Minimum ventilation rates to prevent condensation; a case study.

Moisture and mould in buildings have become fairly common problems in Italy, particularly since regulations aimed at energy conservation have been enforced in the seventies. Results of a case study conducted within IEA Annex XIV are presented in this paper. Two flats belonging to the same building (one with and the other without moisture problems) have been monitored during the winter 1987-88. Indoor temperature and air humidity, wall surface temperature and weather parameters were recorded for several weeks using two automatic data loggers. Airchange rates were measured using the tracer gas technique. Processing of the experimental data indicates that the moisture problems in one of the flats are probably due to insufficient airchange rates in a building which presents some noticeable thermal bridges. Differences between the two flats can be attributed primarily to occupants' behaviour (airing habits, retrofits performed on the windows, etc.) and, to a lesser extent, to orientation. The paper also shows that a good insight on condensation phenomena can be derived from fairly straightforward simplified analyses of temperature and humidity data. The importance of incorporating guidelines on thermal bridge correction and ventilation strategies into building codes is pointed out.