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joschy19762 Mar 2024 17:02Hello!
This year, the flat roof will be renovated.
Everything is planned so far; the last uncertainty concerns the vapor barrier.
The house is 50 years old. Cold roof.
Since the house is occupied, it is not possible to insulate the roof from the inside and install a proper vapor barrier. Therefore, everything will be done from above.
The first drawing shows the current roof construction. I think it is clear where everything is located.
7 - Vapor barrier membrane.
There are many questions about this because it is probably just thick PE foil, like the house itself, which is 50 years old. Its condition can only be assessed after the roof is opened from above.
Basically, no visible moisture issues have been observed, and no moisture ran down the walls. Either everything is properly fastened and sealed, or water vapor has been successfully drained.
The roof repair will also include replacing the insulation. It was decided to add a second layer of vapor retarder foil (10) underneath, raise the edges by 5cm (2 inches), and seal it tightly to the joists. The second drawing shows the roof construction after the renovation.
Does a second foil layer make sense at all? I am concerned about the battens (6), to which the drywall panels (8) are attached, being enclosed between these two foils (even if not completely). And if it does make sense, which foil should be used? Vapor barrier or vapor retarder with an Sd value of 2-5 meters?
Above the joists and insulation, a vapor-permeable membrane (9) will be installed that allows vapor coming from below to pass through and protects against moisture entering the insulation from above. Is this solution correct, or could it be omitted?
The last question concerns the area where the vapor barrier should end on the exterior walls. This is shown in drawing no. 3. Currently, the roof insulation only reaches the wall, but it is planned to extend it to the outer edge of the facade insulation, while the vapor barrier extends only up to the purlin.
I would be very grateful for an evaluation of the solution, identification of errors, and useful advice.
This year, the flat roof will be renovated.
Everything is planned so far; the last uncertainty concerns the vapor barrier.
The house is 50 years old. Cold roof.
Since the house is occupied, it is not possible to insulate the roof from the inside and install a proper vapor barrier. Therefore, everything will be done from above.
The first drawing shows the current roof construction. I think it is clear where everything is located.
7 - Vapor barrier membrane.
There are many questions about this because it is probably just thick PE foil, like the house itself, which is 50 years old. Its condition can only be assessed after the roof is opened from above.
Basically, no visible moisture issues have been observed, and no moisture ran down the walls. Either everything is properly fastened and sealed, or water vapor has been successfully drained.
The roof repair will also include replacing the insulation. It was decided to add a second layer of vapor retarder foil (10) underneath, raise the edges by 5cm (2 inches), and seal it tightly to the joists. The second drawing shows the roof construction after the renovation.
Does a second foil layer make sense at all? I am concerned about the battens (6), to which the drywall panels (8) are attached, being enclosed between these two foils (even if not completely). And if it does make sense, which foil should be used? Vapor barrier or vapor retarder with an Sd value of 2-5 meters?
Above the joists and insulation, a vapor-permeable membrane (9) will be installed that allows vapor coming from below to pass through and protects against moisture entering the insulation from above. Is this solution correct, or could it be omitted?
The last question concerns the area where the vapor barrier should end on the exterior walls. This is shown in drawing no. 3. Currently, the roof insulation only reaches the wall, but it is planned to extend it to the outer edge of the facade insulation, while the vapor barrier extends only up to the purlin.
I would be very grateful for an evaluation of the solution, identification of errors, and useful advice.
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