Zero condensation – how Treevia solves the biggest problem of timber houses

Zero condensation – how Treevia solves the biggest problem of timber houses

"Timber houses rot." "Frame walls sweat." "After 10 years you need to replace the insulation." These myths circulate on building forums for years – and they contain a grain of truth. A poorly designed timber partition can indeed have moisture problems. But a well-designed one – does not. We explain why condensation does not occur in any layer of Treevia walls.

What is condensation in a wall?

Water vapour condensation occurs when warm, humid air from the interior passes through the wall and reaches a layer at a temperature below the dew point. Vapour turns to water. Water accumulates in insulation or on membranes.

Consequences:

• Wet mineral wool loses insulation properties (λ increases)
• Damp C24 timber becomes a breeding ground for fungi and mould
• Wet PE film can corrode at sealing points
• U-value worsens – the house "loses heat" faster year by year

In extreme cases, condensation inside the wall leads to structural degradation – and that is the source of the myth about "rotting timber houses."

Why is this a problem in standard timber-frame houses?

A typical timber-frame wall has 6–8 layers. The key question: where in the wall does the dew point fall?

In many constructions, the dew point falls inside the insulation – especially in winter, when the temperature difference between interior (+22°C) and exterior (−20°C) is large.

Problems are compounded by:

1. No ventilated air gap – moisture has no escape route
2. Single insulation layer – dew point always in the same place
3. Installations piercing PE film – uncontrolled vapour flow
4. Low-grade membrane – limited diffusion

Manufacturers rarely publish moisture-thermal calculations for their walls. The customer does not know if condensation occurs in their wall.

How does Treevia eliminate condensation?

The Treevia wall is engineered so that no layer experiences condensation – even in extreme winter conditions. This is confirmed by ubakus moisture-thermal calculations with parameters:

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

Result: zero condensation in all 12 layers.

5 mechanisms that eliminate condensation

1. Three insulation layers on independent battens

Wool 75 mm (external batten) + wool 150 mm+ (C24 structure) + wool 50 mm (internal batten). The temperature gradient is distributed evenly across the full partition thickness – the dew point does not "concentrate" in one spot.

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

The vapour-permeable membrane on the outside allows water vapour to "escape" outward. Key: the better the membrane's diffusion, the faster the wall releases moisture. Delta-Vent S+ is premium grade – used in buildings with elevated requirements.

3. Ventilated air gap 30 mm

Air circulating in the 30 mm gap between cladding and membrane collects moisture from the membrane surface and carries it away. A natural wall drying system that works 24/7, 365 days a year.

4. PE film in the optimal position (sd = 20 m)

Vapour barrier placed after internal wool (50 mm), before the shaft and GK. It blocks 95%+ of interior water vapour before it reaches the main insulation. Film continuity is preserved thanks to the shaft – installations do not pierce the membrane.

5. Installation shaft as buffer

The 4–6 cm space between PE film and GK means:

• PE film is protected from mechanical damage
• No socket/cable holes piercing the vapour barrier
• Any minimal vapour that passes through GK disperses in the shaft before reaching the film

What do the calculations say?

ubakus is a recognised tool for moisture-thermal simulation of building partitions, used by designers and certifiers across Europe.

Simulation for the Treevia wall at extreme conditions (−20°C / 80% / 90 days) shows:

• Humidity inside the partition: ~58–59%
• Mould risk: none (per ubakus criteria)
• Condensation: zero in all layers
• Drying capacity: the wall releases more moisture than it absorbs in the annual cycle

This is not a marketing claim – it is a physics calculation result that anyone can verify.

Myth: "timber always works with moisture"

C24-grade structural timber used in Treevia is a material with controlled moisture content (12–15% after kiln drying). In a correctly designed partition, timber is not exposed to additional moisture because:

• From outside it is protected by membrane + ventilated gap
• From inside it is protected by PE film + shaft
• There is no contact with damp ground (foundation insulation)
• Factory prefabrication eliminates moisture exposure during construction

In traditional construction, timber elements sit on the building site, exposed to rain, snow, and frost. In Treevia, the structure is built in a dry hall, transported and assembled within days – not months.

How to check if your house has a condensation problem

If you are considering a modular house from any manufacturer, ask about:

1. Moisture-thermal calculations – has the manufacturer performed them? Can they share them?
2. Calculation software – ubakus, WUFI, U-Wert or other? Certified tools give reliable results
3. Calculation conditions – at what temperature and humidity was the simulation run?
4. Dew point – in which wall layer does it fall? Is it in the insulation?
5. Vapour barrier continuity – do installations pierce the PE film?

If the manufacturer cannot or will not answer these questions – that is a serious warning sign.

Summary

Zero condensation in Treevia walls is not a slogan – it is the result of:

• 12 layers designed as a coherent system
• Dörken Delta-Vent S+ membrane (outward diffusion)
• PE film in the optimal position (interior barrier)
• 30 mm ventilated air gap (natural drying)
• Installation shaft (no vapour barrier piercings)
• Factory prefabrication (dry C24 timber from day one)

Ubakus calculations confirm: at −20°C / 80% / 90 days – humidity in the partition is 58–59%, mould risk zero, condensation zero. Anyone can verify this.