Eh, give it a rest now. No one has argued that humid air leaks like a sieve straight through the wall. It finds other ways out.
Did you read the links I included? They say that the air tightness in your example is good, i.e., the convection tightness is probably fulfilled in your example. Is it the diffusion tightness you mean? I think the links also gave good explanations here, which are probably backed up by some kind of test from SP's side... Unfortunately, I think few people on the forum have the testing resources to perform the tests you suggest, so one can do as many have done, read up and use a method one believes in, and sooner or later you'll find out if it worked or not...Ribons said:
And as vectrex writes, moisture always gets in everywhere. Making something completely airtight is extremely difficult, both in theory and practice. That's why I personally believe more in the method that it should be able to dry out rather than be completely airtight... The easiest way is to use a method, a system of materials, that someone else has tested.
If you read my post, you'll see that houses with plastic aren't really good. Moisture barriers are only there to sparingly protect an insulation material that is cheap but not particularly good.Ribons said:
Stop fantasizing about diffusion-tight wallpaper glue. It has nothing to do with reality.
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Isn't thermal radiation a physical phenomenon? I don't quite understand the reasoning.Ribons said:
Unfortunately, you seem to have misunderstood the basic physical principles. When heat (not warm air) warms up cooler air in the insulation, it decreases relative humidity. Heat doesn’t carry moisture; it follows with warm air.
Have you measured Rf against the inside of the facade in winter? If not, do so, and you will get the answer to your question. Film-forming organic paint is relatively diffusion-tight, but how does it look at wall/ceiling angles, electrical outlets, and window trims?
If you have ftx that creates overpressure in the house, you should complain about the installation, mej cent should always establish a negative pressure, albeit small.
Self-builder
· Stockholm
· 10 307 posts
I will build completely diffusion-open. Only wood or cellulose. (and a little gypsum on the walls)
Having read through the thread, I’m a bit tired. Someone who has already made up his mind asks for proof from the other side. Several pieces of evidence are presented. These are met with echoing silence followed by renewed claims that evidence cannot be found. Several balanced writers have tried to say that when all components work together in a well-thought-out system, it works.
Heimlaga points out what I have seen in reality during thirty years of professional activity. Thick insulation means that condensation must be managed. If you scrutinize the documents that manufacturers of natural building products themselves produce, the message is the same. The materials in an exterior wall/roof must be more vapor-tight inside than outside. The thicker the insulation, the more important it is. No one recommends overpressure. Everyone agrees that mechanical ventilation must be performed so that there is underpressure in the house. Natural draught ventilation, in my opinion, is the same as no ventilation in houses that are not continuously heated with oil or wood. So I hope we will avoid discussing that kind of ventilation again.
Plastic is a simple way to increase vapor tightness. Done correctly, it works. It is possible to build without plastic too. Done correctly, of course. I have demolished some houses where it has been wrong. Both with and without plastic. Also demolished where it was right. The differences lie more on the outside of the constructions than the inside. If moisture can escape in a sensible way, it works, otherwise not. I refuse to build without an air gap as I have not yet seen such a construction with damage from condensation. However, I have torn down the facade of a "natural" Aneberg house (natural was code for houses without plastic at the time) with lots of black mold on windproof fabric and in the underlying paper pulp insulation about one and a half meters down from the eaves.
Look at the entire construction. Not at an individual detail that perhaps in itself is not the main problem.
Regards, Findus
PS. The natural insulation in the Aneberg house was impregnated with bromine and was to be sorted as environmentally hazardous waste. So much for that naturalness. DS
Heimlaga points out what I have seen in reality during thirty years of professional activity. Thick insulation means that condensation must be managed. If you scrutinize the documents that manufacturers of natural building products themselves produce, the message is the same. The materials in an exterior wall/roof must be more vapor-tight inside than outside. The thicker the insulation, the more important it is. No one recommends overpressure. Everyone agrees that mechanical ventilation must be performed so that there is underpressure in the house. Natural draught ventilation, in my opinion, is the same as no ventilation in houses that are not continuously heated with oil or wood. So I hope we will avoid discussing that kind of ventilation again.
Plastic is a simple way to increase vapor tightness. Done correctly, it works. It is possible to build without plastic too. Done correctly, of course. I have demolished some houses where it has been wrong. Both with and without plastic. Also demolished where it was right. The differences lie more on the outside of the constructions than the inside. If moisture can escape in a sensible way, it works, otherwise not. I refuse to build without an air gap as I have not yet seen such a construction with damage from condensation. However, I have torn down the facade of a "natural" Aneberg house (natural was code for houses without plastic at the time) with lots of black mold on windproof fabric and in the underlying paper pulp insulation about one and a half meters down from the eaves.
Look at the entire construction. Not at an individual detail that perhaps in itself is not the main problem.
Regards, Findus
PS. The natural insulation in the Aneberg house was impregnated with bromine and was to be sorted as environmentally hazardous waste. So much for that naturalness. DS
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Completely agree with your thoughts, I myself live in a healthy timber house.
You can't just focus solely on the walls... a ceiling is often just paneling, which dries out over the years and develops cracks and gaps, so the vapor transmission resistance isn't particularly high there...
