Counter battens in the interior area for roof insulation

I will have the blower door test carried out after completing the insulation work.

Once again, addressing this critical point:

For me, the primary benefit of such a measurement is not primarily to determine the so-called air exchange rate and compare it with Energy Saving Ordinance or DIN limit values in order to ensure a limitation of ventilation heat losses.

If such a test is conducted at a time when the airtight layer is still accessible, even the smallest defects can be localized and professionally eliminated!

I consider this differential pressure-supported leak detection to be one of the most important quality assurance measures in interior construction.

Wishing a successful building year 2010
KPS

But I still don't know what I should do regarding the [Zwischensparrendämmung] .....

Hello @Venice,

You surely mean the insulation below the rafters.

In case of uncertainties, I consider it indispensable to call the hotline of (in this case Isover) and provide the complete constructive detailing of the relevant components. For the roof slope, for example, from outside to inside:
Hard roof covering (roof tiles or slates)
Battens + counter battens
Underlay or roofing membrane (designation, manufacturer, SD-value)
Rafter dimensions and spacing
Insulation between rafters (designation, manufacturer, thickness, thermal conductivity class)
Vapor barrier/airtightness membrane (designation, manufacturer, SD-value, ...)

Further planned:
If applicable, insulation below the rafters between
Wood substructure for (e.g. single-layer) gypsum plasterboard (12.5 mm) at approx. 30 cm spacing.

Question: Is insulation below the rafters possible without reservations and if yes: In what thickness and thermal conductivity class?

Such assemblies must be professionally planned! For this, the above-mentioned inquiry option with the manufacturer is not an alternative... and neither is inquiry in internet forums ever sufficient.

(3 answers - 3 opinions, and everyone says something different ... but no one will be liable for their statement!)

The state building code and the Energy Saving Ordinance rightly require that such services be carried out by trained professionals.

This applies both to the planning, as well as the construction and its inspection. Anyone who does not possess the necessary expertise must purchase external knowledge.

Public building law therefore applies here, which the client (as "general contractor") cannot simply opt out of and replace, for example, with (possibly dubious) internet "knowledge."

Best regards
KPS

Hello KPS,

of course, I meant the insulation between the rafters.

I will call Isover tomorrow, inquire, and get their opinion.

Until then, many thanks for the information and tips.

Information about the manufacturer’s response would be great!

The tension direction of the foil is from rafter to rafter. So approx. 60 cm, the deflection can also be seen in the photos.

That means whether it is supported only over a "point surface" or over an "area surface" makes a significant difference, especially with thin foils. The surfaces differ by a multiple.

The wind forces are indeed relevant if the underlay membrane is not glued. Especially the suction.