ᐅ Optimizing Insulation for a Gable Roof

Hello everyone,

Since the construction of the roof frame for my extension is in its final phase, I need to consider insulation and material ordering.
Because this topic is quite complex, I would appreciate your help. It is a 45° (45-degree) pitched roof with a bedroom and an unheated attic. The energy consultant suggested the following setup.

I would like to improve this a bit with a 60mm (2.4 inches) exterior insulation using wood fiber boards for better summer performance.
Since I’m not exactly sure how the ventilation space (counter-batten layer) should be installed and I often read about ventilated insulation, I hope to benefit from your combined knowledge.
The planned layers are:
- Clay roof tiles
- Counter-batten
- Battens
- Underlay membrane
- 60mm (2.4 inches) wood fiber board
- 240mm (9.4 inches) mineral wool insulation
- Vapor barrier / vapor retarder
- 30mm (1.2 inches) mineral wool with battens
- 25mm (1 inch) double-layer drywall

1. Question: Is a true vapor barrier really necessary between the layers of mineral wool?
2. Question: Which type of vapor retarder or barrier should be used (which specifications or values)?
3. Question: Which kind of mineral wool insulation is best (which specifications or values)?
4. Question: Is the construction setup correct as planned, or can it be improved?

Thank you very much for your help. I’m looking forward to lots of input.

Oh yes, I forgot half of it. The roof should be insulated all the way up to the ridge to use the attic as an additional buffer. How should I construct the intermediate ceilings (160mm (6.3 inches) joists)? Where exactly does a vapor retarder need to be installed if I want to put mineral wool in the ceiling? Thank you.

So, this is about the already existing or at least fabricated roof frame of the extension section, and you want to add a 6 cm (2.4 inches) wood fiber insulation (5a) on top of the thick 24 cm (9.4 inches) mineral wool (5); the 4 cm (1.6 inches) air gap (7) is supposed to accommodate both battens (what exactly are they supposed to support?) beneath the roof tiles???

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11ant schrieb:

So, this is about the already existing or at least constructed roof truss of the extension section,

Yes

11ant schrieb:

and you want to apply a 6 cm (2.4 inches) wood fiber insulation (5a) on top of the mineral wool (5) which is a hefty 24 cm (9.5 inches);

Yes

11ant schrieb:

the 4 cm (1.6 inches) air gap (7) is supposed to contain both battens (what are they actually supposed to support?) beneath the roof tiles???

That question confuses me. On top of the underlay membrane comes a vertical counter-batten, and on that the horizontal batten for the roof tiles. Is that incorrect?

In der Ruine schrieb:

The question confuses me. A vertical counter batten is installed on the underlay membrane, and then the horizontal battens are fixed on top to support the roof tiles. Is that incorrect?

You mentioned an exterior insulation above the rafters (for insulation between the rafters, that would be a very thick layer as well). To which structural fasteners are the battens attached? You probably don’t want to nail them through the (then perforated) underlay membrane and insulation – that’s where my confusion begins to make some sense.

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https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/

The counter battens are fastened directly to the rafters through the sarking insulation. See the image in the PM.