*{TP, DBT, ITH, A0, V0, Awin, ntot, Uwall, Uroof, Ufloor, Uwin, HCOP, OV, SV}*

{1, −4.30, 0.00, 134.31, 330.80, 23.10, 0.60, 1.18, 0.65, 1.75, 2.75, 0.59, 225, 6}

Some validation of the predefined ANN was made in order to check the capability and accuracy of the network for heating demand predictions of the Polish single-family sector. The validation of the trained ANN was performed comparing the predicted values with the results obtained using the *Energy Plus* software. The used temperature range and variety of values within that assortment seem sufficient to perform accurate predictions for various localizations (outdoor climates). Here, an examination of the weather parameters (thus different building locations), particularly the outdoor temperature values, is presented, for scenarios before and after building retrofitting. The performed validations can be seen in Figure 5, for Extreme Winter Week (EWW) periods, for better results legibility. The EWW is the coldest week of the year for the examined locations. The validation was performed for cities Czestochowa and Olsztyn, which were not used as input data during ANN training. In both cases, very good prediction accuracy was obtained, despite the fact, that the used weather data was unknown for the network. The network is also capable to predict the trend of heating demands. An interesting fact is that the predictions are almost perfectly in the most meaningful moments (peaks), while some differences are observed for very low demands (lower than 0.5 kW).

**Figure 5.** Comparison of heating demands obtained using the *Energy Plus* (solid lines) and the ANN pre-dictions (markers) for Czestochowa (**a**) and Olsztyn (**b**).

A short collation out of the preformed validation is presented in Table 1. It can be seen, that annual heating demand (HCA) is predicted with a high accuracy—the difference is less than 9% compared to the *Energy Plus* outputs. Similar outputs are observed for the predicted heating demand during EWW periods (HCEWW). The accuracy of peak demands (HDmax) varied from approx. 2% up to 14%, nevertheless, the higher differences are usually observed for the modernized buildings, for which peak demands are overall low. Based on the performed validation it can be concluded, that the defined network is an effective tool for the heating demand predictions for Polish climate conditions. In practice, the trained network is capable to perform heating demand predictions regardless of the analyzed building location, aside from extremely harsh places in terms of their climates, such as for example Zakopane city.


**Table 1.** Comparison of the results obtained by means of the *Energy Plus* (E+) and the TEAC software.

Symbols used: HDmax—maximal heating demand; HCEWW—heating demand for EWW period; HCA—annual heating demand; Rel. Diff.—relative difference.
