Hello
After browsing the forum, it's time for a first question.
We currently have a 1950s house with natural ventilation as the only ventilation. We are now planning to extend the house and in conjunction with that, we plan to add extra insulation and install an HRV ventilation system in the existing house along with the extension.
Our heating system currently consists of a water-based system with geothermal heating. In the extension, we plan to have underfloor heating.
Today's wall construction consists of (from inside to outside)
-gypsum wall/wood fiberboard
-plank wall,
-insulation (3 cm)
-building paper
-panel
After additional insulation, the wall would look as follows
-gypsum wall/wood fiberboard
-plank wall,
-insulation (3 cm)
-vapor retarder or vapor barrier
-insulation + framework 19.5 cm
-insulation + framework (cross-laid) 5 cm
-building paper
-panel
My concern is whether to use a vapor barrier plastic as the 4th layer or to choose something that is a vapor retarder like building paper. I assume you should then choose the same solution in the ceiling under the insulation there.
So, what do the byggahus members say, the carpenters I have talked to basically say no plastic in an old house. But I can't understand what distinguishes an additionally insulated wall as per the above from a newly built wall.
/Tobias
After browsing the forum, it's time for a first question.
We currently have a 1950s house with natural ventilation as the only ventilation. We are now planning to extend the house and in conjunction with that, we plan to add extra insulation and install an HRV ventilation system in the existing house along with the extension.
Our heating system currently consists of a water-based system with geothermal heating. In the extension, we plan to have underfloor heating.
Today's wall construction consists of (from inside to outside)
-gypsum wall/wood fiberboard
-plank wall,
-insulation (3 cm)
-building paper
-panel
After additional insulation, the wall would look as follows
-gypsum wall/wood fiberboard
-plank wall,
-insulation (3 cm)
-vapor retarder or vapor barrier
-insulation + framework 19.5 cm
-insulation + framework (cross-laid) 5 cm
-building paper
-panel
My concern is whether to use a vapor barrier plastic as the 4th layer or to choose something that is a vapor retarder like building paper. I assume you should then choose the same solution in the ceiling under the insulation there.
So, what do the byggahus members say, the carpenters I have talked to basically say no plastic in an old house. But I can't understand what distinguishes an additionally insulated wall as per the above from a newly built wall.
/Tobias
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The issue of plastic in old houses is quite a hot topic. Unusually harsh words are often exchanged when the subject is debated here on the forum. My somewhat simplified answer is that you need to use some form of barrier, but diffusion, i.e., moisture movement in vapor phase, is actually the smaller problem. Instead, it is convection that you should be concerned about. Convection is, as is well known, the movement of air, in this case, into the outer wall through gaps, holes, and joints.
Plastic or a more modern membrane - a matter of taste. But you need to have something!
If you want to know more, I recommend a book called "Vandrande fukt strålande värme. Så fungerar hus" written by Carl-Eric Hagentoft, professor of building physics at Chalmers.
Plastic or a more modern membrane - a matter of taste. But you need to have something!
If you want to know more, I recommend a book called "Vandrande fukt strålande värme. Så fungerar hus" written by Carl-Eric Hagentoft, professor of building physics at Chalmers.
what is it insulated with today and will you keep that insulation?
Normally, I believe one should stay as far away from plastic as possible in old houses. We ourselves have a house from the '50s that we are completely renovating, and of course, it will be additionally insulated as well. We will not use any plastic but choose to insulate with a material that works without plastic, i.e., neither stone wool nor glass wool.
We will use linfiber insulation throughout the house.
Normally, I believe one should stay as far away from plastic as possible in old houses. We ourselves have a house from the '50s that we are completely renovating, and of course, it will be additionally insulated as well. We will not use any plastic but choose to insulate with a material that works without plastic, i.e., neither stone wool nor glass wool.
We will use linfiber insulation throughout the house.
Today, there is sawdust as insulation in the attic. In the walls, I've only observed that it is not sawdust but something fabric-like. However, I haven't removed a larger piece of the wall, I've only looked when installing new junction boxes.
I am planning to remove the sawdust and install fiberglass instead, is that a bad idea?
In the walls, I plan to keep the existing insulation and put fiberglass on the outside.
/Tobias
I am planning to remove the sawdust and install fiberglass instead, is that a bad idea?
In the walls, I plan to keep the existing insulation and put fiberglass on the outside.
/Tobias
I haven't heard of Duk either, what kind of duk do you mean Husvagnsthord?
By 'fabric' I mean what you referred to as a vapor barrier at the beginning of the thread. That is, a fiber fabric that is windproof but not completely diffusion-proof. The biggest advantage of the fabric is that it is easy to work with. It is durable and flexible. There is a wide range of manufacturers and price ranges. I insulated the attic of my 1920s house with fabric + fiberglass.
It doesn't matter what material you insulate with, mineral wool, cellulose, flax, or wool. You must still use some form of convection or diffusion barrier. Anything else is a misconception. It is widely spread among readers of Gård och Torp. All insulation manufacturers require this for any warranty to be valid. I have never seen otherwise...
Also, switching from natural ventilation to a heat recovery ventilation system (FTX) reduces the risk of moisture problems in the building envelope.
Regarding the attic! The choice of insulation is not the most important thing; however, you must use some form of convection or diffusion barrier. The additional insulation makes the attic space colder. If warm air then rises from inside, the moisture load increases. You should place the fabric under the wood chips, in the spaces between the rafters. Clamp them on the inside of the bottom frame with thin strips/battens. If you feel comfortable with mineral wool in the external walls, I see no reason for you to fear the same in the attic.
