We are renovating the surface layer in our house from 1932.
The house:
Vertical plank wall. Over the old plaster, an insulation of 80mm mineral wool has been added and then there is thick plaster, Serporock. In the attic, there is sawdust, and the sloping walls will be insulated with 15cm ecofibers. The heating will be pellets.
Now my question is how we should handle potential moisture barriers in the walls and the ceiling and the sloped roof.
The house:
Vertical plank wall. Over the old plaster, an insulation of 80mm mineral wool has been added and then there is thick plaster, Serporock. In the attic, there is sawdust, and the sloping walls will be insulated with 15cm ecofibers. The heating will be pellets.
Now my question is how we should handle potential moisture barriers in the walls and the ceiling and the sloped roof.
Columns have been written about this topic. Use the search function. Generally, one can say that if you add insulation to an old, leaky house, you should install a vapor barrier. The reason is that with new thick insulation, the warm moisture will not be able to travel out through the wall as it did before. It will condense inside the wall.
The difficulty is in determining exactly how much insulation (what k-value) you can have without it condensing in the wall. In your case, I would guess that the house would benefit from a moisture barrier.
The difficulty is in determining exactly how much insulation (what k-value) you can have without it condensing in the wall. In your case, I would guess that the house would benefit from a moisture barrier.
Thank you for your reply. I have searched the forum but haven't found an answer. Could you help me with links? And then I have some more specific questions.
Slanted ceiling: Age-resistant plastic as advised by the insulation installer. The carpenter has put up the plasterboard so that every screw goes through the plastic. The plastic is inside the studs so it is not compressed.
Roof: we are keeping the old roofing felt that lies beneath the sawdust. Patching here and there.
Walls: I have put up windproof paper. However, it has many holes. How precise should one be here? How do you handle it around the windows?
Slanted ceiling: Age-resistant plastic as advised by the insulation installer. The carpenter has put up the plasterboard so that every screw goes through the plastic. The plastic is inside the studs so it is not compressed.
Roof: we are keeping the old roofing felt that lies beneath the sawdust. Patching here and there.
Walls: I have put up windproof paper. However, it has many holes. How precise should one be here? How do you handle it around the windows?
I'm chiming in a bit...
If you must have a vapor barrier somewhere, you should have it everywhere, and it should be tight. Screw holes, however, you can stop worrying about—it's likely challenging to screw drywall without also piercing the vapor barrier, except if it's part of the construction, which should never be the case here.
Windproofing paper is not a vapor barrier at all but merely windproof, taping can be helpful.
Mixing windproofing paper (non-vapor barrier) and vapor barrier in the same house seems crazy to me, but it's better if everyone comes to their own conclusion about it with their own economic consequences.
Personally, I sometimes wonder if I should start a course on how to search on, for example, Google or forums. It's pure idiocy that it's impossible to find the answer to this question here.
http://www.byggahus.se/search.php?searchid=1468978
/Kent
If you must have a vapor barrier somewhere, you should have it everywhere, and it should be tight. Screw holes, however, you can stop worrying about—it's likely challenging to screw drywall without also piercing the vapor barrier, except if it's part of the construction, which should never be the case here.
Windproofing paper is not a vapor barrier at all but merely windproof, taping can be helpful.
Mixing windproofing paper (non-vapor barrier) and vapor barrier in the same house seems crazy to me, but it's better if everyone comes to their own conclusion about it with their own economic consequences.
Personally, I sometimes wonder if I should start a course on how to search on, for example, Google or forums. It's pure idiocy that it's impossible to find the answer to this question here.
http://www.byggahus.se/search.php?searchid=1468978
/Kent
Kent, Thank you for your polite response
Of course, I have searched and found answers about diff barriers in bathrooms, roofs, basements but not what I wanted to know. Now I've committed a mortal sin by asking about something that someone else has already asked...
Windproof barrier is not airtight, I know that. I was recommended paper by a building conservator. The innermost layer should be 12 times more moisture-proof than the outer layer. The paper fulfills this.
Of course, I have searched and found answers about diff barriers in bathrooms, roofs, basements but not what I wanted to know. Now I've committed a mortal sin by asking about something that someone else has already asked...
Windproof barrier is not airtight, I know that. I was recommended paper by a building conservator. The innermost layer should be 12 times more moisture-proof than the outer layer. The paper fulfills this.
Oh, my. Plastic or no plastic in 1930s houses made of solid wood. I've also tried to get good answers on that. Completely impossible. As a reference, I can tell you how we chose to do it. And our house hasn't started molding yet, at least.
No extra plastic or paper in the old walls, which in our case already contained three layers of wind paper, under the facade and in front and behind an inch of sawdust insulation inside the wall. We kept the old windows and renovated them. Added 5 cm of insulation on the outside.
Extension with plastic and insulation in the walls according to modern methods.
We have torn off the attic on the roof and rebuilt it into a parallel roof with about 50 cm of insulation. We drilled ventilation into the eaves, but not at the ridge. Installed boards for the air gap under the rafters, insulation, and plastic on the inside. We chose to plastic the old roof based on recommendations from Svensk Byggtjänst. The humid air from inside the house is the main reason for moisture in the roof and therefore it's important to stop it before it seeps up into the roof.
So we have mixed plastic and non-plastic in the same house, so we might be crazy. But I've never had any ambition to turn our house into a modern, tight low-energy house. We still want to let fresh air in through the windows and maintain the old natural ventilation in the house. The new windows in the extension have vents.
No extra plastic or paper in the old walls, which in our case already contained three layers of wind paper, under the facade and in front and behind an inch of sawdust insulation inside the wall. We kept the old windows and renovated them. Added 5 cm of insulation on the outside.
