Vapor barrier or not?
I am going to remove the plaster on my house from 1948 and add additional insulation with one layer of 45mm and one layer of 95mm insulation.
I am tearing down so that only the wooden plank wall remains on the outer wall, which is about 45mm thick.
Should I install a vapor barrier on the plank wall before I add insulation to the wall?
The wall's construction from the inside out will then be
Gypsum/ Trätex/ Plank wall 45 mm/ Vapor barrier/ 45mm insulation/ 95 mm insulation/ wind paper/ Air gap 20mm/ Panel.
I am going to remove the plaster on my house from 1948 and add additional insulation with one layer of 45mm and one layer of 95mm insulation.
I am tearing down so that only the wooden plank wall remains on the outer wall, which is about 45mm thick.
Should I install a vapor barrier on the plank wall before I add insulation to the wall?
The wall's construction from the inside out will then be
Gypsum/ Trätex/ Plank wall 45 mm/ Vapor barrier/ 45mm insulation/ 95 mm insulation/ wind paper/ Air gap 20mm/ Panel.
I have exactly the same conditions for this summer's project.
I will let the plaster remain and place 70mm tongue-and-groove EPS directly against the plaster, then I will fasten nail battens to the EPS with long screws that go through the plaster into the plank wall.
I will not use any plastic.
A 2" plank wall is a very effective accumulator that can absorb and release any diffusion over the seasons, and I also have 20mm raw timber cladding in the walls that also evens out the moisture balance over the year.
I believe it's more important to have a functioning negative pressure in the house than to have tight plastic.
However, note that these are my own conclusions based on my own research.
I will let the plaster remain and place 70mm tongue-and-groove EPS directly against the plaster, then I will fasten nail battens to the EPS with long screws that go through the plaster into the plank wall.
I will not use any plastic.
A 2" plank wall is a very effective accumulator that can absorb and release any diffusion over the seasons, and I also have 20mm raw timber cladding in the walls that also evens out the moisture balance over the year.
I believe it's more important to have a functioning negative pressure in the house than to have tight plastic.
However, note that these are my own conclusions based on my own research.
so here it is! In a house, we have the same air inside as outside, but we add moisture when we breathe/shower cook potatoes/shower,,,etc. which means we always have more humid air inside than outside. Then it is so that warm air can hold more moisture in gas form than humid air. so when you add extra insulation to the wall, the wall becomes colder inside its existing construction than it was before, which increases the risk that the added moisture condenses in the wall and thus has a much harder time drying out than before. Older houses managed solely because they leaked heat which prevented the moisture from condensing.
Why are you trying to pretend you know things with certainty when either you can't be bothered to read the question or you know nothing about the issue?hagaby said:
When we talk about relative humidity, it is certainly not higher inside than outside in all situations.
And a wall that is additionally insulated on the OUTSIDE (which this thread is about) can not possibly become colder (in winter), on the contrary.
I have approximately the same conditions, a house from '36 with an old facade, plank wall, and tretex internally, and we will install a vapor barrier on the inside.
We will add insulation both inward and outward. Internally, the tretex will remain. On it, we'll put plastic/vapor barrier and then put up studs with 45mm and insulate. In this layer, we will also run new electricity and various other cables (alarm, network, speaker, telephone). Inside will then be OSB and drywall.
Externally, the old facade is torn down to the plank wall. Then I have two options to choose between.
1. West Coast board or similar around 100mm, large boards without studs/thermal bridges
2. Two layers of insulated stud wall 70 (or 95) +45 with crossed studs and windproof paper on the outside.
In both cases, there will then be nail battens 28mm for an air gap and outermost lock panel.
Option 1 should be the fastest to install, but the material might be a little more expensive? The U-value doesn't differ that much, does it?
Will replace/move out all windows and also redo the roof so the eaves and gable overhangs can be adjusted to the new facade thickness.
We will add insulation both inward and outward. Internally, the tretex will remain. On it, we'll put plastic/vapor barrier and then put up studs with 45mm and insulate. In this layer, we will also run new electricity and various other cables (alarm, network, speaker, telephone). Inside will then be OSB and drywall.
Externally, the old facade is torn down to the plank wall. Then I have two options to choose between.
1. West Coast board or similar around 100mm, large boards without studs/thermal bridges
2. Two layers of insulated stud wall 70 (or 95) +45 with crossed studs and windproof paper on the outside.
In both cases, there will then be nail battens 28mm for an air gap and outermost lock panel.
Option 1 should be the fastest to install, but the material might be a little more expensive? The U-value doesn't differ that much, does it?
Will replace/move out all windows and also redo the roof so the eaves and gable overhangs can be adjusted to the new facade thickness.
After much hesitation about how I should proceed, I have decided not to install a vapor barrier.
1. remove the old facade down to the plank wall
2. between the plank wall and the first layer of insulation, I will use vertical battens to create approximately a 20mm air gap.
3. insulate with two layers of criss-crossed insulation
4. then roofing felt, air gap, and facade panel
I have asked carpenters, engineers, and others who should know exactly how to do it, but no one has dared or been able to say, "This is how you should do it."
I replaced the roof last summer, so I extended the eaves and overhang, and new windows are waiting in the garage. That thing with the west coast board sounds interesting; I will take a closer look at it.
1. remove the old facade down to the plank wall
2. between the plank wall and the first layer of insulation, I will use vertical battens to create approximately a 20mm air gap.
3. insulate with two layers of criss-crossed insulation
4. then roofing felt, air gap, and facade panel
I have asked carpenters, engineers, and others who should know exactly how to do it, but no one has dared or been able to say, "This is how you should do it."
I replaced the roof last summer, so I extended the eaves and overhang, and new windows are waiting in the garage. That thing with the west coast board sounds interesting; I will take a closer look at it.
Well written hagaby!
But in this case, it involves external additional insulation, then the existing construction becomes warmer, but the risk then shifts to the new, outer part of the wall which becomes cold.
And without an air barrier on the inside of the construction, you risk releasing humid indoor air into the new cold construction, which could cause problems!
A good idea might be to place a diffusion-open fabric on the existing plank wall and then insulate externally (e.g., 45 + 95mm). This prevents humid air from migrating into the new, cold construction.
-The absolute largest amount of moisture is transported through air movement, only a smaller portion is transported through diffusion.
(e.g., plastic is diffusion-tight)
Then you have a diffusion-open wall ("breathes" as it's a bit romantically called by some) but which is still airtight, which is absolutely the most important!
But in this case, it involves external additional insulation, then the existing construction becomes warmer, but the risk then shifts to the new, outer part of the wall which becomes cold.
And without an air barrier on the inside of the construction, you risk releasing humid indoor air into the new cold construction, which could cause problems!
A good idea might be to place a diffusion-open fabric on the existing plank wall and then insulate externally (e.g., 45 + 95mm). This prevents humid air from migrating into the new, cold construction.
-The absolute largest amount of moisture is transported through air movement, only a smaller portion is transported through diffusion.
(e.g., plastic is diffusion-tight)
Then you have a diffusion-open wall ("breathes" as it's a bit romantically called by some) but which is still airtight, which is absolutely the most important!
The idea with the air gap is that if I place a vapor barrier on the plank wall, the condensation will remain in the plank wall, and that's not good.
If I create an air gap between the plank wall and the new insulation and seal it with wind paper so that it doesn't blow directly through the air gap, the condensation should dry up in that air gap, or am I wrong?
If I create an air gap between the plank wall and the new insulation and seal it with wind paper so that it doesn't blow directly through the air gap, the condensation should dry up in that air gap, or am I wrong?