Thank you for reading our previous series, “The Truth About ‘Breathing Homes’ Revealed by Building Physics.”
Despite its technical nature, we have received a great response from many people who are serious about learning how to build a house.
At the same time, the more you study, the more likely you are to have formed some “sharp questions” or “objections” when comparing our concepts with today’s “common sense of high airtightness and high insulation.”
Today, I will answer three of the most frequently asked questions from the perspective of Building Physics.
Q1: If moisture gets into the walls, won’t the insulation performance decrease?
A: That is correct. However, that applies to “mineral-based insulation such as fiberglass.”
When common insulation materials like fiberglass get wet from condensation, the air gaps (air layers) that are supposed to provide insulation fill with water, causing the thermal conductivity to spike (and insulation performance to drop significantly).
However, the mechanism for handling water is fundamentally different in natural materials like PAVATEX (Swiss wood fiber insulation), which WALD uses as standard. Wood fibers absorb water vapor from the air not into the cell cavities (lumen), but into the interior of the “cell walls.” Therefore, the air layers that act as insulation are never crushed by water.
Even more remarkably, when wood fibers absorb moisture, they release “Heat of sorption (Latent heat).” It has been proven that even if the humidity inside the wall rises in winter and the insulation absorbs moisture, this exothermic reaction offsets the cooling, allowing the house to maintain a thermal environment in dynamic, real-life conditions that exceeds its catalog specifications.
Q2: Don’t “High Airtightness (C-value)” and “Breathing (Vapor Permeability)” contradict each other?
A: This is a complete misunderstanding. “Drafts (Air leakage)” and “Vapor permeability at the molecular level” are completely different things. In fact, without high airtightness, proper “breathing” cannot be established.
The “Airtightness” of a home plays a crucial role in preventing unintended drafts. Actually, condensation inside the walls, which causes damage to the building, is largely caused by moisture carried in by these drafts.
First, we must increase airtightness to firmly prevent drafts. Only then can the inherent “ability to absorb and release moisture” of the wood and insulation work evenly and safely throughout the entire wall.
Another important point is that “simply making it easier for moisture to escape (high vapor permeability)” is not enough.
What WALD practices is the “design of proper pathways” where moisture naturally escapes to the outside. We carefully analyze the properties (Water vapor diffusion resistance) of each insulation material (like PAVATEX) and building component, balancing them so that moisture moves smoothly from the indoors to the outdoors.
Even if moisture does get in, it is gently caught by the moisture buffering capacity and slowly released outdoors through a gradient of vapor resistance.
It’s not just about “high vapor permeability” to let moisture escape, but about “carefully designing the movement of humidity while maintaining high airtightness.” We believe this is the most logical shortcut to building a truly comfortable home.
Q3: Aren’t natural materials more likely to become food for mould?
A: Once you understand the mechanism of mould generation, that concern will be swept away.
For mould and mites to multiply explosively, they need an environment where the relative humidity exceeds 70% or where moisture remains on the surface (dampness). Since common vinyl wallpapers repel water, condensation droplets stay on the surface for a long time, eventually becoming a perfect breeding ground for mould.
However, the wood fibers and natural materials used by WALD excel not only in moisture buffering but also in “Capillarity.” The moment water vapor tries to turn into droplets (liquid) on the surface, capillary action quickly draws the moisture inside and diffuses it using the entire volume of the wall (material). Because it has the ability to keep the surface continuously dry without letting moisture stagnate, natural materials actually dramatically reduce the risk of mould growth.
A truly healthy home building where both the building and the people can breathe
What do you think? A “breathing home” is not just an intuitive catchphrase or nostalgia. It is highly rational engineering built upon a foundation of precise physics data and a track record of proven results.
Taking a step beyond home building that merely chases theoretical U-values and C-values, WALD’s homes achieve both essential “building health” and “occupant comfort.”
We welcome any technical questions you may have. Please come to our open houses or model homes and ask me directly. I will answer everything from the perspective of Building Physics.