Extension with plastic and insulation in the walls according to modern methods.
We have torn off the attic on the roof and rebuilt it into a parallel roof with about 50 cm of insulation. We drilled ventilation into the eaves, but not at the ridge. Installed boards for the air gap under the rafters, insulation, and plastic on the inside. We chose to plastic the old roof based on recommendations from Svensk Byggtjänst. The humid air from inside the house is the main reason for moisture in the roof and therefore it's important to stop it before it seeps up into the roof.
So we have mixed plastic and non-plastic in the same house, so we might be crazy. But I've never had any ambition to turn our house into a modern, tight low-energy house. We still want to let fresh air in through the windows and maintain the old natural ventilation in the house. The new windows in the extension have vents.
Never plastic inside a structure is the only thing most agree on, I think. Otherwise, there are as many answers as there are "askers." I'm currently adding insulation to my garage and not using plastic. When we extended our first house, where the original part was from the 1870s, and our new build was done in 1988, we used plastic according to the -88 regulations on the new construction but not on the old house and not in the roof. That house is still standing today, 21 years later, without any moisture or mold damage. You can't insure against everything, and sometimes things don't work out even if you did everything right, so there are no guarantees, but it seems like we did the same as "pinebar," so maybe it could be a functional method 
The tone in various posts varies here as well, I've noticed
The tone in various posts varies here as well, I've noticed Thank you for your answers. My conclusion is that if everyone responds differently, it's because there's no really right way to do it. As Pinebar says, we won't build for low energy either. It's better to have it a bit too cold if the heating cost becomes too high. The chimney will be warm and contribute to natural ventilation.
We have mold stoppers (holes in the ceiling for ventilation) both upstairs and downstairs. We have masonite sheets to create an air gap. We chose plastic in the slanted ceilings because the new roof is being built in a new way, with thicker insulation, etc. We put wind-proof paper on the exterior walls because it was there before (ordinary paper though) and we didn't want to reduce the diffusion resistance now that we've added insulation and also have "wetter" habits than the original owners. The insulation is on the outside, so the wood wall is warm.
What I don't understand in this matter is that high-quality plastic is recommended. At the same time, it's OK to make holes in it because it's unavoidable???!!!. It's also OK not to put plastic against, for instance, walls that are in the way. Because it's not possible!! What kind of reasoning is that? Either it is truly needed or it isn’t. The plastic should also contribute to any damage due to leaks from the outside being discovered later.
Thanks also to Jan-Å for your reference.
We have mold stoppers (holes in the ceiling for ventilation) both upstairs and downstairs. We have masonite sheets to create an air gap. We chose plastic in the slanted ceilings because the new roof is being built in a new way, with thicker insulation, etc. We put wind-proof paper on the exterior walls because it was there before (ordinary paper though) and we didn't want to reduce the diffusion resistance now that we've added insulation and also have "wetter" habits than the original owners. The insulation is on the outside, so the wood wall is warm.
What I don't understand in this matter is that high-quality plastic is recommended. At the same time, it's OK to make holes in it because it's unavoidable???!!!. It's also OK not to put plastic against, for instance, walls that are in the way. Because it's not possible!! What kind of reasoning is that? Either it is truly needed or it isn’t. The plastic should also contribute to any damage due to leaks from the outside being discovered later.
Thanks also to Jan-Å for your reference.
The most important thing when renovating old houses (according to what I have concluded) is to have good ventilation. If you remove the moist air through ventilation, the issue of vapor barrier/no vapor barrier isn't as crucial.
However, if you seal everything and block the natural draft that usually exists in old houses, you'll encounter problems...
Personally, I have installed a barrier on the upper floor against the ceiling (however, it is not 100% tight due to beams in the ceiling, old walls, etc.).
However, if you seal everything and block the natural draft that usually exists in old houses, you'll encounter problems...
Personally, I have installed a barrier on the upper floor against the ceiling (however, it is not 100% tight due to beams in the ceiling, old walls, etc.).
Of course, you are right Niblom!
The mistake many make when adding insulation to an old house is that they do it too well. They apply thick insulation and seal up holes, cracks, and various defects because they want a comfortably tight and warm house. If you do this, for obvious reasons you must INCREASE natural ventilation. Perhaps install a couple of extra mechanical vents to ventilate away the increased amount of trapped humid air.
This matter of insulation/moisture barrier is not an exact science but depends on a multitude of factors, as everyone above describes.
So those of you adding insulation, use common sense and if you increase your house's tightness without installing moisture barriers everywhere; increase natural ventilation if it is currently inadequate.
The mistake many make when adding insulation to an old house is that they do it too well. They apply thick insulation and seal up holes, cracks, and various defects because they want a comfortably tight and warm house. If you do this, for obvious reasons you must INCREASE natural ventilation. Perhaps install a couple of extra mechanical vents to ventilate away the increased amount of trapped humid air.
This matter of insulation/moisture barrier is not an exact science but depends on a multitude of factors, as everyone above describes.
So those of you adding insulation, use common sense and if you increase your house's tightness without installing moisture barriers everywhere; increase natural ventilation if it is currently inadequate.
Do NOT put plastic in the house (walls) if it is old and without any air conditioning! It traps moisture in the insulation, and the consequences will be mold damage that can harm health! Additionally, do not insulate the attic without first replacing the roof, as there must be a tight underroof so that the water that freezes in winter on the underside of the roof can drain down the underroof and away. It pays off to tear out everything old and repair everything new, then the end result will be the best =)