Inner insulation sandwich panel: useful air gap?

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Christophe
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Inner insulation sandwich panel: useful air gap?




by Christophe » 16/10/12, 09:23

I have an insulation improvement project.
I have no choice but to insulate from the inside.

For reasons of conditions (humidity), performance and size I go to sandwich panels based on polyurethane (I don't know ... but no eco alternatives there ...).

I intend to use Renotherm panels of which here is the datasheet:
https://www.econologie.info/share/partag ... y9IOKY.pdf

The inside face of the wall is not straight (block of silicate of limestone) I have to make a lathing in order to fix the panels (I thus do not glue them directly).

I was advised to leave this lathing "ventilated". As much as I can understand the need to leave ventilated from the outside (breathable wall), I do not understand the logic when it is done from the inside, on the contrary there will be risks of condensation in the air gap ( wall more after insulation even colder than before).

Here is the product implementation instructions: http://www.unilininsulation.com/be/be_f ... fault.aspx I have not seen talk of air gap ...

ps edit: these are walls that look outwards.
Last edited by Christophe the 16 / 10 / 12, 12: 00, 1 edited once.
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by Obamot » 16/10/12, 10:30

Anyway, the air knives, um ... how to say ... ( : Cheesy: )

Is it an internal wall, which gives the interior on both sides?

Anyway, I think the guy was mistaken about the term "air gap", quite simply ...

Perhaps he wanted to say "technical gap" between the wall and the insulation panels (a term that would have been happier)? If this is the case, the air trapped between the wall and the panels will serve as additional insulation, much like the air present in double-glazed windows ...

And then if that is the case, no, this vacuum must not be "ventilated», But well hermetically partitioned amha (otherwise it's not ... isolated, seen?). If so, is there a door in this wall?

The guy says "ventilated air", like that if you have condensation, he washes his hands, since he will tell you silly if you have a complaint:
- "but I told you that you needed a ventilated air space"

It's stupid but unstoppable! And that means nothing, because if the air space is "ventilated" as much do nothing : Mrgreen: : Cheesy:

As for humidity, it is impossible to answer without any temperature data, without examining the sanitary condition of the walls, etc. You have to ask Bidouille for that. He has field experience in renovation ... (Too bad, we hardly see it anymore ...)

The condensation will rather come from the anchoring of the interior wall in the gable wall (facade) because of a possible cold bridge! This is why it is recommended to put panels on both sides about 1m wide, from floor to ceiling and to drown it in the wall at the time of construction (same for the ground anchoring zones + ceilings on the facade side ).

Otherwise, in the "nut tips" genre, I have better: you just need to put two ventilated air blades, one on each side of the wall! ( : Lol: )
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by Christophe » 16/10/12, 11:03

+ 1 I have exactly the same analysis of the problem.

And the more this air will be immobile, the better the gain of insulation thanks to the air gap! See this fairly complete subject: https://www.econologie.com/forums/isoler-des ... t8971.html

By cons it me not understand:

Is it an internal wall, which gives the interior on both sides?


Well, we generally insulate the walls that give outwards, right? : Cheesy: : Shock: :?: Except rare cases like bathroom and still ...
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by Obamot » 16/10/12, 11:33

Bein if you have a wall and on the other side a large closet or a garage, which in principle are not heated ...

And I think I remember that you have one!

In addition, your intro did not specify that it was a facade wall!

The interest of your panels:
- is that you can grout with polyurethane foam in a spray (all the perimeter in the interstices). And that's great!
- does a "fire test", but I believe that in addition, it is non-flammable (it burns but does not burn!)

So, since it is a facade wall, we must also think:
- to a return of insulation on the partitions overlooking this facade (to avoid as much as possible the risk of condensation, there's no better as a preventive measure, especially if you have a load-bearing wall).
- you can for example put cork on 1m wide (from the front). If it's placo, in principle it's useless, except really big cold bridge ...
- on the ceiling, if it is a slab: extruded polystyrene panels (on 1m). If it is a wooden floor, it is useless.

But why can't you isolate from the facade? Do you think about the "cachet" of your house?
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by the middle » 16/10/12, 11:39

But why can't you insulate by the facade? Do you think about the "cachet" of your house?

This is the big problem of many houses in the Ardennes ...
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by Christophe » 16/10/12, 11:43

Again + 1 :) for the offset it is already planned there are 2 cross walls.

Yes to insulate towards unheated rooms but inefficient method because for often the same surface as much to insulate the external walls of these rooms because there will always remain thermal bridges "interior interior"!

Difficult insulation from the outside because the wall is actually in stone and there is no offset between the cellar and the upstairs wall ... and that eventually I plan to make an extension in a few years on this side of the house ...
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by dedeleco » 16/10/12, 13:01

Before any action, the origin and the mechanism of humidity must be completely understood, without error, quantified in water flow and resolved.
Otherwise big big risk of surprises, even with polyurethane, as an architect, not careful enough, made me the blow, losing in justice, 12 years ago?

In a sealed air space, water accumulates over months, even if it arrives in vapor form, which my architect had not imagined !!!

On the contrary, ventilate if bad luck, little increase the water flow with the humid air which arrives and condenses quickly !!

It is very easy to make mistakes on this thorny issue.

Draining water at its source as far as possible is, so well done, the best solution.

Well done means having understood the physics of this humidity and its journey, without making a mistake. It can be detective work.

Non-flammable means stuffed with brominated organic compounds that we breathe ???
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by Christophe » 16/10/12, 13:17

Ben the fact is, except to completely dry out the air during the construction (idealist) that there is always water in the air!

What is necessary is not to add too much (not at all) to avoid condensation on the wall or insulation ... although with PE or PU the condensation is not so harmful!
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by Alain G » 16/10/12, 13:46

Hi Christopher!


The guy is right, you need to waterproof from the inside and ventilate slightly between the 2 to avoid condensation, this is how we build here in Canada, ditto under renovation.


So batten and insulating panel, polythene film, batten and plasterboard taking good care to seal the film with adhesive tape to seal.

The film is not essential and you can use adhesive tape directly on the insulating panel with the correct good tape.
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by dedeleco » 16/10/12, 13:47

Is it sure that it is condensation of humid indoor air? or the humidity of the ground, which is always damp, which rises viciously in the wall, a case that I had with my architect. (even drained soil is always damp), and moisture rises in a wall, not only by pure capillarity (20 to 30 cm max), but also by repeated evaporation and condensation, in the air which always circulates in a wall, slowly, going up very high then.
It can be vicious, with both at the same time !!!
The beginning of winter is ideal to have this, cold wall outside and the soil even warmer and humid which lets this humid air go up very slowly in the wall, without any arrival of liquid water by pure flooding.
This allows to have humidity with foundations, however well drained, case with my architect !!
The legal expert concluded that it was better to drain outside, which can not solve, given this phenomenon, that of the clouds that make it rain, but, for the walls, ignored by many pros.
It was necessary to drain outward this humid air which rises.

A waterproof plastic sheet stuck on the wall for several days allows testing, depending on the face of the sheet which becomes wet.

So beware of too fast certainties, it's a real job of detective with scientific analysis.
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