Risk of condensation when installing the vapor barrier

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Magi
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Risk of condensation when installing the vapor barrier




by Magi » 08/12/20, 10:13

Hello everybody

I just registered on this forum following an Internet search which brought me to a related subject but which does not answer my questions.

I am building my timber frame house.
The walls respect the following construction system (int -> ext):

Siding in gypsum board + recycled paper
Against partition wall metal frame insulated in cotton wool + hemp over 45 mm
Hygrovariable vapor retarder membrane SD 0,25 to 25
Wood wool 145 mm
Bracing plate made from wood over 16 mm
[Rain shield with high water vapor permeance]
60 mm wood fiber exterior insulation
Lime plaster in 3 passes (two adhesive mortar + one finishing plaster)

I finished the interior insulation a few weeks ago and am tackling the steam brake.

By rereading the manufacturer's doc I read this:

"To avoid the formation of condensation, the airtight bonding of the XXXXXXX membrane should be done immediately after the installation of the thermal insulation (in rolls or in panels). This particularly applies to work in winter."

The interior insulation work has dragged on and some panels have been in place for almost a year.

What do you think?

Thank you for your help.
Magi
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Magi
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Re: Risk of condensation when installing the vapor barrier




by Magi » 08/12/20, 15:23

I did not have an answer or comment to my questions but I think I found it on my own.

By reading other documentation from the manufacturer (and not the manufacturer as I wrote in the initial post) I see that this is advice for "DIY enthusiasts".

advice to handymen
Install the vapor retarder together with the thermal insulation. If it remains without vapor retarder for a relatively long time in winter, there is a risk of condensation.


So I think this is the case where the house is heated and new insulation installed without vapor retarder for too long. In this case, in fact, the water vapor will migrate from the inside to the outside and condense in the insulation.

In my case, the humidity and the temperature inside and outside the house are almost the same, so it is impossible for the water vapor to condense in the insulation. I checked in an online simulator and called the manufacturer who confirmed to me that in the event of an unheated site there was not too much risk.

So I certainly scared myself for nothing.

Hoping it will be useful for someone else.
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izentrop
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Re: Risk of condensation when installing the vapor barrier




by izentrop » 08/12/20, 15:53

Hello,
Mages wrote: I called the manufacturer who confirmed to me that in the event of an unheated site there was not too much risk.
So I certainly scared myself for nothing.
You are reassured : Wink:
I mostly renovated and did not practice airtightness. It is sure that it is essential in wood frame with an insulation which risks degrading if it takes moisture, much less with brick walls and glass wool.

Just reaching into the core of the insulation will tell you if it has taken in moisture.
If this were the case, would there still be the possibility of heating the room to evacuate it before installing the vapor barrier?
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Magi
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Re: Risk of condensation when installing the vapor barrier




by Magi » 09/12/20, 16:21

izentrop wrote:Just reaching into the core of the insulation will tell you if it has taken in moisture.
If this were the case, would there still be the possibility of heating the room to evacuate it before installing the vapor barrier?

Hello,

Apparently the test with the hand is not sufficient. Wool may appear perfectly dry to the touch and yet be too wet to process. And impossible to know which tester to use to measure this rate or the humidity rate not to be exceeded.
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