The term "low-energy building" means a building that is designed and constructed in such a way as to present a significantly higher degree of energy efficiency than the requirements of national standards for the energy performance of buildings. As a rule, it is assumed that the operation of such houses and buildings consumes at least 50% less energy than in ordinary buildings.

If for a normal building we assume an annual energy consumption of about 100-150 kWh of energy, for a low-energy building the consumption must be below 50 kWh of energy.

The conversion of an existing building into a low-energy one is primarily related to the addition of some energy-efficient systems. Through them, energy costs will be reduced up to 3 times.

External thermal insulation - minimum 16 cm.
Ground heat pump - water.
Solar collectors and recuperator - ventilation system. It must use the heated air from the interior (bathrooms, kitchens, rooms) to transfer the heat to the fresh air coming from outside.

It is known that 2/3 of the total energy consumed in buildings goes to heating and air conditioning. Most of this energy is wasted due to unsatisfactory insulation. With proven methods to increase energy efficiency, we can save up to 90% of these costs.

The best combination of energy efficiency measures is applied in the so-called PASSIVE HOUSE standard. In this case, this must be set in the initial design and construction of the building.

According to the US Energy Bureau and the International Energy Agency, if no action is taken, annual energy consumption will continue to rise by an average of 2%. One of the key methods for limiting carbon dioxide emissions to 50-80% by 2050 is to reduce energy consumption in buildings.

According to the European Energy Efficiency Action Plan adopted on 19 December 2006 and an integral part of the energy package, the improvement of energy efficiency by 2020 and the realization of the potential of energy saving measures must exceed the level in 2005 by 20% . By 31.12.2020, all new buildings must be low-energy, provided that the cost-income analysis of the energy efficiency of the building is positive for the period of use.

According to the new energy policy, by 2020 the so-called triple indicative target, namely:

• Reduce electricity consumption by at least 20%.
• Increase the use of renewable energy sources by at least 20%.
• Reduce carbon dioxide emissions by at least 20%.