Hello everyone,
I’d like to briefly introduce myself: my name is Daniel, and a few days ago we purchased a house built in 1971, which we plan to thoroughly renovate. One of the projects is the roof.
The roof covering and the wooden structures underneath are still in excellent condition, so we want to install insulation between the rafters in the upper floor (1.5 stories), the wooden beam ceiling, and possibly in the unheated attic space. This topic is causing me some difficulties because, according to u-wert.net, condensation is expected.
The current roof assembly from outside to inside is: interlocking roof tiles on battens, an air ventilation layer (ventilation tiles at the ridge), bitumen roofing felt, 2cm (0.8 inch) insulation, wood fiber insulation board, plaster.
The rafters need to be doubled in size to fit at least 180mm (7 inches) of mineral wool insulation. However, the existing bitumen membrane creates an outward vapor barrier—resulting in condensation issues, because the ventilation unfortunately lies on the "wrong layer." Somehow it must be ensured that the ventilation can also run above the insulation. A friend who is an architect said, “Just remove the bitumen membrane,” but I have concerns about moisture entering the structure this way. My idea is to carefully open the existing bitumen membrane in several places (adding openings approximately 2cm x 20cm (0.8 inches x 8 inches) per meter), so that air can flow over the insulation and carry away moisture. I’ve attached a draft for discussion.
P.S.: This is not meant as a permanent solution, but to protect against mold and fungi for the time being (about 10 years, until a new roof is installed) and, of course, to save on heating costs.
I look forward to your feedback. Best regards,
Daniel
I’d like to briefly introduce myself: my name is Daniel, and a few days ago we purchased a house built in 1971, which we plan to thoroughly renovate. One of the projects is the roof.
The roof covering and the wooden structures underneath are still in excellent condition, so we want to install insulation between the rafters in the upper floor (1.5 stories), the wooden beam ceiling, and possibly in the unheated attic space. This topic is causing me some difficulties because, according to u-wert.net, condensation is expected.
The current roof assembly from outside to inside is: interlocking roof tiles on battens, an air ventilation layer (ventilation tiles at the ridge), bitumen roofing felt, 2cm (0.8 inch) insulation, wood fiber insulation board, plaster.
The rafters need to be doubled in size to fit at least 180mm (7 inches) of mineral wool insulation. However, the existing bitumen membrane creates an outward vapor barrier—resulting in condensation issues, because the ventilation unfortunately lies on the "wrong layer." Somehow it must be ensured that the ventilation can also run above the insulation. A friend who is an architect said, “Just remove the bitumen membrane,” but I have concerns about moisture entering the structure this way. My idea is to carefully open the existing bitumen membrane in several places (adding openings approximately 2cm x 20cm (0.8 inches x 8 inches) per meter), so that air can flow over the insulation and carry away moisture. I’ve attached a draft for discussion.
P.S.: This is not meant as a permanent solution, but to protect against mold and fungi for the time being (about 10 years, until a new roof is installed) and, of course, to save on heating costs.
I look forward to your feedback. Best regards,
Daniel
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