Total renovation - Install vapor barrier or not??

[ricebridge]

I am completely deflated and have been so all day and evening.

Before I respond to your statement, I want to know why you think indoor humidity would be "good" for the construction. What are your actual (not emotional) arguments?

I have already outlined my arguments, which are highly factual. I don't understand where you get the idea that it's emotional to suggest building in a similar way to how the house was originally constructed? It's precisely the laws of physics that I base this on. Retrofitting with plastic to make it airtight is difficult and risks increased moisture load where moisture sneaks past. Therefore, one prefers hygroscopic insulation material with a vapor barrier that helps to ventilate the moisture out. How do you deduce that the moisture would accumulate in the walls from that?

Again, in what way has the moisture load increased besides us showering more?

Sorry if I upset you by stating that we might have to accept some heat waste in old houses. But I speak from my own experience. Of course, we should try to minimize the waste. But one cannot expect an old house to function like a new one.

This is the essence of the more sweeping expression about renovating in line with the old style. Had I thought that this expression would be perceived as an emotional argument, which it is not, I would have phrased myself differently. I'm not so foolish to believe one can wish away the laws of nature.

 

[Daniel 109]

No, I don't think that was the meaning of what justus wrote.
I think he's writing that you shouldn't have two impermeable layers enclosing a part of the construction (in this case, enclosing the insulation and surrounding wood in the attic between impermeable plastic and impermeable roofing felt).

And I agree with that, I believe you do too.

You cannot dry out material against a damp space.

 

[Mikael_L]

What bothers me when reading threads like these is that someone always comes in and writes that if you just choose cellulose-based insulation, everything will be fine and dandy. As if such insulation is magical in some way.

But the truth is that there is no magic. The only thing that happens is that you add insulation with a little more moisture-buffering ability, meaning the insulation (if it's completely dry) can absorb a few grams of water or water vapor without the relative humidity reaching the level where mold starts to grow. But for this to work over the years, the moisture must then dry out, meaning in practice, the house should probably have a yearly cycle where the moisture level rises during one period and falls during another. And it only works as long as the drying out is stronger than the moistening, and there are materials that can absorb all the moisture we've let into the building component. Older houses almost always work according to this principle and often worked very well.

But anything that changes the balance can be dangerous. And some houses are close to the limit of what they can handle. The old houses had poor insulation, meaning heat extended far into the roof and wall construction and drove out moisture effectively; in old houses, there was a fire burning all year round, as the kitchen stove was constantly used for cooking, and in slightly newer ones, the oil burner ran almost constantly, for heating and hot water. There was a heat source in the houses and a draft in the chimney year-round. Nowadays, our moisture load has probably increased. We exhale about 1kg of water vapor per person per day; that remains the same. But there is more showering, more pasta boiling, etc. Clothes are more often hung indoors than before, or run in a dryer.

Today's houses with today's energy requirements are probably not possible to build without maximally preventing moisture from entering the construction, and cellulose fiber does not change this.

If you have an old house that has functioned all this time, you can naturally choose not to change the winning concept. You neither remove, add, nor replace insulation. And if you replace sawdust/wood shavings insulation, you naturally replace it with cellulose, not mineral wool. And you don't start showering more than previous generations did.

In this way, you maintain a winning concept, where the only cost is the heating expense.

But if you want to modernize things... then it starts to get tricky. Cellulose insulation can be the solution, but it is absolutely no guarantee.

 

[Mikael_L]

You cannot dry out material against a damp space.

It may not be 100% of the time, year-round, higher vapor pressure in the dwelling than in the attic. So at some time of the year, it might be able to dry out, releasing moisture into the living space.

No, I don't like this, but it has worked reasonably well in some older houses.

I think it's at least better than two tight layers, as that almost guarantees problems.

 

[Daniel 109]

It can also be mentioned that moisture problems were not uncommon in the past either. But the problem houses do not remain.

 

[guggen]

What bothers me when I read threads like these is that someone usually comes in and writes that simply choosing cellulose-based insulation will make everything perfect.
As if such insulation is magical in some way.

But the truth is, there's no magic.
The only thing happening is adding insulation with a bit more moisture-buffering capacity, meaning the insulation (if it's completely dry) can absorb a few grams of water or water vapor without the relative humidity reaching the level where mold begins to grow.
But for this to work over the years, this moisture must then dry out, meaning in practice that the house likely needs an annual cycle where the moisture content rises during one period and falls during another.
And it only works as long as the drying process is stronger than the moistening, and there is material that can absorb all the moisture released into the building component.
Older houses almost always operate on this principle and often work/worked very well.

