Liege for renovation under crawling insulation

[ned54]

Bonsoir a tous

I've been sailing on this for a long time forum to find answers to my questions.
the question is very simple but the answers may be less so
Glass wool insulation between creeping to change
A thickness available of 16 cm, lambri inside and no rain screen on the outside.
I was wondering if the rigid cork panels could not solve the problem of the absence of the rain screen since the cork is water repellent.
When the thickness available, the lambda of the product would allow me to strengthen the insulation without having to raise the roof or remove the lambri.
Thank you in advance for your answers.
Edit
Good. I think I got a little carried away for the lamba du liege
A commercial site indicated 0.032 while the ACERMI certificate indicates 0.040

[ATE.Conseil]

Hello,

Indeed, the thermal conductivity of cork is indeed 0.040W / m².K, suddenly the installation of 16cm of such insulation between rafters gives a R of 4m².K / W... which corresponds roughly to what you already have ... and, is much less than what it would take to make the roof effective ... and that's not to mention the interior vapor brake or the outdoor rain shield

Indeed, nowadays, when we decide to isolate a position, it must be done so as not to return to it for at least 30 years ... therefore consider putting an R of at least 7.0 on the crawling and attic floors .... but also to treat the airtightness of the wall!

To do this you have 2 possible choices:

- Isolate everything from the inside. In this case, it is necessary to place a rain screen - at least - between each rafters. Place the insulation between rafters + the interior complement + vapor retarder + technical sheath (2 to 4cm to pass electricity, allow holes in the placo ... without damaging the waterproofing) + Interior facing
- Do everything from the outside. In this case, you start by placing the vapor brake then the insulation between rafters, then the sarking + rain shield + battens / counter battens + cover.

Why is the vapor brake important?
Because it is this which will prevent the humidity from being blocked in too large a quantity in the insulation and thus create, over time, a premature aging of the product. Air leaks are also responsible for the discomfort and therefore for a higher heating setpoint (Remember the + 1 ° C = + 7% consumption)

Why choose natural products?
Natural products under the roof provide inertia (up to 10-12 hours compared to 1 to 3 hours for mineral wools and barely 1 hour for EPS and PU). This inertia is source of summer comfort under the crawling ... very appreciable when it's 35 ° C outside and barely 22 ° C in the bedrooms.
We can also talk to you about thegray energy saved by switching to natural products, or even to #CO2 offset by storage in the product ... this is the case with hemp, for example

Hoping to have lit your lantern
Philippe DESON
http://www.ate-conseil.eu
http://www.theia-energies.com
http://www.construction-rt-2012.fr

[ned54]

Thank you for this very comprehensive response.
Indeed as for doing things, you might as well do them well.
However I am a little scared by the price that one could ask me if I chose to raise the roof (ridge, banks)

I was also wondering if such an investment would be wise considering my age (55 years old). in any case I would focus on a plant insulator for the phase shift and on your advice for the lambda

I had already done research among local artisans (Toulouse) 2 years ago and I was disappointed by the answers to this question. Hence my request for advice from you
cordially

[ATE.Conseil]

Indeed, the insulation and the repair of the roof is an important item ... it may not be the most essential in your home.
A complete thermal study would remove any doubt and direct you to the most efficient work and therefore with the best return on investment.

Otherwise, you also have to think about the near future ... when you retire, your income will drop by 20 to 30% depending on the case ... and your means to finance a renovation or even fuel to heat the house. may drop somewhat ...

Greetings