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First pellets heated social housing project in Belgium

Type: CaseStudy

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Zonnige Kempen is a progressive social housing company, building lots of new projects in which renewable and sustainable techniques in materials, water and energy are integrated. Together with VITO they started up this pellet boiler project. The pellets project consists of the building of 26 new collective heated dwellings. The project is located in the municipality of Grobbendonk.

The heating installation consists of a wood pellets boiler (100 kW) in combination with a gas fired boiler (100 kW). The aim is to cover 90% of the heat demand with wood pellets, resulting in a pellets consumption of about 42 tons/year or 61 m³/year. Integration of a pellets boiler results in a reduction of fossil fuel consumption with 85% or 190 MWh/year and a CO2-emission reduction with 38 tons per year.

Zonnige Kempen finances the main part of the project itself but receives 35% of the additional cost of a pellet boiler instead of a gas boiler from the programme of the demonstration projects of the Flemish government.

Plan of the social housing project

Plan of the social housing project


The implementation of this pellet boiler will realise a reduction of the primary energy consumption of 85% or 190 MWh/year in comparison to the reference situation (only a gas fired boiler). The CO2-emission reduction of the pellets boiler would be about 38 tons per year or 85% compared to the reference situation. For the calculations a CO2-emission factor for natural gas of 56.1 g/MJ was taken.

Duration of heat demand
Running hours of pellets boiler
Running hours of gas boiler

6.054 h/year
4.246 h/year
1.831 h/year

Heat production pellets boiler
Heat production gas boiler
Total heat demand
180 MWh/year or 90%
20 MWh/year or 10%
200 MWh/year
Pellets consumption
200 MWh/year
41,6 ton/year
61,1 m³/year
Natural gas consumption 22 MWh/year
2.400 m³/year
Primary energy consumption reference
Primary energy consumption project
Reduction of primary energy consumption
222 MWh/year
22 + 10 MWh/year
190 MWh/year or 85%

Lessons learned and repeatability

The following experience had the team with the set-up of the project:

  • Implementing the pellet boiler and the storage capacity into the social dwellings, was new for all the parties working on the project. The extra space needed for the pellets storage, the extra safety measures for the storage of the pellets gained special attention during the design and construction.
  • Finding pellet boiler suppliers was easy, but selecting one was more difficult
  • The supply of pellets is not completely secured in Belgium because at the moment certified pellets have to come from abroad. That€s why the social housing company decided to install a gas boiler too as back-up system.

The know-how of implementing a pellet boiler in dwellings has increased with this project. The knowledge will be shared through a building centre, demonstrations of the installation and brochures which should encourage other companies to implement this renewable technology.

Further information

Other literature available: Eerste sociale woningbouwproject verwarmd met pellets - ODE-nieuwsbrief, September 2005,