Whether such energy-saving measures actually do “pay off” is a very important question for many people. This cannot be properly answered generally, because the starting situation may be very different: with an uninsulated concrete wall it will always be worthwhile, while other measures may be more important in a new build which already has 20 cm thick thermal insulation.

A way to calculate economic profitability under specific conditions in each individual case was needed, so we created an easy-to-use online calculator exactly for this purpose. Everyone considering such measures can at least estimate their economic efficiency here.

Quick start using this tool: under “Wall type”, select the exterior wall that is most similar to your case. Under “Insulation system” select the interior insulation measure (German only) which you wish to implement. Then select the climate location.

Interior insulation calculator (German only)

_{No results? Note: input for the area only permits whole numbers, so enter e.g. “12” instead of “11.8”.}

The tool will do the rest for you; there are a number of clever data stored in here, e.g. the current costs charged for materials. Self-evidently, this quick calculation cannot be a substitute for a detailed energy consultation. Where can I get such advice? Here is a list of experts for "Energy efficiency NOW".

Explanatory notesThe specified percentage savings refer to the losses of the specified building assembly alone (that is for example the wall surface). In the process we assume that this is a normally heated room (temperature 21 °C), and that the heating is working and is properly adjusted. The energy price for conventional fuels was assumed to be 11 cents/kWh, so the peak prices that many people are currently having to pay (often more than 14 cents/kWh) due to the gas crisis have not been used. In this tool we have even assessed the “DIY implementation time”¹⁾. First the heat loss of the building assembly (before and afterwards) is calculated from these initial values; the difference is the amount of heating energy saved - and its present value is credited to the energy saving measure. Usually, there is a little more than the investment cost left over - and this additional profit is shown at the end. If this additional cost saving is “negative”, then this measure will not “pay off” in your case. You can then decide whether the improved comfort and security in times of crisis is worth this amount for you, or whether you already estimate the future energy price to be higher. Or your look for a measure that is more worthwhile. We have not included any subsidies in this tool - “funding prospects” are currently also very unclear, unfortunately²⁾.

The measures are described in detail here: Measures for interior insulation (German only) . Indeed, interior insulation is far better than is commonly believed, provided that a few basic principles are adhered to when implementing it, especially those relating to airtightness³⁾ and mitigation of thermal bridges⁴⁾.

Here is the homepage relating to structural measures for saving energy for the building envelope.