But anything that changes the equilibrium can be dangerous. And some houses are close to the threshold of what they can handle.
Old houses had poor insulation, meaning heat reached far into the roofs and wall constructions and effectively drove out moisture; in old houses, there was year-round heating, as the kitchen stove was always used for cooking, in slightly newer ones, the oil furnace ran almost continuously for heating and hot water.
There was a heat source inside the houses and provided a draft in the chimney all year round.
We have likely increased our moisture load nowadays. We breathe out about 1 kg of water vapor per person and day; that's the same. But there's more showering and more pasta cooking, etc. Clothes are hung indoors more than before, or they go in the dryer.

Today's houses with today's energy requirements are probably impossible to build without maximally preventing moisture from entering the structure, and eco-fiber doesn't change this.

If you have an old house that has functioned through the ages, you can naturally choose not to change the winning concept.
You neither remove, add, nor replace insulation. And if you replace sawdust/wood shaving insulation, you naturally replace it with cellulose, not mineral wool.
And you don't start showering more than past generations did...

In this way, you maintain a winning concept, where the only price is the heating cost.

But if you want to modernize things..., then it becomes tricky. Cellulose insulation can be the solution, but it's definitely not a guarantee.

I think the problem is equally significant with the handful of individuals who, without argument, always have to point out that an older structure cannot be maintained without renovating the house into something completely airtight.

The system with ventilation from outside (air gap or behind panel), mineral wool, and a completely airtight interior works very well in newly built houses or where the renovation is extensive enough to change the structure.
In the same way, hygroscopic solutions evidently work excellently. This also requires an airtight interior for proper function.
After all, with increased tightness and insulation, the need for changed ventilation often arises.

Having insulated with all methods in older, sometimes really old houses, the problems have always fundamentally been in the foundation or upper floors due to reduced supply of outside air. This has (apart from the foundation) been remedied with improved/changed ventilation, regardless of whether insulated with mineral wool or wood fiber. What always comes back to is the importance of air tightness, and this applies to both methods.

There is no silver bullet, and when intervening in any old house, as they are always unique, a measure of engineering is required.
My point was and is that it's never black or white.

Justus's solution for TS in this case seems correct. I have personally conducted such a project more than once with very good results.

 

[ricebridge]

@Mikael_L You are right in much of what you say in post #33. I agree that there is no magical solution — on either side. We should be humble about the fact that not even today's building codes have the absolute truth: the impact of moisture load wasn't understood until the 1990s, for example.

But I don't agree with everything. I don't agree with you about the moisture load. We may cook more pasta today — but less potatoes. Long cooking of dishes like mashed root vegetables or pork doesn't occur in the same way. At the same time, we use the kitchen fans when we cook — even if we’re just boiling pasta (at least I do).
Meanwhile, we have fewer residents per family and square meter = less exhaled air per square meter. The fact that we like it warmer indoors today actually helps to dry out, not increase the moisture.

Clothes that are air-dried are said — according to information I have not been able to double-check, I admit — to be the single largest cause of moisture damage in basements. Correct me if I'm wrong, but even that moisture has to go somewhere. But hanging clothes on a line indoors was done in the past, before there were clothes dryers.
We still hang laundry outdoors on sunny summer days — at least we and many others do — because it becomes fresh and is environmentally friendly.

The moisture from clothes dryers goes straight out, so the moisture from the laundry room has probably neither increased nor decreased.

 

[guggen]

Currently working on a sloped roof without an air gap, originally filled with peat. Modified with partial mineral wool without plastic. Now I have replaced the mineral wool with Isolina, peat remains around where I could reach. Put Isolina's paper on the inside. [link]

Does this seem like a reasonable solution? Or is it better without paper???

I converted a cold attic with massive mold infestation and a relative humidity of 90% (insulated with mineral wool in the beams without any barrier...) A few years ago to a warm attic. The house is a timber-frame house from the early 1700s. I sanitized, insulated with a reasonable amount of Isolina, and made it airtight with Isolina's paper. I got the relative humidity down to an average around 50 and haven't had any problems. So it worked excellently. I used Isolina because I was curious, but based on my experiences today, I would definitely have chosen wood fiberboard. Partly because I think the linen smells somewhat, and wood fiberboard is easier to work with. I also cannot see what advantages linen would have over wood fiber.

