Airtightness and ventilation are key factors for energy-efficient and healthy construction in Switzerland. With increasing requirements for thermal insulation in accordance with MuKEn and SIA standards the building envelope is becoming increasingly tight.

This brings clear benefits: less energy loss, greater living comfort and better control over the heat balance. At the same time, however, a new challenge arises: without sufficiently planned air exchange, moisture can accumulate in the building and lead to mould or structural damage in the long term. For this very reason, airtightness and ventilation must always be considered together and must not be planned as separate issues.

Airtightness according to SIA 180: basis for energy efficiency

The SIA 180 "Thermal insulation, moisture protection and indoor climate" requires a state-of-the-art airtight building envelope. The aim is to avoid uncontrolled air currents and increase energy efficiency. An airtight building envelope prevents warm and humid indoor air from penetrating uncontrolled into building components. This not only protects the energy balance, but also the structure itself.

An airtight design has several advantages:

• Reduction of heat loss
• Avoidance of draughts
• Protection of the construction against moisture damage

At the same time, the tighter a building is, the more important a functioning ventilation concept becomes. This is because a lack of or insufficient air exchange cannot be replaced by the tightness of the building envelope.

MuKEn: Energy efficiency and building envelope

The MuKEn (model regulations of the cantons in the energy sector) form the basis for energy requirements in Switzerland.

Among other things, they demand

• an airtight building envelope
• Minimised energy losses
• harmonised building technology

However, the MuKEn do not define any specific air exchange rates, but require that the necessary air exchange is controlled and planned. This makes it clear that energy efficiency does not end with insulation or the tightness of the building envelope. It is crucial that the hygienically necessary air exchange is also reliably ensured.

Ventilation in residential buildings: SIA 382/5 as a central basis

For the specific design of ventilation in residential buildings in Switzerland, the SIA 382/5 "Ventilation in residential buildings" authoritative.

This standard ensures that:

• moisture is reliably dissipated
• hygienic requirements are met
• the air exchange functions independently of user behaviour

This is particularly important in modern, well-insulated residential buildings. Moisture protection ventilation is particularly important. It must be guaranteed at all times, even when windows remain closed. It forms the basis for ensuring that moisture is removed from the building and that no critical conditions build up on surfaces or in building components.

In addition, SIA 382/1 defines the general requirements for mechanical ventilation systems and forms the technical basis for planning and implementation.

Avoid mould: Interaction of insulation and ventilation

Mould develops when moisture comes into contact with cold component surfaces. This is precisely where the strength of high-quality insulation comes into play. It becomes particularly critical when warm indoor air contains a lot of moisture and this condenses in unfavourable places.

A well-insulated building envelope ensures:

• Higher surface temperatures
• Less condensation
• Lower risk of mould growth

You can also find out more about the role of insulation in our Article on the origin of glass wool materials.

Our SAGLAN glass wool optimally supports this interaction. It helps to reduce heat loss and at the same time reliably fulfils the building physics requirements in accordance with SIA 180.

Ventilation systems: solutions for every application

Different systems are used depending on the building and utilisation:

• Window ventilation
• Mechanical exhaust air systems
• Supply and exhaust air systems with heat recovery
• Combined systems

Modern ventilation solutions enable controlled air exchange regardless of user behaviour and are particularly important for tight building envelopes. Which solution makes sense depends on the type of building, the utilisation, the moisture loads and the desired level of comfort. It is crucial that the system matches the building envelope and the utilisation concept.

Planning determines quality

A functioning solution can only be created if airtightness, insulation and ventilation are planned together at an early stage. If these issues are only brought together at a late stage, there is a risk of unnecessary interface problems and avoidable defects in the design.

Important success factors:

• integral planning concept
• Coordinated materials and systems
• Clean design without leaks
• Consideration of utilisation and moisture loads

Conclusion

Airtightness and ventilation must always be considered together. While the airtight building envelope in accordance with SIA 180 and MuKEn improves energy efficiency, a correctly planned ventilation concept in accordance with SIA 382/5 ensures healthy indoor air and reliable moisture protection.

In combination with high-quality insulation, durable, energy-efficient and comfortable buildings are created. Only the harmonised interplay of these factors creates solutions that work in the long term. Integrated planning of airtightness, insulation and ventilation reduces risks and improves the quality of the building at the same time.

Are you planning a project and want to optimise airtightness and insulation? Our specialist advisors will support you with the right choice of system.