The thermal insulation of a passive house but also of every building is a key element to be considered. Indeed, according to ADEME, the majority of heat losses of an uninsulated building are coming through:
When talking about the envelope of a building we consider all the elements that separate the interior from the exterior.
The first rule to minimize heat losses is to avoid thermal bridges as much as possible. To do so, the insulating layer has to be continuous. Moreover, it is essential to consider the heat transfer coefficient U of each building element.
In order to meet the Passive House standard requirements, a maximum U value has been defined for each element. Obviously, the values will depend of the type of climate. The figure opposite shows the values recommended for a Central European climate, for instance Germany.
For warmer climates such as Lisbon, the value of U for exterior walls can reach 0.50 W/m²K (0.15 W/m²K for colder climates such as Germany).
The choice of an insulation material is made according the following criteria:
The ACERMI (Association for the Certification of Insulation Materials) platform provides a list of certified materials. It can be used as a starting point for choosing insulation materials.
They are made from natural inorganic materials, they are generally fire-resistant and are in the form of panels. The most commonly used are glass wool and rock wool.
They are produced from plant or animal materials. Among the most commonly used are cork, wood fibre, cellulose wadding, hemp, and straw.
Most of them come from fossil resources (e. g. expanded polystyrene).
Thermal conductivity of some materials – source : DIN 4108-4, EN 12524
