Insulate cold roof with clamp felt, price

  • Erstellt am 2019-02-15 17:39:26

Nordlys

2019-02-18 22:14:39
  • #1
In my opinion, an insulated attic must be ventilated and aired out, therefore install a Velux. Our roof has a Velux that I sometimes open for half a day. It quickly becomes dry up there with some wind and dry weather outside.
 

boxandroof

2019-02-18 22:22:14
  • #2
Thank you for the answer.

I have windows in the gable. I can ventilate, heat, and dry. The question is how I approach this systematically and possibly identify problems. It is also clad.. and not plastered.
 

Dr Hix

2019-02-18 22:36:52
  • #3
To be able to answer this somewhat seriously, one would need to know:

- Structure of the ceiling
- Structure of the roof truss
- Ventilation of the attic so far?
- Rooms below the attic
- Access to the attic
 

boxandroof

2019-02-18 22:48:39
  • #4
It is a new building, moved in July 2018. Solid construction with a wooden gable roof.

Intermediate ceiling: plasterboard, vapor barrier, 20cm mineral wool (+OSB board)
Roof structure: inside plasterboard + vapor barrier, insulation between rafters, foil, roof tiles
Access: insulated pull-down ladder
Rooms below: several bedrooms, bathroom
Ventilation: irregular manual ventilation, now occasionally electrically heated for safety during the first winter and dehumidifiers running (without significant water yield)
 

Dr Hix

2019-02-18 23:26:46
  • #5
Basically, the same applies here as with Nordlys, the insulated roof with vapor barrier is rather uncool as long as it is not heated. Adding to the difficulty in your case is the OSB as the floor covering. This means your top floor ceiling is completely wrapped up (also acts as a vapor barrier). Especially if the underlying vapor barrier – as you wrote – was not executed correctly, there is a considerable risk for the construction. Moisture penetrates from below but can no longer escape upwards.

Due to the complexity (OSB, controlled residential ventilation), I don’t want to give concrete advice here, but in my opinion, at least the floor covering should be replaced with tongue and groove (diffusion-open). It might also be sufficient to cut "strips" out of the panels or drill larger holes into them. But please consult an independent expert for this – they will also be liable for their recommendations.

But to make one thing clear: I see urgent need for action here. Something like this can go well for decades, but can also lead to rotting ceiling beams within a very short time. The risk would be too high for me personally.
 

boxandroof

2019-02-18 23:58:01
  • #6
Thank you for the assessment. Ok – I understand where problems might possibly arise. Ventilating in the roof doesn’t help then either.

Sorry, I realize I am sparing with the information myself: I had an expert (called in too late) on site to ask about the moderate result of the BDT. He said I should observe it during the first winters (but how? hence my original question), but had no other suggestions. Of course, he advised against a complete dismantling – BDT was passed. Regarding the controlled residential ventilation, he generally saw the risk of moisture damage as lower than without it.

But of course, it is also possible that the controlled residential ventilation is pushing the moist air upwards somewhere.
 

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