Mineral insulation vs. wood fiber insulation prefab house

The relevant difference here corresponds rather to the U-values of the respective wall constructions: this indicates the duration of heat transfer difference between inside and outside, and thereby also the phase shift of the temperature fluctuations of the outside air.

Since mineral wool is probably used with WLS035 and wood fiber probably with WLS036, the U-value will not differ measurably. The thermal transmittance value, U-value, is however only part of the equation. The amplitude attenuation (mitigation of temperature peaks during heat transfer with dynamic temperature conditions) and phase shift (time it takes for the temperature peak to reach the other side) are significantly influenced by the heat capacity of the wall. The heat capacity of wood fiber per kg is twice as high as that of mineral wool, and the bulk density of the wood fiber insulation boards is three times as high. Overall, the heat capacity is therefore six times as high as that of mineral wool, and amplitude attenuation and phase shift are significantly greater. Therefore, in roof insulation, wood fiber has a clear advantage over PUR/PIR insulation boards or mineral wool in summer heat protection – with the same U-value.

Due to the already existing mass and storage capacity of the outer 12 cm wood fiber and other components of the wall, it is no longer relevant in this case whether mineral wool or wood fiber is used in the middle. Regarding the different layers, I generally agree with you. However, at least here the principle "inside more diffusion-tight than outside" is not violated, so I would be very relaxed about that.

Thank you very much for your answers and explanations, they were helpful! We have now decided on the climate wall with mineral insulation.