Zero Energy Building (ZEB) is a building with high energy performance. The nearly zero or very low energy demand should be generated from renewable energy sources, including the energy generated on site or very close to the building. These buildings, however, are still producing greenhouse gasses when there is a lack of available solar energy (on cloudy winter days or during the night) or wind energy (for possible wind turbines installed), so they cover their demands powered by the grid and therefore by conventional sources. In fact, most of the zero energy buildings receive half or more of their energy demand from the grid. Buildings that produce more energy than consuming during a year (they have a surplus of energy) are called “positive energy buildings”, while the ones that consume a bit more than they generate are called “nearly zero energy buildings” or “ultra low energy buildings”.

Traditional (conventional) buildings consume 40% of the total energy generated from fossil fuels in the EU and the USA while they contribute to greenhouse gas emissions. The principle of “zero energy consumption” is a means for reducing the CO₂ emissions and the dependence on fossil fuels. At the moment zero energy buildings are not very widespread even in the developed countries, however, they continuously gain more and more importance and recognition.

Most of the zero energy buildings use the grid to “store” their generated energy, but some of them are also autonomous. Energy is usually generated on site from a combination of RES technologies (solar, wind), while savings are achieved due to extremely efficient heating, cooling, ventilation, and lighting systems. As the cost of conventional energy sources (fossil fuels) tends to rise and the cost of alternative sources technologies tends to decrease, the goal for zero consumption seems more and more achievable.

The construction of modern zero energy buildings became feasible by the technological progress of the construction methods but also facilitated significantly by the academic research. Energy performance data from conventional and experimental buildings were collected and used as input to computational simulation models to predict the performance of new solutions and designs. Some of the zero energy buildings’ advantages are the integration of RES technologies which also allows the capability of electrical vehicle charging and the application of various zero energy balance concepts/ designs and therefore called “smart buildings”. The term of zero energy balance offers a wide range approach due to the multiple energy generation and conservation potential in combination with the energy valuation with different parameters (energy cost, CO₂ emissions etc.).