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

I would suggest contacting the local building materials supplier to ask which manufacturers they carry. I recently bought materials from Knauf and URSA at a lower price than Isover. However, this always depends on the suppliers.

I don’t think Styrofoam is easier to install since the amount of cutting required is quite high. Additionally, Styrofoam has poor sound insulation properties. This material therefore seems rather unsuitable to me.

If you plan to add roof insulation later, why choose interior insulation now?

Hello,

thank you very much in advance for the responses.
From a cost perspective, Isover currently seems to be the most affordable option.

My biggest questions at the moment are about the connection to the roof tile level. Is the planned 10mm (0.4 inches) ventilation gap without an underlay sufficient there, or does a sealing against external influences need to be installed?

An external roof insulation is planned only as step 2 along with the roof covering renewal, which may still be delayed for some time. Since I need a cross battens and an installation cavity anyway for the ceiling construction with gypsum boards, I can insulate those areas accordingly right away.

Regards

Are you aware that membranes and adhesive tapes do not last forever?
Then moisture can penetrate into the thermal insulation.
Do you have information from manufacturers regarding their lifespan?

Jochen

Commercially available membranes typically last several decades. The weak points are usually adhesive tapes and glues. However, it should be clear that this type of insulation is generally considered outdated after 20-30 years, and a renovation or replacement will likely be necessary, especially for roofing.

It is unlikely that anyone expects it to last 100 years, and even if it did, it would probably be removed and replaced with something new before that time.

I hardly know any houses or apartments where no work has been done for 50 years or more and everyone is still satisfied.