First hand experiences

• Architectural influences may have a strong impact on the retrofit concept regardless whether a building is listed or not. In the case of Filderhof it caused the change from external insulation to internal insulation on the outside walls. This may lead to less energy savings and results in more planning work on details in order to prevent thermal bridges.

• Economic influences may change the material used for buil-
ding parts. At Filderhof, the glazed atria roof has now only small glazed parts. The designer had to react on the situations
and transfer the planned PV system to the opaque roof parts.

• The use of rooms in the cellar has to be carefully planned in order to keep the heated zone as compact as possible. However, the total space available and flexibility of usage are more important factors for the building owner than compactness and energy efficiency.

• The planning process over five years requires changes in the retrofit measures of a building. Therefore detailed information
about the planned measures and the resulting energy savings at the proposal time of the EU project is not always possible. Necessary modifications at the retrofit measures have to be presented and elaborated at the Commission. This requires extra time in the planning process of the project.

• There is much coordination needed with several partners within the project, especially with the financial people of the local government. The project duration is has been stretched to five years from the earliest planning phase up to the end.

• It is necessary that the operation staffs are trained in energy efficiency. It has to be explained to them, when a special operation is necessary for the economical performance of the systems. This concerns also the substitution staff as was realised when the CHP in the Filderhof lied idle for a longer time while the main staff was away.

• With this project it was shown, that it is possible to reduce the primary energy of existing buildings by over 50 % and the minimized energy consumption can be supplied by a good deal of renewable energy."