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Energiesprong performance in the UK – our top 10 findings (part 2)

Having launched our first comprehensive review of Energiesprong retrofitted properties in the UK, we’ve been diving deep into what we’ve learned. In this blog, we’re focusing on what can be done to take future projects further – and help drive wider change in the industry.

We need better monitoring to ensure technologies are working

These pilot projects, while relatively successful, have demonstrated that the industry is underdeveloped, and elements are not always specified or installed correctly. We are already working to improve this and drive the industry forwards, but there is still room for improvement and collaboration with more innovators, installers, manufacturers, designers, contractors, housing providers – everybody who lives in a home!

7. Metering and monitoring systems need a bit more work

a) Immersion heaters should be sub-metered as part of the energy services rather than resident appliances
b) Data communications from monitoring systems is often poor and needs improving
c) Monitoring needs to be automated better and outputs standardised across projects

Having monitoring and analysis will enable us to share what is and isn’t working with the Solution Providers so they can look at how to move more homes into the over-performance category.  But how do we best do this?

On some projects there are challenges with the way monitoring systems are identifying energy use. For instance, accounting for immersion energy consumption on the resident energy supply rather than the hot water metering. This makes it difficult to draw conclusions about why there is a high actual energy consumption in some homes – is it resident behaviour, is it due to systems not being commissioned effectively, or is it just incorrect metering?

Likewise, data quality from monitoring systems is occasionally unreliable and reporting of performance metrics can be misinterpreted by the Solution Providers. A number of suppliers are now dedicating significant resource to resolving the identified issues with the monitoring systems and ensuring that future projects are simpler and more cost effective to monitor and manage.

In response to these findings and to help the Solution Providers, ESUK has developed pro formas and additional guidance for monitoring systems and reporting performance data which will be applied to future projects.

8. More work is needed to identify whether the range of results for most metrics are down to the users or due to the solution operation / efficiency / thermal performance etc.

Considering net energy consumption (one of the fundamental ESUK performance specification targets), one property with very low consumption is demonstrably net zero energy – producing almost twice the energy it uses annually. However, there is a wide range of adjusted net consumption results from the monitored homes, almost evenly spread around the target value (1,500 kWh/yr) ranging from +107% (i.e. consuming double the target value) to -186% (i.e. producing 86% more energy than it consumes).  

Resident engagement and expectations management is a critical element in the success of any retrofit project and should be improved upon wherever possible. The inclusion of a detailed occupant survey (meeting the requirements of BS40101:2022 and PAS2035:2019) in all forthcoming ESUK projects is the first step to gathering more insight and learning from projects and thereby engaging better with the residents.

What will we do differently on future developments?

9. Comparing design and reality can be tricky with some of the Energiesprong metrics (in particular space heating kWh/m2/yr). We are improving the methods to do this i.e. using pro formas, encouraging HTC measurement and airtightness testing etc. We are also reviewing our performance spec to account for this complexity

The basic elements of an Energiesprong retrofit are working, but it has been a complex process to extract and analyse the appropriate data from these pilot projects. In particular, space heating demand (measured in kWh/m2/yr) is directly linked to the internal temperatures chosen by the resident and, given that these are typically 2°C warmer than design, it is not possible to directly compare the results to the targets. Manual data analysis has to be conducted to enable comparison, but this is quite time consuming.

However, we have begun using techniques to measure the Heat Transfer Coefficient (HTC) of each property which is a value that determines the space heating demand but is not affected by the operating temperatures. Coupled with airtightness testing, these two measurements can more rapidly validate that the retrofitted property meets its design targets. More detailed investigation and manipulation of the ongoing performance data can therefore be performed only by exception (i.e. where a problem is identified by the resident or the data on an individual property).

Furthermore, we are helping the Solution Providers to establish better monitoring systems by providing them with pro formas for design and measurement (which directly align, and can therefore be easily compared and more cost effectively analysed).

We also periodically review and update our performance specification and guidance to account for these validation techniques and thereby reduce excessive data analysis time and cost.

10. The combination of fabric insulation + solar PV + heat pumps is relatively well established now as the main approach for these deep retrofits. But, we must ensure that we as an industry allow innovation to continually flourish, and this is a central focus for our work at Energiesprong UK as we explore the following:  

We need help from government to open up innovation

Funding and standards (i.e. PAS2035/2030) need development to encourage rather than restrict potentially viable solutions. We believe that the ESUK performance guarantee and measurement model can be used to strategically validate new technologies and methods. Given the monumental retrofit challenge ahead in the UK, we should continually aim to open up the retrofit market further rather than constrain it. We recently outlined how an innovation investment for energy efficient retrofit from Government could help unlock a self-financing retrofit market and tackle the cost of living crisis.

What’s the impact of Electric Vehicle (EV) charging as it becomes the norm?

We are looking at the potential use of V2H (Vehicle to Home) services rather than ever installing dedicated domestic batteries. We’re also considering incorporating access to EVs as a method to increase retrofit funding. After all, homes are just part of a bigger system and so solutions from outside the four walls (“box”) might hold the key to affordable and effective retrofit...

How does the model apply to shared blocks of houses and new build?

We have already piloted projects in shared low-rise blocks of flats and are underway with more follow-on projects. Challenges are often linked to space constraints (i.e. incorporating heat pump technology and hot water storage into tight footprints) and sharing and distribution of solar PV (making sure everyone gets their fair share of a communal system.

We are also exploring how the performance guarantee model can be applied to new build properties to ensure that homes built today don’t require retrofitting in the future!  We’re delivering our first Energiesprong new build in Plymouth with PEC Homes. We will continue to work together collaboratively to explore and resolve these challenges.

Smarter methods for underfloor insulation and improving airtightness are required

The floor insulation (or lack of) and air leakage from properties are regularly two challenges to achieving stringent post-retrofit performance targets, and they therefore end up as the main heat loss areas in a home post-retrofit if not treated. Floors are hard and disruptive to access, and airtightness can be tricky to control. We are already piloting innovative solutions to insulating floors, including Q-Bot, Airex, and perimeter insulation combined with enclosed sub-floors treated by MVHR.

We have also explored innovative methods to achieve excellent airtightness, including airtight liquid vapour control paint, and spray foam cavity insulation. But more work is needed to routinely and cost effectively integrate these measures into retrofit projects. The Energiesprong model can help to significantly reduce the risk when trialling these technologies methods because performance is measured as standard.

Download our performance report for the full details:

We’d like to thank our partners and funders for supporting the schemes, monitoring and analysis outlined in this report:

Engie (now Equans), Exeter City Council, Melius Homes, Mi-Space, Moat, Nottingham City Homes, North Devon Homes, Sanctuary and Sutton Housing Partnership.

Department of Business, Energy and Industrial Strategy, ERDF, Interreg NWE and the Mayor of London