What is a Passive Building?


« The passive building is a building in which the internal thermal comfort (ISO 7730) is guaranteed only by preheating or precooling the amount of fresh air required (DIN 1946) for the optimal internal atmosphere without the use of additional air recirculation. »

The passive building (Passiv Haus in German and Passive House in English) is a building standard that offers both high energy efficiency, comfort, economy and environmental friendliness.


Regardless of the climate or area, Passive Buildings maintain a comfortable and pleasant temperature all year with minimal energy requirements. Buildings are passively heated meaning  that  they make efficient use of the sun, internal heat sources and heat recovery, so conventional heating systems are not necessary even in the coldest winter days. During the summer, Passive Building uses passive cooling techniques, such as the right shading design and night-time natural ventilation to keep it cool. In any case, the excellent quality and technology materials and careful design guarantee that the temperatures remain constant throughout the year, stable and pleasant for the occupants / users levels.

Five basic principles

The Passive Building works like a thermos, which passively keeps its contents at the right temperature, without the use of active cooling or heating.

  1. Insulation: A properly insulated building shell during the winter keeps the heat inside the building while in the summer prevents it from entering.
  2. Windows: Properly designed, insulated and positioned frames are involved in making the best use of solar profits.
  3. Ventilation with Energy Recovery: Passive Building ventilation systems provide clean, pollen-free and dust-free air with maximum energy efficiency through heat recovery and humidity control.
  4. Air-tightness: Passive buildings are designed to prevent air leakage in the building shell, thus increasing energy efficiency and preventing air and moisture from flowing out.
  5. Thermal bridges: The minimization of thermal bridges and weak spots in the building shell contributes to the creation of a pleasant and stable temperature, while eliminating the damage from moisture while increasing energy efficiency.

Shading, Night Ventilation, Light Geothermal Air and True Thermal Mass Design contribute to the best performance of passive buildings in Mediterranean climates.

How does it work

Passive Building works by minimizing heat losses and maximizing heat gains. To minimize heat loss, first of all it needs good insulation (about 15 cm +, depending on the location in each part of Greece). Insulation with thermal conductivity ≤ 0.1 W / (m K), aiming for a shell U to be between 0.10 and 0.25 W / (m2K).

All windows also have to be very well insulated. It is advisable not to be overestimated (cost increase), to have “energy glasses with Ug value <0.80 W / (m2K) total Uw value <1.00 W / (m2K). All profiles of the frames,can be used , if they meet these specifications.

An airtight inner dam of the insulation layer should then be constructed. The airtightness of the building should not exceed 0.6 air changes / hour. This can be done by any material that is and remains airtight. Paper, polyethylene sheet, wood chipboard, plaster, etc. Just do not forget about the connections. They should be particularly airtight.

It is obvious that the house should be ventilated. But the inner warmth should not be lost in this way in the winter. Mechanical ventilation with heat recovery is the solution. It works well only in airtight houses and offers up to 90% energy recovery. In summer, natural night ventilation and the use of light geothermics give the desired levels of thermal comfort.

Minimizing losses maximizes heat gains. These come from the sun, which has to be rich in winter at home, but it is also avoided by proper shading in the summer, and by the activities of the users and the appliances inside the house. The building needs good south-facing and good bioclimatic design. Auxiliary heating and hot water also come from the sun or from other passive or energy-efficient systems with low consumption.

As a result, the building needs only 15 Kwh / m2 per year for cooling or heating and DHW. In addition, the primary energy does not exceed 120 Kwh / m2 per year.