VMC upside down?

[Did67]

I didn't understand your explanation on the Ytong. :?::?: It is naturally porous to water vapor: water will therefore not accumulate in it ...

I can only tell you one thing: the parts where the Ytong is still "bare" (no finish coating) are very dry (more than the others).

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I'll try to explain myself better then:

- your vapor usually crosses the Ytong, thanks to its porosity ...

- if it's 20% inside and let's say - 10 ° C outside, and if the Ytong is homogeneous, there is a regular temperature gradient in the Ytong ...

- somewhere, in my opinion, your water vapor will condense because it will reach the Ytong layer where the dew point is reached; it will "imbibe" your Ytong; in the example, which will not be every day (- 10 ° C), it must even freeze a few cm under the Ytong on the outside side ???

Honestly: 1) I'm not sure; 2) this is what I understood about glass wool vapor barriers; 3) I am convinced that it "should logically" be the same for the Ytong without being sure ...

PS: obviously, it does not change anything inside, it is dry, because the humidity will "start to pass through", and in the wall, somewhere, it will condense ... I fear for the wall at the long ... Of course, it will dry out when the weather is better, but is it sustainable ????

[Christophe]

Yes, it is a little clearer.

But do you honestly believe that if your thesis was realistic that the Ytong had been "approved" for the building industry for decades (Ytong is 80 years old and has been used by the general public for 30 years)?

Because if I follow you: a Ytong wall is supposed to be damaged with each frost because of the water vapor it contains? I just think that for various physical reasons, "steam" water cannot reach a frozen state in a block of cellular concrete ...

HOWEVER, what is certain is that wet Ytong does not like freezing at all, but the water must be stagnant ABOVE and in this case there is a risk of the block breaking up effectively ...

But this case is, logically, not the case of a house wall ... where then it is that there is a problem of cover or design (serious) ...

ps: interesting but we still deviate really compared to the VMC there ...

[Did67]

Yes, it is a little clearer.

But do you honestly believe that if your thesis was realistic that the Ytong had been "approved" for the building industry for decades (Ytong is 80 years old and has been used by the general public for 30 years)?

ps: interesting but we still deviate really compared to the VMC there ...

Yes, we deviate. Is it approved by being used "naked" so as to allow water vapor to pass through ???

Because if there is a "skin" on the internal side (paint? Plaster?) Maybe this is sufficient vapor barrier? (I remind you that the vapor barrier is a simple sheet of kraft paper on glass wool, but if it is not there, it may condense) ... But if there is skin, then that slows down the evacuation of the vapor and one is returned to the VMC ... There, end of deviation. And since I don't know more, I'll let you dig ...

[Did67]

You have to patent that, and quickly. : lol:

I believe this has been around for a long time: instead of extracting (and therefore having a house in slight depression) we breathe in and we have a house in slight overpressure ... For the rest, not much has changed (if the house is well sealed) ...

View: http://www.preventica.com/dossier_qualite_air.php ("VMC by insufflation") or http://www.techni-murs.com/pages/activi ... lation.php

Advantage: no inversion of the draft when you have a stove or insert ...

[nutt]

Must patent this, and quickly.

I believe this has been around for a long time: instead of extracting (and therefore having a house in slight depression) we breathe in and we have a house in slight overpressure ... For the rest, not much has changed (if the house is well sealed) ...

View: http://www.preventica.com/dossier_qualite_air.php ("VMC by insufflation") or http://www.techni-murs.com/pages/activi ... lation.php

Advantage: no inversion of the draft when you have a stove or insert ...

This is the problem with us! But the companies that offer this equipment are seriously abusing in my opinion !! Finally, I don't know, but the order of magnitude of an installation seems to be around 3000 €. I find that very expensive for a blowing outlet, a box with the motor, filters and a resistance (to heat the air) ... Finally, it is my opinion probably a little simplistic, I admit it. ..

This is the principle also used in operating theaters. Thus the incoming air is perfectly controlled (filters, temperature) and the overpressure prevents parasitic entries (which could bring germs)

[nutt]

ps: interesting but we still deviate really compared to the VMC there ...

Well at least we discover new things!

[Did67]

But the companies that offer this equipment are seriously abusing in my opinion !! Finally, I don't know, but the order of magnitude of an installation seems to be around 3000 €. I find that very expensive for a blowing outlet, a box with the motor, filters and a resistance (to heat the air) ... Finally, it is my opinion probably a little simplistic, I admit it. ..

This is the whole issue of the interventions of artisans.

What is more when it is for "small sites" which do not interest them much ... and for installation mdofications akin to DIY (little new material to install, on which they have reductions from suppliers. ) ...

Now, we have already discussed this elsewhere, we must not forget the charges, the overheads (pubs, van, accounting, etc ...) and that the employee's counter "turns", for his employer, as soon as 'he took service at the depot, including when he's chatting with you ... all with hours with loads ...

Finally, it does not seem to me that the ventilation by insufflation is more difficult to install than a CMV ...

[pieroxy]

Yes forgotten outside

Hygrometer but I would also put a switch (to cut when there is no one) when the humidity rises naturally following a storm and it works for nothing ...

Uh well, evacuating the humidity even of a storm is not "for nothing" is it?

Well it depends! If the air outside is more humid than that inside, it is better to cut everything ...

In fact, you would need two humidity sensors: one inside (wet rooms) and one outside. When it's more humid in it, you have to blow, when it's kif-kif, blow medium just to renew the air. If it's wetter outside, blow the minimum vital!

Obviously it's not that simple, we don't want to dry out the house either, so we need thresholds I imagine, but the principle is there.

That said, I don't know anything about it ;-)

[oiseautempete]

You all seem to forget the primary purpose of CMV: ventilation ... particularly important for health, especially in our modern insulated and airtight housing, riddled with chemical pollution (furniture, construction materials, household appliances) ... Ventilation "to the old one "is pipeau, especially for those who live in regions with radon (granite), often without crawl space in old houses ... A neighbor complained of having mold in his bathroom ( at home no mold although the bathroom is also used for drying clothes): he had cut the CMV, me not ...