I have searched online, asked builders, talked to colleges regarding this, but I have yet to receive a single piece of evidence that the vapor barrier serves any function. Most people say it is to prevent water vapor from the living space from getting into the insulation. Okay, I understand the argument as it is, but can the vapor go through 1. wallpaper (usually paper) 2. diffusion-tight wallpaper glue 3. 13mm drywall 4. 12mm OSB and then into the insulation without being reduced???? I don't think so... according to me... just a bluff unless someone can provide me with scientific evidence for this claim. Anyone up for the challenge?
S
sinuslinus
Träskalle
· Östergötlands län
· 6 027 posts
sinuslinus
Träskalle
- Östergötlands län
- 6,027 posts
There was nothing about the vapor barrier. What was the point of that article?
Now you can discuss materials endlessly, I am myself opposed to vapor barriers but the fact is that in most new constructions, with the materials that are used today and the building techniques, a vapor-tight membrane of some kind is often needed. It's not about it being good, rather that most people today can't calculate. We have many factors that come into play when it is needed, or in cases where someone is fortunate enough to have a property constructed by professionals who know and understand how to build with vapor-open methods. The vapor barrier will cause everything from worse moisture damage to a poor indoor climate if used without the right materials in the construction, where we dispute and always will with those who want it. In my opinion, there aren't many advantages to using a vapor barrier, but as long as we have "interesting" regulations, I won't build for others in the future. I myself have an older model house, no vapor barrier, no moisture or mold problems, no bad ventilation or indoor air, I will never build a house with these materials that ultimately do not live up to their promises.
The fact is that I have worked with insurance claims before and most houses with damage are precisely those with vapor barriers; I've only encountered a few vapor-open ones and those have been due to external influence. In some, not all, with incorrect vapor barriers, there has been mold growth and moisture directly in connection on both sides of the vapor barrier, so for that very reason, I want nothing to do with the inconvenience!
There are better ways to build, but you will likely not get an impartial investigation that can prove whether it's good or bad with vapor barriers. The investigations that everyone conducts can simply be manipulated at their own discretion so that they show a good test result in the desired direction, that's how most things work, surprise!
"no to vapor barriers"
The fact is that I have worked with insurance claims before and most houses with damage are precisely those with vapor barriers; I've only encountered a few vapor-open ones and those have been due to external influence. In some, not all, with incorrect vapor barriers, there has been mold growth and moisture directly in connection on both sides of the vapor barrier, so for that very reason, I want nothing to do with the inconvenience!
There are better ways to build, but you will likely not get an impartial investigation that can prove whether it's good or bad with vapor barriers. The investigations that everyone conducts can simply be manipulated at their own discretion so that they show a good test result in the desired direction, that's how most things work, surprise!
"no to vapor barriers"
Very interesting topic. What would also be interesting is to know which materials are good to use when building without plastic film and what insulation thickness is acceptable. As I understand it, to some extent old houses are built on the principle that they are not so extremely well insulated, allowing moisture to dry out... In my (100-year-old) house, previous owners have placed fiberglass and plastic on the inside in some places. Ideally, I would like to remove all of this, but it's not practically feasible, at least not in the near term. However, I believe it is relatively thin and the old wall/ceiling/sheeting hopefully has some form of air gap or sawdust, so my hope is that it will dry out another way, as I find it hard to see how one could make it completely airtight with the plastic, for better or worse. When I am renovating, I have installed studs for electricity etc., on the inside and used Isolina's flax insulation 45mm and their paper behind gypsum and OSB. However, it would be good if there was something cheaper that works well, as I don't want to use fiberglass...
I've read a bit about how to ensure that it's completely airtight if you use plastic film, and the only way that seems reasonable is to place the film and then stud the 45 to pull all the electricity inside the film. I find it hard to believe that all those houses with wiring on the outside of the film are airtight. However, one could, as TS wrote, assume that it works tolerably well in many cases even without the plastic film since in many houses it is likely so perforated that it no longer has much function?
I've read a bit about how to ensure that it's completely airtight if you use plastic film, and the only way that seems reasonable is to place the film and then stud the 45 to pull all the electricity inside the film. I find it hard to believe that all those houses with wiring on the outside of the film are airtight. However, one could, as TS wrote, assume that it works tolerably well in many cases even without the plastic film since in many houses it is likely so perforated that it no longer has much function?
Thanks for that comment😁
It would be at least a little fun to read a proof even though it is probably a bit biased.
I have myself worked with moisture and mold remediation plus energy efficiency for about 5 years.
So I understand where you're coming from.
It would be at least a little fun to read a proof even though it is probably a bit biased.
I have myself worked with moisture and mold remediation plus energy efficiency for about 5 years.
So I understand where you're coming from.
...but if you have a very drafty house with positive pressure indoors, it's not entirely impossible for warm, humid air to be pushed into the walls and condense there, and if you then have plastic, fiberglass, and such good insulation that you don't "dry out" the wall, the mold will come as sure as postal delivery... I would think (without knowing, but based on what I've read) that this doesn't occur in the middle of a wall, but rather in corners, around electrical boxes, window recesses, etc. In the middle of the wall, it's unlikely that humid air will "blow" out. So gypsum and OSB being airtight doesn't guarantee that it's sealed around electrical boxes, etc.
If this is the case, it argues that the plastic only worsens the situation UNLESS you have been very careful around all connections.
