole house retrofit in the UK, transforming 136 occupied council properties into desirable, warm and affordable homes, tackling both climate change and fuel poverty. The scheme comprises 1960s non-traditional concrete cross wall homes, including terraces of three-storey houses, low-rise flats, and bungalows. While the homes are well located and have an established community, they were cold and draughty with an inefficient design, particularly the houses with an unheated garage under the living room and an under-croft below the kitchen. Tenure is 100% affordable social rented housing, both before and after the retrofit. The solution was a tenant-focused, highly-efficient whole house retrofit delivering super insulated, low maintenance near ‘net zero operational energy’ homes. The retrofit has also transformed the neighbourhoods with brighter finishes and increased passive surveillance from converted garages and first floor Juliet balconies to some houses. The design team, led by Studio Partington, involved residents in developing the design brief during the competitive tender process. The community came together to establish a ‘wish list’ and choose the colour of their own window surrounds. The solution provider was able to include small items which make a big difference to residents’ lives, such as light tubes making stairs brighter, outside taps for watering, and doorbells. The tenants were able to remain in residence throughout the retrofit of their home and each home was completed in around twelve days..

How does this project make use of an existing structure, place or building in a creative way? Is it innovative? How will this project continue to evolve or enable future flexibility and adaptation? Have you considered its resilience? 

A deep retrofit, extending the dwelling’s life by 60 years, avoids considerable construction waste and embodied carbon. The total embodied carbon associated with the retrofit works undertaken was calculated as 26t CO2e compared with circa 120t CO2e for demolition and rebuild. People remain living in their homes during the works, which typically take twelve days. Demolish and rebuild would have increased the project cost and broken up the community. Measurement by HACT UK social value bank shows social value up to £4,500 a year per retrofitted home. One of the innovations underpinning the model is that the Solution Provider signs a performance guarantee, ensuring the in-use energy use and generation are in line with the approved design. The design of solutions and selection of components were considered in detail within the energy modelling, including factors to account for actual performance expected rather than manufacturers stated performance. Additionally, the fabrication and construction details were carefully developed to ensure site works could be competed without compromising the intended airtightness and thermal continuity. Both intent and outcome were to eliminate the ‘Performance Gap’. Metering and monitoring were included as part of the solution to enable actual performance to be measured and monitored. The retrofit has transformed the neighbourhood with light finishes and new on street entrances and passive surveillance from Juliet balconies. Bright colours around windows, chosen by the residents, give each terrace its own identity and deliberately make a city-wide statement, that the area is embracing renewal, energy efficiency and healthy living.

What is the environmental impact of the project? How will the carbon use and material impact of the development be mitigated? What is the sustainability strategy?

Energiesprong focuses on creating warm, affordable, near net-zero homes that people want to live in. Two important innovations: 1) people remain living in their homes during the retrofit; 2) it’s an assured performance scheme. The Solution Provider signs a contract to meet the energy and comfort targets. This is achieved is through monitoring every home after the project is complete. Energiesprong approach is designed to unlock zero carbon retrofit at scale, paid for by energy and maintenance savings, delivered by a new British offsite manufacturing industry. Key innovations: • Pioneering Energiesprong in the UK. • Retrofit undertaken over 12 days; residents remain at home. • Contractor assures performance through monitoring the completed project • Advanced offsite construction factory established in Nottingham, creating local employment and training opportunities. Delivered benefits: • Fabric first: full external insulation; triple glazing; improved air-tightness; reduced thermal bridging. • Energy supplied efficiently using heat pumps (gas removed) and solar panels to minimise grid imported electricity (around 1,500kWh/year per home). • Measured performance shows average space heating consumption of 58 kWh/m2/yr (within 2% of target value). • Measured solar PV production is, on average, 35 kWh/m2/yr (per home). • All surveyed tenants said they were comfortable or very comfortable in their retrofitted homes (October 2021). • Social value up to £4,500 a year per home (measured by HACT). • Total embodied carbon = 26t CO2e compared with circa 120t CO2e for demolition and rebuild.