You still paint the ceiling according to a wet room system, and then you get moisture protection. I don't believe in incorporating plastic in houses that are previously "unplasticized." I've always been against plastic. Old houses without plastic often do well, while more modern solutions have some issues. It's so incredibly important that the vapor barrier is executed correctly if it is to function, and no builder can achieve it 100%.Peter_K said:
Build without an air gap, but with a sealed facade panel/roof and a semi-permeable membrane inward. Insulate with eco-fiber or mineral wool. This way, you avoid moisture problems, as the construction is ventilated inward. Exhaust ventilation cooperates. The construction is recommended by experienced moisture experts.
Heat can be transferred in several ways. Radiation (which you refer to as "waves"), conduction, and convection. Moreover, "temperature" is a measure of the thermal energy in something, e.g., the air with associated water in gaseous form. Thus, if the medium (oxygen, nitrogen, water vapor, pollutants) is warm on one side and cold on the other side, energy will also be transferred via conduction. And if it is 100% diffusion tight, no gas passes through the barrier layer, only heat energy.Ribons said:
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No one will find any scientifically acceptable evidence whatsoever on this subject, that's a fact. Whatever will be written, whether it's for or against diffusion tightness in the form of plastic in walls, there will always be someone to provide a counterargument. There are those who can demonstrate that a membrane is tight, but they cannot demonstrate the same on a larger scale in practice. In theory, I agree that if everyone knows how it should be used, it will be fine, but in practice.......... not a chance, it goes wrong in the long run, then you can discuss who made the mistake!Matstj said:
There are guidelines for how tight a house should be both for energy saving and safety from moisture damage. The requirement is 0.3 l/s m2 unless it is adjusted down. 0.11 is what many advocated for. The concerned party must prove that a wallpapered house meets this requirement without a vapor barrier. Until then, the claim is discarded.Pagno said:
I will give you a straightforward answer:Ribons said:
The moisture goes straight through all these layers you list here!
It's only a question of how much and how quickly!
Even plastic bottles let moisture through – this is because the liquid evaporates (as moisture) and seeps through the plastic, so after a certain time the contents of a soda bottle, for example, have changed so much that it tastes completely different despite being stored in the dark and cool.
A denser material to compare with is aluminum (like soda cans) which, as far as I know, can be considered gas/vapor-tight, so metallized plastic may be better in terms of being a barrier.
Regards.
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I also want to add (for those who didn't know) that the basic rule of thumb is that the vapor barrier must be installed so that it is always in the warm zone of the wall/insulation, which should clearly remain above 0 degrees in temperature. Otherwise, you get condensation and ice formation (from warm, moist air coming from inside) before the vapor barrier and thereby a growing accumulation of ice and moisture that conducts cold well, and also creates a breeding ground for unwanted organisms.
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Without insulation, there is less risk of condensation in the wall; the more interior insulation, the greater the risk of condensation in the wall. A modern well-insulated house becomes a mold house after one winter. There is plenty to read about this, if you want to see the truth. SP has a good report regarding interior vapor barriers in well-insulated exterior walls.
Indoor air always contains as much water vapor as outdoor air. When we use a building, we add moisture from people, showering, cooking, green plants, and construction. An adult human expels about 2kg of water per day. The larger amount of water vapor in the indoor air is called humidity addition.
On a winter day at 0C and with normal humidity (80%), the air outside contains about 3.5g of water vapor per m3.
Adding a normal humidity addition in a normal building of about 2g/m3, indoor air contains about 5.5 g/m3. The dew point at 0C is about 4.5g/m3. Under normal conditions, about 1g of water per m3 of air will precipitate on a surface maintaining 0C.
The temperature on the inside of a facade of a modern exterior wall is only slightly higher temperature. This makes interior vapor barriers necessary in a well-insulated exterior wall.
You deceive yourself if you compare expected moisture conditions in a poorly insulated wall. The more insulation, the more important it is to have a vapor barrier on the warm side of the wall.
