Written evidence submitted by the UK Collaboratorium for Research on Infrastructure and Cities (DHH0030)


UKCRIC is an integrated research capability with a mission to underpin the renewal, sustainment and improvement of infrastructure and cities in the UK and elsewhere.




This is the combined response of UKCRIC researches to the above call for evidence. Responses have been collated by Prof. Patrick James, National Infrastructure Laboratory, University of Southampton. The contributing research institution [name] is given above each section.


The list of contributors is as follows:


[UoS] University of Southampton, Anderson B., Aragon V., Bahaj A.S., Gauthier S., James P.A.B., Manfren M., Powrie W., Rushby T., Singi R., Turner P.A.D.


[UCL] University College London, Yukun Hu, Associate Professor of Infrastructure Systems, UCL


[CSIC] University of Cambridge, submission by Dr Jennifer Schooling, Director of the Cambridge Centre for Smart Infrastructure and Construction (CSIC). [CSIC] contributions have come directly from Chapter 4 of the report, ‘A Blueprint for a Green Future’ [Cambridge Zero Policy Forum 2020 A Blueprint for a Green Future] which was written by Dr Jennifer Schooling, Prof Peter Guthrie, Prof Michael Ramage, Dr Judith Plummer Braeckman, and Dr David Reiner of the University of Cambridge.


Corresponding author Prof. Patrick James, paj1@soton.ac.uk




  1. What has been the impact of past and current policies for low carbon heat, and what lessons can be learnt, including examples from devolved administrations and international comparators?



If a policy is targeting saved carbon as its metric it will prioritise interventions against high energy use households (who are generally high income). Policies need to focus on delivering affordable comfort. This means that we need to consider both the de-carbonised provision of heat/cool and also vastly improved building fabric performance. The latter will require less energy to attain comfort and so make the former much easier to achieve. In some cases this may lead to interventions which actually save little or no carbon due to the pre-bound effect, but rather deliver better health and therefore societal impacts. Deep retrofits in a social housing context are such a case in point (Teli D. et al, 2016).


Past policies seem to ignore the important role of local authorities who govern cities, where most consumption occurs, in delivering low carbon heat. The past Eco scheme is something to refer to as partially successful, especially in social housing. However, it was totally undermined by as a sudden national policy announcement that pulled down the carbon price, making most projects nonviable.


In international cities, especially in Scandinavia, low carbon heat is delivered through CHP based heat networks. These can be low carbon, through many energy vectors. This can be an important and flexible infrastructure which will need financial support through coherent and sustained policy.


  1. What key policies, priorities and timelines should be included in the Government’s forthcoming ‘Buildings and Heat Strategy’ to ensure that the UK is on track to deliver Net Zero? What are the most urgent decisions and actions that need to be taken over the course of this Parliament (by 2024)?



In the UK there is a significant skills gap in terms of both capacity and expertise to deliver on any buildings and heat strategy. It is imperative that skills gap is addressed by training / apprenticeship programmes. The skills gap is across assessors, system designers, installers and maintenance teams.

Low carbon comfort is synonymous with highly efficient buildings (see 1 above). It is therefore crucial that the UK legislates to ensure any new refurbishment or new build should have the highest standard possible through mandating the lowest practically achievable energy intensity outcome – such as the PassivHaus space heating standard of 15 kWh/m2. This will need national policy change and we note that New Zealand has just closed a consultation on exactly this approach for new builds as a pathway to a similar standard for retrofits (https://www.mbie.govt.nz/have-your-say/building-for-climate-change-transforming-operational-efficiency-and-reducing-whole-of-life-embodied-carbon/). At the same time, it is important to ensure that building retrofit strategies do not result in a transition from winter heating to summer overheating risk.



  1. Which technologies are the most viable to deliver the decarbonisation of heating, and what would be the most appropriate mix of technologies across the UK?



Although the future of heating is less certain, with a range of possible different pathways to decarbonise in homes, the active and passive technologies mode would be the most appropriate mix of technologies across the UK. The trade-off between active and passive technologies could also provide flexibility. In terms of technology, there is no single most viable technology or most appropriate mix, that suits the whole UK. The decarbonisation of heating should consider the availability and sustainability of heat sources, that is the basis of large-scale applications. Relying solely on electrification appears impractical, certainly in the short to medium term. No doubt, to build new and upgrade existing supporting power infrastructure to meet the needs of decarbonised heating will: be very costly; create widespread disruption to services; and, increase the consumption of fossil fuels thereby transferring rather than solving air quality and green-house gas concerns. With Net Zero ambitions, H2 penetration into legacy energy systems provides an important pathway to decarbonise heating. However, currently no country has realised the commercial application of H2 energy by replacing natural gas with H2 due to challenges with H2 storage and transportation. Therefore, a promising alternative source to H2 with largely compatible with transmission using gas pipelines is important and its production should rely on nation’s energy reservation in view of energy safety.





