# NZEB Renovation Definition in a Heating Dominated Climate: Case Study of Poland
### Potential Indicators of the NZEB renovation Definition: Results of a Survey
These two indicators would make the definition very flexible (reduction of Q\({}_{\rm P}\) can be achieved in many ways, e.g., use of renewable energy sources (RES), increase of systems energy efficiency, reduction of energy need for heating or DHW) but, at the same time, very demanding. The energy need for heating (Q\({}_{\rm H}\)) depends on, among other things, the thermal transmittance of the building elements, the thermal bridges, the air tightness, and the type of ventilation system. A low value of the energy need can be achieved in different ways depending on the building's condition. For example, in case it is not possible to insulate the ground floor, other elements of the building's envelope, e.g., external walls, roof, windows, or doors, can have a better thermal resistance. In addition, ventilation with heat recovery can be applied in order to reduce the ventilation heat loss and as a result Q\({}_{\rm H}\). The energy need for heating (Q\({}_{\rm H}\)) as an indicator gives flexibility and provides the opportunity to choose the best renovation measures for the particular building. The indicator referring to the reduction of primary non-renewable energy demand (Q\({}_{\rm P}\)) includes aspects like efficiencies of the heating and hot water system, energy source type and use of renewable energy sources (RES). Depending on the building's conditions, different solutions can be chosen. Additional use of the first indicator--the energy need for heating (Q\({}_{\rm H}\))--prevents the situation in which only RES (with low primary energy factor (PEF)) will be implemented in order to decrease the primary, non-renewable energy demand. In Poland, the value of PEF (only non-renewable part) for biomass is 0.2 and for coal 1.1, so a change from coal to biomass will reduce the primary, non-renewable energy demand by about 82%, whereas the energy demand for heating can stay at the same level. For comparison, the value of PEF (total renewable + non-renewable part) for biomass in other EU countries [30] is: AT: 1.08, ES: 1.25, and IT, RO, FR, DE, and FI: 1.50. Additionally, the use of primary energy (total renewable + non-renewable) mitigates against the situation in which only RES are applied in order to reduce the Q\({}_{\rm P}\). The total PEF for other energy carriers are as follows [31; 32; 33]: \begin{table}
\begin{tabular}{l c c c} \hline \hline \multicolumn{1}{c}{**Should the NZEB Renovation Definition Include**} & \multirow{2}{*}{**Yes**} & \multirow{2}{*}{**No**} & **Importance** \\ \multicolumn{1}{c}{**Requirements Regarding:**} & & & **(Yes** \\ \hline Index of energy need for heating Q\({}_{\rm H}\) & 15 & 2 & 13 \\ Energy efficiency of renovation improvement—percentage reduction of the primary, non-renewable energy Q\({}_{\rm P}\) demand Thermal transmittance (U-value) of diverse building elements & 13 & 3 & 10 \\ Index of non-renewable, primary energy demand Q\({}_{\rm P}\) & 12 & 4 & 8 \\ CO\({}_{\rm 2}\) emission index Index of final (delivered) energy demand Q\({}_{\rm F}\) & 12 & 5 & 7 \\ Share of RES & 10 & 5 & 5 \\ Ventilation systems and the efficiencies of heat recovery & 10 & 6 & 4 \\ Efficiencies of heating and DHW systems & 10 & 7 & 3 \\ Index of final (delivered) energy demand Q\({}_{\rm F}\) for cooling Air tightness & 10 & 1 \\ Energy demand of auxiliary systems & 10 & 7 & 0 \\ Summertime comfort—overheating risk & 10 & 8 & \(-\)2 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results of the survey on the potential indicators of NZEB renovation definition. DHW: domestic hot water; RES: renewable energy resources. * Electricity: AT: 1.91, ES: 1.89, IT: 2.18, RO: 2.53, FR: 2.72, DE: 2.45, and FI: 2.69;
* Gas: AT: 1.13, ES, IT, RO, FR, DE, and FI: 1.0;
* District heating: AT: 1.0, ES, IT, RO, FR, DE: 1.20, and FI: 0.7; and
* Heating oil: IT: 1.0, CH: 1.15, and AT: 1.12.