Residential building is a system of interconnected functional units. System is affected by external and internal factors. For normal function system needs energy to ensure optimal conditions: heating cooling, hot water preparation, home appliances operation and other. The amount of energy consumed by the unit and by the building itself depends on user routine and desires but also depends on the quality of built material and its implantation. Efficient energy performance of the building implies high thermal gains ande low thermal losses. Construction sector has a major impact on climate change and environment therefore the expectations for energy efficiency development are high. Due to the lack of legal regulations until 1970, we have buildings in Croatia that consume too much energy and do not provide optimal living conditions. Developing the awareness of the possible exhaustion of non- renewable energy sources, the legal regulations are being developed, in 1970 stipulates the obligation to use insulation materials in the building envelope. The material is set but with thickness the smallest possible only to fulfill the legal obligation but to spend at least possible. Doing so the energy consumption was not significantly reduced and inadequant detail implementation and the appearance of thermal bridges increased the possibility of uncontrolled air passage throughout building envelope. Further social and economic develpment of the society sets the life comfort and care for the environment in front of minimal costs. Cities are being developed in green cities and building are becoming 'smarta' and effective. Recycled and reusable building materials are used and optimal combinations are chosen for maximum thermal and sound protection performances. To provide evidence of quality there are tests being performed before and after the instalation. Construction of airtight building envelope becomes a growing factor in total energy consumption. In addition to energy costs, a properly constructed airtight building envelope prevents moisture and mold, improves indoor air quality, contributes to better sound insulation and, in the case of fire prevents the spread of smoke and toxic gases.