Mold in dwellings : field studies in a moderate climate

Mold in dwellings is a persisting complaint in moderate climates. Nine parameters intervene in it: (1) climate, (2) inside temperature, (3) vapor release, (4) ventilation, (5) lay out, (6) envelope thermal performance, (7) sorption inside, (8) presence of preferential condensation surfaces and (9) type of finish. Exterior climate acts as boundary condition while inside temperature, vapor release and ventilation belong to the living habits. The five others are design and construction related. Several mold cases have been reanalyzed with as major objective to evaluate if the nine parameters explained the problem. The answer is yes. Especially lack of ventilation, large surfaces of exterior walling, low inside temperatures and poor envelope thermal performance rank high. A low inside temperature anyhow is typically the result of a rebound effect, the fact that the dwelling has such poor thermal performance that people accept lower comfort to keep heating payable. Ventilation in turn is to a large extent building-related. In most cases, no intentional ventilation system is provided. In insulated dwellings, thermal bridging is the main cause. If there is an impact of sorption, preferential condensation surfaces and type of finish could not be confirmed.