# NZEB Renovation Definition in a Heating Dominated Climate: Case Study of Poland
### Country-Specific Definitions  
Criteria for NZEB renovation of buildings have been identified in 11 countries and regions [15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26], but definitions have so far only been established in eight (Austria, Cyprus, France, the Czech Republic, Denmark, Latvia, Lithuania, Brussels Capital Region). Poland does not have an official definition of NZEB renovation. Of these, France, Austria, and Brussels Capital Region have established primary energy use requirements for renovation at a less strict level compared to new buildings. Ireland, Germany, and Slovenia foresee doing likewise, though the renovation definitions for these countries have still not been set. Lithuania and Denmark have identical NZEB definitions for new and existing buildings, as do Cyprus, Bulgaria, Italy, and Latvia, where the NZEB definition for new buildings is also used for deep renovations. Some more information on the NZEB renovation requirements for existing buildings is described in Table 1.  
For example, NZEB renovation in the Brussels Capital Region is defined with identical parameters as for new buildings [27; 28; 29]. These parameters apply whenever the renovation improvements include at least 75% of the heat loss surface area and the building systems. In this case all parameters for new buildings are multiplied with a factor of 1.2, except for the summertime comfort requirement. The indicators include energy demand for heating, primary energy demand, risk of overheating, and air tightness. For renovated residential buildings the parameters are the following:  
* energy need for heating QH \(\leq\) 18 kWh/(m2 year);
* primary energy demand QP \(\leq\) 54 kWh/(m2 year), for heating, domestic hot water (DHW) and auxiliary electricity;
* summertime comfort (overheating risk), excessive temperature frequency (>25 \({}^{\circ}\)C) \(\leq\)5%; and
* air tightness of the building envelope: n50 \(\leq\) 0.72 h\({}^{-1}\). Slovenia's definition of NZEB [27; 28; 29] renovation envisages a tightening of the minimum requirements regarding the maximum permitted heating, cooling, or air-conditioning needs, the preparation of DHW, lighting within the building, and the increase in the headline share of RES in total energy use for the operation of buildings. For renovated buildings the requirements are as follows:  
* energy need for heating QH \(\leq\) 25 kWh/(m2 year), where the requirement for primary energy may be met only by means of a distinctly higher actual share of RES (an envisaged increase from 25 to 50%) in the overall final energy for the operation of the systems in the building;
* energy need for heating QH \(\leq\) 15 kWh/(m2 year), if the technical possibilities for the use of RES at the building's location are insufficient;
* primary energy demand QP \(\leq\) 95 kWh/(m2 year)--single-family houses, the requirements apply to the total sum of energy for the heating, ventilation, DHW and cooling;
* primary energy demand QP \(\leq\) 90 kWh/(m2 year)--multi-family buildings; and
* primary energy demand QP \(\leq\) 65 kWh/(m2 year)--non-residential buildings. According to Slovak [27; 28; 29] regulations deep renovation is renovation of a building at the ultra-low-energy performance level. A complex renovated building must meet the NZEB requirement (the same as for new buildings) if it is technically, functionally, and economically possible.