Insulation under crawling roof of dead volumes

[Christophe]

I would like to improve the insulation of dead volumes that we have under the roof but I find myself faced with a dilemma: as they are dead volumes (storage, storage ...) unheated, I do not know where to place the 'insulating.

So I made a small diagram of explanations to show the 2 solutions that I think possible:



Erratum: the floor under the roof is insulated:



This insulation will most likely be made with 6 cm of sylvactis, soft wood wool panels of which here is a quote for 8 and 10 cm: https://www.econologie.com/forums/devis-pann ... t8353.html

Solution A: better thermally for the whole house but more insulating surface and an unmanned volume is heated (indirectly) (as at present since the roof is already insulated).

Solution B: easier installation, less insulation surface but there remains 1 thermal bridge through the floor (coming from the lower floor) and through the door.

Note:

- I am not 100% sure that the floor is insulated in the heated room but as they are heated floors I think there is an insulating screed but not on ...

[Christophe]

Up !!

[elephant]

The general principle is that the isolated volume should be as small as possible. (Too bad, your suitcases will be cold) But I do not quite understand your sketch: what is there in your lost attic? a heated room?

[Christophe]

Uh i don't understand you don't understand

There are no lost attics on the diagram. These are roof spaces "under crawling" with access with a door which serve as storage (occasional opening).

Yes, underneath (the "uninsulated ground" part) there is a heated room and 1 end of the garage ... Unheated obviously.

This is why I spoke of the "ground thermal bridge"

[elephant]

Yes, it is not really lost ... but it is hardly habitable ....
So I think you need to insulate the floor of your attic and the wall that separates them from your bedroom. This is how you will get the least losses on the ground and upstairs. However, do not cut the hair in 4: if the whole roof is well insulated, the losses should not be catastrophic.

that said, the comfort of the room must be higher if there is insulation between the room and the attic.

No offense to some of our friends, I would recommend an aluminum foil on the inside.

[Christophe]

Houla I had not planned to isolate the ground ...

Floor + wall = more surface (therefore more expensive) than crawling alone ... So is it really more interesting?

Uh you advise to put a sheet of aluminum between the insulation and the wall to be insulated, is that it?

[elephant]

No photo: isolated or not your roof, when it is very cold will be at maximum 10 ° C, or even less. So there is going to be a call for heat in the room below.
If you insulate your ceiling, the heat stays in the room below and your "space to heat" will be smaller.
The aluminum foil, placed behind a thin surface (gyproc plate) increases the impression of comfort.

[Christophe]

Well not insulate the ceiling ... for the floor will see what we can do.

I didn't know that the aluminum it worked "through the walls" I will test

I await other opinions before making my decision between A and B (or C ????)

[elephant]

if there are planks or plates on the floor of your attic, it should not be rocket science, I think. (well if there is not too much brol)
(I have a certain habit of walking in this kind of places, providence of alarm installers)

[Christophe]

No no everything is 100% concrete! Armed, cellular or cellular ... for the little that I know about construction

That's why insulating the floor will be boring ...