Modern passive stack and ventilated schools - evaluation of ventilation and moisture conditions.

The aim has been to determine ventilation rates and risk of moisture damage in three modernschools with passive stack ventilation. The users are supposed to control the ventilation byusing the lantern windows and the outdoor air is assumed to enter through an undergroundduct. The paper presents results, analysis and conclusions from the performed measurementsand calculations.The ventilation rates are sometimes low and vary with the use of the windows in the facadeand the lantern. It is, however, always possible to arrive at a sufficient ventilation rate. Thesupply air flow through the underground duct can, without a supply fan, be low and even gobackwards during warm weather. To obtain desired ventilation rates and energy conservationthe building must have a good airtightness.High relative humidities and even periods with condensation occur in the underground supplyduct during spring and summer. Microbial growth has been found in two of the schools. Twoimportant factors are choice of material and cleaning, where the knowledge is insufficienttoday. Moisture and microbial growth have been found in the roofs. The leakage paths,supply of moisture indoors and an interior pressurization have contributed. In order to reducethe risks the building must have a good level of airtightness.