Based on the EMPA studies and other scientific investigations into the effect of various insulating materials, it has been shown that the choice of insulating material in timber construction has only a very limited influence on the indoor climate in summer. These research results contradict the widespread belief that insulating materials such as wood fibre insulation have a significantly better cooling effect than mineral wool, for example. According to the EMPA results, the choice of insulation material only leads to temperature differences of a maximum of 1°C.
To summarise:
Limited influence of the insulation material:
Even in timber construction, insulation materials with a higher heat storage capacity, such as wood fibre insulation, only have a minimal effect on the room temperature compared to lighter insulation materials such as mineral wool. Studies show that temperature differences are usually in the range of 0-1°C, which is hardly noticeable for the indoor climate in summer.
Phase shift:
Although the phase shift - i.e. the delay until the time of maximum heating - occurs slightly later with organic insulating materials such as wood fibres, this effect is less pronounced in practice than is often assumed. Compared to solid masonry, however, timber construction offers less heat storage overall due to its lower mass.
Normative specifications:
Structural and utilisation-related measures are crucial for summer heat insulation in timber construction. These include the use of sun protection devices, targeted ventilation (especially night ventilation) and the use of high-mass interior surfaces such as plasterboard or screed, which store heat and buffer peaks. In addition, sunlight entering through window areas is critical; without adequate sun protection, this can contribute to overheating.
Important influencing factors:
The SIA standards set out clear guidelines for summer thermal insulation in timber construction and require a comprehensive planning approach that includes all structural and design measures to reduce solar radiation. The exclusive focus on insulating materials does not correspond to the recognised rules of technology.
Conclusion
The study shows that an integral planning approach is required for summer thermal insulation in timber construction, in which all room-enclosing components and the usage behaviour of the occupants are taken into account. The choice of insulation material plays a subordinate role in comparison. The decisive factors are sun protection measures, ventilation strategies and high-mass materials that optimise summer heat insulation in timber construction.
