ᐅ The vapor barrier is discolored brown, and the insulation is damp.
Created on: 4 Feb 2018 17:40
T
tomthomson
Hello everyone,
Our house construction started in 2017, and we are now just before the screed stage. The interior plasterwork, underfloor heating, and so on are currently completed.
Two weeks ago, I noticed a brownish spot on the vapor retarder.
We contacted the building supervisor, cut into the vapor retarder, and the result was damp wood and insulation.
At other spots where we cut in, it was not wet but also not 100% dry—maybe around 95% dry, if that can be quantified.
The building supervisor now suggests that once the screed is poured and the heating system has run through its full cycle, the vapor retarder should be opened, the insulation removed, allowed to dry, and possibly replaced.
This may help at that location temporarily, but perhaps not permanently, since it is unclear where the moisture is coming from (the roof has been inspected, so it cannot be from above).
Construction layers:
Brick
Battens
Breathable underlay membrane
22mm OSB board with tongue and groove for structural bracing
22cm (9 inches) insulation
Pro Clima Intello Plus vapor retarder
Later, there will be a suspended ceiling with gypsum board.
I currently suspect a design issue where the moisture, which can be absorbed by the variable vapor retarder, cannot escape upwards because of the OSB board. However, we need the OSB with tongue and groove for structural bracing.
Are there any experts here who can advise how this could be ventilated? Cutting slots with a router? Or drilling holes? If so, how many slots or holes would be recommended for an area of 10 by 15 meters (33 by 49 feet)?
Or is there no solution at all?
Thank you in advance for your support.
Our house construction started in 2017, and we are now just before the screed stage. The interior plasterwork, underfloor heating, and so on are currently completed.
Two weeks ago, I noticed a brownish spot on the vapor retarder.
We contacted the building supervisor, cut into the vapor retarder, and the result was damp wood and insulation.
At other spots where we cut in, it was not wet but also not 100% dry—maybe around 95% dry, if that can be quantified.
The building supervisor now suggests that once the screed is poured and the heating system has run through its full cycle, the vapor retarder should be opened, the insulation removed, allowed to dry, and possibly replaced.
This may help at that location temporarily, but perhaps not permanently, since it is unclear where the moisture is coming from (the roof has been inspected, so it cannot be from above).
Construction layers:
Brick
Battens
Breathable underlay membrane
22mm OSB board with tongue and groove for structural bracing
22cm (9 inches) insulation
Pro Clima Intello Plus vapor retarder
Later, there will be a suspended ceiling with gypsum board.
I currently suspect a design issue where the moisture, which can be absorbed by the variable vapor retarder, cannot escape upwards because of the OSB board. However, we need the OSB with tongue and groove for structural bracing.
Are there any experts here who can advise how this could be ventilated? Cutting slots with a router? Or drilling holes? If so, how many slots or holes would be recommended for an area of 10 by 15 meters (33 by 49 feet)?
Or is there no solution at all?
Thank you in advance for your support.
Classic case.
Climate membrane with variable SD value sealed from below and above with OSB.
The interior of the house has probably already been plastered?
The moisture from plastering and laying the screed (which you haven’t done yet) rises through the climate membrane into the insulation. However, the amount is so large and the space below is still damp, so the indoor air cannot release moisture. As a result, the insulation wool continues to absorb moisture. One spot is probably affected more due to faulty installation.
According to the manufacturer’s instructions, for example, of the Ursa climate membrane including insulation, it should only be installed after plastering and screed application. Also, residual moisture in the rooms should be low. So first let the building dry, then install the insulation with the membrane.
Climate membrane with variable SD value sealed from below and above with OSB.
The interior of the house has probably already been plastered?
The moisture from plastering and laying the screed (which you haven’t done yet) rises through the climate membrane into the insulation. However, the amount is so large and the space below is still damp, so the indoor air cannot release moisture. As a result, the insulation wool continues to absorb moisture. One spot is probably affected more due to faulty installation.
According to the manufacturer’s instructions, for example, of the Ursa climate membrane including insulation, it should only be installed after plastering and screed application. Also, residual moisture in the rooms should be low. So first let the building dry, then install the insulation with the membrane.
G
garfunkel4 Feb 2018 20:59I would only make the holes after consulting with the site supervisor. I wouldn’t want it to backfire later on.
It is quite possible that the problem only occurs during the construction phase; as saar2and described, that sounds plausible.
It is quite possible that the problem only occurs during the construction phase; as saar2and described, that sounds plausible.
T
tomthomson4 Feb 2018 21:06I also see this as a logical response from saar2and.
Yes, the plaster is already applied on the inside, and the screed will follow next week.
If that is the case, then everything should work again once the moisture in the rooms has decreased, allowing the moisture to be released back into the room or into the drywall of the suspended ceiling.
Do you possibly have a recommended value for the moisture level that should be present within the insulation layer? I am considering installing a permanent meter there, to be able to monitor and take action later, even after the ceiling has been suspended.
Yes, the plaster is already applied on the inside, and the screed will follow next week.
If that is the case, then everything should work again once the moisture in the rooms has decreased, allowing the moisture to be released back into the room or into the drywall of the suspended ceiling.
Do you possibly have a recommended value for the moisture level that should be present within the insulation layer? I am considering installing a permanent meter there, to be able to monitor and take action later, even after the ceiling has been suspended.
G
garfunkel4 Feb 2018 21:32In theory, it should be possible to use a probe with temperature and humidity sensors designed for household use. You simply place the probe between the insulation and monitor the conditions over time. The problem is that eventually the battery will run out.
Permanently powering the transmitter could be challenging due to fire safety regulations, and possibly also due to costs.
This raises the question of how meaningful spot measurements really are—an expert might have insight on this. Individual values may vary. It is generally said that indoor humidity below 70% usually prevents mold, but conditions inside the insulation might be different. I once read a figure of 60% (but I’m not a specialist).
It is also possible that any resulting condensation might occur and not be interpreted correctly.
Permanently powering the transmitter could be challenging due to fire safety regulations, and possibly also due to costs.
This raises the question of how meaningful spot measurements really are—an expert might have insight on this. Individual values may vary. It is generally said that indoor humidity below 70% usually prevents mold, but conditions inside the insulation might be different. I once read a figure of 60% (but I’m not a specialist).
It is also possible that any resulting condensation might occur and not be interpreted correctly.
Once insulation gets wet, it is damaged—regardless of whether it’s fiberglass or mineral wool. The area that was once damp or wet means the vapor barrier was unable to properly vent moisture, which will always result in poorer insulation performance compared to the rest of the structure and could create a thermal bridge. If the wood above is or was already damp, then this indicates a significant amount of water. The screed (floor screed) will be even more problematic than plastering. My advice is to remove everything and, after the screed is installed, put back only the materials that are still usable.
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