Abstract
Several school buildings in Sweden have indoor air quality problems. The contaminant source is often assumed to come from within the construction, for example from the crawl space or attic space. Contaminants, in these cases, are transported by air leaking between compartments in the building. Here, the driving force for the air leakage is difference in pressure and, therefore, determining pressure also determines the direction of contaminant transport. In many cases, measures to improve the air quality are taken without a thorough understanding of how it might affect the pressure distribution in the building. In this paper a numerical model is used to examine how different climate scenarios and different building configurations affect the leakage and contaminant transport in a building with a crawl space. Results show that for leaky buildings the ventilation rate increases with increased wind and therefore the contaminant concentration decreases. The worst scenario in terms of high contaminant concentration is mild days with little wind. Also, when installing an exhaust fan in the crawl space with the purpose to prevent air from leaking from the crawl space to the classroom it is advisable to also consider the airtightness and the climate, not only the pressure difference across the floor.
Highlights
Some school buildings in Sweden have indoor air quality problems and contaminants are often assumed to come from the crawl space or the attic space
The purpose of this paper is to investigate in what way different climate scenarios and building configurations affect the pressure difference between crawl space and classroom as well as concentration levels in the classroom
The neutral pressure plane is situated within the height of the classroom and the pressure difference across the floor is positive, which means that contaminants are coming up from the crawl space
Summary
Some school buildings in Sweden have indoor air quality problems and contaminants are often assumed to come from the crawl space or the attic space. Transport of mould spores from the crawl space to the indoor air was investigated in [1] resulting in the conclusion that a building with a crawl space and a pressure difference over the floor could be a potential risk for indoor air quality problems. The contaminants are transported between the compartments in leakages in the construction. In order to take efficient measures to prevent contaminants from reaching the classroom, it is important to understand how the pressure distribution is affected by different climate scenarios and different building configurations. The purpose of this paper is to investigate in what way different climate scenarios and building configurations affect the pressure difference between crawl space and classroom as well as concentration levels in the classroom
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