I find the thesis below to be interesting reading; I haven't read it just now, but when I did, I recall that their investigations showed that it's difficult to ensure the houses are airtight...
https://docs.google.com/viewer?url=...ftt%C3%A4thetsrapport%2020100929(updated).pdf
If this is the case, it argues that the plastic only worsens the situation UNLESS you have been very careful around all connections.
I find the thesis below to be interesting reading; I haven't read it just now, but when I did, I recall that their investigations showed that it's difficult to ensure the houses are airtight...
https://docs.google.com/viewer?url=...ftt%C3%A4thetsrapport%2020100929(updated).pdf
I actually have some personal experiences that may be relevant in this context.
During an extension we did a few years ago, for various reasons, we ended up completing it to the point of applying plastic on the inside and then put the project on hold for a while. Due to bad tape and nothing holding the plastic together, the taping started to peel after just a few weeks, creating gaps in the seams. After a few more weeks, we noticed that small amounts of water were dripping on the top side of the plastic. The main suspicion was initially that the roof (corrugated metal) was leaking somehow, but after a thorough investigation where we more or less tore out the entire roof from the inside, we determined that it was steam condensing on the inside of the vapor barrier that lay on top of the roof beams. The problem disappeared when we redid the plastic installation with more expensive and better tape.
In our specific circumstances, it was very clear that the plastic was beneficial, or at least that sealed plastic was beneficial. Whether we would have had the same problem if we had been completely without plastic or if the moisture could have somehow dried inward, I don't dare to say, but instinctively, it doesn't seem like it. It was (and is) the plastic that is saving us.
During an extension we did a few years ago, for various reasons, we ended up completing it to the point of applying plastic on the inside and then put the project on hold for a while. Due to bad tape and nothing holding the plastic together, the taping started to peel after just a few weeks, creating gaps in the seams. After a few more weeks, we noticed that small amounts of water were dripping on the top side of the plastic. The main suspicion was initially that the roof (corrugated metal) was leaking somehow, but after a thorough investigation where we more or less tore out the entire roof from the inside, we determined that it was steam condensing on the inside of the vapor barrier that lay on top of the roof beams. The problem disappeared when we redid the plastic installation with more expensive and better tape.
In our specific circumstances, it was very clear that the plastic was beneficial, or at least that sealed plastic was beneficial. Whether we would have had the same problem if we had been completely without plastic or if the moisture could have somehow dried inward, I don't dare to say, but instinctively, it doesn't seem like it. It was (and is) the plastic that is saving us.
Ok. Thanks for the experience. Personally, I don't have a vapor barrier anywhere (built the köimarskalet about 2-3 years ago, as far as I know, no moisture issues).
If a hole is made in the plastic, moisture will almost immediately appear behind it. But there is a difference, as all the vapor pressure then focuses on that leak. There are many studies that demonstrate the vapor resistance of different materials. Through these, it is then easy to calculate the total vapor resistance through several different materials. But even here, as an old designer, I am skeptical. 1+1 is not always two when it comes to combining materials. Moisture is extremely complicated. There are so many factors that influence it. The only thing that is certain is that the more we insulate and seal, the more the risk of moisture problems increases. In new construction, plastic is still preferable, in my opinion. In additional insulation, it should be avoided as much as possible.
I completely agree with the last part. The humidity is indeed 100% dependent on the temperature difference, the heat is directly crucial for the issue because as the heat goes through all the material, you cannot solve moisture migration by just straightening up the houses.
Member
· Västernorrland
· 12 034 posts
If you want to prove something, you need to conduct extensive studies with every type of house and construction, and no one is interested in that price increase, so that's why construction follows general standards. Rigorous tests and calculations are needed to determine if that particular house requires a vapor barrier or not, and as mentioned, it's simpler to build with it in everything.
Gibs and wallpaper might provide as much vapor resistance as a vapor barrier, but on the ceiling, there are often ceiling panels that vapor can easily pass through at the seams, so a vapor barrier is needed.
If you have an FTX ventilation system that many on this site are very interested in, it often creates overpressure that pumps vapor into the walls if they lack a vapor barrier.
If you have an FTX ventilation system that many on this site are very interested in, it often creates overpressure that pumps vapor into the walls if they lack a vapor barrier.
How would you reason here then?
I currently have a toilet on the upper floor that is to be renovated and also have a shower. The house was built in 1929. No vapor barrier today. The attic is additionally insulated with eco fiber. Good exhaust ventilation with a ceiling fan. Should I install a vapor barrier in the ceiling when we renovate the toilet? It feels a bit risky with a shower and no vapor barrier up against the attic.
I currently have a toilet on the upper floor that is to be renovated and also have a shower. The house was built in 1929. No vapor barrier today. The attic is additionally insulated with eco fiber. Good exhaust ventilation with a ceiling fan. Should I install a vapor barrier in the ceiling when we renovate the toilet? It feels a bit risky with a shower and no vapor barrier up against the attic.
I have a house built in 1975 with plastic behind the wall panels, and even if I turn off the air supply fan, set the exhaust fan to max, set the kitchen fan to max, and start the central vacuum (which has the exhaust outdoors), I still can't notice any negative pressure at the front door, not even with a 1 mm gap. So in my house, it doesn't feel like the plastic is properly installed to be of any use at all, and the question is, is poorly installed plastic better than no plastic? If a changed construction technique requires different precision than before, how is that knowledge transferred through several levels to the subcontractor who does the practical work?