Students: C. Aalders, N. Verboven Tutor: T. van Druenen
This report describes the investigation into the causes of mould growth in a 1960s house in Eindhoven’s Vaartbroek district.
The problems included mould growth, cracks in walls, broken joints, and broken bricks in the façade of the house. As the authors are mainly focused on building physics, they will focus on mould growth.
Firstly, a theoretical study has been conducted which shows that the ideal conditions for mould formation are organic materials that can retain water, a relative humidity between 90 and 100 percent, and a PH between 4 and 9 for most moulds. However, most fungi already thrive at a relative humidity of 55% or higher. The ideal relative humidity should be between 30 and 60% in a house.
Causes of high relative humidity and thus mould growth are insufficient ventilation, wet materials caused by, for instance, leaks or seeping moisture from outside as well as from the soil, or thermal bridges where condensation occurs.
Research into the values of relative humidity and temperature in the bedroom, combined with previous research in the house, concluded that the relative humidity in the house (or at least the bedroom) is higher than the standard set by RIVM. This is due to insufficient ventilation, as there are no further leaks or seeping moisture. The window frame forms a thermal bridge, cooling the air close to the frame and raising the relative humidity. This can sometimes lead to condensation if the temperature of the window frame is low enough and there is enough moisture in the air, but this hardly ever happened during the measurements. The higher humidity close to the window can already cause mould to form, and no condensation is needed.
The advice is to ventilate more by keeping the vents open and opening the windows whenever possible. It is also advised to brush dust, cat hair, and soap scum off surfaces so that it does not form a breeding ground for mould. Finally, the students looked at Woonbedrijf’s renovation plans for the house. These mainly focus on improving and compacting the thermal envelope. There will be insulation, a new roof, mechanical ventilation, and new HR++ glass in the existing window frames. These seem to partly solve the problem of high humidity through mechanical ventilation, but not in all rooms. The only aspect that Woonbedrijf should pay attention to is whether the window frames with the new glass do not form a worse thermal bridge, as the calculation in this report showed that the window frame conducts twice as much heat as the glass.
Until the renovation, the situation should be controlled with more ventilation and cleaning. Hopefully, after the renovation, the mould problems will be remedied, which will benefit the health of the residents.