Winter 2010-11 was very energy consuming. We heated both houses, but saw how much energy consuming the old house was. Neither the old walls nor the old windows were tight any longer. The old house is composed of two parts, one dated from 1929 and one from 1992. In the old part you thought sometimes that you were in a fridge, when the wind was blowing in the bad direction. We decided not only to replace the old windows, but the old wall too, because it would be a pity to put new and energy saving windows in an old untight wall. Though our passive house is not finished yet!

  • the construction of the new wall: there are 3 sides to renovate - east, west og north. The wall of the old house is a cavity wall, composed of an external and internal wall, 10 cm thick each, and of a 9 cm cavity. In order to give place to proper insulation, we need to enlarge the cavity. As the structure of the house is resting on the internal wall, it is possible to take away the external wall without interfering with the interior of the house. We just have to board the window openings in the rooms, so that we can avoid both dust and draft. We renovate one side at a time, so only one side of the house is darkened.

The construction steps are following:

    A foundation of 15 cm concrete is cast in front of the old wall below ground level.


    The external wall is removed, as well as the PU foam that was in the cavity. The internal wall can be seen from outside now.

    naked wall

    Above ground level there are 40 cm clay ball bricks before the wall itself, built out of red clay bricks.

    new Wall

    This construction gives place to 25 cm insulation, so that the wall got an U-value of 0,12.


  • the replacement of the old windows: the window frames of the oldest part of the old house is from 1929. In 1974 the previous owner replaced the windows, but not the frames. They looked like that:

    old frame

    We replaced all the frames and windows. We bought windows in Austria, as we did for the passive house. But we didn't want to buy passive windows, because we thought the old house never gets passive, even if insulation has been reinforced. If we had to do it again, we would buy passive windows for both houses, because the price difference is indeed very little.

    new windows

  • the covering of the enlarged roof: the renovated house got 35 cm broader and 20 cm longer. Therefore we have to enlarge the roof too and cover it with red tiles. At the same time we mount the new gutters.


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