Insulation insulation filling the voids of a wall?

[Bearpanda]

Hello,
My walls are made of standard 20cm brick + 4cm air space + 4cm flat brick + plaster.
I can not invest in an external insulation (cost) and an internal insulation would reduce quite a bit the surface of my rooms (+ radiators to move + rounded between ceiling and wall to redo !!).

What do you think of the technique I was told about which consists of injecting either Polyurethane, cork or even SLS 20 silicate into this interior void?
What material seems to you most effective?
Do you have an idea of ​​the cost of this type of insulation?
Do I have a risk in terms of humidity for my interior walls if I fill this air gap? Knowing that I don't have a VMC for the moment.

In fact I wonder if
1) either I would like to keep this air space to make the walls breathe, but do not install a CMV (opening of the shower room window after each shower + hood for the kitchen), so not too much loss by the VMC, but almost zero insulation of the walls.
2) either isolate this air gap as explained above (I hope to gain R = 1?) + Install a humidity-sensitive VMC A (being on the Landes coast, I'm not sure that a B is really useful?) with serialization of a mini heat pump to recover calories and heat my cumulus of DHW.

Lots of questions.
Can someone bring me their experience and advise me on the best solution to consider

[Obamot]

Very good question, but first of all it should be specified that the good name would be rather "insulation by insufflation in the technical gap between partition and facade wall".

First point, these foams give off cyanide, so you must be sure to ventilate the rooms well and if possible do not sleep in the premises for a few days ...

The problem is that when you do that, you don't always know where you're going, and if the foam has gone well to meet what you wanted. Because to isolate means that there must be nothing going on, otherwise it is not .... isolated!

If we were able to see through the walls, it would often happen that we have surprises. We can do this by going to examine this space with a camera at the end of a hose that we would pass through a previously drilled hole (this is what we should do ...). Then, it does not remove the thermal bridge between front wall and slab or interior walls, this is where the heat comes out (replaced by cold which penetrates). So if we insulate, it would also be necessary to put expanded polystyrene panels against walls and slab in junction with the facade, to avoid any thermal bridge, and this over a distance of at least 1m (ceilings + walls) from the facade towards the inside. For the top of the tiles, it's a bit tricky, because you have to know what type of coating you have. In many cases, only a synthetic floor can be a fairly good display, see adding carpet or carpet over the entire length (taking on a substantial thickness of foam ...)

Ideally, a thermography of your building should be done, to see what would be the most suitable insulation method.

The foam is especially when you are not an owner and want to improve your comfort amha ... Or to fill specific sections "where you know exactly what you are doing". But in absolute terms, nothing would be worth a facade insulation!

[Bearpanda]

You are probably talking about Polyurethane. ?
But what about cork or SLS 20 silicate foam?

[Obamot]

I don't see how we could put cork between the partition and the front wall in a compact enough way that it prevents air from circulating!

The grains of silicate foam, I do not know but it looks good to me. You should know the performance. However for insuflation, I do not see what advantage compared to cork, since it is not foam but grains (it seems).

In any case, there is no difference with the observations of my previous post. It's so-so ...

But difficult to say without seeing photos with details of the construction and an inventory of fixtures in due form ...

[ach31]

I have this type of insulation, but on one side (south) to the north, I have double (glass wool + placo).
I used vermiculite, I had access through the attic, I drilled the aglo floor at the top of the air gap, (with a hole saw for the switches), a hole every meter approximately, and emptied the bags into a "DIY funnel". We manage to fill the void to the top. It's been 6 years, no humidity, good comfort (this wall is a little colder than the north wall on the surface, but a lot less than before)

[phil53]

It would be nice to change the title!
Actually this one is not serious

[Christophe]

Title changed.

In my opinion, when feasible (continuous vacuum access over the entire wall from the attic), this solution does not allow to isolate properly.

For example, with 2-bedroom breeze blocks you still have at least 3 thermal bridges per breeze block, it does a lot in the end ...

In the case of a concrete floor with slabs, there is a good chance that you will only access the voids of the top floor. Then we can imagine "opening" the concrete blocks near the ceiling, but imagine the work?

By cons this will prevent convection in the void of the wall. So there is a certain gain ... but less than if we used the same amount of insulation in a conventional way.

Finally, I think that the technique would be used in construction if the results (cost / efficiency) were really interesting because it would cost much less than insulating from the outside.

[I Citro]

I am in the same situation.
Several "energy info" advisers offered me the same thing (filling the air space with insulating aggregates such as cork, perlite, vermiculite ...).

The idea is attractive but as far as I'm concerned, I do some electrical work in my house from time to time and I sometimes slip new sleeves into this vacuum. I could not do it once this space filled ...


The postulate of the experts is that the filling makes it possible to immobilize the air space and therefore to eliminate the phenomena of convection.

[Christophe]

I am in the same situation.
Several "energy info" advisers offered me the same thing (filling the air space with insulating aggregates such as cork, perlite, vermiculite ...).

With concrete blocks?
Do you have an "official" page of these advisers that explains the practice?

[ach31]

Who's talking about concrete block?