Rural house, Herselt

Rural house becomes low-energy house

Download the full project file (Dutch, pdf)




Independant house

Construction date/

after WWI

Renovation date/


Heated Surface/


Heating demand/

31,55 kWh/m².year (PHPP calculation)




S. Corten


This project concerns an independent house with garage in the annex building. When the owners purchased the building in 1996, a renovation was already being executed. Contrary to the previous owners, the new owners preferred a low energy renovation which started two years later in 1998. Due to urban development disputes the renovation was delayed, but around Christmas 2004 it was finally completed.

Because of urban development stipulations the owners were constrained not to exceed the existing volume and to preserve the existing/original window openings. For energetic reasons the dormers were removed.


  • Insulation of the building shell
  • Erection of a new façade in front of the existing masonry with 12 cm of mineral wool in between
  • Replacement of the roof structure
  • Replacement of the lower brick layers of the existing walls by insulating construction elements in cellular glass
  • Airtightness of the building
  • System of balance ventilation with heat recovery and underground heat exchanger
  • Replacement of outer joinery by aluminium 5-chamber profiles and high performance glazing
  • Airtight shutter housing + minimisation of thermal bridge
  • External solar protection by means of eaves and electrical shutters
  • Solar collectors 22m²
  • Photovoltaic cells 28m²
  • Individual water purification by means of a reed land
  • Collection of rain water


The house is equipped with a system of balance ventilation with heat recovery which ensures the incoming air is heated by the outgoing air and thus allows a reduction of the heating demand.


Because the building had already been renovated just before the start of the passive renovation, the architects decided to stay on the safe side and installed different systems. A floor heating system powered by solar collectors was intended to heat the sanitary hot water, but since the collectors’ winter performance was insufficient, this solution turned out to be unprofitable. If necessary a condensing boiler will step in. In addtion a fireplace (wood) was installed in the living area.

Sanitary hot water

Sanitary hot water is heated by solar collectors mounted on the roof of the building. In the winter period the condensation boiler will guarantee its heating, considering the solar collectors’ poor winter performance.


A large part of the electricity need is produced by photovoltaic cells mounted on the garage roof.


before renovation
after renovation
Primary energy consumption*
275kWh/m².year (PHPP calculation) 31,55kWh/m².year (PHPP calculation)

*only heating + sanitary hot water

The annual energy consumption is less than 3000 kWh, more than 2000 kWh of which is produced by the photovoltaic cells.


Total costs: € 351 595
Costs per m²: € 1260
Energy costs before renovation: € 2000/year
Energy costs after renovation: € 300/year

Download the full project file (Dutch, pdf)