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Modernisation of the building envelope without insulation (“cosmetic refurbishment”) is not efficient. The first column in the graphic in Figure 1 on the right shows the costs arising from energy losses through an uninsulated exterior wall over a 20-year period. The other four columns give the overall costs (i.e. additional investment plus energy costs) for an insulated exterior wall, each based on different levels of insulation (compound insulation system, EIFS) for the same period of time [AKKP24]. Depending on the type of building component, these figures may be even more extreme. In the case of a roof, the U-value of an uninsulated roof is even higher and the difference in investment costs for increased insulation levels is even less significant, as additional costs are practically limited to the additional insulation material [Kah / Feist 2008].
On the other hand, the question that arises in connection with step-by-step modernisation is, how to realise the connection details between refurbished and un-refurbished buildings components. If, for example, the exterior wall is to be renovated first, the existing roof overhang will usually be too short for a 30 cm insulation layer. Alternatively, if the roof is to be refurbished first, the new roof overhang should be extended to allow for future insulation of the exterior wall. Solutions to both these problems will be presented in the following sections of this article.
[AKKP 24] Feist, W. (Editor): Refurbishment with Passive House components, Passive House Institute, Darmstadt, Research Group for Cost-effective Passive Houses, Protocol Volume No. 24, 1st edition 2004
[Feist / John / Kah 2003] Feist, W.; John, M.; Kah, O.: Passive House technology in existing buildings – Quality Assurance for the Jean-Paul-Platz 4 building project in Nuremberg, Final Report, in: Jean-Paul-Platz 4 in Nuremberg – energy-efficient building refurbishment with Faktor 10, final report of the accompanying scientific research, published by Schulze Darup, Dr. Burkhard, Nuremberg, 2005.
[Kah / Feist 2008] BMVBS / BBR (Editor): Evaluation of energy-efficient requirements for EnEV and KfW funding in view of rising energy prices, online publication of the Federal Office for Building and Regional Planning 18/2008. urn:nbn:de:0093-ON1808R222
[Kaufmann / Pfluger / Peper / Feist 2009] Kaufmann, B.; Peper, S.; Pfluger, R.; Feist, W.: Refurbishment using Passive House components, support and advice during the planning phase and quality assurance for the Tevesstraße project in Frankfurt a. M., on behalf of the Hessian Minstry of Economics, Transport and Regional Development, Wiesbaden, Darmstadt February 2009. Download from www.passiv.de
[Meyer 1994] Meyer, Prof. Paul et. al.: The aging behaviour of building components and maintenance costs, published by the Federal Office of Economic Issues within the framework of the stimulus programme IP BAU, Bern, 1994.