Natural ventilation - conditions and means for its improvement in existing buildings.

In new buildings, the requirements for indoor air quality and energy efficiency cannot be met with natural ventilation. In renovations of existing buildings it is, however, often difficult or uneconomic to install a mechanical system. What is often forgotten is that the conditions for natural ventilation will have changed, even if no alterations are made to the ventilation system. Examples are given of changes in the outdoor air quality, airtightness and usage or layout of rooms, and on maintaining the conditions of satisfactory indoor air by natural, combined natural/mechanical or mechanical systems.