That eternal question about moisture migration 
It has to do with vapor pressure and related factors. If you have a cooler space, the risk is low that moisture will migrate towards the heat. In such cases, it would have to be extremely humid and have a minimal temperature difference. Hence, there is a moisture barrier inside over warm and humid areas; it's not needed between regular rooms. A double-sided vapor barrier is not a good idea because if moisture gets in, there's a risk it won't get out, and that will definitely cause problems with mold and other unpleasant issues. As for the crawl space, it's another question that has been discussed here many times; moisture is more likely to migrate out through the floor in a crawl space rather than in.
It has to do with vapor pressure and related factors. If you have a cooler space, the risk is low that moisture will migrate towards the heat. In such cases, it would have to be extremely humid and have a minimal temperature difference. Hence, there is a moisture barrier inside over warm and humid areas; it's not needed between regular rooms. A double-sided vapor barrier is not a good idea because if moisture gets in, there's a risk it won't get out, and that will definitely cause problems with mold and other unpleasant issues. As for the crawl space, it's another question that has been discussed here many times; moisture is more likely to migrate out through the floor in a crawl space rather than in.I just noticed that our newly built house has a vapor barrier on the entire long side of the upper floor, even though the lower part (under the windows) of that long wall is an interior wall (the upper part is an exterior wall).
Is this something to be concerned about, or is it insignificant?
I also noticed that the bathroom had vapor barrier foil over the entire exterior wall, but I've removed it now (except for a narrow strip in each corner that I couldn't reach).
/M
Is this something to be concerned about, or is it insignificant?
I also noticed that the bathroom had vapor barrier foil over the entire exterior wall, but I've removed it now (except for a narrow strip in each corner that I couldn't reach).
/M
The bathroom is the place where it is absolutely most important to have a vapor barrier. In a newly built house, you should probably have it everywhere where the climate shell exists. The ceiling is most important since otherwise you get movement of warm humid air upwards to the cold attic where it will condense and cause moisture.
Yep, I've left the foil in the ceiling, but in a bathroom, there shouldn't apparently be organic material between two tight layers (vapor barrier and moisture barrier).
But, what I'm wondering about is whether the foil in the interior wall could cause issues?
/M
But, what I'm wondering about is whether the foil in the interior wall could cause issues?
/M
Read on Gyproc's website. The vapor barrier could remain if you used the new type of vapor-resistant wet room mats as a moisture barrier. Otherwise, it should be removed. I still think the latter feels a bit "olusigt".
Read further on the Boverket's website and found a report.
http://www.boverket.se/upload/publi...er 5/Artikelarkiv/Farlig_fukt_i_badrummen.pdf
This is what it said:
Our most common constructions for exterior walls in bathrooms are completely unsuitable. If such a wall is exposed to water splash (e.g., showers), it takes a few minutes for moisture to penetrate – and the longest time to dry out. This concerns walls made of tiles, waterproofing, gypsum board, and plastic foil. The damage with this construction is "immensely many" stated Anders Jansson, SP (Swedish National Testing and Research Institute).
– The waterproofing is not a moisture barrier, pointed out Anders Jansson, and warned against the primer-free products available on the market.
Removing the plastic foil is also not a solution, he emphasized. When it gets cold outside, condensation forms causing moisture damage to the wooden stud frame. The best – and perhaps the easiest way to avoid the moisture problem is not to place bathrooms against exterior walls.
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Nowadays, gypsum is not placed behind the wall, but even the furring strips are living material that can be attacked. And one cannot escape the problem with the condensation. The best seems to be to keep the vapor barrier to avoid condensation formation and to use new wet room panels and vapor-resistant waterproofing. The wet room panels against exterior walls can be set in 2 layers with the seams staggered, which eliminates a major risk. Just keep your fingers crossed that the new waterproofing is as good as believed...
What do you think about this?
http://www.boverket.se/upload/publi...er 5/Artikelarkiv/Farlig_fukt_i_badrummen.pdf
This is what it said:
Our most common constructions for exterior walls in bathrooms are completely unsuitable. If such a wall is exposed to water splash (e.g., showers), it takes a few minutes for moisture to penetrate – and the longest time to dry out. This concerns walls made of tiles, waterproofing, gypsum board, and plastic foil. The damage with this construction is "immensely many" stated Anders Jansson, SP (Swedish National Testing and Research Institute).
– The waterproofing is not a moisture barrier, pointed out Anders Jansson, and warned against the primer-free products available on the market.
Removing the plastic foil is also not a solution, he emphasized. When it gets cold outside, condensation forms causing moisture damage to the wooden stud frame. The best – and perhaps the easiest way to avoid the moisture problem is not to place bathrooms against exterior walls.
