Overview
- On Monday, the Umweltbundesamt and multiple Verbraucherzentralen reiterated that drying clothes inside in winter raises indoor moisture enough to increase mold risk and should be avoided when possible.
- For bathrooms with windows the consumer centres advise leaving the door closed and immediately shock-ventilating by fully opening the window for about 3–10 minutes so moist air is expelled rather than spread through the home.
- Authorities set practical targets to guide action: simple hygrometers should show roughly 40–60% relative humidity in living spaces while some regional Verbraucherzentralen recommend lower winter ranges such as 30–45%, and surface RH near 70–80% signals a real mold danger.
- When airing and heating cannot control moisture, recommended technical options include heat-pump tumble dryers (far lower electricity per 100 cycles than older models), room dehumidifiers, and, for windowless bathrooms, mechanical exhaust systems sized to DIN 18017-3 standards.
- Cold surfaces and building faults limit what ventilation can fix; DIN 4108-2’s test condition corresponds to a roughly 12.6°C minimum surface temperature under 20°C/−5°C conditions and persistent low surface temperatures or recurring condensation should prompt professional inspection and, for renters, landlord notification.