Back in the day when there were roll-applied waterproof membranes, vapor passed through the joints and through the roll-applied membrane and began to mold on the paper. A tile is almost completely watertight, and the joints are cement-based and should transport moisture fairly well, yet they mold, not always but sometimes. Just because you've built a house that has held up doesn't mean it would work with another family in a different part of the country, I would think?
Back in the day when there were roll-applied waterproof membranes, vapor passed through the joints and through the roll-applied membrane and began to mold on the paper. A tile is almost completely watertight, and the joints are cement-based and should transport moisture fairly well, yet they mold, not always but sometimes. Just because you've built a house that has held up doesn't mean it would work with another family in a different part of the country, I would think?
The physical performance of buildings differs from how calculation models are intended... Moisture loads on walls, roofs, and floors depend on the climate inside and outside... well, the inside is simpler as there is somewhat less variation than outside. Inside, moisture loads come from people and everything that happens like cooking, bathing, using the toilet, and washing... scrubbing and accidents. Outside, we have the entire nature with rain, snow, wind, etc...
The question of whether or not to use plastic sheeting in a construction can be answered by saying that if the lifespan of the construction is to be equated with the rest of the building, plastic sheeting is not okay.
Thus, only what's mentioned in the thread remains: a moisture-absorbing drying construction... The moisture that must exist for people to feel good must be the basis for the construction. This means that the construction should release moisture to the indoor air during winter so that a too dry indoor climate is not created. At the same time, the facade, roof, and foundation must dry out insulation so that balance is achieved. This means that outdoor air gaps should be designed so that they do not generate moisture loads... i.e., they should be ventilated where no humid air can come in with moist winds, temperature differences, etc.
If the plastic sheeting can be replaced every 30 years and it can be kept intact, an outward-drying construction can still function if the moisture balance in the indoor environment is managed with ceiling and wall materials... but it becomes unnecessary.
When heating, a negative pressure is created in winter, which indeed dries out constructions if they are without sheeting... and the material in the insulation is moisture-balancing.
1. Choose a construction with air gaps and moisture-balancing effect... also choose a lifestyle without silly moisture loads.
The question of whether or not to use plastic sheeting in a construction can be answered by saying that if the lifespan of the construction is to be equated with the rest of the building, plastic sheeting is not okay.
Thus, only what's mentioned in the thread remains: a moisture-absorbing drying construction... The moisture that must exist for people to feel good must be the basis for the construction. This means that the construction should release moisture to the indoor air during winter so that a too dry indoor climate is not created. At the same time, the facade, roof, and foundation must dry out insulation so that balance is achieved. This means that outdoor air gaps should be designed so that they do not generate moisture loads... i.e., they should be ventilated where no humid air can come in with moist winds, temperature differences, etc.
If the plastic sheeting can be replaced every 30 years and it can be kept intact, an outward-drying construction can still function if the moisture balance in the indoor environment is managed with ceiling and wall materials... but it becomes unnecessary.
When heating, a negative pressure is created in winter, which indeed dries out constructions if they are without sheeting... and the material in the insulation is moisture-balancing.
1. Choose a construction with air gaps and moisture-balancing effect... also choose a lifestyle without silly moisture loads.
and the wallpaper almost always comes loose behind radiators over time, as well as in ceiling angles, inner corners, and at the baseboard.The idea of plastic in walls is that the "outer" part, which is insulated, should have a thicker amount of insulation than the "inner," meaning the one that is on the inside of the plastic. If the plastic is to function correctly in its "proper" environment, it should be warmer inside than outside; otherwise, condensation will occur against the plastic. If it is warmer indoors than the outside temperature, the plastic works just fine. But if someone installs a climate control system making it cooler/colder inside than outside without understanding how humidity works, during the summer months, if the sun decides to show itself, moisture will migrate into the wall to stay until autumn, winter, spring, and finally get a little refill during the summer when some want it cool inside again, then the plastic will cause major problems, otherwise not. Now, this comes from someone who doesn't like plastic, knows a bit about ventilation, moisture ratios, can do physics, mathematics, understands Swedish and a couple more languages, but that doesn't matter. The important thing is to adapt the house to the conditions the customer wants to achieve, and if a house with plastic in the walls hasn't had "air conditioning" before, there are several ways to solve it if you want to keep the plastic. You install better ventilation that can handle high humidity; it's not more complicated than that, if you want plastic, that is! It is just as good, if not better, sometimes to use other construction methods than to put up plastic that most likely will be "punctured" quite soon, then that method does not work and causes moisture problems in the construction that has no possibility to ventilate itself precisely because of the plastic! I'm not saying plastic is wrong; I just won't/never will use it! My uncle, who was also a "builder," used it; I had to dig out an attic space with topsoil, and when I was done, the entire house had to be demolished; there was water in all the walls, in this case, thanks to the plastic but with external influence combined with a poorly constructed roof! It is not always black or white; this is a solid gray area that each individual customer should be aware of; it is not fun to have a 5-year-old house completely torn down due to faulty construction with the addition of conveniences (air conditioning) if the ventilation is not supplemented!
There will be no "proof" in any direction whether plastic is good or bad, it is simply not possible to create a template that applies to all constructions, you can always fill a balloon with water and claim that it is currently watertight since it is not leaking right now!