polokrausi
2014-10-22 17:35:31
- #1
Hello everyone,
first of all: I am an absolute construction layman and have registered here out of great desperation to get an objective opinion.
Currently, we are planning the attic conversion of our house built in 1982. The roof consists of wood, roofing felt, and tiles on top. The masonry is 36.5 cm bricks with the then-mandatory 4 cm styrofoam external insulation.
The eaves face towards the roof structure - so currently no air exchange.
The rafters are 18 cm thick.
Currently, the attic space is completely uninsulated.
As part of the renovation, the outer roof is to be insulated to comply with the 0.24 of the Energy Saving Ordinance.
My construction planner has planned a ventilated insulation between the rafters with 16 cm WLG 035 filler and additionally 8 cm WLG 035 as insulation above the rafters in front of the drywall enclosure. The whole thing with a vapor barrier. Openings would have to be made in the walls for ventilation.
The drywall builder I trust now said that personally he would not make ventilation at this point and also, in the interest of gaining space, would only insulate with 18 cm WLG 035 - the whole thing then equipped with a climate membrane. His calculation assumes that a value of 0.22 should be achieved - which would be enough. Furthermore, he inspected the roof and found by measurement that it is absolutely tight. Accordingly, he is of the opinion that in this constellation his approach is the more sensible one. I also told him that I do not want to engage in insulation orgies.
Further calculations showed no problematic approaches regarding dew point issues or similar. He rather sees the problem that when adding ventilation afterward, the existing roof would be subjected to more moisture (through humidity from the outside air).
Calculated values with this insulation variant:
U = 0.224
TA insulation 11.8 (not masterly but no problem)
What do you think? What should I do? I am sitting on the fence and cannot professionally assess who is right or wrong. Cost-wise, the architect’s solution is about twice as expensive. I am also looking for the solution with which I definitely do not catch problems regarding rot, mold, etc.
Thanks for your help,
a desperate renovator - Matthias
first of all: I am an absolute construction layman and have registered here out of great desperation to get an objective opinion.
Currently, we are planning the attic conversion of our house built in 1982. The roof consists of wood, roofing felt, and tiles on top. The masonry is 36.5 cm bricks with the then-mandatory 4 cm styrofoam external insulation.
The eaves face towards the roof structure - so currently no air exchange.
The rafters are 18 cm thick.
Currently, the attic space is completely uninsulated.
As part of the renovation, the outer roof is to be insulated to comply with the 0.24 of the Energy Saving Ordinance.
My construction planner has planned a ventilated insulation between the rafters with 16 cm WLG 035 filler and additionally 8 cm WLG 035 as insulation above the rafters in front of the drywall enclosure. The whole thing with a vapor barrier. Openings would have to be made in the walls for ventilation.
The drywall builder I trust now said that personally he would not make ventilation at this point and also, in the interest of gaining space, would only insulate with 18 cm WLG 035 - the whole thing then equipped with a climate membrane. His calculation assumes that a value of 0.22 should be achieved - which would be enough. Furthermore, he inspected the roof and found by measurement that it is absolutely tight. Accordingly, he is of the opinion that in this constellation his approach is the more sensible one. I also told him that I do not want to engage in insulation orgies.
Further calculations showed no problematic approaches regarding dew point issues or similar. He rather sees the problem that when adding ventilation afterward, the existing roof would be subjected to more moisture (through humidity from the outside air).
Calculated values with this insulation variant:
U = 0.224
TA insulation 11.8 (not masterly but no problem)
What do you think? What should I do? I am sitting on the fence and cannot professionally assess who is right or wrong. Cost-wise, the architect’s solution is about twice as expensive. I am also looking for the solution with which I definitely do not catch problems regarding rot, mold, etc.
Thanks for your help,
a desperate renovator - Matthias