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