We've sold our Passivhaus and are now renovating a larger victorian terrace property, our previous learnings don't seem to be translating to a solid wall victorian conversion!
We're considering permeable (no gap) timber fibre IWI as we're in a conservation area and can't do EWI. We have solid walls and are currently removing the wallpaper from lime plaster.
Pavatex said that reducing U-values beyond 0.4 was inadvisable as would have too significant effect on rate of drying of the (exterior) wall, hence frost damage. This seems to be confirmed by Jospeh Little in Breaking The Mould: "It seems reasonable to deduce from this that once driving rain is dealt with internally-insulated walls appear to work best with less insulation than 0.45 W/m2K" https://www.buildinglifeconsultancy.com/content/breaking-mould-5 (link not secure)
However, I wondered if there was an alternative to accepting a worse U-value (for IWI) by reducing humidity (heat recovery from bathrooms for example) as the improved interior environment might provide better external wall performance during dry spells? Or is this madness?
Should I be less focussed on U-values?
