Is this construction on the exterior wall ok?

[Alex Holmén]

I have received quotes from two builders and both specified the outer walls exactly the same except for two points:
- 22 mm painted falspanel
- external casing of windows and doors
- 34x70 mm batten for air gap
- 45 mm facade board
- 0.2 mm age-resistant vapor barrier
- 34x70 mm installation wall
- OSB plywood
- 13 mm gypsum board

Difference:
- 300 mm lightweight beam frame / 220 mm lightweight beam frame
- 300 mm warm fiber / 220 mm warm fiber
Where one outer wall is 440 mm thick and the other only 390 mm thick.

I wonder if the thinner outer wall is sufficient since the quote is much lower or if it's foolishly cheap not to choose the thicker one.

Sorry if this is a dumb question and if the information isn't enough to get the "right" answer from you. I know absolutely ZERO about constructions and insulations. Thanks in advance.

 

[Kallebo]

I don't know where you live but 35 cm insulation is not wrong..

We have the thicker facade board and an internal insulation layer called Installationsskikt where all the electricity and other pipes have gone.

 

[witten]

I think it is inappropriate to have a vapor brake in a wall this thick as it lets in more vapor into the wall than a regular vapor barrier.

 

[Alex Holmén]

I don't know where you live, but 35 cm of insulation is not wrong..

We have the thicker facade board and an internal insulation layer called an installation layer where all the electricity and other pipes have gone

Västergötland
Do you think the thinner outer wall at 3900 mm is sufficient?

 

[Alex Holmén]

I think it's inappropriate to use ångbroms in such a thick wall as it lets more steam into the wall than a regular vapor barrier.

I have no idea what ångbroms is. Do you think I should bring this up with the builders?

 

[witten]

Have no idea what a steam brake is. Do you think I should bring this up with the builders?

It is a vapor barrier that is not as tight, mainly used in bathroom exterior walls. It is much more expensive.

 

[Kallebo]

Västergötland
Do you think the thinner outer wall at 3900 mm is enough?

Yes, I absolutely think so!

Regarding vapor barrier vs. vapor brake, it's probably connected to the fact that eco fibers are hygroscopic and then a vapor brake is usually used instead of a vapor barrier. There is a lot of discussion about one or the other. I have a vapor brake myself and I feel completely safe with it. The important thing is that it is properly sealed so that moisture cannot get into the structure via convection - i.e., with drafts.

 

[Alex Holmén]

Yes, I definitely think so!

Regarding vapor barrier vs vapor retarder, it probably has to do with the fact that eco fibers are hygroscopic, and then you usually have a vapor retarder instead of a vapor barrier. There's a lot of discussion about one or the other. I personally have a vapor retarder and think it feels completely safe. The important thing is that it is properly sealed so that moisture cannot get into the construction through convection - in other words, through drafts.

Thank you very much, now it feels a bit safer to choose the thinner wall.

 

[witten]

Regarding vapor barrier vs. vapor brake, it probably has to do with the fact that eco fibers are hygroscopic and then you usually have a vapor brake instead of a vapor barrier. There is a lot of discussion around one or the other.

I am reluctant to get into a discussion on the subject but I must point out the obvious lack of logic in letting more moisture into the wall just because it consists of a certain insulation material.

No accusation against you, but the explanation is tossed around without thought all the time. It's like installing a leaking shower mixer just because there's a floor drain.

 

[Kallebo]

... thrown around without thought all the time. It's like installing a leaking shower mixer just because there is a floor drain.

Don't have time to detail all arguments, but a wall with a vapor barrier could release moisture that would otherwise get trapped behind the plastic. Moisture that can come from nail holes, poorly taped joints, or a careless electrician. Moisture can also come from outside... in the summer most have cooling etc.

The vapor barrier is also not as permeable as it sounds, so the shower mixer analogy is a bit off.

 

[Tomture61]

I rarely engage in discussions about the subject but must point out the obvious lack of logic in letting more moisture into the wall just because it consists of a certain insulation material.

No accusation against you, but the explanation is thrown around without thought all the time. It's like installing a leaking shower mixer just because there is a floor drain.

Living in a house built in 2008, in winter it's 20% RH!
I don't know if it's due to the moisture barrier in the walls/ceiling or the mechanical ventilation
(exhaust air heat pump)
Cellulose insulation can also release moisture.

 

[witten]

Don't have time to outline all arguments, but a wall with a vapor barrier could allow moisture to escape that would otherwise get trapped behind the plastic. Moisture can come from nail holes, poorly taped seams, or a careless electrician. Moisture can also come from outside... in the summer most have cooling etc.

No, the moisture migration goes outward in a ventilated wall construction.

 

[Daniel 109]

Live in a house built in 2008, in winter it's 20% RH!
Don't know if it's due to the moisture barrier in the walls/ceiling or the mechanical ventilation
(exhaust air heat pump)
Cellulose insulation can also release moisture.

Not on building materials. Even if some think so.

 

[Tomture61]

Not on construction materials. Even though some believe so.