Since the IET published our report “Scaling Up Retrofit 2050” several people have asked me why the emphasis on ‘deep retrofit’? Taking today’s properties and upgrading them to 2050 energy efficiency standards in one step. Wouldn’t it be better to make a series of incremental improvements across as many properties as possible? Progressively improving the energy efficiency of the housing stock as new solutions become available until we reach the near net-zero energy demand required for 2050.

The goal is to reduce the carbon emissions from domestic space and hot water heating, and space cooling to zero by 2050. We must do that to meet the targets in the 2008 Climate Change Act.

The drive for deep retrofit comes from two pressures; the need for capital and resource efficiency, and the need for whole house thinking.

Don’t put in interim solutions we will have to rip out later

The problem with an incremental approach is that many solutions will make a worthwhile improvement to the energy efficiency of the property today, but are not compatible with reaching the 2050 target of zero-carbon. That means that the upgrades will need to be removed and replaced before 2050. This is disruptive, wasteful and potentially very expensive.

For example, cavity wall and loft insulation will help reduce energy demand today but will probably not be to the standard required for a zero-carbon future. And you can’t just keep adding insulation. It may be necessary to switch to a different technology altogether, requiring removal of the previous insulation. Not too bad if it is loft insulation, but a nightmare if it part of the building fabric.

Similarly, you can improve the energy efficiency of the property by replacing an ageing gas boiler with a new one, or replacing oil-fired heating with gas. But gas cannot form part of a 2050 future. It’s still a carbon emitting fossil fuel, and there are no plans for carbon capture and storage on the domestic scale.

The Netherlands is already tackling this problem. The Dutch plan to phase out gas altogether by 2050 and the default assumption for all new building planning permissions is that the building will not connect to the gas grid. Local authorities can grant exemptions, but they are expected to become increasingly rare. There is also a programme to disconnect existing homes with 31 municipalities, including the largest cities, signing up to create gas-less neighbourhoods over the next couple of years. This policy pressure is encouraging the supply chain to come up with practical and cost-effective solutions ranging from heat pumps to district heating schemes.

So, from the point of view of good use of capital, efficient use of resources, and minimising disruption, it makes sense to focus on the properties that can be taken straight to 2050 standards using the methods available today. That’s around 9 million homes. We can then progressively build 2050 solutions for the rest of the housing types.

Whole house thinking is critical for zero-carbon

The other requirement is for whole house thinking. To reach zero-carbon, we need to think about all the different components of a building, and how they interact. We need designs that consider every source of energy demand, every point of loss or wastage, and create high quality, desirable and comfortable homes. You can’t do that piecemeal. It has to be an integrated design and a cooperative set of solutions.

Sneinton Pilot – Nottingham City Homes, Energiesprong, Melius Homes

There is a good example of how important whole house thinking is in the pilot project at Sneinton in Nottingham. Procured by Nottingham City Homes and delivered by Melius Homes, this project carried out a deep retrofit on ten homes. The plan was to deliver the heating demand from ground source heat pumps. Traditionally, ground source heat pumps work with underfloor heating as the output temperature of the heat pumps is not high enough to directly connect to the existing pipework and radiators of the conventional central heating system. That means ripping out the existing hardware and replacing it with a new system. Expensive, and in many properties not even practical.

In Sneinton, the ground source heat pumps combined with all new and efficient wall, roof, window and door insulation. The amount of heat required was much lower, radiators could operate at lower temperatures, and the output from the ground source heat pumps was perfectly adequate. They were able to connect the heat pump system to the existing pipework radiators, minimising disruption and conversion cost.

A simple example of how by looking at the design of the whole building you can get the maximum benefit for the minimum cost. We know that you can’t get to zero-carbon by piling up the series of separate point interventions. Whole house thinking and design is essential to reach the 2050 goals.

Make the jump to 2050 with deep retrofit

The best route to the 2050 target of zero-carbon for domestic space and hot water heating and space cooling is deep retrofit. Taking existing buildings all the way to zero-carbon in one jump. Making one comprehensive intervention and not a series of small steps over many years. It makes the best use of capital and resources, minimises disruption, and makes best use of our supply chain capacity. We start by deep retrofitting those properties where we already have practical solutions and build additional solutions for more difficult property types as knowledge and experience grows.


2 Reasons Why Deep Retrofit is Vital for Zero Carbon Homes

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