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The National Energy Foundation and Energiesprong UK / High-impact retrofits

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Energiesprong is an innovative solution to improving poorly insulated and draughty homes, making them more energy-efficient and comfortable. Off-site manufacturing allows whole-house retrofits to be done quickly and with minimum disruption to tenants.

Energiesprong could radically cut carbon from the UK’s housing stock, and work comes with a 30 year energy performance guarantee – while giving homes a modern makeover.

86% reduction in CO2 emissions from Energiesprong homes in Nottingham 

30 year energy performance guarantee 

5,000 Energiesprong retrofits complete in the Netherlands, 171 in progress in the UK

"This is a pay as you save model that actually works, because of the performance guarantee."

Emily Braham, Energiesprong UK

The UK has over 27 million homes, but very few of them are as efficient as they need to be for the UK to reach net-zero CO2 emissions, with energy used in homes responsible for about 14% of UK emissions. Many people are putting up with cold, damp homes even while spending much of their income on heating.

While some inefficient homes may be demolished and rebuilt, most need retrofitting to bring them up to the required standards of energy efficiency and comfort; this can be a slow and expensive process, with multiple tradespeople visiting and a lack of co-ordination raising costs while reducing the effectiveness of the work.

The Energiesprong (Dutch for ‘energy leap’) approach was conceived in the Netherlands in 2009, as a way of retrofitting houses to achieve net-zero energy use. Energiesprong UK, which is hosted by the Ashden Award-winning National Energy Foundation, has been working to scale up the UK Energiesprong market, building demand and the capacity to meet it.

One house opted out of this Energiesprong development

The Energiesprong approach treats the whole house in one go, dealing with electricity, heat, hot water and ventilation to deliver a home that has net-zero or very low energy use. Whole new walls and roofs are manufactured off-site and delivered with doors and windows already fitted. These sections can then be fitted around the existing house, giving a new exterior and bringing its insulation and airtightness up to the required standards.

Typically, mechanical ventilation with heat recovery is used to ensure a supply of fresh air without cold draughts, and a new heating system that runs on renewable electricity is installed. But the exact technologies employed are up to the solution provider, which is responsible for carrying out the design and delivery of the retrofit.

The effectiveness of the Energiesprong approach is ensured by a 30-year guarantee from the solution provider, which promises that a retrofitted house will deliver the required energy performance as long as a specified maintenance programme is carried out. The guarantee is based on comfort targets such as keeping bedrooms at 18C and living rooms at 21C, supplying enough hot water for washing and showering and enough electricity for normal domestic use. This is what most households really want, rather than any specific type of technology or design approach.

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The Energiesprong standard requires that each retrofit delivers a warm, dry and well-ventilated home for no extra cost to the household. Tenants pay an affordable amount for their energy, much less than they would have paid if they were adequately heating their home before the retrofit. They also pay a fixed monthly ‘comfort plan’ payment, which can help with financial management as it replaces fluctuating energy costs. People who were under-heating because they had limited money for bills will be warm and comfortable for the same cost.

By delivering a warm, dry and well-ventilated home, Energiesprong improves people’s physical health and comfort as well as how they feel about their home. Inclusion is also an important benefit – tenants don’t normally get much of a say in how their homes are maintained, but through Energiesprong they can reap the benefits of the latest retrofit technology, and they are also consulted throughout the process.

Energiesprong is most cost-effective when it is applied to lots of similar homes, so it has initially been targeted at social housing. Although the cost per retrofit is high at the moment, and requires grant funding to be viable, the Dutch experience proves it will fall rapidly as the work scales up. The retrofit will eventually be paid for through avoided maintenance costs for the landlord and the tenant’s regular ‘comfort plan’ payment.

Energiesprong was brought to the UK in 2015 with the National Energy Foundation being granted funding from both the EEU’s Horizon 2020 and Interreg programmes. The first Energiesprong retrofits in the UK were carried out in Nottingham, and each home is saving about five tonnes of CO2 per year, while the embodied CO2 per home is about 25 tonnes – much lower than the estimated 45 tonnes produced by demolition and new build. The five-year payback of the embodied CO2 means that the retrofits can contribute to near-term reductions in CO2 emissions, which are essential in tackling the climate breakdown.

Nottingham City Homes has been pleased with the first round of Energiesprong retrofits it carried out, and a second round was already underway in early 2019. From its point of view, Energiesprong makes good sense as it improves the lives of the tenants, cuts the long-term maintenance costs of homes and makes them look much nicer. Moat Homes is similarly satisfied with its 5-home pilot project in Maldon where the planning officer set the solution provider the additional challenge of keeping the look of the facades unchanged.

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