Air Source Heat Pumps offer a decarbonised heat pathway which is not site specific which makes them attractive for deployment at scale, in both retrofit and new build contexts. In terms of new build housing, the use of Mechanical Ventilation and Heat Recovery (MVHR) provides the opportunity of extremely low / net zero housing.  Furthermore, ground source pumps can also be adopted as solutions at scale not only at building level but also as part of district heating and cooling networks. The start will be to augment existing networks with such technology coupled with interconnectivity and expansion with city boundaries. However, analysis of the use of heat pumps suggests that they may add substantially to morning and evening peak electricity demand peaks (Eggimann et al, 2019). Even without this extra demand, these peaks are problematic for a non-dispatchable renewables-based electricity system. Sufficient energy storage whether thermal, grid based or through system flexibility will be needed to ensure that air source heat pumps do not inadvertently increase the carbon intensity of supplied electricity. (Anderson B. et al, 2018)



  1. What are the barriers to scaling up low carbon heating technologies? What is needed to overcome these barriers?



Currently, green electricity is more affordable and available than before (e.g. solar, wind) and related technologies also seem to be ahead of green hydrogen production. For example, the definition of smart grid was proposed as early as 2007, but the concept of smart heating network was not proposed until 2015. Progress in decarbonisation from gas heating delivered via a gas network has not been achieved to a large degree despite substantial efforts, suggesting this is a particularly challenging aspect of heat decarbonisation. This is especially important for the UK, as it has the highest penetration of on-gas-grid heating in the OECD countries. In addition, the UK housing stock is also among the least energy efficient in Europe, which is a barrier to the uptake of some low carbon technologies which provide heat at lower flow temperatures. With the continuous expansion in the overall scale of gas network injecting by green gas, the productivity, security, efficiency and sustainability of the network are facing new challenges from the demand growth of decarbonisation. There is a significant opportunity to manage the benefits from utilisation of hydrogen and its potential carriers to achieve joint decarbonisation of commercial cooling and residential heating at the local level.



As per 2, the skills gap in the UK to design, deploy and maintain low carbon heating systems at scale is a current barrier. The UK’s electricity grid was not developed to accommodate significant additional household electricity demands, to which heat pumps and electric vehicles represent a particular challenge. (Anderson B. et al 2020). Electricity charging mechanisms which support the aggregation of domestic loads by electricity providers to maintain grid demands within limits will be required. Households will have to accept third party control of significant loads (electric vehicles, heat pumps, hot water – as has historically been the case in France and New Zealand), probably scheduling / dynamic control by their energy provider in return for a preferential per kWh tariff.


The SENSE study undertaken by UoS has recently (2019-20) assessed hybrid heat pump (HHP) acceptability with predominantly high income, owner-occupier households. Here we report the key findings of the online workshops. "Regarding the HHP most of the people feel it is very expensive and not affordable. Even when the Renewable Heat Incentives by the government are mentioned people have trust issues with the RHI because of prior failure of the government incentives and loan schemes. A positive response about the HHP is that the system is suitable with the existing boiler. So, the participant doesn’t have to abandon the boiler which is still working. On the whole people are only ready to invest in a technology if there is good support from the government in the form of promising incentives and scheme." Raveena Singi, MSc Dissertation, 2020


In addition to technology barriers there is a poor understanding of domestic occupancy profiles in a UK context. Aragon et al (V. Aragon et al, 2017) showed that the occupancy categories most frequently used in UK building simulation of (a) a family with dependent children where the parents work full time; and (b) a retired elderly couple who spend most of their time indoors, represent only 19% of England’s households. We simply cannot robustly estimate heating demand on this basis. This topic will need to be revisited post COVID-19 where we would expect a sustained change to increased homeworking and therefore heating practices.



Heat accounts for about one third of the UK’s greenhouse gas emissions, and half of that is from the residential sector. The vast majority of properties currently rely on gas boilers for water and space heating, with a small percentage using oil. Passive measures such as those described in question 6 below will reduce gas/oil use to some extent, however much of the UK’s housing stock is very old and difficult to fully retrofit.


Therefore, it is vital that a systematic approach is taken to reducing dependency on gas/oil. There must be a rapid move to renewables both at local (house or district) and national level. Measures should include exploiting rooftops for PV, using ground- source and air source heat pumps where appropriate, and adapting gas-fired central heating radiator systems to run on electrically heated water. The installation of gas boilers in new buildings should be phased out as soon as possible. A switch to heat pumps should be encouraged for the 15% of homes not currently connected to the gas network, and retrofitting of existing buildings for maximum energy efficiency should be accelerated to increase the feasibility of switching to heat pumps for these buildings.


