Written by Nele Renders, Project Manager Energy and Climate Policy at EnergyVille/VITO, Ann Wouters, Programme Manager Thermal Energy and Energy Markets at EnergyVille/VITO and Pieter Vingerhoets, Researcher Smart Energy and Built Environment at EnergyVille/VITO.

Expert Talk Green Heat: From Fossil to Green Heat

Heating and cooling in our buildings and industry accounts for half of the EU’s energy consumption. In EU households, heating and hot water alone accounts for 79% of total final energy use (9.348 PJ); for Belgian households, the share of heating and hot water amounts to in total 85% of the final energy use (290 PJ). 87% of Belgian’s space heating is still generated from fossil fuels while only 10% is generated from renewable energy, mainly from biomass[i]. In order to fulfil the EU’s climate and energy goals, the heating sector must sharply reduce its energy consumption and cut its use of fossil fuels. The revised Renewable Energy Directive aims at mainstreaming renewable energy sources in the EU heating and cooling sector by setting an indicative target of 1.3% annual average increase in renewables between 2021-2030. At the same time, the EU is committed to decarbonize the energy sector, including heating and cooling in buildings and industry in order to arrive to a net-zero greenhouse gas emissions economy by 2050. These commitments are also reflected in the Belgian Energy Pact: the objective is to no longer heat our buildings with fossil fuels by 2050, but with renewable and low-carbon technologies (e.g. heat pump, district heating, geothermal heat, solar heat, biomass, biogas or syngas). Additional policy measures in the building sector are introduced in the draft Flemish climate policy plan 2021- 2030 to reach these objectives, which could result in approx. 44% reduction of fossil fuels by 2030 compared to 2005[ii].

The aforementioned ambition levels imply strong challenges for the heating sector in Europe which is characterised by high level of heterogeneity. The heating sector consists of many small actors at local and national levels, relying on a diversity in technologies, infrastructure and energy sources, and operating under different climatological and geographical conditions. In contrast to electricity, heat cannot be transported efficiently over long distances, therefore the heating generation capacity needs to be deployed relatively close to its point of use. Since buildings differ in size, age and purpose, the heating systems for buildings need to be tailored to the buildings' characteristics. To cater to these diverging needs, a broad range of technologies has been developed on the supply side, ranging from single-building solutions (based on e.g. fuel oil, natural gas, solar thermal appliances, heat pump systems such as air source heat, ground or water-based systems) to multi-building solutions or district heat networks (based on fossil fuels, industrial excess heat or renewable heat from geothermal, waste, biogas or biomass, solar thermal, or large-scale heat pumps)[iii]. Due to the high local context dependence, the high variety of technological solutions and the fragmented actor structure, the process of decarbonization means a strong challenge to the heating sector, in comparison to other sectors like onshore wind and solar electric power.

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Addressing both the technical and the non-technical complexity of the process is fundamental to speed up the implementation of low-carbon heat. Crucial ingredients for decarbonization are the existence of a clear long-term strategy including the local context boundaries, the identification of barriers and enablers to build common knowledge among the low-carbon heat actors next to an adequate monitoring system to assess progress towards the targets. EnergyVille is offering extensive support to policy makers from local to European level in these areas.

To no longer heat our buildings with fossil fuels by 2050, a fuel switch is needed, away from fossil fuel sources such as fuel oil and natural gas. A recent study[iv] of EnergyVille in support of the Flemish climate policy plan 2021-2030 indicated that low-carbon heat solutions where fuel oil boilers are phased out, come out relatively cheaper compared to natural gas boilers. From system perspective, it can therefore be recommended to prioritize replacing fuel oil installations towards more sustainable alternatives. The phase-out of fuel oil boilers is a trend going on already for decades: in the Flemish Energy Balance[v], we notice a decrease of the share of fuel oil in the residential energy consumption from about 50% in 1990 to about 25% in 2017. This trend was mainly induced by a replacement towards natural gas boilers and only to a small extent towards low-carbon solutions. Therefore, the ambition levels of the recent coalition[vi] of manufacturers, energy suppliers, installers, environmental organizations and experts are to halt the installation of new fuel oil boilers by 2021 and to allow only the sale and installation of sustainable heating alternatives by 2030.

Replacing fuel oil boilers by low-carbon alternatives will be cost efficient to reduce greenhouse gas emissions, but this is not sufficient to meet a fully decarbonized heating demand by 2050. Other technology options to cover the heating demand exist, such as electrification using heat pumps, biomass, deep geothermal energy, valorization of industrial excess heat, or on the long term hydrogen or green or synthetic methane. All these energy carriers may have a place in covering the future energy demand towards 2050, but strongly depend on the typical barriers and enablers of each technology.

