Cross-section of a Timber-Frame Wall – See What Protects Your Home from the Cold
What do the layers of a timber-frame house wall hide?
To understand why a modern barn-style house is warm even in severe frosts, we need to look inside the structure. It is not enough to simply "stuff" insulation between the studs. It is the evolution of Canadian construction that has allowed us to eliminate the problem of water vapor condensation and create houses that are as airtight as a thermos, yet offer a healthy microclimate. Below we present a schematic description of what the layers look like in the System-S standard, going from outside to inside:
Layers of a timber-frame house wall:
- Exterior facade – e.g., facade board, standing seam metal, or plaster. This is the first line of defense against rain and mechanical damage.
- Ventilation grid (battens and counter-battens) – a key element creating a ventilation gap. Thanks to it, moisture can evaporate freely, and the wall does not degrade.
- Wind barrier – a highly vapor-permeable membrane. It protects the structure and wool from wind washing (which drastically reduces the effectiveness of insulation) and water, while allowing the wall to "breathe" to the outside.
- Exterior sheathing board – stiffens the frame structure.
- Load-bearing structure + Thermal insulation – the heart of the wall. Certified structural timber (C24) tightly filled with insulation material.
- Vapor barrier film – an absolutely essential barrier on the inside of the house. Its job is to stop the moisture produced by the residents from penetrating deep into the wool.
- Installation grid + additional insulation – a space for running cables and pipes without breaching the main vapor barrier, often filled with an additional layer of wool.
- Interior finish – e.g., plasterboards, wooden paneling, or furniture board.
Wind barrier vs. vapor barrier – why are they not the same?
Many contractors confuse these terms, which leads to catastrophic errors. As experts, we must emphasize: a wind barrier and a vapor barrier are two different shields with opposite functions.
A wind barrier (on the outside) acts like a Gore-Tex jacket – it doesn't let wind and rain in, but it allows sweat (technological and living moisture) to get out. If we didn't use it, cold wind would "blow out" the heat from the wool, drastically reducing its effectiveness. On the other hand, a vapor barrier (on the inside) is a sealed dam. Damp wool loses its insulating properties – a wet sweater doesn't keep you warm. That's why we are so strict about the tightness of the joints during the installation of the vapor barrier film. It is this attention to detail that makes houses in timber-frame technology so energy-efficient.
Mineral wool or PUR foam – the eternal dilemma
When analyzing the cross-section of a timber-frame wall, we face the choice of insulator. The market is divided between supporters of wool (rock/glass) and polyurethane foam (PUR). What to choose? The answer depends on expectations, but physics points in certain directions.
Mineral wool or foam? Wool is a naturally non-combustible material and, crucially, has excellent acoustic properties. In timber-frame houses, soundproofing is extremely important, and heavy rock wool dampens sounds very well. In addition, it is vapor-permeable, which works well with the vapor-open structure of the wall. PUR foam (open-cell), on the other hand, fills hard-to-reach gaps perfectly, eliminating thermal bridges, but its application requires a technological regime (appropriate wood moisture), and its acoustic parameters are sometimes worse than those of high-density wool.
In our projects, we rely on proven solutions that guarantee not only warmth but also fire safety and acoustic comfort, which is why we most often recommend systems based on high-quality wool.
Heat transfer coefficient U – the numbers don't lie
The ultimate test of a partition's quality is the heat transfer coefficient U. The lower the value, the better – the less heat escapes from your home. According to the current Technical Conditions (WT 2021), external walls must have a U-value no higher than 0.20 W/(m²K).
For us, the norm is not enough. Our walls, thanks to the use of appropriate wood cross-sections and high-class insulation materials, achieve much better parameters, often oscillating around U = 0.13 – 0.15 W/(m²K). This means your home is ready for the future, and your heating bills are minimal. Remember that the final result is determined not only by the thickness of the wall but above all by the elimination of thermal bridges at the joints of the boards and in the corners, which is easier to control in timber-frame technology than in masonry.
