Figure 4.7 Characteristics of the Passive building

Figure 4.7Characteristics of the Passive building26

During cold periods (in the northern hemisphere) the building interior temperature is higher than outside due to heating of the space. The heat is lost through the envelope and the building cools down demanding more heat for maintaining desirable interior temperature. The inverse applies for summer periods (in the northern hemisphere) the excessive heat from the outside enters the building through its envelope. Therefore, it is required to restrict the heat flow in any building irrespective of the climate by applying insulation. By designing high performing building envelope the heat loss can be substantially decreased.

Thermal transmittance (U-values) of external walls, floor slabs and roof areas of Passivhauss range from 0.10 to 0.15 W/(m²K) (for Central European climate; these values may be slightly higher or lower depending on the climate). In countries in northern Europe, the buildings should have wall insulation up to around 33-35 cm (U=0.10 W/m2K), roof insulation thickness around 50 cm (U=0.067 W/m2K) in order to meet the criteria of the Passivhaus Standard.

The Passivhaus standard has been developed for the mid and northern European climates however its guidelines perform well in hot climates as well. High levels of airtightness and insulation work equally well in protecting buildings from overheating provided there is adequate solar shading in place.

The Passivhaus Institute has listed the following recommendations for Southern European climates, such as::

 Double glazing is acceptable in more temperate climates  Thermal mass and moisture absorbing (hydrothermal) materials gain in importance  Movable external shading is essential  Maybe need for active cooling and/or dehumidifying  Any additional cooling demand 15 kWh/(m²a)  The ground can be used as a heat or cold buffer for tempering the supply air

26 https://www.bobvila.com/articles/passive-houses/