Written evidence submitted by Newcastle University (DHH0016)


This evidence has been prepared by Dr Sara Walker, Director of the Centre for Energy at Newcastle University and Director of the EPSRC National Centre for Energy Systems Integration, which brings together energy experts from around the world to help unravel the energy network and understand future supply and demand. Dr Walker has significant experience from over 20 years working in energy efficiency and renewable energy projects, working with local authorities and private providers in academia and consultancy.



This submission sets out an overview of areas where our academics and policy experts can support the Committee’s inquiry by providing research, insights, and analysis. We have answered some of the Committee’s specific questions to highlight policy findings of work to date, but have also outlined other initiatives we are working on that can support the inquiry’s focus on how to decarbonise heat in homes.


We would welcome the opportunity to brief the Committee on the University’s initiatives in more detail and provide further evidence to support the inquiry.




Newcastle University is a world-leading research intensive university and its Centre for Energy – a Newcastle University Centre of Research Excellence – brings together a wealth of expertise across disciplines to unify efforts towards a new way of thinking about energy systems. From piloting technologies and ensuring success when they are deployed, to providing evidence to Select Committees and being seconded to government, our academics are a key part of the policy ecosystem and are at the forefront of the UK’s energy policy development at a critical time in the country’s efforts to decarbonise and tackle climate change.


Taking a whole systems approach


Exploring the role of hydrogen


Designing and building homes of the future


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?


Retrofit reality: Exploring the reality of retrofit programmes; their impact on landlords, customers, and product suppliers; and the implications for future policy development, including Pay as You Save and Green Deal type schemes. The retrofit programme led to improved home comfort, slightly lower than expected contribution of solar thermal technology, and did not lead to the expected reduction in energy use and energy bills. Results show that policies which support repayment of capital costs through energy bill savings may overestimate bill saving contributions.



The installation of energy efficiency retrofits in existing social housing could play an important part in reducing UK carbon emissions. However, within both research literature and in practice, there is a limited understanding of how the performance of properties that are retrofitted to a higher energy efficiency standard is affected by the behaviour of those in the household, and how informational interventions impact on behaviours. The success of CO2 emission reduction policies and strategies rely on feedback from practical and ‘real world’ research projects to build this knowledge base.


Newcastle University worked with Gentoo (a large social housing provider) as a partner on their “Retrofit Reality” bid to The Housing Corporation (now the Tenant Services Authority). The Retrofit Reality project aimed to be the largest retrofit of social housing to energy efficiency standards in the UK and went beyond the legislatively required Decent Home standard. The project aimed to establish the ‘reality’ of the situation for landlords, customers and product suppliers when attempting to meet the challenge of the huge national retrofit programme that lay ahead.


Research and findings


Key policy finding: Modelling the contribution of technologies to decarbonised heating systems needs to be informed by occupant behaviour.

Newcastle University explored the technical performance of solar thermal collectors. Solar thermal systems comprise a collector on the roof, running water through collector pipework which is heated by absorption of energy from sunlight. They can typically provide around 40-60% of the annual hot water needs of a UK home. Research on this technology to date had failed to consider all of the factors which influence the performance of solar thermal systems, relying on information from laboratory studies.


Monitoring in-situ, on the other hand, allows for researchers to take into account the way in which end users influence solar fraction and other performance related factors. Solar fraction is used to describe the fraction of hot water demand which is met by the solar thermal system. Over the monitoring period, a large variation in solar fraction was found when used in-situ, due to the timing and volume of hot water usage. It was found that computer models of the solar thermal systems over-estimated the contribution which the system made to hot water provision by an average of 14% [3, 6].


Key policy finding: For social housing tenants, cost is a key driver for behaviour and improved building fabric may lead to comfort take back (i.e. improving the energy efficiency of the fabric of the home resulted in occupants being able to afford to heat their homes for longer periods).


A second strand involved Newcastle University considering the behaviour and attitude of households. Newcastle University conducted before and after interviews with a sample of households which received a retrofit. Researchers implemented an information intervention to tenants, but no significant difference was found with tenants that received this intervention. Analysis of the survey showed that tenants were primarily motivated to reduce energy in order to save money, that a significant number of tenants switched to showering, that more than half of tenants did not understand how to control their new central heating, that some tenants reported using the heating for longer periods and reducing energy saving behaviours such as draft proofing since the house felt warmer, and that the focal fire continued to be used despite the running expense of new electric fires compared to the replaced gas fires [1, 2, 4, 5, 7, 8, 9].


Outcomes and application

Newcastle University contributed to three Gentoo reports on the project [10, 11, 12] and one technical report to the Tenant Services Authority [not in public domain].


