ᐅ 5.5 hours of discussion. Breathable or airtight?

Created on: 18 Nov 2015 00:17
3
305er
Hi everyone,

We had a really exhausting day today.
We had two meetings at the prefabricated house center in Mannheim.
In the morning, we visited Keitel-Haus, and in the afternoon, Hanse Haus.

Our problem is: after meeting with Keitel-Haus, we thought we finally had clarity. But Hanse claims exactly the opposite.

At Keitel-Haus, this was our second long discussion, and this time we went into detail with a precise written quote and detailed descriptions of the individual building materials.

Now to the different statements, and we would appreciate your opinions as well.
You have the experience and are independent.

Exterior wall:
Keitel-Haus: vapor-permeable wall WITHOUT a vapor barrier (vapor retarder).
Including:
60mm (2.4 inches) wood fiber insulation board
200mm (7.9 inches) timber frame construction
200mm (7.9 inches) mineral fiber insulation
Wall thickness 29.2cm (11.5 inches)

Hanse: vapor-permeable wall WITH vapor retarder
Including:
150mm (5.9 inches) thermal insulation, thermal conductivity class 032
8mm (0.3 inches) OSB board
125mm (4.9 inches) timber frame construction (with mineral insulation)
8mm (0.3 inches) OSB board
vapor-permeable vapor retarder fleece
12.5mm (0.5 inches) gypsum board

So,
Keitel-Haus says: We build a proper vapor-permeable wall, so without any vapor retarders. This allows moisture to really escape outside, preventing mold growth.
Hanse says: That’s nonsense, there are no houses that can "breathe". We have a vapor retarder because we want to hold back water vapor, i.e., moisture. We don’t want it to enter the wall, as it would cause damage. Without a barrier, mold would eventually develop.

What is correct here?

Topic 2
Heating technology / ventilation:

Keitel-Haus:
They considered our wishes and said that while they think controlled residential ventilation is good, they do not recommend controlled ventilation with heat recovery. I don’t remember exactly why, but there was a lengthy explanation. Anyway, probably because of underfloor heating, we wanted a heat pump.

Hanse:
They tried to persuade us to get a different kind of heat pump and insisted it would be better to have controlled ventilation WITH heat recovery.
It would save energy, and windows can still be opened (which we want, especially at night while sleeping and sometimes in summer).

If I remember correctly, I recently read only negative things about that kind of heat pump, and that it would financially disadvantage us.
Hanse says: Nonsense. If the house is built properly and the system is installed correctly, this kind of heat pump is best, and they can ensure it is the most cost-effective.

Topic 3
KfW 40/55 standards

Keitel-Haus:
KfW 55 is optimal and can be achieved without problems according to our requirements (photovoltaics, underfloor heating, heat pump, vapor-permeable wall).
KfW 40 requires too much effort and is much too expensive. The savings wouldn’t justify it.

Hanse:
KfW 40 or better yet Passive House, since from 2020 Passive House standard is mandatory anyway.
The difference from KfW 55 to KfW 40 would only be about €9000 and corresponds to additional insulation under the slab and roof. No extra technology would be needed, and the savings would be enormous!
Their walls already meet KfW 40 as standard.

Topic 4:
Exterior wall insulation

Keitel-Haus builds with wood fiber insulation board. Styrofoam (EPS) is standard but not recommended because it is vapor-tight. That’s why they offer a better "open" wall.
I know Styrofoam is extremely poor in fire performance. I don’t like it at all.

Hanse:
I had no clear answer; I couldn’t really get details. They just said Styrofoam is not so bad, and their thermal insulation contains some graphite.
It seemed to me like Styrofoam with graphite additives or something similar.

I know, lots of questions again.
I have already spent many hours reading but still don’t feel much wiser.
These topics are very complex and sometimes a bit beyond me.

From the feeling we have, we would build with Keitel-Haus.
The Hanse representative was arrogant and "aggressive." I even almost argued with him because he was unwilling to discuss most points, including providing a written offer. He said he only bothers if he knows you really want to build with them. For me, a comparison makes no sense without different offers and service descriptions to compare.

We also looked at Fingerhut, but after 6 weeks they still haven’t provided an offer. So that’s a no-go for us. The "salesperson" seems to prefer working his side job (entertainer).
Rensch-Haus gave us many verbal promises that everything would be possible (of course, for extra money, everything is possible), but 90% of what should have been standard was not in the service description.
EveundGerd20 Nov 2015 02:12
To compare timber frame construction and monolithic building methods, I recommend having your preferred house design costed by a developer or general contractor.

You can find these companies in model home centers, as well as those you have already visited. It is also possible to contact them online. Just try using search engines to look for the major companies.

Smaller, local firms are usually even more affordable.
305er20 Nov 2015 11:15
Hi, I read through the whole topic several days ago, and just yesterday I looked at the page where your yield is shown.

It sounded like it might not be worth it.

Who did you build with, Wrobel?
From what I understand, the installation level at Hanse Haus is in the timber frame, right?

I think at our prefab home center, they all build with timber frame only.
I contacted many companies, especially architects, but only about 5% responded.
And the local authority wants me to have an architect commissioned beforehand.


------------------------
Duplicate entries/paragraphs deleted for better clarity.
Building expert
wrobel20 Nov 2015 18:31
Hello again

At the installation stage within the stud wall, every cable, water pipe, and electrical outlet penetrates the airtightness layer.
I am building most of my house myself. I contracted the shell construction on the concrete slab to a local carpentry company.

Olli
BastianB20 Nov 2015 19:25
wrobel schrieb:
Hello again

At the installation level within the stud wall, every cable, water pipe, and electrical outlet penetrates the airtightness layer.
I am mostly building my house myself. I contracted the shell construction on the concrete slab to a local carpentry company.
Olli

Note for non-experts:
As far as I know, the airtightness against outdoor air is ensured outside of the insulation layer, for example, by rigid panels. The vapor retarder is actually supposed to slow down diffusion to prevent condensation.
I
Irgendwoabaier
20 Nov 2015 20:09
BastianB schrieb:
Attention, non-expert knowledge:
[..]

Then the airtight layer on the inside of the main insulation would not need to be sealed so carefully. Unfortunately, that is not the case – see the attached picture (our kitchen – it looked like this 16 months ago). After that, some wood wool boards were added on the inside, followed by drywall. On the other side of the OSB board: cellulose insulation / timber frame, then 60mm (2.4 inches) wood fiber boards (certainly not airtight), then plaster...

Regards
I.

Interior shell construction with OSB walls, wooden battens, and installations during the building phase
wrobel21 Nov 2015 19:06
Hello

that is exactly correct.
Airtight on the inside, windproof on the outside
Tighter on the inside than on the outside
and always with the installation level.

Olli