ᐅ Is it possible to change the insulation after obtaining the building permit / planning permission?

Hello,

we have received the building permit / planning permission for our house.
The exterior wall is planned to be 24cm (9.5 inches) Poroton brick plus 14cm (5.5 inches) external thermal insulation composite system (ETICS).
More and more people are advising me against this, but using a 36cm (14 inches) brick would have been too expensive (and the construction company probably wouldn’t agree).
Now I am considering switching from polystyrene to stone wool insulation – is this still possible?
Is polystyrene really as bad as some claim, or can it still be acceptable?

Thank you very much in advance.

We have 17.5cm (7 inches) of sand-lime brick + 1cm (0.4 inches) air gap + 14cm (5.5 inches) mineral wool + 12.5cm (5 inches) facing brick. Our architect installs only mineral wool.

chrisw81 schrieb:
More and more people are advising me against it now

chrisw81 schrieb:
Is expanded polystyrene really as bad as people say?

What exactly are people claiming?
The production of stone wool requires more primary energy than EPS, so environmentally it’s about the same.
Also, if stone wool gets wet, it loses its insulating properties. But apparently, it insulates very well when dry?!
Maybe the structural design would need to be revised? After all, it’s heavier than EPS…

Is the insulation material specified in the building permit or planning permission, or is it only listed as ETICS (external thermal insulation composite system)? If not, that’s not a problem. EPS and mineral wool boards should be available with the same thermal conductivity values, so there would be no change in the exterior appearance, overall dimensions, or energy performance ratings, since the render remains the same.

Are you considering switching to mineral wool because of its higher thermal mass and resulting lower surface temperature fluctuations, or due to its vapor permeability, sound insulation properties, ecological reasons, or fire safety?

dertill schrieb:
Is the insulation material even specified in the building permit / planning permission, or only the ETICS?

Switching to mineral wool because of higher thermal mass and resulting smaller temperature fluctuations on the surface, or due to vapor permeability, or for sound insulation, or for ecological reasons, or for fire protection?

Probably only ETICS, but I would need to check again carefully.

For various reasons... ecological, sound insulation, but also the problems with EPS (algae growth, dark spots, ...), durability.

The question is only whether the extra cost of presumably several thousand is worth it... what bothers me most is the algae growth, meaning I would have to repaint or do similar maintenance every few years.

chrisw81 schrieb:
Probably only external thermal insulation composite system (ETICS)

In that case, you have the freedom to choose. You can opt for jute, wood fiber, or mineral wool depending on your preference.

Algae growth can be reduced by using insulation materials with higher heat capacity, but the render also plays an important role (mineral silicone resin render with appropriate coloring helps in this regard). Regarding ecology and the primary energy used, @ypg has already provided some input; things improve with the mentioned jute or wood fiber—however, in this case, the insulation layer will be somewhat thicker because the thermal conductivity is higher.
Durability should be similar for all; EPS is even the most resistant when it comes to moisture—it does not collapse or stick together like mineral wool does. If that happens, something has gone wrong beforehand.