How can we establish an energy-efficient way to renovate historical buildings? This topic has been largely neglected to date – as have developments in the corresponding systems technology. But researchers at the Fraunhofer Center for the Energy-Saving Renovation of Old Buildings and the Preservation of Monuments at Benediktbeuern have addressed precisely this question. What’s particularly interesting about their research is that it is carried out in an actual old building. Using a series of heating systems, some innovative, the researchers installed one of the heating systems in each of four adjacent rooms of similar size. However, their investigations showed how complex comparative energy analyses are in real buildings. Despite best efforts, they were unable to create comparable conditions.
So the researchers tried a new approach. They compared the energy consumption values of the heating systems in each room against a reference heating system, an electric heater in the window recess. In other words, they compared each room with itself. Every day, they recalculated the characteristic values they used for the comparison and averaged them over several weeks. Taking this average, they calculated the consumption values – compared to the reference heating system. The result showed that almost all the wall heating systems studied consumed similar amounts of energy as the conventional, convective heater. Only the component “tempering” proved significantly more energy-intensive than the electrical reference heater.
When it comes to planning, however, energy is not the only consideration. Potential positive effects that protect the building structure or raise the level of comfort must also be taken into account. The results show that all the systems achieve lower stratification of room air temperature. In other words, the room temperature is more even from floor to ceiling. A further advantage is that wall heating systems are much better at preventing damage, making them an interesting alternative to conventional heat transfer systems. They prevent damage because they heat the wall and warm up parts of the building structure that are critical in terms of their physical properties. In this way, they reduce the risk of moisture damage. As the studies described above revealed, however, the heat losses with these wall heating systems can be higher than for conventional systems. It is therefore a matter of weighing energy efficiency against preservation benefits on a case-by-case basis.