ᐅ Luxhaus and Competitors – Breathable Wall Systems

Water vapor should be able to escape from the wall to the outside (if present), but of course, it must not penetrate from the outside into the wall. Therefore, there is a vapor retarder somewhere in the wall assembly. In the past, vapor barriers like foil were commonly used to make the wall vapor-tight. Today, glued joints of oriented strand board (OSB) are often used instead, as they also help to stiffen the stud frame.

The ease with which water vapor can pass through a material depends on its thickness and composition and is expressed by the Sd value. Values below 0.5 are considered vapor permeable (diffusion-open). Values between 0.5 and 1500 indicate vapor retarders (diffusion-reducing), and values above 1500 represent vapor-tight materials. Depending on its thickness, OSB has an Sd value of around 3.

...and how much water vapor in grams or milliliters per unit of time do you think diffuses through there?
How long would it, for example, take to reduce the humidity from 60% to 50% after cooking, or from 80% to 50% in the bathroom after showering?

Daniel-Sp schrieb:

Water vapor

What percentage of the relative humidity can these "vapor-permeable" building components absorb or buffer? Over what time scale do these exchange processes typically occur?

This is not about the water vapor generated inside the rooms. Ventilation, either manual or mechanical, is responsible for managing that.

nordbayer schrieb:

A wall system that is not vapor permeable but includes ventilation makes EXTREMELY more sense than a vapor-permeable system without ventilation. At least one exhaust fan in the bathroom is absolutely necessary for me.

Opinions can be very different. In the bathroom, I just open the windows for ventilation, and that’s enough. It’s great if you have two windows to create a cross breeze. With clay plaster, even a fogged-up mirror in an unheated bathroom clears within minutes. There’s no need for mechanical ventilation or fans.
I’m not a fan of all the ventilation systems because I can hardly imagine they wouldn’t eventually become breeding grounds for germs. It’s technology I prefer to avoid in my house.
My gut feeling favors the “vapor-permeable construction” method.
The ventilated rainscreen facade (larch wood in our case) is fantastic.

Daniel-Sp schrieb:

It's not about the water vapor generated inside the rooms. Ventilation, either manual or mechanical, is responsible for that.

Ah, then which one is it about?