Tools now exist to assess the potential for renewable energy solutions for heating and cooling at the building and district level (Pickering and Choudhary, 2019, District energy system optimisation under uncertain demand: Handling data-driven stochastic profiles), enabling maximum exploitation for heating and cooling at the local level and hence reducing demand on the national network. This surplus supply can then be put to other uses such as electric vehicle charging.

  1. How can the costs of decarbonising heat be distributed fairly across consumers, taxpayers, business and government, taking account of the fuel poor and communities affected by the transition? What is the impact of the existing distribution of environmental levies across electricity, gas and fuel bills on drivers for switching to low carbon heating, and should this distribution be reviewed?



Having exemplar projects as learning entities to guide the decarbonising of heat will unboundedly provide the evidence needed on costs shared whilst protecting the fuel poor. Furthermore, any Green Deal type mechanism should not apply the 7.5% interest rate. Ensure that any such approach does not by pass vulnerable sectors such as private rented.


  1. What incentives and regulatory measures should be employed to encourage and ensure households take up low carbon heat, and how will these need to vary for different household types?



There is a major opportunity to improve the energy efficiency of buildings through adopting passive measures such as high levels of insulation, design for solar gain in winter, measures for preventing overheating in summer, and the use of direct solar for water heating. Many commercial and industrial properties exhibit a ‘performance gap’ between the anticipated energy use when designed and the actual energy consumed post-occupancy. This performance gap can be closed through performance feedback loops to designers and contractors, and through requiring post-occupancy measurement and certification of energy use. This should be combined with a programme of surveying existing buildings to understand where heat losses are occurring, and carrying out targeted retrofits – while monitoring the performance of these measures, as emissions reductions from many retrofit activities to date are much less than anticipated.


Where buildings are commercially or publicly owned, retrofit can be incentivised through regulation. However, other approaches are required for owner-occupied domestic properties. A long-term plan for a net-zero carbon retrofit programme for existing homes (Construction Leadership Council, 2020, Letter to the Chancellor of the Exchequer) would have the additional benefit of providing new employment for those losing jobs elsewhere in the economy, while safeguarding existing employment. For properties not covered by the programme, the UK Construction Leadership Council’s suggestion of a ‘Help to Fix’ interest-free loan scheme, predicated on energy efficiency, would be one way to encourage homeowners and improve the quality of the nation’s housing stock.



  1. What action is required to ensure that households are engaged, informed, supported and protected during the transition to low carbon heat, including measures to minimise disruption in homes and to maintain consumer choice?



Trusted partners are key to ensuring both initial and sustained engagement with households. Giving leadership to local authorities in any engagement is a must. Furthermore, universities and colleges could also play a role in surveys and establishing community-based focus groups. Younger generation leadership in required to provide longevity and acceptability as we progress to 2050.    


  1. Where should responsibility lie for the governance, coordination and delivery of low carbon heating? What will these organisations need in order to deliver such responsibilities?



It is our view that governance must be central with nationally defined standards or regulations which Local Authorities are at liberty to exceed. Local Authorities are best place to ensure local co-ordination and delivery should be left to agile contractors bidding for contracts let by large owners or developers. Local Authorities can play a key role here in aggregating local demand from private home owners, acting as a procurement mediator ensuring best value and quality so that national standards are met or exceeded.

Governance will require the alignment of both:

MHCLG – who must set appropriate standards and processes via planning and building control documents for both new build and retrofit so that no building constructed after 2021 needs any decarbonisation intervention at all;

BEIS – who must ensure appropriate mechanisms and support for interventions in those buildings that for whatever reason escape the planning and building control process




Teli D. et al (2016) Fuel poverty-induced ‘prebound effect’ in achieving the anticipated carbon savings from social housing retrofit, BSERT, https://journals.sagepub.com/doi/pdf/10.1177/0143624415621028)


Eggimann et al, (2019) A high-resolution spatio-temporal energy demand simulation to explore the potential of heating demand side management with large-scale heat pump diffusion, Applied Energy, vol 236, pp 977-1010,  (http://www.sciencedirect.com/science/article/pii/S0306261918318725


Anderson, B., Rushby, T., & Jack, M. (2018, November). Electrifying Heat: Patterns of electricity consumption in electrically heated households in the UK and New Zealand. 8th International Conference on Energy and Environment of Residential Buildings. 8th International Conference on Energy and Environment of Residential Buildings, Wellington, New Zealand.)


Anderson B. et al, (2020, February 12). Will Flipping the Fleet F**k the Grid? 7th IAEE Asia-Oceania Conference 2020: Energy in Transition. 7th IAEE Asia-Oceania Conference 2020, Auckland, New Zealand. https://eprints.soton.ac.uk/437541/)


Aragon V. et al (2017) Developing English domestic occupancy profiles, Building Research and Information, vol47, pp 375-393. https://doi.org/10.1080/09613218.2017.1399719

November 2020