But as I said, this is demonstrated in many places if you just want to see reality. I recommend SP's website for a more detailed explanation.
Indoor air always contains as much water vapor as outdoor air. When we use a building, we add moisture from people, showering, cooking, green plants, and construction. An adult human expels about 2kg of water per day. The larger amount of water vapor in the indoor air is called humidity addition.
On a winter day at 0C and with normal humidity (80%), the air outside contains about 3.5g of water vapor per m3.
Adding a normal humidity addition in a normal building of about 2g/m3, indoor air contains about 5.5 g/m3. The dew point at 0C is about 4.5g/m3. Under normal conditions, about 1g of water per m3 of air will precipitate on a surface maintaining 0C.
The temperature on the inside of a facade of a modern exterior wall is only slightly higher temperature. This makes interior vapor barriers necessary in a well-insulated exterior wall.
You deceive yourself if you compare expected moisture conditions in a poorly insulated wall. The more insulation, the more important it is to have a vapor barrier on the warm side of the wall.
But as I said, this is demonstrated in many places if you just want to see reality. I recommend SP's website for a more detailed explanation.
Sorry, you have a lot of good facts there but draw some incorrect conclusions and miss simple details.per solsjö said:
With the same indoor air as before, no barrier and less insulation - you're just moving the condensation closer to the room and wasting more energy due to poor insulation, among other things...
-In the end, you might get ice formation on the inner wall.
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#70 and #71 are clear examples that it is possible to "disprove" or disagree with each other, the point is that they are both right! But with the right ventilation system and other factors, these two posts can work. #70 it's enough to have an air conditioning system to "ruin" the warm air/wall that lies with little insulation against the plastic layer, cooling inside creates moisture with properly installed plastic! #71 ice formation on the inner walls will probably never occur as long as there is air circulating in the building... If, against all odds, ice forms on inner walls, it is a catastrophic flaw in the basic construction. Overall, it is the manufacturer who cannot live up to delivering an acceptable complete system for plastic in the wall; it cannot be the case in today's society that one is allowed to deliver a substandard product to the construction market and call it good. If all builders reject these systems, the manufacturers will be forced to develop acceptable systems that cannot be incorrectly installed, but it is easier to blame other occupational groups, improvement is needed, or if you now want plastic in the walls, the insurance companies should raise the deductible by astronomical amounts, then maybe customers will react! "No to plastic" but intelligent enough to know that with the right use it works!
Of course, Pagno, that's what I'm trying to say.Pagno said:
But it's the consequence of removing the insulation, if it's cold and damp enough I don't even know if hurricane strength would be enough to prevent ice formation in all corners.
Sure, it’s a catastrophic flaw if that's the case - but I'm talking about extremes here, as the thread has developed towards the extremist edge
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· västra götaland
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I would like to add something here. I have worked for many years with moisture damage mostly, for insurance cases. In a construction where you have studs and mineral insulation (fiberglass, stone wool, rockwool, or other names they are called), there is no moisture migration in the insulation. The moisture remains in the insulation and can cause damage. Indoor air is almost always more humid than outdoor air. Moisture always travels from the warm side to the cold side, which is why there is a vapor barrier on the inside. Since moisture does not travel in these modern insulating materials, condensation occurs at the so-called condensation point, which simply put is a bit inside the insulation (if there is no vapor barrier). Therefore, it is very important to have plastic in modern construction with studs and fiberglass or stone wool. Just as important is to not puncture the plastic and to make sure it is really sealed around sockets, penetrations, etc. This can be partly solved by, after you have plasticized inside of the studs and insulation, attaching an additional stud that is deep enough to mount a socket without puncturing the plastic, i.e., a 45x45mm.
