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In the summer term 2011 during the USE Efficiency training course, the internal insulation of the buildings was an interesting and important topic for the students. They were working on a building which was built in 1896 and has a typical Hamburg brick façade. All outer walls have massive brick structures, about 51 cm in diameter, having a U-value of about 1.4 W/m²K. This means that the temperature of the inner surface of the outer walls does not fall below 12.6 °C.
The current situation does not show a good balance concerning the energy demand for heating, but on the other hand does not cause any problems with water condensation. Insulation on the outer walls of the building will always lead to higher temperatures on the surfaces, but an internal insulation does not always have the same effect!
For this reason one group of our students did a simulation of the thermal bridges with the program Therm 5.2
The results are the following:
1. Initial Situation
The Situation has changed, the heat loss mainly occurs where the inner wall causes a thermal bridge. The coldest temperature on the inner side of the wall is below 12,6 °C, condensation water will occur.
2. Internal Insulation of 4 cm
The Situation has changed, the heat loss mainly occurs where the inner wall causes a thermal bridge. The coldest temperature on the inner side of the wall is below 12,6 °C, condensation water will occur.
3. One solution of this problem: the insulation continues on the interior wall
The temperature of the coldest part of the wall surface is only 5 °C, but this is no longer the inner surface. This means no problems with condensation water, but the Architect might not be happy how the room looks like!
4. Increasing the thickness of the insulation (16 cm)
With an insulation of 16 cm in this case the lowest temperature on the surface is 12.8 °C, for other constructions even 11 cm can be enough.
Conclusion
These simulations showed possible solutions to avoid condensation water and mould when implementing an inner insulation for a building. Using the acquired knowledge the students of this training course could present solutions for an energy efficiency restauration of a historic building to the City of Hamburg, without changing its apperance.
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