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Assessment of carbon dioxide transmission through porous building materials in relation to indoor air quality

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2016
Yüncü, Başak
There is lack of knowledge on breathing features adequacy of porous building materials for sustaining indoor air quality. There is necessity to examine gas diffusion characteristics of breathing porous building materials and the relation of those characteristics with IAQ. A comprehensive study, therefore, was conducted on mud brick as a traditional building material and AAC as a contemporary building material which are well-known by their high breathable characteristics. Their air permeability features were examined in terms of water vapor and carbon dioxide diffusion characteristics. A practical experimental method composed of single and double chamber diffusion tests was developed representing the gas diffusion from inside to outside through a porous wall. CO2 was used as a tracer gas since its presence at certain level adversely-effect the indoor air quality. The results have shown that single chamber setup is useful for assessing CO2 diffusion rate, while double chamber setup is obligatory to identify whether the material is vi attracted to the tracer gas or not. That knowledge is crucial to clarify how much tracer gas is actually permeated through or retained in the material. If a porous material is attracted to CO2, the data on diffusion rate obtained from single chamber setup is misleading. Both mud brick and AAC are highly-porous, -water vapor permeable and lightweight materials while differing in their CO2 permeability characteristic. Mudbrick is more CO2 transmissive than AAC, while AAC absorbs/adsorbs CO2 more than it transmits. However, no evident correlation between water vapor permeability and CO2 diffusion characteristics was identified.