Older materials such as flax, logs, sawdust, newer insulation based on cellulose, etc., allow moisture to naturally travel through the material. You can have 30-40 cm of cellulose insulation without risking the moisture stopping in the insulation and then causing moisture damage, if there's no plastic sealing it. That said, it is not always wrong to have plastic. In a newly renovated bathroom in an older house, I would install plastic in the ceiling inside the ceiling panel to reduce the increased moisture load due to showering, etc. Today we have a completely different moisture load from bathrooms than in the past when people may not have showered and bathed as often as now. There is no reason to have plastic in an older house except possibly as mentioned above. Not so much because it's wrong, but more because it's not needed. Then it can absolutely be wrong with plastic in an older house. Older houses often have spots where water runs, splashes in from rain, etc., but this dries out year after year without causing damage. Part of the drying is simply done by slight drafts here and there, both from indoor air going out, but also from outdoor air being drawn in, or outdoor air going through and out on another outdoor side. This keeps it naturally "dry" or at least dry enough not to cause damage. In such a house, it would absolutely not be good to install plastic indoors if, for example, you decided to add insulation inward in the house and then plaster or pull new wiring or whatever you had planned. Much of the "draft" would have disappeared due to the plastic.
A problem you can have with modern construction with plastic, fiberglass, and regular studs can be an unheated house, such as a summer cabin. It becomes minus 20 degrees outside for several days. It might not become minus 20 degrees inside, but it reaches several minus degrees. The next day there is a significant thaw, and maybe 15-20 degrees on the south wall. Then you have moisture traveling from the warm side to the cold. Which here becomes from outside to inside! The moisture goes into the wall, and either it stays in the insulation, or if it’s a thin wall, it can get all the way to the plastic where it obviously goes no further.
Older materials such as flax, logs, sawdust, newer insulation based on cellulose, etc., allow moisture to naturally travel through the material. You can have 30-40 cm of cellulose insulation without risking the moisture stopping in the insulation and then causing moisture damage, if there's no plastic sealing it. That said, it is not always wrong to have plastic. In a newly renovated bathroom in an older house, I would install plastic in the ceiling inside the ceiling panel to reduce the increased moisture load due to showering, etc. Today we have a completely different moisture load from bathrooms than in the past when people may not have showered and bathed as often as now. There is no reason to have plastic in an older house except possibly as mentioned above. Not so much because it's wrong, but more because it's not needed. Then it can absolutely be wrong with plastic in an older house. Older houses often have spots where water runs, splashes in from rain, etc., but this dries out year after year without causing damage. Part of the drying is simply done by slight drafts here and there, both from indoor air going out, but also from outdoor air being drawn in, or outdoor air going through and out on another outdoor side. This keeps it naturally "dry" or at least dry enough not to cause damage. In such a house, it would absolutely not be good to install plastic indoors if, for example, you decided to add insulation inward in the house and then plaster or pull new wiring or whatever you had planned. Much of the "draft" would have disappeared due to the plastic.
A problem you can have with modern construction with plastic, fiberglass, and regular studs can be an unheated house, such as a summer cabin. It becomes minus 20 degrees outside for several days. It might not become minus 20 degrees inside, but it reaches several minus degrees. The next day there is a significant thaw, and maybe 15-20 degrees on the south wall. Then you have moisture traveling from the warm side to the cold. Which here becomes from outside to inside! The moisture goes into the wall, and either it stays in the insulation, or if it’s a thin wall, it can get all the way to the plastic where it obviously goes no further.
You should never let the temperature in the house drop too low; low temp = high RH, risk of growth on surfaces and furnishings. Keep 15°C in the summer cottage, yes it costs, but so do microbial damages with associated odor problems. Strange that the discussion about vapor barriers is still ongoing. I would never settle in a house with insulated walls without a vapor barrier; the thicker the insulation, the more important the moisture barrier. But by all means, ditch the vapor barrier in a modern well-insulated wall, then the moisture damage investigator will have plenty of work in the future as well.
The old houses without issues you mention are poorly insulated. In this case, the insulation level was increased, and then condensation problems arise in the attic if the attic floor is not airtight.