Indicators of natural ventilation effectiveness in twelve New Zealand schools.

Classrooms in New Zealand schools are mostly low rise buildings with natural ventilationdesigns, sized for summer cooling. This study has investigated winter ventilationperformance in twenty-four classrooms in twelve primary schools in the Wellington region.Its purpose has been to provide baseline data on the effectiveness of existing naturalventilation, along with approximate pollutant profiles on which to base new mixed modeventilation designs. Detailed measurements of indicator airborne micro-organisms, totalvolatile organic compounds, respirable particulate, and formaldehyde were completed intwelve classrooms, along with longer term logging of carbon dioxide concentrations andphysical conditions. Records of metabolic carbon dioxide were used to estimate ventilationrates, which were later compared with mean infiltration rates determined from airtightnessmeasurements. Airtightness data for the twenty-four classrooms followed the same trendseen in residential buildings, which is for modern construction to be much more airtight thanolder buildings. In contrast to residential buildings the indicated ventilation rates were muchhigher than background infiltration rates.