Interior insulation in masonry wall

[Alberto Morales]

Hi guys,

I have the next build-up

25mm lime render
500mm Stone wall
20mm unventilated air cavity
100mm mineral wool
15mm plasterboard

1- Should I add 1 % of driving rain? if yes, where should I place it? In the outermost 5mm of the render in contact with external ambient?
2- Should I add a air leakage as it is an historical building? if yes, Where to place it that moisture source? which value is recommended? where to find that resource of info?
3- what layers to analyze? innermost side of the stone wall and outermost side of the insulation? which thickness should the layer be --> 10mm?

Regards and thanks

[Daniel]

Hi Alberto,

1- Should I add 1 % of driving rain? if yes, where should I place it? In the outermost 5mm of the render in contact with external ambient?
ANSWER: No - this is only used in case of EWIS / EIFS or facade claddings, where rain can run behind the most exterior layer, but not for rendered facades.


2- Should I add a air leakage as it is an historical building? if yes, Where to place it that moisture source? Which value is recommended? where to find that resource of info?
ANSWER: No, masonry walls with render at least on one of the two surfaces are considered to be completely air tight. If they have bigger cracks, maybe some airflow can occur, but air infiltration moisture can cause problems in lightweight structures with low moisture storage, but remain of negligable relevance for masonry.

3- what layers to analyze? innermost side of the stone wall and outermost side of the insulation? Which thickness should the layer be --> 10mm?
ANSWER: Permanent moisture accumulation with resulting high moisture levels in the whole wall should be avoided. Also increased moisture level on the cold side of the insulation layer...
Please refer to this guideline: https://wufi.de/download/guideline/WUFI ... 251202.pdf
And the other guidelines on this section: https://wufi.de/en/service/downloads/

best regards
Daniel

[Alberto Morales]

Thanks for the reply. I really appreciate it.

when I want to calculate the final conditions (water content) of the original wall (just stone wall and render) which will be the initial conditions of the proposed wall (with interior insulation), do I also need to set an air leakage rate (q50) on the inner face of the original wall? Where to place that air leakage to calculate those end conditions?

If I include a text file for the water content and distance (wall thickness) in the proposed wall for the initial conditions, what initial conditions will the other materials (insulation, plasterboard, air cavity) be based on? Because I can't select any "initial moisture" option like "assign typical built-in moisture." What I see It is all the rest of material of the proposed wall has the same wáter content at the beginning. Do you understand what I mean?

[Alberto Morales]

Regarding to the other answers 1 and 2 of your previous reply, if I don't put any moisture source air leakage q50 for historical building could be well assumed or rain leakage (I doubt that there is not crack around old windows in contact with the wall), WUFI "says" that it is not risk for the wall but having an unventilated air cavity in the cold side of the build-up, mineral wool as an internal insulation and the wall is located in Ireland, I doubt a lot that the wall is moisture safe.

best regards and thanks once again