**6. Conclusions**

The basic task over the course of maintaining a building is the prospective planning of renovation works and predicting the resources necessary for their execution. The dates of renovation works ought to be planned in accordance with the guidelines of rational management. The proposed method may be helpful when planning renovation works on buildings.

The proposed model allows for the proper estimation of the costs of renovation and repair works and their relationship with the value of the technical wear of a building at each period of its use. Residential buildings constructed using traditional technologies were subjected to analysis. In the carried out analysis, the PRRD (prediction of reliability according to Rayleigh distribution) model of changes in the performance characteristics was applied.

The conclusions resulting from the conducted analysis are the basis for further research on the costs of restoring performance. The value of technical wear signifies the cost recreating the level of wear. Changes in the performance characteristics of a building over the course of its use expressed by cost are the loss of performance characteristics. It might seem that the consumption values and the cost of renovation works are at a similar level, but in practice, it turns out that the cost of restoring the functional properties of the building is different from the value of the building's consumption. And this is the essence of the problem presented.

Anticipating the aging process is essential when maintaining a residential building. However, the problem remains unrecognized in many respects. No data indicate the need for research and analysis related to this topic. Building degradation curves are just the beginning of the research. Forecasting damage to a building can be developed and predicting changes in operating costs over the entire life cycle of a building requires many simplifications. Further research will cover the subject of LCA, the impact of renovation works on the environment. It will also analyze changes in prices of building materials and renovation works over time in Poland and in other countries.

**Author Contributions:** Conceptualization, B.N., J.K.; methodology, B.N., J.K.; formal analysis, B.N., J.K.; investigation, B.N., J.K.; resources, B.N., J.K.; data curation, B.N., J.K.; writing—original draft preparation, B.N., J.K.; writing—review and editing, B.N., J.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
