ᐅ Polystyrene Insulation or Mineral Wool in Winter

We are currently building a KfW40 new construction using solid construction methods. For the exterior walls, the plan is as follows: on the inside, aerated concrete blocks, then 160mm (6.3 inches) of insulation (thermal conductivity class 032), an air gap, and finally facing brick. Our contractor usually installs mineral wool insulation. Since our house will be built over the winter, the contractor suggested using polystyrene insulation with the same properties (160mm, WLG 032) instead, to avoid moisture-related issues during the construction phase. Of course, mineral wool would not be installed in the rain and would always be covered with tarps, but here in the north the wind can sometimes tear off the tarp over a weekend, which could cause the mineral wool to get wet. In principle, the reasoning seems plausible to me, but the final decision should be ours. In terms of cost and quality, both options are comparable. I would appreciate your assessment.

Pros of mineral wool:
- Non-combustible
- Easier to dispose of
- Better heat protection in summer due to greater thermal mass (is this relevant with our wall build-up?)
- Better sound insulation (also relevant with our wall structure? It’s a rather quiet area...)

Pros of polystyrene:
- Resistant to moisture, resulting in fewer issues and potentially faster construction

Have I overlooked anything? How would you decide?

The mineral wool must be water-resistant. It can constantly get damp, even later on, because the dew point is located on the inside of the brickwork.

It is probably cavity insulation – water-repellent.
I would stick with mineral wool. If it gets damaged, the builder has to replace it.
However, mineral wool is not that sensitive.

Mineral wool is also significantly more expensive and much more complicated to install. You simply stick polystyrene to the wall, whereas mineral wool needs to be fixed with dowels. That might be why this suggestion was made...

If the general contractor really finds installing mineral wool too difficult in winter, that doesn’t reflect well on them... Have they ever built a house before, or is yours their first...? 😉

Best regards,

Andreas

The mineral wool is simply slid onto the masonry ties in clinker brick construction. I also suspect that the builder wants to cut costs.

@ Knallkörper:
Is it really just pushed onto the wires and done? And it holds? Learned something new today...
Then the installation probably won’t be much different.
It would still need to be checked whether the material is more expensive.

Best regards,

Andreas