Energy certification of buildings is to establish the energy performance of buildings and a legal obligation. Based on the determined data by energy certification shall be made Energy passport.

The certification is based on the main project from which data are taken, checks on the building and entered into the budget for building energy efficiency by which manufactures energy passport of the building. By Energy Efficiency Elaborate, which is an integral part of the project for the building permit, in some cases not shown the right condition so it is necessary to determine the true state of the building.

Reasons for this may include:

1. Projects are not well-defined material or method of construction.
2. Contractors use materials worse than those defined by the project.
3. Performers do not perform the work according to the rules of the profession and thus resulting errors in the construction of buildings that affect the energy performance.

Errors in the project, the choice of materials and method of construction become visible during the operation of buildings. Considering the above mentioned possible causes of inadequate construction should be in making energy certificates to think about testing the building prie making certificates. There are various methods of test and measurement parameters which influence the energy efficiency of the building.