The Hiss Reet Panel used as an insulation on top of the Rafters in the Process of an Ecological Redevelopment of an Office Building

Due to their good diffusion properties, their high bending strength, their excellent price-performance ratio and their natural composition reed panels are perfectly suitable for the insulation of buildings.
Reed insulation panels combined with clay have proven their worth over the years as an insulation on top of the rafters. Thanks to their coarse texture the reed insulation panels can serve as a plaster base at the same time.

This building, built in the 1930s had been a “pure” timbered house until its destruction in World War II. The parts of the building which were destroyed have been rebuilt in double-shell masonry.
The renovation tried to focus on ecological aspects as well as on building biology. This was the reason for the particular use of the ecological building materials clay and reed.

The insulation on top of the rafters can be fitted in three steps:

1. Two layers of Hiss Reet panels extra have been placed on the new roof framework, creating a total insulation thickness of 16 cm. The reed stalks of the first layer (the bottom one) have been laid out crosswise to the rafters. Thus, you make use of the high bending strength of the reed. The reed stalks of the insulation panels of the second layer should have an orientation parallel to the rafters.

2. After the installation of the insulation panels a non-vapour retarding Deltamax®-film has been applied and the roof insulation has been fixed with a cross lathing. Roof battens were screwed on the cross lathing. The highest possible roof battens according to DIN 4070-1 (40 mm x 60 mm) were used in order to properly ventilate construction moisture and humidity produced by inhabitants. Then, pantiles were placed on the roof battens (Unfortunately, we do not have an illustration for this step).

The installation of the insulation tried to avoid cross joints. Later on, the area between the rafters was plastered. At this point, the Hiss Reet panels extra still contained the spikes of the reed stalks. However, as we found out in the course of the further development of our panels, the spikes seem to have a negative effect on the adhesive strength of the clay plaster so that we decided to remove them in future versions of our insulation.

3. After the completion of the roof the insulation on top of the rafters was plastered from the inside. Clay plaster and rafters have been separated by a cut with the trowel in order to prevent the connection from cracking due to contracting and expanding movements of the wood. An alternative would have been to lubricate the sides of the rafters – this would have prevented the joining of clay plaster and wood.