In the MIRA study ‘Milieuverkenning 2018, Achtergrond document Oplossingsrichtingen voor het Energiesysteem’[vii], stakeholder workshops were organized to map urgent barriers and enablers of sustainable heat in Flanders. Some conclusions for low-temperature heat pumps: for heat pumps to become a credible low carbon solution, three transitions unrelated to heat pumps have to occur: 1) transition to low carbon electricity supply, 2) transition to well-insulated housing stock via retrofit and 3) transition to low temperature household heat distribution systems (e.g. floor heating). The most difficult condition for the success of a transition to heat pumps might therefore be entirely unrelated to the technology itself[viii]. On top, the structure of the current energy bill hampers a strong implementation of heat pumps as they are currently both more expensive to purchase and to use in comparison to gas boilers. As indicated in the draft Flemish climate policy plan 2021-2030, a green tax shift that increases the natural gas bill and lowers the electricity bill will improve the business case for heat pumps.

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While district heating or heat networks are not solely linked to renewable energy sources, the EU-28 assessment ‘Policies and measures on renewable heating and cooling in Europe, ETC/ACM’[ix] shows that district heating is an enabling factor for higher shares of renewable heating: EU Member States with a particularly high share of renewable heating and cooling in general are also the Member States with extensive district heating networks (Denmark, Finland, Sweden, and the Baltic countries). This assessment also stresses the importance of regulations as a policy instrument type to support district heating: countries are required to set-up national legislation to regulate their district heating market. District heating is considered to be a cost-effective option for providing heating and domestic hot water to buildings located in densely populated areas. For Belgium it is expected that 37% of the heat demand could be supplied via DHC (baseline<5%)[x].  An important advantage of district heating consists in the possibility of valorizing excess heat from industries or heat generated by combined heat & power plants CHPs, biomass, solar or (deep) geothermal systems. To decarbonize heat, the challenge is to integrate as much as possible these available sustainable energy sources, which unfortunately are fluctuating and are often not available when needed. Utilising the intrinsic flexibility of a district heating network makes it possible to deliver more energy from a smaller sustainable energy source, resulting in more efficient and more competitive district heating networks. Furthermore, district heating can even support the electrical grids by operating heat pumps and CHPs at moments of excess or scarce of renewable power on the electrical grids[xi]. The main barriers of district heating compared to gas or electricity networks is a higher installation cost and higher efficiency losses during transport. To minimize the latter barrier, the district heating networks of the future will work on lower temperature levels compared to nowadays, causing less heat losses and allowing the utilization of low-grade excess and renewable heat. Digitalizing the networks will be key in this transition, which was, among other projects, further developed in the European H2020 project STORM[xii]. For instance, the STORM controller optimizes the heat demand of buildings and neighborhoods in function of the heat supply by means of self-learning algorithms. This controller was successfully tested in two demonstration networks (NL and SE), resulting in significant CO2 reductions, and is currently valorized as a commercial product. In the follow-up H2020 project TEMPO[xiii], the features of this controller are extended.


Due to the high local context dependence and the high variety of technological solutions a region-wide assessment taking into account the local geospatial opportunities and boundary conditions is essential in defining a decarbonization strategy. This strategy cannot simply be imposed top-down from the regional or national authorities; local authorities have an important role to play in the transition towards sustainable heat in the built environment as they are well placed to deal with local social, environmental as well as economic aspects. From this perspective, the subsidiarity principle seems to play a role in favor of the local authorities, which, for example, are preferably assigned the responsibility to develop local heat zoning plans7. This is acknowledged in the draft Flemish climate policy plan 2021-2030 stating that by 2030 each municipality should draft a spatial energy strategy to reach climate neutrality by 2050. Next to the heat zoning plans, an important instrument to support local authorities in drafting spatial energy strategies is ‘de Warmtetoets or Heat check’. This is an instrument to stimulate low-carbon heat solutions during transition moments on municipal territory, by providing a thorough consideration framework between different heat solutions. Under authority of the Flemish Energy Agency, EnergyVille is currently mapping the requirements of the Heat check, by consulting relevant stakeholders in the field.

EnergyVille offers tools and studies to support the long-term energy scenarios for municipalities, both for concrete technology advice, renovation strategies as high-level geospatial studies. These tools and studies are described in the next BOX.

EnergyVille tools and studies to support local energy strategies to decarbonize heat

In 2015, the ‘Warmtekaart Vlaanderen’[xiv] was published, visualizing the geographical distribution of heating demand and possible excess heat supply sources in Flanders. It presented a theoretical exercise for the economic potential of district heating. This effort will be updated next year in close collaboration with the different stakeholders, where a more recent and detailed analysis will be presented. More broadly, EnergyVille/VITO published the ‘Hernieuwbare EnergieAtlas Vlaamse gemeenten’[xv] in 2016, including also potential for wind, solar, local biomass sources etc. As mentioned, this type of study is a high-level geospatial analysis and presents a starting point for local stakeholders to draw up energy plans. Within the European H2020 PLANHEAT project, an open source version of such GIS-based analysis tools is being developed[xvi] by EnergyVille.

