ᐅ Breathable Wall Construction – I Don’t Understand It!

A house provider places particular emphasis on a vapor-permeable wall construction in their house descriptions. This is one of the main reasons why the provider does not install a central ventilation system. Another reason is that biomass (small dust particles, etc. in the air) can be drawn into the duct system, which can quickly lead to contamination (mold growth) within the distribution system.

I have two issues with this.

1. We generally wanted a ventilation system, but the provider does not install one at all.
2. We are now unsure how effective this vapor-permeable wall construction really is and whether it might be reasonable to forgo the ventilation system because of it.

Here is a brief outline of the wall construction (Swedish house facade) from inside to outside:

15 mm (0.6 inches) high-quality Fermacell solid construction panels
40 mm (1.6 inches) timber frame structure with Knauf Insulation, 40 mm (1.6 inches), thermal conductivity class 040
0.2 mm (0.008 inches) vapor retarder, diffusion equivalent air layer (Sd) 100 m (328 feet)
160 mm (6.3 inches) timber frame structure with Knauf Insulation, 160 mm (6.3 inches), thermal conductivity class 040
30 mm (1.2 inches) wood fiber insulation board
24 mm (0.9 inches) battens
Approx. 20 mm (0.8 inches) SL boarding, spruce (color according to color chart)

It would be very helpful if someone could explain the advantages of this vapor-permeable wall construction compared to other timber frame walls. The relationship to the ventilation system is especially important for us. With Hagemann Haus, we would have to forego this ventilation system altogether.

Hello,

MStorm schrieb:

With Hagemann Haus, we would at least have to do without this ventilation system.

I am familiar with this provider based on the documents that a user from this forum shared with me.

The managing director is generally against ventilation systems and relies on outdated arguments that no longer apply to modern systems; however, his offers are quite affordable considering that his company is not very large.

Nowadays, I would no longer want to do without a ventilation system, let alone be forced to; this applies to solid construction, conventional prefabricated houses, and also timber houses. Ultimately, it is your decision whether to accept the provider’s arguments or look for other options. Any discussion or assessment of the wall structure is pointless if you are set on this particular provider.

Regards, Bauexperte

Bauexperte schrieb:


..... but his offers are quite affordable, considering that his company is not that large.

Regards, Bauexperte

However, the price is really the main factor that makes this provider attractive to us. That’s the challenge....

The issue with breathable (vapor-permeable) construction requires caution. In theory, this type of wall system can work, but in practice, it can also lead to problems, since buildings must primarily be airtight according to energy-saving regulations (building codes). The question then is whether the moisture can be removed to the outside within the necessary time and volume without causing mold to develop anywhere.

If the installation of a ventilation system is categorically ruled out, that alone would be enough for me to consider looking for a different provider.

By the way, there are wall constructions that are breathable and can do without a vapor barrier. Properly sized and correctly positioned OSB boards can also act as a vapor retarder, so there is no need to worry about the barrier foil being damaged by rodents or other causes over time.

However, even in that case, I would definitely not want to do without a ventilation system. Today, having a ventilation system is simply standard. While there are opponents who have their reasons, I personally see it as a major comfort improvement and a sensible contribution to preserving the building structure.

Hello,

MStorm schrieb:
However, price is definitely an argument that makes this provider attractive to us. That’s the difficulty....

I don’t see it that way –

if you want to choose this provider, then take their offer as it is. If you can’t accept that, look for an alternative. There is absolutely no room for negotiation, as the managing director – as mentioned above – is not open to discussion on this matter.

Foolish regards

I doubt there is a wall construction that both complies with the energy saving regulations and allows enough moisture to diffuse outward so that ventilation can be completely omitted. Moisture is removed through ventilation. The walls themselves have no significant lasting effect (certain wall constructions or surface treatments can of course temporarily absorb peaks).