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UK needs to retrofit 26 million homes by 2050 to reduce greenhouse gas emissions

Marjan Sarshar, Professor of Sustainability and the Built Environment | The Institution of Engineering and Technology (IET)

4 min read Partner content

Professor Marjan Sarshar, co-author of the IET & Nottingham Trent University report, Scaling up retrofit 2050, suggests that the task of retrofitting 26 million UK properties should begin with social housing, which represents 4.5 million properties and 17% of UK housing stock.

In the UK we face a demanding challenge. The Climate Change Act of 2008 sets a legal target to cut greenhouse gas emissions by 80% by 2050. Domestic energy consumption accounts for about 30% of the total UK energy budget, and about 20% of total UK carbon emissions. We must minimise demand in our homes, and decarbonise what is left.

The UK has and old housing stock, and turnover is low. About 80% of the homes we will be occupying in 2050 already exist. We can’t just rely on decarbonising the grid or building new energy efficient homes. We have to improve the energy efficiency of the existing stock. That means retrofitting around 26 million homes.

A recent report by the Institution of Engineering Technology (IET) and Nottingham Trent University (NTU) sets a vision for retrofitting our homes for 2050. The report calls for ‘deep retrofitting’; and a whole-house approach to design which takes a property from its current state to near net-zero energy demand in one step. Bit-wise approaches will result in higher costs over the next few decades. Many of the ‘shallow’, less carbon efficient measures will have to be dismantled and re-retrofitted to meet the stringent 2050 targets.

Is it technically feasible to retrofit homes to zero carbon?

We know how to do deep retrofit. Innovate UK’s Retrofit for the Future programme demonstrated technical feasibility in a range of property types, and pilot projects in Nottingham and other national and international locations show that you can scale up some of the approaches.

The simplest approach is “throwing a duvet over the building”. You put external insulating cladding on the building with integrated high-efficiency doors and windows, a new highly insulating roof with built-in photovoltaics. This combined with some micro generation and / or a sustainable heating system can result in near zero energy home. This was the approach used in the Nottingham project, and it is estimated that there are 9 million properties in the UK that are suitable for this method right now.

What do successful retrofit programmes do?

The joint IET and NTU report examined a number of successful domestic retrofit programmes both in the UK and internationally to discover what works. Despite differences in objective and approach, they all shared common success factors including:

  • Having a clear policy lead
  • Having a long-term strategy
  • Public sector subsidy, or access to low-cost finance
  • A whole-house approach to retrofit
  • Aggregation of properties into larger projects to reduce costs
  • Having a single, trusted point of contact for owners and tenants that will stay with them throughout the retrofit process
  • Making a good consumer proposition

Most of the examples target modest improvements in energy efficiency (‘shallow’ retrofitting). The exception is Energiesprong; an approach to net-zero carbon retrofit piloted in the Netherlands and now spreading to other countries. This was the methodology behind the Nottingham pilot.

What should the UK do now?

Deep retrofitting is currently very expensive. It is possible to bring down the costs to a level which is commercially viable. The IET / NTU report sets out an approach to tackle this challenge while creating new economies which are internationally scalable. The report suggests we need to pilot deep retrofitting on a large number of houses, with public subsidise, to cut costs to a point where the solutions become market ready.

Four strands of activity are necessary to overcome the barriers.

First, we need to develop a long-term national cross party strategic plan. We need to agree as a society that achieving the 2050 goal for housing is important and justifies concerted action. The UK cities need to develop their aligned regional strategies.

Second, we need a drive to reduce costs and build the capacity of the supply chain in the UK. This requires a piloting stage, allowing innovation and scale to cut the costs per property.

The logical place to start is with social housing. At 17% of the UK housing stock, it represents 4.5 million potential properties. Social landlords have large numbers of similar properties and a longer time horizon than many other owners. This piloting stage will require public support for around 25,000 houses on a sliding scale.

A national centre of excellence for research and innovation is needed to explore improved approaches and appraise quality standards for the novel transformations.

Third, we must engage with the end-users; the householders. There needs to be a strong and easily understood consumer proposition that makes the benefits clear and suppliers which can be trusted.

Finally, we need to encourage investment in deep retrofit. This requires innovation and flexibility in financing, public sector support in the piloting phase, and developing large-scale projects for commercial investment.

These strands need to work together, so the next step will be to get the key players around a table to discuss how to create the programme we need.

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