Study of mould occurrence in buildings of tropical climate

Abstract

Indoor mould contamination portends grave consequence to the inhabitants and well as the content of the infested buildings. Such defilement, which is due to favourable growth environment for micro-organisms, is often associated with Sick Building Syndrome (SBS) and other Building Related Illness (BRI). There are limited guidelines existing for indoor air quality (IAQ) and mould proliferation in Malaysia and the knowledge among the public is lacking. Therefore, a holistic approach is needed for not only the hygrothermal performance but also the associated mould assessment and prediction in these edifices as early detection of the menace is often difficult until growth has advanced. The study combined in-situ, analytical and numerical experiments to investigate mould growth problem in selected case studied building with a known history of mould proliferations. Microclimate and microbial data were obtained from the in-situ experiments. The numerical experiments developed computational fluid dynamics (CFD) simulation models and routines for mould growth prediction from the interaction between the building envelopes and hygrothermal differentials of the indoor and outdoor microclimate in mechanically ventilated building. Results of the in-situ experiments revealed that the case study buildings are operated in overcooled and elevated hygric conditions. The results also revealed the identified mould as mostly xerophilic (dry-loving) species mainly Penicillium sp., Cladosporium sp., Chaetomium sp., Rhodotorula sp., Fonsecaea sp., Aspergillus sp. and few other species. The numerical simulation was able to predict the hygrothermal profiles triggering the mould growth. The findings also revealed that over cooled buildings increase condensation risks on the warm side of the envelopes separating air-conditioned and non-air-conditioned spaces. This study provides a holistic approach to designing and retrofitting energy efficient buildings that will be free of microbial infestation due to elevated hygrothermal profiles and increased condensation risk. Equally, this study provides awareness of the effect of differential operations in space air-conditioning on indoor moisture as well as adoptable procedures for mould assessment and predictions in the hot and humid climate of Malaysia. Above all, the study will assist in policy formulation that incorporates hygrothermal performance with energy efficiency.