Chemical emissions from building structures : emission sources and their impact on indoor air
Abstract: Chemical compounds in indoor air can adversely affect our comfort and health. However, in most cases there is only a limited amount of information available that can be used to assess their health risk. Instead the precautionary principle is often applied, i.e. efforts are made to ensure that the concentrations of pollutants are kept at a minimum when constructing new buildings or conducting renovations by using low-emitting building materials. Today, when investigating buildings in order to solve indoor air quality problems, volatile organic compounds (VOCs) are sampled in the air within rooms. The chemical composition of indoor air is complex and there are many sources for the chemicals present. The potential for emissions from sources in hidden spaces such as wall cavities is poorly understood and little information exists on the toxic potential of chemical releases resulting from moisture-related degradation of building materials. Most of the non-reactive VOCs that have been detected in indoor air in field studies and from building products are not believed to cause health problems. However, reactive compounds and chemical reaction products have the potential to negatively influence our comfort and health even at low concentrations. Even though the impact of chemical compounds on health is unclear in many cases, they can be used to identify technical problems in buildings. When a building is investigated, the air inside building structures could be sampled. This method would eliminate emissions from sources other than the construction materials and the samples would contain higher levels of individual compounds. The aims of this work was to identify emissions profiles for different types of building structures, to see if the emission profiles for moisture damaged and undamaged structures differed, and to determine whether any of the emissions profiles for specific structures also could be found in indoor air. Technical investigations and VOC sampling were performed in 21 different buildings with and without previous moisture damage. Seven of the buildings were investigated in the years 2005-2006 (study 1) and fourteen in the years 2009-2010 (study 2). In study 1, sixty samples were analyzed by PCA at the chemical group level (18 chemical groups, i.e. aldehydes, ketones etc). 41 % of all identified chemical compounds belonged to the hydrocarbon chemical group. The second largest chemical groups, each of which accounted for 5-10 % of all identified compounds, were alcohols, aldehydes, ketones, polyaromatic hydrocarbons (PAHs) and terpenes. The results indicated that one of the main factors that determined the emissions profile of a building structure was the materials used in its construction. Notably, concrete and wooden structures were found to have different emissions profiles. The sum of VOC (TVOC) concentrations for all 241 samples from both study 1 and study 2 was used to compare total emissions between different building elements (ground and higher floors, external walls and roof spaces). Most building elements exhibited relatively low emissions compared to concrete ground floors, which generally had higher TVOC emissions. Emissions from both polystyrene insulation and PVC flooring could be identified in concrete ground floors and were the main cause for the higher emissions found in these structures. Profiles for wood preservatives such as creosote and pentachlorophenol were also identified in external walls. The emission profiles found in the structures could not be identified in the indoor air in the adjacent rooms, although individual compounds were sometimes detected at low concentrations. Our results showed that the main factors influencing emissions in building structures were the construction materials and the nature of the building element in question. Because of difficulties with finding active water damage at the times of sampling and because of sampling inside closed building structures with old dried-out moisture damages, the field method used in this work was unsuitable for identifying differences in emission profiles between moisture damaged and undamaged structures. It will thus be necessary to investigate this difference in a laboratory where the precise composition of all tested structures is known, a range of RH values can be tested and the accumulation of emissions can be followed.
CLICK HERE TO DOWNLOAD THE WHOLE DISSERTATION. (in PDF format)