Insulate roof with WLG 032 or 035?, 180mm mineral wool

Hello,

I have an offer for insulation with 180mm mineral wool with WLG 035. Now I am wondering if insulation with 180mm WLG 032 would be more sensible and if it would pay off cost-wise.

I have already played around a bit with the U-value tool and quickly got a U-value of 0.20 and with WLG 032 of 0.18.

Would this difference be meaningful or noticeable?

The roof structure is planned as follows from inside to outside: plasterboard 12.5 (possibly double) - insulation between rafters 30mm (if sensible) otherwise only battens as installation plane - foil (airtight layer) - 180 mm between rafters - underlay membrane - tiles

What would you suggest? The search often only compares the different WLG values in relation to the thickness of the material. I have not found any cost advantages.

Regards Jonny

Hi, I’d say: it depends. How big is the price difference? From an economic point of view, it will pay off late or very late. But I would do it anyway. Keyword: sustainable building Regards

Hello,

of course it is better and costs more, that is clear.
That it is generally better to insulate more is also clear.

However, I don’t quite see the point in handing money over to the "industry" if the insulation (the higher WLG) doesn’t bring any real advantage.

When I compare it on a U-value calculator, the U-value difference is a maximum of 0.03. And whether this makes a noticeable difference is the crucial point for me.

Thanks, regards Jonny

Hello,

..Now I wonder whether insulation with 180mm WLG 032 would be more sensible and whether it would be cost-effective.

The U-value will certainly be more favorable. Whether this actually results in improved cost-effectiveness cannot be reliably answered in a general way. It is often forgotten that while improved insulation reduces transmission heat losses, the demand for domestic hot water preparation remains unaffected.

...What would you suggest? The search often only compares the different WLG with regard to the thickness of the material. I did not find any cost advantages..

Cost advantages should be clearly defined! Presumably, it is about overall cost-effectiveness? Here, the investment required for improved insulation, or the capital service for it, must be seen in relation to the actual demand (capacity, energy) for heating and domestic hot water preparation. There is, among other things, a significant connection with the intended heat generator or energy source. There are quite a few examples where excessive insulation effort is actually not worthwhile!

Best regards.

I have calculated the following variants...

032 WLG without under-rafter insulation -> U-value 0.21 ->1178€

035 WLG without under-rafter insulation -> U-value 0.22 ->786€

032 WLG with 6 cm under-rafter insulation (no 30mm wool found) -> U-value 0.18 -> 2060€

035 WLG with 3 cm under-rafter insulation -> U-value 0.19 ->1300€

035 WLG with 5 cm under-rafter insulation -> U-value 0.17 ->1400€


Heating pellet, currently no solar support planned, also no hot water.

The ten percent lower U-value from 035 to 032 corresponds to a cost increase of 50-60%. (I hope I calculated correctly).

The question: Is this additional expenditure worth it?
At some point the effort will pay off – of course. But how can this be calculated?

Regards

...I have calculated the following variants... The question: Is this extra expenditure of money worth it?

In this case, one probably does not need to calculate. U= 0.17...0.18 will certainly have a positive effect with pellets.

.... But how can one calculate that?

For a layman, this is probably impossible because the "tools" for it are missing.

Best regards.