Residencial Condor Mallorca
Condor Mallorca

Insulation of the building envelope

Passive House Principle: keep as much heat as possible in the house.

Why is the insulation of the building envelope so important?

The strongest and most efficient heating system is of no use if most of the expensively generated heat is lost again through the building envelope. The heating costs will be high and you will still be freezing in the house in winter. Good thermal insulation and the avoidance of thermal bridges prevent this heat loss through the building envelope.

The heating has to work less because it has to compensate far fewer losses. That saves heating costs. A well-insulated house therefore has a lower heating requirement than a building with insufficient or non-existent thermal insulation. As a result, the heating system can be designed smaller from the outset.

Which components have to be insulated?

All surfaces of the building envelope that are in contact with the outside must be insulated. This affects all exterior walls, but also the ground floor on the floor slab and the ceiling to the basement and the roof. If the attic is not used for living purposes and is therefore not heated, at least the ceiling of the top floor must be insulated.

But it is not enough to provide walls, ceilings and the roof with an insulating layer. Windows also play a role in the heat loss of a building. Of course you can't put insulating material on the windows. It is therefore important to use modern, optimally insulated windows that meet the current standards for low-energy houses.

What insulation does a Low-Energy or Passive House need?

The heat transfer coefficient (U-value) states how much heat (in watts) is transported to the outside via the surface of a component (in m²) at a given temperature difference (in Kelvin) between the inside and outside temperature. The unit of measure is therefore W/sqm*K. The lower the U-value, the less heat the component transports to the outside - or to put it another way: the stronger the thermal insulation effect.

In the case of a low-energy house, the U-value for the outer walls should be less than 0.2 W/sqm*K. 0.15 W/sqm*K is planned for the roof. Basement walls and ceilings should be below 0.3 W/sqm*K. The windows should have a value below 1.3 W/sqm*K.
In a passive house, the U-values for walls, floor panels and the roof are generally between 0.1 and 0.15 W/sqm*K.

Are there any disadvantages with too much insulation?

Greater insulation thicknesses, such as that of a Passive House, have no disadvantages. They lead to the temperature of the inner wall surface approximately corresponding to the temperature of the air in the room.

This avoids cold areas on interior walls where humidity can form condensation, thus preventing the formation of mildew.

In addition to insulation and the prevention of thermal bridges, the building envelope must also be highly airtight. If cold air can penetrate through cracks in the building shell or warm air can escape, even the best insulation is useless. Critical points are connections of components to the masonry, such as window frames. These connections must be sealed and included in the insulation.