Hello
I would like to install internal insulation as shown in the attached picture.
Briefly - Outside: 240mm (9.5 inches) wall with plaster
Inside: 8cm (3 inches) air gap, then rigid PU foam boards, followed by drywall.
According to calculations with WUFI, the moisture content is 132kg/m³ in the masonry and 18kg/m³ in the air gap.
If I enter in the calculation that the exterior wall is “sealed” (for example, by temporarily adding a PE foil), the values change to:
Wall: 16kg/m³
Air gap: 1.7kg/m³
As an experiment, with external thermal insulation composite system (ETICS) I still get 6kg water in the wall.
What is clearly best in this case is external insulation.
1st question: What can be done to minimize moisture ingress from outside while still allowing water vapor to diffuse outward if possible?
Or put differently – if I want to insulate this way, what do I need to pay special attention to in order to ensure that moisture does not condense in the air gap?
The dew point is located within the insulation layer between the 1st and 2nd PU boards.
2nd question: Should the vapor barrier be placed directly behind the drywall (i.e., behind the battens), or could it be installed between two PU boards? Otherwise, I would need to install counter-battens to fix the hollow wall boxes.
Thank you very much in advance
Best regards, Mirko
I would like to install internal insulation as shown in the attached picture.
Briefly - Outside: 240mm (9.5 inches) wall with plaster
Inside: 8cm (3 inches) air gap, then rigid PU foam boards, followed by drywall.
According to calculations with WUFI, the moisture content is 132kg/m³ in the masonry and 18kg/m³ in the air gap.
If I enter in the calculation that the exterior wall is “sealed” (for example, by temporarily adding a PE foil), the values change to:
Wall: 16kg/m³
Air gap: 1.7kg/m³
As an experiment, with external thermal insulation composite system (ETICS) I still get 6kg water in the wall.
What is clearly best in this case is external insulation.
1st question: What can be done to minimize moisture ingress from outside while still allowing water vapor to diffuse outward if possible?
Or put differently – if I want to insulate this way, what do I need to pay special attention to in order to ensure that moisture does not condense in the air gap?
The dew point is located within the insulation layer between the 1st and 2nd PU boards.
2nd question: Should the vapor barrier be placed directly behind the drywall (i.e., behind the battens), or could it be installed between two PU boards? Otherwise, I would need to install counter-battens to fix the hollow wall boxes.
Thank you very much in advance
Best regards, Mirko
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