The Retrofit Reality project has been used as a case study of good practice in several documents aimed at the housing sector to enhance professional practice [13, 14, 15, 16]. It is also detailed on housing/retrofit databases (see for example “Rethinking refurbishment” [21]) and was referenced in written evidence provided to the Environmental Audit Committee’s Green Economy inquiry by Gentoo [19].


The project led to Gentoo changing its practices, using their experience with the energy efficiency retrofit, they have gone on to undertake retrofit projects funded by the Technology Strategy Board, and were one of a handful of housing projects provided funded by the former Department of Energy and Climate Change to undertake a Pay As You Save trial [20]. Gentoo went on to develop a new product, the Energy Saving Bundle, under the Green Deal initiative, which was picked up widely including by Which? in a memorandum submitted to the Public Bill Committee on the Energy Bill 2012 [17, 18].


Question 2: 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)?


Active Buildings as Virtual Power Plants: The importance of a fabric first (energy efficiency) approach with heat pumps. Results showed there is significant potential for buildings to offer flexibility to the energy network, with the building load able to reduce by around 40%, since the building cooled (in winter) or warmed (in summer) slowly due to good thermal performance.



The building sector has been reported to be responsible for 20% of total delivered energy worldwide [22]; 31% of global final energy demand [23]; and 40% of primary energy consumption in International Energy Agency (IEA) member countries [24]. At the same time, change is being driven by decarbonisation, digitalisation, and decentralisation.


Newcastle University led a piece of research to better understand the role which buildings could play in supporting energy networks, if they were considered to be “active” or “virtual power plants”. The research evaluated the performance of an existing commercial building with over 15,000 meters, sensors and HVAC components, and analysed 1 billion data points.


The building was commissioned in 2016 and is considered a typical “good” air conditioned office space when compared to UK benchmarks. The building is electrically heated and cooled by a number of heat pumps, a key technology of interest to those considering decarbonisation of heat in buildings. The 22 distributed heat pumps are configured for optimum start to achieve comfort temperatures by 8am and are turned off at 5pm. A combination of adequate insulation, high thermal mass and internal gains mean that in the absence of winter-time heat injection, the temperature drift in the building is notably slow.


Research and findings

Researchers looked at the potential for the building to “turn off” a number of loads, which might help future networks at periods of congestion or high demand. To evaluate the potential to do this, we needed to determine the impact of turning off loads on the comfort of building occupants, particularly with regards to fresh air and comfortable indoor temperature.


Key policy finding: Well-coordinated demand response events (interruption of heat pumps, circulating pumps and air handling units) have intangible occupant comfort implications, and therefore such commercial buildings are well-placed to be operated as stationary electrical energy storage assets within a dynamic and interactive energy system [25].


The duration of a demand response event was limited to 4 hours (as imposed by ASHRAE 55) in order to limit excessive thermal drifts. In the absence of HVAC[1] operation and providing windows can be opened, simulation results showed that CO2 concentration would stay below 1000ppm (guideline threshold for indoor air quality) across a 4-hour demand response event in areas with the highest occupant density. The installed mechanical ventilation was able to restore CO2 levels to below 1000ppm in 15 minutes and to pre-demand response levels in 45 minutes.


Annual room temperatures showed that with no HVAC input, thermal drifts would exceed the threshold of imperceptibility (0.5°C/hr) for only 1.2% of wintertime and 14.5% of summertime instances in the worst case zones. This demonstrates that building designers can achieve substantial resilience in large, well-insulated buildings with exposed thermal mass and openable windows, allowing comfort to be maintained in free-float mode and enabling buildings to operate as a Virtual Power Plant asset.


Key policy finding: If we decarbonise heating with a significant proportion of homes and non-domestic buildings switching to heat pump technology, demand on the electricity network can be better managed if the buildings are of a good thermal performance standard. For electrically heated buildings with good thermal fabric standards, building loads can be controlled to offer flexibility to local networks without compromising occupant comfort. A recommended policy priority is, therefore, to support a programme of radical retrofit of the UK building stock. This is consistent with the Committee on Climate Change work with the Institute of Health Equity [28].


As a result of this work, Newcastle University is currently working on two further research programmes. One, Active Building Centre Research Programme [26], is investigating further the way in which large numbers of Active Buildings might interact with, and support, energy networks. The second, NetZeroGeordie [27], is looking at the potential for geothermal energy to provide heating to a cluster of buildings with diverse heating demand.


Question 3: 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?


