The story of how a newly built building was saved: breathe easy thanks to sheep's wool
With a lightweight timber construction, wood pellet heating and an 11 kW photovoltaic system – the theme of sustainability played a decisive role in the construction process of the Oberstufenzentrum East in Felben-Wellhausen. However, after the school holidays, health symptoms began to affect children and teachers, which then led to a nasty discovery: formaldehyde levels in the interior rooms were far too high! By using materials containing sheep wool as a solution to this issue, costly and time-consuming deconstruction or demolition processes could be avoided.
In summer 2004, the new building was ceremoniously opened, allowing pupils and teachers to move into their new classrooms. However, as autumn came around, the first few complaints began to trickle in as many started to notice the poor quality of the indoor air or developed symptoms such as irritation of the eyes or respiratory tracts, as well as headaches. In 2005, the first measures were taken to get to the bottom of the problem.
“At the beginning, we did not know where exactly the problem was and what was causing the complaints of the children and teachers. Therefore, we carried out various measurements and got to the bottom of the issue relatively quickly: formaldehyde. Due to the large number of wooden materials used as load-bearing structures and as panelling, the concentration was too high", says Stefan Schrader, a graduate environmental scientist (ETH).
The renovation work and consequent reduction of the high formaldehyde concentration took place gradually. This process involved the removal of the 3-layer panels on the walls and of the perforated 3-layer panels on the ceiling – all of which emitted the most formaldehyde. However, the load-bearing elements were an additional complication. For instance, the wooden ceiling, a hollow box construction, was also covered with a 3-layer board containing formaldehyde. The gypsum fibre boards installed in the partition walls absorbed the formaldehyde and released it back into the room air.
“Here too, the school wanted to find a sustainable and permanent way to reduce the concentration. The load-bearing elements were therefore covered with a special 1 mm thin sheep wool fleece. Sheep wool can absorb formaldehyde and other aldehydes and can significantly reduce any effects of the chemical. In this case, it has done so successfully for over 20 years", says Stefan Schrader.
Especially for the challenge of how to solve the high levels of formaldehyde being emitted from the load-bearing wooden construction, the use of sheep's wool was vital. Because replacing the load-bearing construction would have been tantamount to demolishing the building, only to build a new one. Thanks to the sheep wool solution, the formaldehyde concentration dropped back to normal relatively quickly. The renovation work on the school building could be completed in summer 2006 after 9 months of renovation and the pupils could move back into their classes.