ᐅ Planning a Roof Renovation from 1963

Proposal Isover, U=0.197

Hello everyone,

I recently purchased a house built in 1963 and now want to insulate the roof structure. (currently no insulation, just plastered bamboo mats)

The roof structure consists of rafters measuring 130x100mm (5x4 inches), with a cross battens and concrete tiles on top.

Step 1: (current -> target: Energy Saving Ordinance)
- Insulation between rafters
- Insulation under rafters
- Interior finishing with drywall

Step 2: (in 3 years)
- Insulation above rafters (alternative to roofing boards)
- Replacement of roof tiles

Current limitations:
- Due to ceiling height in the first-floor living area, it is not possible to double the rafters (length of roof slope: 2.20m (7.2 ft))
- In the attic, doubling the rafters is generally possible (rafter length in attic to ridge: 3.10m (10.2 ft))
- Therefore, insulation between rafters is limited to max. 120mm (5 inches) with 10mm (0.4 inches) ventilation gap to battens/tiles

Current questions:
- I have planned ISOVER insulation based on the manufacturer’s recommendation – are there alternatives? (better, cheaper)
- Does anyone have experience with the variable vapor barrier "ISOVER Vario KM Duplex UV"? Alternatives? (better, cheaper)
- Can the insulation under the rafters be done with polystyrene? Reason: cheaper and easier to install

I have already planned the assembly as described on u-wert.net – what do you think?

Thanks in advance for your help,
Feder