Help for the insulation of a half-timbered house

[leaf]

Hello,

I need your help to determine the choice of my insulation.

It is a half-timbered / cob house with stone stone underlay in Calvados (quite cold and humid in winter), I wish to insulate only from the inside in order to keep the half-timbering outside visible.

I think to put 80 cm of hemp / linen wool to mount on wooden frame as close as possible to the interior wall of the wall, a vapor barrier, counter-bedding, and fermacell plates. in order to obtain an R of around 2.5

I want with this combination to avoid the rotting of timber framing and cob by taking breathable materials.
the old insulation was in plaster + polystyrene which creates some disorders on some woods.

but here is after contact with several suppliers, the opinions are different, some say that there needs to be a vacuum between the insulation and the wall others no need, then no need for a steam brake other than it needs one ....

in short, I am lost.

can you give me your opinion on the choice of materials?
the right combination of air vacuum or not, steam brake ...?

the cost of materials are quite expensive, if you have other combination of materials, please tell me.

thank you in advance for your help.

Furcy

[stipe]

Hello !

Great project!

80 cm of hemp wool inside, that makes walls 1 thick thick ???
Is your house a longère? Because it might turn it into a corridor, right?

How thick was polystyrene before? Was there an air gap, or was the polystyrene stuck to the walls?


Personally I would have put an air gap (and not an air vacuum ... if?) And one by steam. what is the argument for not putting one or the other?

good luck

[dedeleco]

the old insulation was in plaster + polystyrene which creates some disorders on some woods.

I advise to look at current disorders to understand their precise physical mechanism, which quite often is not understood by the pros, who think more by habits and analogy.

All the basic knowledge is in the dew point:
http://fr.wikipedia.org/wiki/Point_de_ros%C3%A9e

So we must avoid that warm indoor air with always a little humidity, comes out by ill-defined paths and arrives to cool on the cold walls and exterior woods to condense its humidity there as soon as the temperature is below the dew point!!
The usual concrete blocks resist condensed liquid water but not wood !!

The vapor barrier is responsible for blocking the passage of hot air with steam to the outside, but it often has leaks and holes.
It's not obvious at all avoid unexpected leaks which condense on the outside cold and wet the entire wall and its wood.
The BBC measures and requires this tightness with great precision, and it risks destroying itself over time, especially on old houses which are easily deformed !!

So, then the opinions diverge, easily, especially if unexplained and justified with the path of this hot air which condenses below the dew point, a quantity of water which is enormous (flooding to believe that it is a leak) if the warm indoor air circulates well !!

The ideal is to require a waterproofing and insulation guarantee by a competent company such as for a wooden BBC house, with checks and measurements by independent expert , considering the thickness of insulation of 80cm that you take, which eats a good part of the interior surface !! !!


So it is not up to you to be competent, but to the company !!

If your insulation is waterproof like for a new wooden house, a slow cold outside air circulation (not interior) between this insulation and the old wall will avoid the accumulation of condensation with unexpected low leakage, but it is not a total certainty, if bad luck.

Especially ask to justify the advice with logical, verifiable and clear physical dew point arguments !!

[Did67]

80 cm (centimeters) or 80 mm (millimeters) insulation ... ???

Even on superpassive in Germany, I don't think we're going to be 80 cm of insulation!

In principle, agree with décéléco. Somewhere clean inside at 20 ° and easily at 80% relative humidity and an outside at - 10 °, there is necessarily somewhere a "front" where we reach the dew point, so where it will condense .. .

Do not "fantasize" too much about "breathing": if you blow on a cold window taken out of your freezer, you will see that your "breathing" will produce ... condensation. Or even if you hiss on the bottle of cold water for the pastis, if you want to experience it in more pleasant conditions.

So for me, no photo: interior side vapor barrier. And as dedéléco says, without flaws, otherwise, it amounts to channeling the flow of humidity on the place of the leak!

I would add then also: if "vapor barrier" which inevitably, if it is effective, slows down the passage of humidity by the walls, it takes a CMV to renew the air otherwise, condensation inside on the corners the coldest! And mold ...

So for me, it's either "vapor barrier" + VMC or indeed, the traditional "breathable" materials but then you have to do it properly: traditional wax wash, etc ... (which naturally act as a vapor barrier! ) on lime plaster on cob .... The assembly of the two techniques often amounts to creating "fronts" of rupture

[leaf]

Bonsoir

First of all thank you for your advice.
I was wrong in the dimension of the insulation, it is not 80 cm but 8 cm.

for stipe: there was a polystyrene of 4 cm see 2 in place (the walls are not plumb) stick to the map so 5 mm air space.

for dedeleco: it's not a company that will insulate, but myself, that's why I don't want to be wrong about my choice. I understood the importance of properly sealing the steam brake properly with a sika 11fc type glue joint.

for did67: ok for VMC, I forgot that one.


according to it is necessary that I stick the insulation on the wall, or vacuum of air?

Furcy

[dedeleco]

according to it is necessary that I stick the insulation on the wall, or vacuum of air?

Since the wall has wooden half-timberings which must not stay in the humidity, which can happen if bad luck, I would tend to keep a minimum ventilation on the inside of the wall with an air space, with possibility for condensation to flow down onto the stone base, with spontaneous drying as before without insulation. The air in this air space is slowly renewing to the outside.
However, the floor of the base in winter is warmer than the exterior wall and the soil of this soil can release water vapor which will condense on the interior of the wall, colder with insulation than without insulation.
It is a possible annoyance, which I have already seen, and therefore avoid any rise of air having passed over the ground which gives off moisture which will then condense on the cold interior wall.

Humidity can come through a circuit that you don't think about and therefore you have to think carefully.

As a precaution, I would tend to keep a lot of hatches in the insulation, waterproof, to inspect the interior condition of the half-timbering, humidity and possible decay, become invisible behind the insulation, so as not to end up with rotten wood without ever being able to know it, in the event of an unexpected leak in an old house which inevitably deforms over time.

It should be noted that if you use an air conditioning and the outside is warmer than the inside like in the USA east coast in summer, 36 ° C outside at 100% humidity and 28 ° C inside, you will have a deluge of condensation in your insulation and accelerated decay as for some US houses, but in France such conditions never happen while in the USA it is very common, with rotten wooden houses in summer !!
This US region happens to have 36 ° C at 100% humidity in summer and -20 ° C in winter !! And the vaporizer must change from interior in winter to exterior in summer !!
!!

[Napo dwarf]

for CMV better a double flow with a high efficiency exchanger
but suddenly the exchangers enthalpy will not serve you anything
you just have to stay on important yield type passivhaus

There are quite a few manufacturers, but Aldes and France Air, to my knowledge, have not obtained this certificate.

I agree with the steam brake on the other hand ventilation becomes an important element it is necessary to control at best the incoming fresh air and to get as close as possible to the temperature of the rooms for reasons of comfort
otherwise for the ventilation network the best is to go rigid and install inspection hatches for cleaning (the pressure losses on rigid are less than flexible and for cleaning the risk of piercing the sheath is almost zero but be careful in the elbows not to go too hard)

heating is done how wood stove, individual boiler?