National Centre for Energy Systems Integration: Vital perspective of Whole Energy Systems in understanding how decarbonisation options for heating interact with other parts of the energy system



The EPSRC National Centre for Energy Systems Integration, headed up by Director Dr Sara Walker,  is looking at energy demand, including from buildings. Researchers are evaluating potential scenarios for development of a lower carbon building stock, and at the same time considering how changes in the buildings sector interact with decarbonisation pathways for other elements of the Whole Energy System.


A Whole Energy Systems Integration approach is vital. Without this big picture, we risk pursuing a decarbonisation of heating which adversely impacts other parts of the energy system. For example, there may be trade-offs between the use of biofuels for space heating in individual buildings, for combined heat and power units in community and district heating schemes, in biofuel-powered vehicles, and in the power sector for generation of electricity.


Possible viable technologies:

  1. The first key “technology” is to reduce demand for space heating through a fabric retrofit approach (see response to question 2).
  2. In the UK approximately 6,000 boilers are installed each working day, and the industry could do better to reduce emissions with these boiler installs. Issues of oversizing, and resultant lower efficiency when operating at partial loads, are a particular concern.
  3. There is no either/or choice for delivery of space heating (once demand has been reduced through fabric insulation) and technologies may be appropriate to certain buildings, geographies and demographics.
  4. Solar thermal systems, air and ground source heat pumps (with decarbonised electricity supply), direct electric heating, and biofuel boilers are possible single building technologies for low and zero space heating. Hydrogen gas boilers may be appropriate in the future, if hydrogen can be made in a low/zero carbon way.
  5. Community or shared asset heating systems such as heat networks are possible for some applications. This might be relevant to dense urban developments, or locations with strong community cohesion.
  6. “Waste” heat from industrial processes and heat from minewater are also sources of heat which could prove useful for district heating and heat pump applications.
  7. Heat storage is common for water heating with gas boiler systems in the UK. Single building systems with new technologies might continue to require heat storage.
  8. Heat storage with capacity to support daily demand, and seasonal demand, may be required. Whilst daily storage is common, seasonal heat storage is less developed in the UK market.
  9. Some applications might incorporate other electrical assets such as photovoltaic panels and electric vehicle charge points. Decarbonisation of heating cannot be seen in isolation from decarbonisation of other assets and the associated use of energy in the home.


Research and findings


Key policy finding: As with question 2, if we decarbonise heating with a significant proportion of homes and non-domestic buildings switching to heat pump technology, demand on the electricity network can be better managed if the buildings are of a good thermal performance standard. Energy efficiency combined with heat pump technology offers greater opportunity for building heating load to be managed in flexible ways, to reduce stress on local electricity distribution networks [25].


Key policy finding: Decarbonisation of heating through large scale uptake of heat pumps will lead to increased peak demand on the local (and national) electricity network. Estimates of the increase in peak demand vary from 14% increase with 20% heat pump penetration[2][29], to as much as 95% additional peak demand for full electrification of all domestic heat demand in a city through independent (single building) air-and ground- source heat pumps [30].


Key policy finding: Domestic building stock modelling methods are varied and it is important to ensure the temporal and spatial resolution of models is understood. If we are to better understand the impact of heat pumps and their associated electrical demand, for example, we need to consider demand for space heating (typically modelled over a day) and the supply-demand balancing (on a sub-minute) operational requirements for an electricity network. “Improper representation of time will therefore overlook basic operational characteristics of integrated energy systems” [31].


Key policy finding: For our study of tower blocks, across 12 future carbon content and 14 economic scenarios, the highest lifetime carbon savings were achieved by centralised biomass boilers and GSHP[3] respectively. Fabric retrofit offers the 3rd highest carbon saving. In multi-dwelling buildings such as blocks of flats, combined heat and power (CHP) has been favoured over electrification of heating systems. However, research has shown that decarbonisation of electricity generation could make natural gas-fired CHP more carbon intensive than other options by 2022 [32].


Key policy finding: Solar thermal technology, with storage, can make a meaningful contribution to domestic heat demand provided the building heat loss is low (to reduce demand) and the operating temperature of the system is low (to reduce losses) [33].


Key policy finding: Certain geographical locations are ideal for access to energy from minewater. Researchers have investigated the use of minewater as an energy source compared with individual closed-loop, ground-source heat pumps, and identified some advantages for domestic applications. The resource is not insignificant, and the UK Coal Authority estimates that abandoned flooded mines contain around 2.2 million GWh of heat [34].