 

[JohanLun]

I converted a cold attic with massive mold infestation and RH at 90% (insulated with mineral wool in the joists without any barrier...) A few years ago to a warm attic. The house is a half-timbered house from the early 1700s. I sanitized, insulated with a reasonable amount of isolina, and airtightened with isolina's paper. I got the RH down to an average of around 50 and have not had any problems. So it worked perfectly. I used isolina because I was curious, based on my experiences today I would definitely have chosen wood fiberboard. Partly because I think the linen smells somewhat and wood fiberboard is easier to work with. I also can't see what advantages linen would have compared to wood fiber.

Thank you. Then it feels like a reasonable solution. I think the paper should work as a vapor brake. The risk is that roofing felt is much denser... In my case, I chose isolina because it was what was available to buy at a reasonable distance.

 

[Cancerman_777]

I have already outlined my arguments, which are highly factual. I don't know where you get the idea that it would be emotional arguments to say that one should build in a similar way to how the house was once built? It is precisely the laws of physics that I base this on. Retrofitting plastic to make it airtight is difficult and risks increasing moisture load where moisture sneaks past. Thus, one would rather choose hygroscopic insulation material with a vapor barrier that helps to ventilate out the moisture. How do you make it out that the moisture would gather in the walls from that?

Again, in what way has the moisture load increased, other than the fact that we shower more?

Sorry if I upset you by stating that we may need to accept some heat loss in old houses. But I speak from personal experience. Of course, we should try to minimize the loss. But one also cannot expect an old house to function like a new one.

This is the meaning behind the more sweeping statement about renovating in line with the old style. Had I thought that this expression would be perceived as an emotional argument, which it is not, I would have expressed myself differently. I'm not so foolish as to believe one can wish away natural laws.

I have never claimed that moisture accumulates in the structure. The problem with continuing to have the construction as it was originally is that then you MUST run the house as they did in that time for those construction solutions to work as intended. Sure, it's hard to get it hermetically sealed, but you still greatly relieve the construction in terms of moisture management. Yes, where it leaks, there will be a higher moisture transfer per sqm than if the whole house were unsealed, but just as you say, these houses are constructed to handle that. It's not like running water is pouring through where plastic is missing.

You didn't upset me at all. Not in the slightest. However, I do contradict your theories as I myself have old two houses that perform at least as well as a newly built one. I speak from my experiences and 10 years of them.

I'm not claiming that you can either, and it applies to wood as well; exposing wood to moisture is anything but good = if you have the opportunity to remove moisture load, then DO IT. Especially if you plan not to heat the air for the birds, not to shower every day, or otherwise run your house like a modern person would.

Regarding my promise; sure, we were more crowded before, and absolutely each person emits moisture which increases moisture load per sqm if you live more crowded. Comparing that with what a shower generates in water vapor or when houses were snow-free 50 cm out from the walls due to waste heat is ridiculous. Sure, there is more person-emitted moisture from a family of 7 people than from one of 4 people, but it is just a microscopic part compared to what modern living and the modern heating philosophy have changed the conditions.

 

[guggen]

It is unlikely that we generate more moisture today than before. Houses are barely used in urban environments; people used to cook all day's meals and there were several people at home all the time.
Or do you have any form of data for that claim?
Then the question of shower/bathtub is obviously crucial, but that applies regardless of when the house was built. If you have a shower, you usually need a different waterproofing layer in the bathroom.

 

[Cancerman_777]

It is unlikely that we generate more moisture today than before. Houses are barely used outside urban areas, before people cooked the entire day's meals and a number of people stayed home all the time.
Or do you have any sort of evidence for that claim?
Then there's the question of shower/bathtub, which is, of course, crucial, but that applies regardless of when the house was built. If you have a shower, you normally need a different seal in the bathroom.

What? Barely used outside urban areas? What would the placement of the house have to do with moisture generated indoors?
So you mean that before, when the population in Sweden was poorer, they cooked three meals a day? They didn't do that. I can say that one of my houses (from the 40s) originally had an outhouse in the same building as the garage/farmhouse and the bathroom wasn't included when it was built.

Yes, you absolutely need that, and a fan, and still moisture from the shower finds its way into the rest of the house. Now, bathrooms are indeed extremely humid environments, but they still work well as guidelines; why not use a vapor barrier there too? Well, because it's not good to have moisture migrating out into and through the structure unless you're heating it unnecessarily. If you can, you should make it as tight as possible.

And once again; if I can choose to spare a wooden structure from moisture, why wouldn't I do just that? I'm still waiting for the answer as to why it would be positive to have moisture migrating out to and through the structure.

 

[guggen]

Now let's calm down a bit.
I meant in urban environments (where most people live). But quite rightly, people are one of the sources that emit the most moisture into the house. If you have a fan in the kitchen and bathroom, that is the absolute primary cause. Today, people are in small numbers in large houses, the exact opposite of before. 7-8 people in a parstuga. And many at home all day working.
You don't have to be an engineer to figure out which scenario loads the house with the most moisture.

