On Strategies to Prevent Condensation in Buildings

It is recognized that the occurrence of condensation in surfaces inside buildings is amajor cause of indoor pollution with relevant negative effects on human health.Scientific reviews on health effects from dampness and moisture in buildings made inrecent years [1, 2] present the common view that, despite intensive research efforts,the relationships between the probability of the occurrence of dampness and mouldsand the building construction and operation parameters have not been fully identifiedyet. However, some authors [2] clearly state that setting limits on indoor relativehumidity does not guarantee a mould-free environment.Nevertheless, it could be stated that dampness and moulds are cases of pollutionsources that could, in theory, be totally removed. This would enable the elimination ofthose sources and effects by the use of a source control strategy. In fact, if the controlof a few physical parameters could be guaranteed, the occurrence of dampness andmoulds would be prevented and the principle of source control could be successfullyapplied.More than exploring the processes through which dampness and moulds are generatedor emit pollutants that are responsible for respiratory diseases this paper aims atcontributing to discuss the extreme conditions by which it would be possible to avoidcondensation.In terms of physics, condensation occurs in a surface of a room whenever thetemperature of the surface is lower than the saturation temperature of moisture in thesurrounding indoor air. Phenomena at the micro-scale may make condensationemergence dependant on the nature, microstructure and micro-geometry (roughness)of the surface material. In addition, when condensation occurs, several phenomenamay take place at the microscopic scale in the microstructure of the materials behindthe surface such as capillarity effects and others. Dampness effects can also be presentat the surface caused by the dynamics of the moisture traveling by capillarity insidethe fabrics once condensation occurred and mass transport could take place. This caseis not considered in this paper.Other causes for the occurrence of humidity in the fabrics due to leaks in pipes,infiltration of rain water, drainage or others are not considered in this paper since theycan be effectively eliminated by different ways, namely, through proper maintenanceand operation of the building envelope and water systems.