Passive houses represent a building standard which allows the user the greatest comfort with a minimal influence on the environment and contains all the qualities of a modern home. It represents houses which save energy and which are practically independent of the urban environment supply network. Since their appearance in the 90ies, the passive houses appear all around the world and also in Croatia. With the trend of sustainable development passive houses are becoming a symbol of a better and environmentally friendly construction. Based on the conducted research via electronic survey the results about the ecological awareness and knowledge of energy certificates of examinees are obtained. The result shows their positive attitude towards ecology and a wish to improve the situation in Croatia. From the total of 207 examinees a majority knows and cares about the environment around them and about the energy certificate connected to current and future real estate. Those examinees who do not consider themselves environmentally conscious are becoming a potential for the future development of the ecology in Croatia. Conclusions based on the research show that ecology awareness in Croatia is not yet on the level of other members of European Union. The consciousness about environmental preservation and concern for the same are the principles which need to be taught since childhood and should lead an individual through the life in order to reduce the negative effects on the environment and to ensure that future generations inherit the world as we now today.