-----------------------------------
Nowadays, gypsum is not placed behind the wall, but even the furring strips are living material that can be attacked. And one cannot escape the problem with the condensation. The best seems to be to keep the vapor barrier to avoid condensation formation and to use new wet room panels and vapor-resistant waterproofing. The wet room panels against exterior walls can be set in 2 layers with the seams staggered, which eliminates a major risk. Just keep your fingers crossed that the new waterproofing is as good as believed...
What do you think about this?
You are not allowed to have wood paneling, plywood, or similar materials behind bathroom drywall nowadays... Wood studs and bracing are fine, but nothing more...
/M
/M
The text below comes from this thread: http://www.byggahus.se/forum/badrum...allmaen-information-foer-badrumsbyggaren.html
Previously, it was common to choose a wood-based material closest to the studs in a stud wall, like raw board, OSB, plywood, or particle board, to create a wall that can withstand heavier mounts. This is not allowed according to BBV. However, you can install the wet room board on an existing solid wood construction (such as a load-bearing plank wall), but you cannot place raw board or similar on a stud wall. Instead, you should make sure to set studs, so-called cross braces, behind the places where items will be hung.
A special case arises with the outer wall in wooden houses, where there is usually a plastic film on the inside of the framework. The panel material on that wall will then end up between the very tight plastic and the waterproofing layer of the bathroom, which can cause problems. The waterproofing under the tiles is not completely tight, allowing small amounts of water to pass through, water which then risks accumulating in the panel material and causing mold and other damage. Among other reasons, this led to a tightening of the industry regulations, which means that the panel material must be moisture-resistant when placed between a waterproof layer and a vapor barrier, and also implies stricter requirements on the waterproof layer's tightness (vapor transmission resistance). All organic material must be positioned behind the plastic, from the inside out.
Previously, it was common to choose a wood-based material closest to the studs in a stud wall, like raw board, OSB, plywood, or particle board, to create a wall that can withstand heavier mounts. This is not allowed according to BBV. However, you can install the wet room board on an existing solid wood construction (such as a load-bearing plank wall), but you cannot place raw board or similar on a stud wall. Instead, you should make sure to set studs, so-called cross braces, behind the places where items will be hung.
A special case arises with the outer wall in wooden houses, where there is usually a plastic film on the inside of the framework. The panel material on that wall will then end up between the very tight plastic and the waterproofing layer of the bathroom, which can cause problems. The waterproofing under the tiles is not completely tight, allowing small amounts of water to pass through, water which then risks accumulating in the panel material and causing mold and other damage. Among other reasons, this led to a tightening of the industry regulations, which means that the panel material must be moisture-resistant when placed between a waterproof layer and a vapor barrier, and also implies stricter requirements on the waterproof layer's tightness (vapor transmission resistance). All organic material must be positioned behind the plastic, from the inside out.
There is a risk of moisture problems when materials are enclosed between two waterproof layers. If you don't want to remove your vapor barrier (which you don't want to do because it becomes untight with other building components unless you are a real skilled professional) during bathroom renovation, then you need to ensure that the bathroom is well-ventilated. The moist and warm air after a shower should not cause any problems. The material that ends up between the layers should be inorganic or at least well-dried.
Convection, meaning airflow through leaks from the inside out in this case, is often a bigger problem than diffusion, referred to as vapor pressure above. Diffusion often passes through porous materials and is a lesser issue in houses compared to leaks, which can quickly cause condensation in colder parts.
Both problems are avoided in a tightly vapor-barriered house with balanced ventilation. Whether you have a vapor barrier or not, there should be negative pressure in the house to prevent moisture migration in the building material.
In the past, fires were used to create negative pressure in this way.
Then they stopped using fires and instead controlled the ventilation.
Today, moisture problems often arise in houses that previously used fires but did not address ventilation when changing the heat source. Often in combination with added attic insulation, which results in a colder attic and condensation due to convection/diffusion.
You could sum up everything above like this: Ventilate, whether tight or not.
Convection, meaning airflow through leaks from the inside out in this case, is often a bigger problem than diffusion, referred to as vapor pressure above. Diffusion often passes through porous materials and is a lesser issue in houses compared to leaks, which can quickly cause condensation in colder parts.
Both problems are avoided in a tightly vapor-barriered house with balanced ventilation. Whether you have a vapor barrier or not, there should be negative pressure in the house to prevent moisture migration in the building material.
In the past, fires were used to create negative pressure in this way.
Then they stopped using fires and instead controlled the ventilation.
Today, moisture problems often arise in houses that previously used fires but did not address ventilation when changing the heat source. Often in combination with added attic insulation, which results in a colder attic and condensation due to convection/diffusion.
You could sum up everything above like this: Ventilate, whether tight or not.