Interior Moisture Management

Natural buildings with breathable walls and living roofs require active moisture management. Without it, winter condensation leads to mold and accelerated decay.

Condensation Risk in Winter

Occupancy generates 2-4 kg of water vapor daily (breathing, cooking, bathing). In an unheated or minimally-heated off-grid structure, this moisture condenses on cold surfaces — especially north-facing walls and the underside of the roof.

Integrated heating and ventilation — compost-generated warmth circulates through underfloor pipes

Ventilation Requirements

• Continuous background ventilation: Install trickle vents in at least 2 windows (opposite walls for cross-flow). Target 0.5 air changes per hour minimum.
• Extract ventilation: Bathroom and kitchen areas need extract fans vented to exterior — do not rely on passive ventilation alone.
• Winter protocol: Open windows briefly (5-10 minutes) each morning to flush humid air, then close to retain heat.

Target Humidity Levels

Season	Target RH	Action if Exceeded
Summer	40-60%	Ensure ventilation if above 60%
Winter (heated)	40-55%	Increase ventilation; check for leaks
Winter (unheated)	50-65%	If sustained above 65%, add dehumidifier or heat source

Monitor Regularly

A simple digital hygrometer (under €10) placed on the north wall will alert you before condensation becomes a problem. If relative humidity consistently exceeds targets, increase ventilation before adding heat.