Then I don't understand why this is so important in your opposition to vapor barriers in certain constructions. Both classic mineral/plastic and wood/barrier insulate equally well. It's the air tightness that is central.

 

[Cancerman_777]

Let's calm down a bit. I meant within urban environments (where most people live). But indeed, people are one of the sources that emit the most moisture to the house. If you have a fan in the kitchen and bathroom, it is the main reason. Today, people stay in small numbers in large houses, quite the opposite before. 7-8 people in a double cabin. And many at home working all day. You don't need to be an engineer to figure out which scenario burdens the house with the most moisture.

Then I don't understand why this is so important in your opposition to vapor barriers in certain constructions. Both classic mineral/plastic and wood/barrier insulate equally well. It is the airtightness that is central.

Calm down yourself since you mention it you must feel agitated.

Honestly, your post is half unreadable; the main reason for what? Many at home? To my knowledge, based on my parents' upbringing in the '40s, the wife was home, but often not in the house, as she had the task of managing all logistical support and what was needed for it. The children were outside playing. We can counter with how much more time we spend in front of TV, computer, and video games today. So no, your/your assumptions are wrong. Additionally, many, many more work from home today compared to the past. No, you don't need to be an engineer to see how flawed the premises you set up are. It's just looking at some documentaries about the interwar period to realize what's claimed is wrong.

I'm not opposing insulating ability or have opinions about it. What I dislike is drawing moisture into and through moisture-sensitive materials when there are no arguments for why it would be beneficial. Why are you so averse to a vapor-tight construction in an old house that will most likely be run in a modern way? Where do you mean it's wrong/dangerous/bad to prevent moisture from moving out into and through the construction? The advantage of a tight layer is that you can run the house exactly how you want; overpressure or underpressure... your choice as it doesn't matter for the health of the construction. What's wrong with that? As for new solutions, we can look at the single-step insulated houses that were praised by many "knowledgeable" people but are now completely condemned. It was a new technique, which you thought should be tried, and it didn't turn out very well. Or did it? So if there are arguments that moisture in and through the construction is beneficial, I'm wide open to changing my stance, but those arguments are absent.

 

[guggen]

Calm yourself down because you mention it, so you must feel agitated.

Honestly, your post is half unreadable; the main reason for what? Many at home? To my knowledge, based on my parents' upbringing in the 1940s, the wife was at home but often not in the house as she was tasked with handling all household services and what was needed for that. The children were outside playing. We can counter with how much more time we spend in front of the TV, computer, and video games today. So no, your assumptions are wrong. Furthermore, many, many more people work from home today compared to before.
No, you don't have to be an engineer to see how incorrect the premises you're setting up are. Just watch some documentaries about the interwar period, and you'll realize that what's claimed is wrong.

I'm not opposed to or have opinions about the insulation capability. What I dislike is drawing moisture into and through moisture-sensitive materials when there are no arguments for why it would be beneficial. Why are you so opposed to a vapor-tight construction in an old house that most likely will be run in a modern way? Where do you think it is wrong/dangerous/bad to prevent moisture from migrating out into and through the construction? The advantage of a tight layer is that you can operate the house precisely how you want; overpressure or underpressure...your choice as it doesn't affect the construction's health. What's wrong with that?
Regarding new solutions, we can look at the one-stage insulated houses that were praised by many "experts" but are now completely condemned. It was a new technique, which you thought should be tried, and it didn't turn out very well. Right? So if there are arguments for moisture in and through the construction being beneficial, I am open to changing my stance, but those arguments are conspicuous by their absence.

Ok, we're talking about different things; in these contexts, an old house for me is not from the 50s-60s but rather 100+ years old. So if you're not following, it could be because of that.

I have nothing against moisture barriers when, for example, I work with mineral wool; it's necessary. In the same way, a hygroscopic solution is very good, although it can sometimes be a bit of overkill.

No one wants a lot of moisture in the walls; I don't really understand where you got that from. However, wood fiber can handle much more moisture load than mineral wool while maintaining its function. And an old house is practically impossible to make completely tight, therefore under certain conditions high moisture load is experienced (if you don't completely renovate/change the house).

Then you have the cold setting, which is a clear advantage if you want to work with that.
Different conditions require different methods, it's not more complicated than that.

In this case, with a tight exterior and insufficient outer ventilation, a hygroscopic solution serves its purpose.
In another case, it does not.