Definition based on the Community Directive 2010/31/EU (article 2):
“A nearly zero energy building is very high energy efficient construction, whose nearly zero or minimal energy quantity required to cover its needs, is mostly done by renewable energy sources, including energy that is produced in situ or close to the building”.
By introducing the nearly zero energy buildings category, the European Union soundly promotes the energy saving in buildings, the largest final energy consumers. The goal, among others, is to cover the 20% energy consumption reduction goal until 2020 and 27% until 2030 respectively. All new buildings must be nZEB from January 1st, 2021. The new buildings that will accommodate public sector services must be nZEB from January 21st, 2019.
The nZEB have: high energy specifications structural elements, high energy performance E/M facilities and a considerable part of their energy consumption will be covered by renewable energy sources in local level.
The great thermal insulation aspect is a fundamental parameter for the construction of a nearly zero energy building.
The passive house is a type of building that offers high energy performance, comfort, economy and is ecofriendly. In essence, the passive house is an nZEB that follows the design principles of this standard, which are the following:
Thermal insulation - A passive house construction requires the use of thermal insulation. A properly insulated building shell keeps the heat inside it during winter and prevents heat from entering it during summer. To minimize heat losses, a good insulation is necessary (about 15 cm+, depending on the position in each part of Greece). Insulation with thermal conductivity ≤ 0.1 W/(m*K), so that the U value of the shell will be between 0.10 and 0.25 W/(m2*K).
Thermal bridging - The elimination or the best possible minimization of the thermal bridging effect is a crucial matter for designers and engineers and demands attention to detail. A thermal bridging-free construction is a good energy performance construction, that creates a pleasant inner climate while minimizing vapor concentrations, humidity and mold.
Windows -A fundamental principle of constructing a passive house is to install proper windows. It is important to check the technical specifications of the windows as well as ensure that they are properly installed, perfectly fitted with thermal insulation, always according to the design. Properly designed, insulated and installed joinery contribute to maximizing the sun’s gains.
Air-proof - Passive houses are designed in a way that does not allow air leakage to the building shell which leads energy efficiency increase and absence of air streams or damages due to humidity.
Ventilation with heat recovery - The passive house is a building where the interior thermal comfort is achieved by pre-heating or pre-cooling fresh air required for proper interior atmosphere, without needing to further recirculate air. For this reason, a mechanical ventilation system with heat recovery (MVHR) is indispensable.
No matter the climate or place, passive houses maintain a comfortable and pleasant temperature with minimal energy requirements throughout the year. The buildings are passively heated, which means that they use an effective use of the sun and the internal heat sources and heat recovery systems, so that conventional heat systems are not necessary even during the coldest days of winter. During summer, the passive house uses passive cooling techniques such as proper shading design and night natural ventilation, to maintain cool temperatures. In any case, the excellent quality and technology materials guarantee that temperatures remain in steady and pleasant levels for tenants/owners throughout the year.