Key policy findings: Local co-ordination of the operation of separate energy networks (gas, electricity, heat) can result in better technical, economic and environmental performance than if operated without any network coupling. Specifically, research has shown that integration of the operation of the gas and electricity distribution networks through Power-2-Gas and Vector-Coupling-Storage has reduced the total energy supplied from upstream gas and electricity networks, reduced total cost of operation of the networks and reduced total GHG emission from the networks [35].


The unasked question: What role for energy justice?


Newcastle University Centre for Energy: issues of energy justice and energy ethics in the transformation of our energy systems.


Newcastle University Centre for Energy – a Newcastle University Centre of Research Excellence – brings together a wealth of expertise across disciplines to unify efforts towards a new way of thinking about energy systems. This includes a theme around energy justice. This encompasses issues of fuel poverty, who pays for the transition, the extent to which social capital which may enable or block engagement with energy transitions, and the potential role of community and sense of place in transitions, for example.


Research and findings


Key policy finding: Flexibility should be enabled and rewarded in a way that enables all members of society to participate. Flexibility in heat load raises questions regarding the extent to which it is primarily derived from technological or social means, which has implications for the (dis)comfort and (in)convenience involved in economising flexibility capital. It is important to consider, in designing market mechanisms to encourage flexibility, whether financial limitations might restrict participation by some members of society [36].


Key policy finding: Hydrogen in the domestic sector has potential to disrupt social practices. The physical and chemical properties of hydrogen may disrupt domestic practices of cooking and heating [37], and research has shown this may shift lived experiences of fuel poverty and energy injustice; and may disrupt or enhance place attachments of the communities [38].