It doesn't matter what material you insulate with, mineral wool, cellulose, flax, or wool. You must still use some form of convection or diffusion barrier. Anything else is a misconception. It is widely spread among readers of Gård och Torp. All insulation manufacturers require this for any warranty to be valid. I have never seen otherwise...
Also, switching from natural ventilation to a heat recovery ventilation system (FTX) reduces the risk of moisture problems in the building envelope.
Regarding the attic! The choice of insulation is not the most important thing; however, you must use some form of convection or diffusion barrier. The additional insulation makes the attic space colder. If warm air then rises from inside, the moisture load increases. You should place the fabric under the wood chips, in the spaces between the rafters. Clamp them on the inside of the bottom frame with thin strips/battens. If you feel comfortable with mineral wool in the external walls, I see no reason for you to fear the same in the attic.
Mineral wool (gullfiber) (_ = 0.035-0.040) cannot absorb moisture, which is why it is always recommended to use a plastic foil on the inside of such a structure. The fibers of mineral wool can come loose and enter the lungs via inhalation. Most mineral wool products contain small amounts of urea and phenol/formaldehyde resin as binders. In case of fire, dangerous gases, mainly phenol, are emitted. Small amounts of silicone and mineral oils are added to reduce dust formation. A lot of energy is consumed during production.Husvagnsthord said:
Flax fiber insulation (_ =0.040) consists of flax fibers that are too short for textile manufacturing. It has good moisture buffering properties, up to 25% of its own weight, and good soundproofing qualities. The material is naturally resistant to pests, tolerates moisture, and doesn’t burn very well. The fibers are glued together with potato starch into mats; to make the mats stiffer, 2-18% by weight polyester fibers are added. To improve fire protection properties, a little borate salt is sometimes added.
Excuse my copy-pasting, but since I have no idea in which moving box I’ve put the books on building ecology, you’ll have to settle for this... I would never use mineral wool in a house, whether new or old... We are renovating our old part with flax fiber + windproof paper in the walls. The extensions we are making will have extra-thick lightweight concrete walls instead. Problem solved...
And if you think a step further, the choice of insulation is one of the most important decisions you can make if you want to feel good in your house. Not to be underestimated indeed...
I think we need to start from the beginning here. What do you think happens to your wall or ceiling if, for example, there's a damage to the roof so that water leaks in? Obviously, mold or moisture damage can occur.
Since you don't know how much water is condensed from the humid indoor air that passes through the ceiling/walls in winter, you also don't know if damage occurs. Unless you stop the air.
Sent from my HTC Vision using Byggahus
Since you don't know how much water is condensed from the humid indoor air that passes through the ceiling/walls in winter, you also don't know if damage occurs. Unless you stop the air.
Sent from my HTC Vision using Byggahus
As stated - a firebrand!
I will settle with noting that t_conradsson trusts mineral wool in the exterior walls. Then he can also feel safe with mineral wool in the attic. And he must have some form of convection and diffusion protection. And that applies regardless of the type of insulation he chooses.
And whether he is building new or renovating old.
I will settle with noting that t_conradsson trusts mineral wool in the exterior walls. Then he can also feel safe with mineral wool in the attic. And he must have some form of convection and diffusion protection. And that applies regardless of the type of insulation he chooses.
And whether he is building new or renovating old.
Thank you for the advice.
I will take a trip to the library and borrow "vandrande fukt strålande värme". We'll see if this makes me more confident or more uncertain about what I should do.
I will take a trip to the library and borrow "vandrande fukt strålande värme". We'll see if this makes me more confident or more uncertain about what I should do.
Hello!
One thing that is often overlooked when discussing whether to use plastic on house walls is ventilation. In older houses, natural ventilation was responsible for air exchange, and nowadays mechanical ventilation with FTX or equivalent is used. Today, plastic serves more functions than just preventing humid air from penetrating and condensing. With the current negative pressure in houses, plastic also acts as a sealant to prevent cold air from being sucked in through the walls, which, of course, also carries moisture. However, to a large extent, it's an economic issue because you are cooling the house and experiencing uncomfortable drafts. Heating is what costs money, which is why additional insulation is used.
So in response to the question, I would say that if you install plastic and then about 200 mm of insulation outside of that plastic, and do this consistently (which can be challenging with detailed solutions), there should not be any issues. Just make sure it's hermetically sealed.
A good way to check this is to apply plastic to all walls and then hire an expert to measure the house's airtightness. This is done with a large fan installed in the exterior door, and you measure how much suction is needed to determine how much it "leaks."
Regardless, I would consult a moisture expert to look at your house before you choose methods.
/Torpalainen
One thing that is often overlooked when discussing whether to use plastic on house walls is ventilation. In older houses, natural ventilation was responsible for air exchange, and nowadays mechanical ventilation with FTX or equivalent is used. Today, plastic serves more functions than just preventing humid air from penetrating and condensing. With the current negative pressure in houses, plastic also acts as a sealant to prevent cold air from being sucked in through the walls, which, of course, also carries moisture. However, to a large extent, it's an economic issue because you are cooling the house and experiencing uncomfortable drafts. Heating is what costs money, which is why additional insulation is used.
So in response to the question, I would say that if you install plastic and then about 200 mm of insulation outside of that plastic, and do this consistently (which can be challenging with detailed solutions), there should not be any issues. Just make sure it's hermetically sealed.
A good way to check this is to apply plastic to all walls and then hire an expert to measure the house's airtightness. This is done with a large fan installed in the exterior door, and you measure how much suction is needed to determine how much it "leaks."
Regardless, I would consult a moisture expert to look at your house before you choose methods.
/Torpalainen