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Comparison of in-situ measurements and hygrothermal simulations of four different interior insulation systems
Old buildings often do not have any insulation on the exterior wall going along with low, uncomfortable surface temperatures and high heating demands. In order to produce comparable thermal comfort conditions to modern buildings insulation is strongly needed. From the view point of building physics, insulating the exterior side of a wall is the better solution. In many cases though, e.g. if a building is listed, this is not possible. So insulating the interior side becomes an interesting option, but a closer look to potential risks has to be taken. Since the old construction will become much colder than it was without interior insulation, the risk of moisture damage increases. Furthermore, often in historic buildings ceilings are made of timber beams. Especially in these cases the decreased temperatures at the beam heads outside the insulation plane can cause a higher risk of damage by increased moisture contents.
All the above issues come together in the residential building complex called “Hohenzollern-Höfe“ in Ludwigshafen, featuring a neo-baroque facade. The complex, including around 180 dwellings, was built in 1923 and is currently being renovated by sections [Zaman 2010].
Photo of the residential complex “Hohenzollern-Höfe”, Ludwigshafen (left).
The wall construction after retrofit (with insulation boards) with the positions of sensor is depicted on the right side.
The reduction of energy demand of the whole complex plays an important role in the retrofit scheme. The exterior facade in neo-baroque style (Figure 1) could not be insulated with an exterior insulation and finishing system since the building is listed. So, the concept of interior insulation was followed and four different insulation systems were applied in different rooms. In order to investigate the influence of the interior insulation systems on the hygric behaviour of the wooden beam heads and to compare the different insulation systems, temperatures and relative humidities at different positions within the construction were measured [Bräunlich 2013]. Direct conclusion from the measured data on the performance of the different insulation systems is impossible because of different indoor conditions. Here the comparison is possible only by simulations. But this just feasible, if the simulation reproduces the reality correctly which is checked in the following.
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After a measurement period of more than 2 years hygrothermal simulations using the measured boundary conditions were done. All insulation systems perform well and there is no evidence for any moisture problems either in the regular constructions or in the joist ends. A very good correspondence between simulation and measurement was found for the temperatures. Only for the insulation plaster clear deviations could be seen. Also the profile of the relative humidity could be reproduced with a deviation of less than ~5 % RH at the end of the considered period. With some variations of the vapour resistances the general tendency of the measurement is depicted quite well by the simulations. Comparing the performance of the insulation systems with the same indoor conditions by simulations (not shown here) results in less differences then seen in the measured data.
The measured strong rising relative humidity in the second winter for the plaster and PU board are caused by an increase of the relative humidity level in the adjacent rooms to over 60 % RH. This was probably by the ventilation unit not working properly at that time. After the change of the filter a steep decrease of the humidity levels appeared. This makes two things clear:
- Indoor conditions are at least as important as the insulation system itself for the moisture level within the construction.
- Especially in the context of interior insulation an air ventilation unit helps to limit the indoor RH and is necessary to achieve low humidity within the construction.
Authors would like to thank the LUWOGE company for financing this project and for the good cooperation. Thanks to [Zimen] for providing the weather data from Mundenheim.
[Zaman 2010] Zaman, A., Hohenzollernhöfe Sanierung einer denkmalgeschützten Wohnanlage mit Passivhaus-Komponenten, LUWOGE, Tagungsband 14. Int. Passivhaustagung 2010, Dresden,
[Bräunlich 2013] Bräunlich, K.; Kaufmann, B., Messung der Holzfeuchteentwicklung in Balkenköpfen bei einer Sanierung mit Innendämmung, 17. Int. Passivhaustagung 2013, Frankfurt,
[BBS 2010] Leimer, H. P., Bode, J.; Hygrothermische Berechnungen für die Holzbalkenköpfe in der innen gedämmten Außenwand, Gutachten 2009 825-1 vom 1.2.2010, BBS Ingenieure, Wolfenbüttel, im Auftrag der LUWOGE
[Nicolai 2010] DELPHIN: Simulation program for coupled heat, air, moisture, salt and VOC transport. Available at: www.bauklimatik-dresden.de
[Zimen] Wettermessdaten vom Zimen-Luftmessnetz des Landesamtes für Umwelt, Wasserwirtschaft und Gewerbeaufsicht Rheinland-Pfalz, Ludwigshafen-Mundenheim