Rock wool vs. EPS exterior wall insulation
I am trying to decide between these two exterior insulation types for a house:
– 200 m2, flat roof
– built with Thermo brick (like f.e. Porotherm)
– ETICS/EIFS insulation system
– location: Croatia, the climate is corresponding to Philadelphia
Trying to achieve at least ~35 kwh/m2/a. Probably will end up better, since ERV is also planned (Zehnder ComfoAir Q350), and most glass will be on an unobstructed south side.
Proponents for rock wool are really passionate. But I am wondering if its advantages would mean anything for me. Well, other than fire resistance. Sound is not a problem. But vapor diffusion is something that, no matter how much I read, I can’t really get it.
Since exterior insulation will be thick (8inches), there should be no condensation whatever I choose?
From what I’ve gathered: vapor moves from hot to cold. During summer, this means vapor would be trying to move into the house. In which case EPS sounds better? And during winter, it would move the opposite direction? Do I need, and where to put vapor barrier or vapor retardant? On the inside of the wall, preventing outdoor vapor diffusion, but letting inside vapor to dry to the outside?
So far, I’ve been able to surmise the following regarding the rock wool:
+ fire resistant
+ better sound insulation
+ vapor permeable
– if not done right, can lead to problems
– 50% more expensive
– fewer installers, and consequently, fewer reliable installers
I have read this article and comments, but I’m still in doubt on some things, since my house would be brick and concrete, with stucco, flat roof.
The price difference amounts to 2% of the whole house. Which is not negligible. Is there a strong argument fo rock wool for someone who does appreciate indoor air quality?
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