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Determination of costs for energy modernisation

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The primary input values for the calculation of economic efficiency are expenses (costs) for energy modernisation. One must differentiate between the full costs and the energy-related (additional) costs of a measure. When coupling the energy modernisation with maintenance / repair measures taking place anyway, it is appropriate to take into account for the calculation of economic feasibility only the energy-related additional costs (=full costs minus the proportionate amount of costs for maintenance / repair).

In general, economic calculations should take into account not only investment costs but also future costs for inspection, maintenance, repair, and, depending on the selected period under consideration, also investments for replacement and residual values. Such influences can be decisive when comparing different modernisation variants. However, in practice, costs for inspection, maintenance, and repair are significant for decisions concerning energy modernisation only when they differ significantly in the modernisation variant compared to the initial state (e.g., ventilation system additionally built-in for energy saving purposes). If the economic calculations are carried out in course of request for exemption, the authority in charge according to regional legislation might have issued special regulations about the consideration/non-consideration of residual values.
Therefore, the costs of a modernisation measure must be considered with differentiation:

  • What costs are incurred nonetheless as part of the necessary maintenance / repair measures?
  • What costs are incurred because of the energy improvement of building components or technical facilities?
  • What costs should be attributed to other modernisation measures (e.g., comfort improvement)?

Determining the costs can be done with different levels of detail. At the onset of plan-ning, it is useful to make a rough estimation, to be ultimately replaced by an exact calculation of costs. Cost parameters for frequent measures are compiled under the menu item Examples of Modernisation. Technical literature (construction cost index – “Baukostenindex” (BKI)) or gathering of specific tenders serve as additional sources for cost parameters. Investment costs can be determined by architects or construction engineers based on specific designs. Offers from construction companies further specify these indications and provide detailed investment and potential follow-up costs. For individual determination of costs, special features of the building should be taken into account with regard to the planned modernisation. For instance, this concerns special connection details of exterior wall insulation with the windows, roof, and foundation in specific cases. But regional differences in construction prices and the current economic situation may also cause significant deviations from the typical prices given under the menu item Examples of modernisation.

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