zero-condensation-in-treevia-houses

Zero condensation: how Treevia solves timber's oldest problem

"Timber houses rot." "Frame walls sweat." "After ten years you'll have to replace the insulation." These lines circulate on building forums endlessly, and they persist because they contain a grain of truth: a badly designed timber partition really can develop moisture problems. A well-designed one doesn't. Here's why condensation doesn't form in any layer of a Treevia wall - and how you can check the claim yourself.

What condensation inside a wall actually is

Water vapour condensation happens when warm, humid air from inside the house passes through the wall and reaches a layer whose temperature has dropped below the dew point. The vapour turns to liquid water, and that water settles into the insulation or onto a membrane.

What follows isn't subtle:

• Wet mineral wool loses its insulating properties (its λ value climbs)
• Damp C24 timber becomes a breeding ground for fungi and mould
• Wet PE film can degrade at its sealing points
• The U-value gets worse - the house loses heat faster, year after year

Left unchecked, condensation inside a wall eventually leads to structural degradation - which is exactly where the myth about "rotting timber houses" comes from.

Why it happens in a lot of standard timber-frame builds

A typical timber-frame wall has 6-8 layers. The question that decides everything is: where does the dew point land inside that stack?

In many builds, it lands inside the insulation - especially in winter, when the gap between +22°C indoors and -20°C outdoors is at its widest.

A few common design choices make it worse:

1. No ventilated air gap - moisture has nowhere to escape
2. A single insulation layer - the dew point always lands in the same spot
3. Installations puncturing the PE film - letting vapour flow through uncontrolled
4. A low-grade membrane - limited diffusion capacity

Most manufacturers simply don't publish moisture-thermal calculations for their walls, so the buyer has no way to know whether condensation is happening inside their own walls.

How Treevia engineers it out

The Treevia wall is designed so no layer experiences condensation, even under extreme winter conditions. That's confirmed by ubakus moisture-thermal calculations run under these parameters:

• External temperature: -20°C
• External humidity: 80%
• Internal temperature: +22°C
• Exposure time: 90 days

The result: zero condensation in any layer.

The five mechanisms behind that result

1. Three insulation layers on independent battens

75 mm of wool (external batten) + 150 mm+ (C24 structure) + 50 mm (internal batten). Spreading the temperature gradient evenly across the full thickness of the wall keeps the dew point from concentrating at any single point.

2. The Dörken Delta-Vent S+ membrane (high-diffusion)

This vapour-permeable membrane on the outside lets water vapour escape outward. The better a membrane's diffusion rating, the faster the wall dries itself out. Delta-Vent S+ is a premium-grade product used in buildings with elevated performance requirements.

3. A 30 mm ventilated air gap

Air circulating in the gap between the cladding and the membrane picks up moisture off the membrane's surface and carries it away - a natural drying mechanism running around the clock, all year.

4. The PE film, positioned correctly (sd = 20 m)

The vapour barrier sits after the internal 50 mm wool layer, before the shaft and plasterboard. It blocks over 95% of interior water vapour before it ever reaches the main insulation, and the film stays intact because the shaft keeps installations from puncturing it.

5. The installation shaft as a buffer

The 4-6 cm gap between the PE film and the plasterboard means:

• The PE film is protected from mechanical damage
• No socket or cable hole punches through the vapour barrier
• Whatever small amount of vapour does pass through the plasterboard disperses in the shaft before it ever reaches the film

What the calculations actually show

Ubakus is a well-established tool for moisture-thermal simulation of building envelopes, used by designers and certifiers across Europe.

Running the Treevia wall through it under extreme conditions (-20°C / 80% / 90 days) produces:

• Humidity inside the partition: ~58-59%
• Mould risk: none, by ubakus's own criteria
• Condensation: zero in every layer
• Drying capacity: the wall releases more moisture across the annual cycle than it absorbs

None of that is a marketing line - it's a physics result anyone can reproduce and check.

The myth about timber and moisture

The C24-grade structural timber Treevia uses is kiln-dried to a controlled moisture content of 12-15%. In a correctly designed partition, that timber never gets exposed to additional moisture, because:

• It's protected from outside by the membrane and the ventilated gap
• It's protected from inside by the PE film and the shaft
• It has no contact with damp ground, thanks to the foundation insulation
• Factory prefabrication removes the moisture exposure that comes with a traditional building site

In conventional construction, timber elements sit exposed on-site to rain, snow and frost for months. In Treevia's process, the structure goes up in a dry hall and reaches the site ready to assemble within days.

How to check whether your own house has a problem

If you're weighing a modular house from any manufacturer, ask these questions:

1. Moisture-thermal calculations - has the manufacturer run them? Will they share them?
2. Which software - ubakus, WUFI, U-Wert or something else? Certified tools give results you can trust
3. What conditions - what temperature and humidity was the simulation actually run at?
4. Where's the dew point - which layer does it land in? Is it inside the insulation?
5. Is the vapour barrier continuous - do the installations puncture the PE film?

If a manufacturer can't or won't answer those five questions, take that as a warning sign.

The short version

Zero condensation in a Treevia wall isn't a slogan - it's the outcome of:

• Two wall build-ups engineered as one coherent system
• The Dörken Delta-Vent S+ membrane (diffusing moisture outward)
• The PE film in the right position (barrier on the interior side)
• A 30 mm ventilated air gap (natural drying)
• The installation shaft (no punctures through the vapour barrier)
• Factory prefabrication (dry C24 timber from day one)

Ubakus calculations confirm it: at -20°C / 80% / 90 days, humidity inside the partition sits at 58-59%, mould risk is zero, and condensation is zero. It's a claim you - or your own engineer - can verify.