Controlled mechanical ventilation of housing improves humidity balance. Kontrollierte wohnungsluftung verbessert feuchtebilanz.

The Heat Protection Ordinance (Warmeschutzverordnung EnEG) issued in 1977 aimed to reduce heating energy consumption and has become part of the building ordinances. Beside the heat transmission resistance (k-value-a measure for the size of the heat transmission losses), also the crack flow exponent (a-value) has been controlled to reduce ventilating heat losses. Practical experience has shown that, without mechanical ventilation, hygienic, physiological and building physical disadvantages will turn up. The author, in his capacity as chairman of the working group "Mechanical ventilation of housing" (Fachinstitut Gebaude Klima) describes the causes and the possibilities of avoiding those disadvantages.