While GIS-based analysis tools such as the ‘Dynamische energie-atlas’ are suitable for a high-level geospatial analysis, EnergyVille offers practical support for local developers as well. One example is the EBECS software, which is used to create renovation advice tailored to the specific building needs. The user can insert a few very simple parameters about the building, and will get concrete renovation advice. A more detailed version for project developers is available as well. Currently, EnergyVille is developing a tool to combine the high-level geospatial analysis, the bottom-up building model of EBECS and the software used to determine the optimal routing of heating grids. This tool, called the ‘Urban Energy Pathfinder’, is expected to be available later this year and may be very useful to tackle the abovementioned challenges with respect to developing long-term decarbonization strategies at the local level.

With respect to heating grids and excess heat recuperation, EnergyVille has excellent experience in supporting local and regional authorities, as well as private companies, in the realization of concrete district heating projects. Hereto, EnergyVille takes the role as independent advisor during stakeholder discussions of project or engineering companies, or conducts complex technical and economic feasibility studies of the concrete cases. For instance, EnergyVille investigates the possibility of district heating with residual heat from industrial processes in the wide area around Antwerp. According to concept studies by EnergyVille the project has a valuable potential[xvii]. Currently heating networks in North of Antwerp and on the industrial site of Terbekehof in Wilrijk are being commissioned.

In the upcoming years, it will be crucial that local, long-term strategies are made and implemented on how to decarbonize the heating demand, as well as to build common knowledge among the low-carbon heat actors. EnergyVille works on a diversity of tools to support these processes from a techno-economical, environmental as well as policy point of view.

Key take-aways

  1. Decarbonization of the heating sector requires a clear long-term strategy, identification of barriers and enablers of low-carbon heat technologies as well as an adequate monitoring system.
  2. Due to a high local context dependence, a high variety of technological solutions and a fragmented actor structure, the process of decarbonization imposes a strong challenge to the heating sector. A region-wide assessment including local geospatial opportunities and boundary conditions is essential in defining a decarbonization strategy. Local authorities play an important role in the transition towards sustainable heat. EnergyVille is offering a diversity of tools and studies to support long-term energy scenarios for municipalities, both for concrete technology advice, renovation strategies as high-level geospatial studies. As an independent advisor, EnergyVille supports authorities in technical and economic feasibility studies of concrete cases on district heating and excess heat recuperation.  
  3. EnergyVille develops the technology necessary for the transition towards the new generation of highly-efficient and sustainable district heating networks, tailored to be combined with low-energy buildings.

[i] Energy consumption in households, Eurostat, March 2018, https://ec.europa.eu/eurostat/statistics-explained/index.php/Energy_consumption_in_households

[iii] Configurational innovation systems – Explaining the slow German heat transition, Energy Research & Social Science, Volume 52, June 2019, Pages 99-113, J.P. Wesche a, b, S.O. Negro b, E. Dütschke a, R.P.J.M. Raven b, M.P. Hekkert, https://www.sciencedirect.com/science/article/pii/S2214629618304304 

[iv] Kosten-potentieelstudie van mitigatiemaatregelen gericht op de reductie van non-ETS broeikasgasemissies in 2030 klimaatdoelstelling, VITO, mei 2018

[v] Rapport Energiebalans Vlaanderen 1990-2017, VITO/EnergyVille, Januari 2019, https://emis.vito.be/sites/emis.vito.be/files/pages/3331/2019/Energiebalans_Vlaanderen_1990_2017.pdf  

[vii] Milieuverkenning 2018: Achtergronddocument Oplossingsrichtingen voor het energiesysteem, VITO/EnergyVille & ShiftN in opdracht van VMM MIRA, November 2018,


[viii] Steunpunt energie: nota potentieel 2030 – warmtepompen, VITO in opdracht van VEA, 2017, https://www.energiesparen.be/sites/default/files/atoms/files/Potentieel_warmtepompen_2030.pdf

[ix] Policies and measures on renewable heating and cooling in Europe, VITO/EnergyVille & Aether, European Topic Centre on Air Pollution and Climate Change Mitigation under authority of European Environment Agency, December 2018, https://acm.eionet.europa.eu/reports/docs/EIONET_Rep_ETCACM_2018_17_RES_PaMs_heating_cooling.pdf

[x] Heat Roadmap Belgium: Quantifying the Impact of Low-Carbon Heating and Cooling Roadmaps, 2018, S. Paardekooper, R.S. Lund, B.V. Mathiesen, M. Chang, U.R. Petersen, L. Grundahl, ... U. Persson.

[xiv] Warmtekaart Vlaanderen, VITO in opdracht van VEA, oktober 2015, https://www.energiesparen.be/warmtekaart

[xv] Hernieuwbare EnergieAtlas Vlaamse gemeenten, VITO & TerraEnergy in opdracht van LNE, september 2016, https://www.lne.be/sites/default/files/atoms/files/Hernieuwbare_atlas_V…

foto nele renders


Nele Renders

Project Manager Energy and Climate Policy at EnergyVille/VITO


Ann Wouters

Program Manager Thermal Energy and Energy Markets at EnergyVille/VITO
Pieter Vingerhoets


Pieter Vingerhoets

Researcher Smart Energy and Built Environment at EnergyVille/VITO