Hello!
Old house built around 1900! A typical pitched roof house. I believe this is called a gable roof.
The exterior wall consists of a single layer of regular red facing bricks. At least that’s the case up in the attic.
That’s what my question is about.
It concerns the attic apartment. The attic is not fully finished, right up to under the gable roof.
Two rooms have been finished there with drywall panels. Timber stud construction. The finishing was done in the 1970s.
One drywall partition that I want to renew is about 30 centimeters (12 inches) away from the red brick exterior wall I mentioned above. So it’s the building’s normal outer wall. I want to replace this drywall partition and move it closer to the exterior wall, and insulate the space in between with mineral wool.
Now the question! Do I need to install a vapor barrier film between the red brick wall and the mineral wool?
So the layers would be, if I were to include a vapor barrier:
Exterior brick wall (10 cm (4 inches) red brick) / vapor barrier film / mineral wool / OSB board / drywall.
Is a vapor barrier really needed there? My concern is that the exterior wall could release moisture into the mineral wool. But the mineral wool is already present in the unfinished (cold) attic anyway.
How should this be approached?
The OSB board I want to install behind the drywall acts as a vapor retarder on the inside, so technically I wouldn’t need another vapor barrier on the inside.
It’s not about doing everything 100% by the book, but about keeping it minimal and practical!
It’s an old house after all. But I want to avoid mold.
I just don’t fully understand the whole vapor barrier issue!
Old house built around 1900! A typical pitched roof house. I believe this is called a gable roof.
The exterior wall consists of a single layer of regular red facing bricks. At least that’s the case up in the attic.
That’s what my question is about.
It concerns the attic apartment. The attic is not fully finished, right up to under the gable roof.
Two rooms have been finished there with drywall panels. Timber stud construction. The finishing was done in the 1970s.
One drywall partition that I want to renew is about 30 centimeters (12 inches) away from the red brick exterior wall I mentioned above. So it’s the building’s normal outer wall. I want to replace this drywall partition and move it closer to the exterior wall, and insulate the space in between with mineral wool.
Now the question! Do I need to install a vapor barrier film between the red brick wall and the mineral wool?
So the layers would be, if I were to include a vapor barrier:
Exterior brick wall (10 cm (4 inches) red brick) / vapor barrier film / mineral wool / OSB board / drywall.
Is a vapor barrier really needed there? My concern is that the exterior wall could release moisture into the mineral wool. But the mineral wool is already present in the unfinished (cold) attic anyway.
How should this be approached?
The OSB board I want to install behind the drywall acts as a vapor retarder on the inside, so technically I wouldn’t need another vapor barrier on the inside.
It’s not about doing everything 100% by the book, but about keeping it minimal and practical!
It’s an old house after all. But I want to avoid mold.
I just don’t fully understand the whole vapor barrier issue!
The vapor retarder is always installed on the warm side, meaning on the interior. Its purpose is to prevent moist air from penetrating into colder layers where it can condense. If you have a wall construction that allows moisture to dry out (for example, a ventilated facade), then a vapor barrier is probably not necessary. The same applies if you have an airtight wall assembly on the inside; apparently, tightly installed chipboard panels are considered vapor-tight.
There is no need for a vapor retarder on the exterior side. The outer wall should be rainproof, preventing any moisture from entering the insulation from outside.
Regarding gypsum boards: I’m generally not a fan of them, especially in older buildings or timber constructions (such as roof structures), since they are combustible. I would prefer gypsum fiberboards instead, as they are non-combustible. However, this is just my personal opinion.
There is no need for a vapor retarder on the exterior side. The outer wall should be rainproof, preventing any moisture from entering the insulation from outside.
Regarding gypsum boards: I’m generally not a fan of them, especially in older buildings or timber constructions (such as roof structures), since they are combustible. I would prefer gypsum fiberboards instead, as they are non-combustible. However, this is just my personal opinion.
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