  1. Walker SL, Lowery D, Theobald K (2014). Low-carbon retrofits in social housing: Interaction with occupant behaviour. Energy Research and Social Science 2014, 2, p102-114.
  2. Lowery, D.M. (2012). Evaluation of a Social Housing Retrofit Project and its Impact on Tenant Energy Use Behaviour. Thesis submitted in partial fulfilment of the requirement of PhD. Newcastle, Northumbria University.
  3. Waggott, A. (2012). Assessing the performance of solar hot water systems in social housing in the UK. Thesis submitted in partial fulfilment of the requirement of MPhil. Newcastle, Northumbria University.
  4. Lowery, D.M., Theobald, K., Waggott, A. and Walker, S.L. (2012). “Barriers to retrofit of housing with low carbon technologies”. Engineering Sustainability. 10.1680/ensu.10.00050
  5. Lowery, D., Theobald, K., Walker, S.L. (2011). ‘Social and behavioural barriers to achieving low-carbon retrofits in social housing’. RGS-IBG Annual International Conference 2011, 31st August-2nd September, Imperial College London.
  6. Waggot, A., Pearsall, N., Theobald, K. and Walker, S.L. (2010). 'Monitoring Useful Solar Fraction in Retrofitted Social Housing'. CIB World Congress 2010, Salford Quays, Manchester, 10-13 May 2010.
  7. Walker, S.L. (2009). ‘Behavioural challenges in the pursuit of low-carbon energy technologies in the domestic sector’. Delivering Sustainable Homes RIBA conference, Newcastle, 18 November 2009.
  8. Greenwood, D., Lowery, D., Theobald, K., Walker, S. (2009). ‘Behavioural challenges in the exploitation of low-carbon domestic energy technologies’. International Conference and Workshop on Sustainable Construction, Cairo, 9-12 March 2009.
  9. Theobald, K. and Walker, S. (Eds.) (2008). Meeting the challenge of zero carbon homes: a multi-disciplinary review of the literature and assessment of key barriers and enablers. Northumbria University, Newcastle.
  10. Gentoo Group (2009). Retrofit Reality: a dissemination report by Gentoo part 1 of 3. Sunderland, Gentoo Group.
  11. Gentoo Group (2010a). Retrofit Reality: a dissemination report by Gentoo part 2 of 3. Sunderland, Gentoo Group.
  12. Gentoo Group (2010b). Retrofit Reality: a dissemination report by Gentoo part 3 of 3. Sunderland, Gentoo Group.
  13. Northern Housing Consortium (2009). Accommodating a greener future II. Sunderland, Northern Housing Consortium.
  14. Rabinowitz, R. and d'Este-Hoare, J. (2011). Financing UK Carbon Reduction Projects. BRE Press. http://www.routledge.com/books/details/9781848061682/
  15. Fusion 21 (2011). An analysis of tenant perceptions towards energy efficiency measures, energy use behaviours and potential interventions. Fusion 21.
  16. Renewable Energy Foundation (2011). Energy Policy and Consumer Hardship. London, Renewable Energy Foundation.
  17. House of Commons (2011). Energy Bill: Memorandum submitted by Which? (EN 18). http://www.publications.parliament.uk/pa/cm201011/cmpublic/energy/writev/m18.htm Accessed 02/10/2015.
  18. WHICH? references “Retrofit Reality” in their evidence to the House of Commons (reference 1).
  19. House of Commons (2012). Environmental Audit Committee - Green Economy. Written evidence submitted by Gentoo Group Limited. http://www.publications.parliament.uk/pa/cm201012/cmselect/cmenvaud/1025/1025vw29.htm Accessed 02/10/2015
  20. DECC (2015). Feasibility study on Green Deal and ECO customer behaviour. London, DECC.
  21. https://www.bre.co.uk/page.jsp?id=2670
  22. U.S. Energy Information Administration (2016) International Energy Outlook 2016. Washington, DC.
  23. Urge-Vorsatz, D., Eyre, N., Graham, P., Harvey , D., Hertwich, E., Jiang, Y., Kornevall, C., Majumdar, M., McMahon, J., Mirasgedis, S., Murakami, S., Novikova, A., Janda, K., Masera, O., McNeil, M., Petrichenko, K., & Tirado Herrero, S. (2012). Energy End-Use: Buildings. In Global Energy Assessment - Toward a Sustainable Future, Cambridge University Press.
  24. International Energy Agency (2013) Modernising Building Energy Codes. New York, USA.
  25. Royapoor, R., Pazhoohesh, M., Davison, P.J., Patsios, C. Walker, S. (2020). “Building as a virtual power plant, magnitude and persistence of deferrable loads and human comfort implications, Energy and Buildings, 213, p109794.
  26. https://abc-rp.com/
  27. https://research.ncl.ac.uk/geoenergy/projects/netzerogeordie/
  28. Institute for Health Equity (2020) Sustainable Health Equity: Achieving a Net Zero UK: Advisory Group Report for the UK Committee on Climate Change. https://www.theccc.org.uk/publication/ucl-sustainable-health-equity-achieving-a-net-zero-uk/
  29. Love, J., Smith, A.Z.P., Watson, S., Oikonomou, E., Summerfield, A., Gleeson, C., Biddulph, P., Chiu, L.F., Wingfield, J., Martin, C., Stone A. and Lowe, R. (2017). “The addition of heat pump electricity load profiles to GB electricity demand: Evidence from a heat pump field trial”, Applied Energy, 204, p332-342.
  30. Calderón,C., Underwood, C., Yi, J., Mcloughlin, A., Williams, B. (2019). “An area-based modelling approach for planning heating electrification”, Energy Policy, 131, p262-280,
  31. McCallum, P. Jenkins, D.P., Peacock, A.D., Patidar, S., Andoni, M., Flynn, D.,  Robu, V. (2019). “A multi-sectoral approach to modelling community energy demand of the built environment”, Energy Policy, 132, p865-875.
  32. Royapoor, M., Du, H., Wade, N., Goldstein, M., Roskilly, T., Taylor, P., Walker, S. (2019). “Carbon Mitigation Unit Costs of Building Retrofits and the Scope for Carbon Tax, a Case Study”. Energy and Buildings, 203, 109415.
  33. Ma, Z., Bao, H., Roskilly, A.P., (2018). “Feasibility study of seasonal solar thermal energy storage in domestic dwellings in the UK”, Solar Energy, 162, p489-499.
  34. Adams, C., Monaghan, A.,  Gluyas, J. (2019). Mining for heat. Geoscientist, 29 (4). 10-15.
  35. Hosseini, S.H.R., Allahham, A., Vahidinasab, V., Walker, S.L., Taylor, P. (2021). “Techno-economic-environmental evaluation framework for integrated gas and electricity distribution networks considering impact of different storage configurations”, International Journal of Electrical Power & Energy Systems, 125, 106481.
  36. Powells, G., Fell, M.J. (2019). “Flexibility capital and flexibility justice in smart energy systems”, Energy Research & Social Science, 54, p56-59.
  37. Scott, M., Powells, G. (2020). “Sensing hydrogen transitions in homes through social practices: Cooking, heating, and the decomposition of demand”. International Journal of Hydrogen Energy, 45 (7), p3870-3882.
  38. Scott, M., Powells, G. (2020). “Towards a new social science research agenda for hydrogen transitions: Social practices, energy justice, and place attachment”. Energy Research & Social Science, 61, 101346.



November 2020












































[1] Heating Ventilation and Air Conditioning

[2] 20% penetration refers to 20% of households using heat pumps

[3] Ground Source Heat Pump