Energy-efficient renovation is a magic word of our time. Especially in public buildings, a lot has been and is being done here. In most cases, the old night storage heaters are removed first, then the facade is dammed up. But what do you do with a castle whose structure essentially dates back to the 16th century?. Century originates? This is the problem facing the municipality of viereth-trunstadt. Especially since every single step in the renovation of the historic building has to be agreed with the relevant authorities for the protection of historic monuments.
Some 25 years after the last comprehensive renovation of trunstadt castle, there is now a need for it again. Above all, a renewal of the facade and the roof is due in the next few years. In order to do more than just cosmetic work on the facade, the municipality, as the owner of the castle, commissioned a comprehensive renovation concept. Architect udo freitag from the bamberger architekturburo eis presented a first draft to the city council as a basis for discussion.
It quickly became clear from the concept that an energetic renovation of the castle was practically unfeasible. This became clearest when it came to the question of heating. Currently, the rooms are heated electrically, and the heating is done with night storage heaters. The disadvantages are obvious: electricity for heating is uneconomical and the price of electrical energy will probably continue to rise. In addition, electric heating systems create a poor indoor climate when hot air meets cold masonry. However, architect freitag conceded that the system was "not so bad" in view of its use.
The current users are the community with the council meeting room, the senior citizens' office, the registry office (in the defense tower), the village archivist, the forestry service and various associations. This means that the castle must be heated both spatially and temporally only selectively. For the electric heating system, which was no longer considered contemporary, freitag nevertheless presented five alternatives – and immediately rejected four of them again.
No room for boilers
An alternative currently being installed in many places was a heating system powered by regenerative raw materials (wood chips, pellets). However, there was no space for a heating center or a storage room for the fuel in the trunstadt castle. On the same space problems, a heating system fired with oil, gas or liquefied petroleum gas has also been pushed. At best, a tank could be installed underground above the castle at a very high cost. In addition, the fossil fuels are no longer up to date.
Even if a fuel store were to be eliminated from the next option, it would not be possible to install a heat pump in the castle. However, setting up a pump outside the palace ensemble would be out of the question for design reasons, freitag noted, referring to the noise level of such a system. In addition, the entire installation in the castle had to be converted to wall and underfloor heating. Not only the space problems, but the entire heating system also speaks against a combined heat and power plant. Since practically no hot water is needed in the castle, the surplus heat could not be used at all in the summer, making the whole system uneconomical.
As the only viable alternative, the architect proposed a district heating system for the area of the castle square. A heat pump could be installed in another building on the site, and from there it could also heat the fire station, the kindergarten and the nurses' home, for example. There would be space for the necessary transfer station in the basement of the castle. The only, but probably decisive, disadvantage of the near-warmth system is that the enclosure would cost around 600,000 euros. Architect freitag therefore recommended that the current heating system be retained in the event that this option is not pursued further. Unfortunately, there is no new, more effective technology for electric heating than the one installed in the castle in the 1980s.
Facade and roof
The only way to save energy and costs in a renovation project is to make other structural changes. An embankment is of course not even up for discussion in the case of the individual monument. And an internal dam would also be problematic and expensive. A "weak point free" heating system it was not possible, said freitag. There was even a risk of structural damage at critical points such as the transitions from the wooden beam ceiling to the outer masonry or at the window reveals.