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 Modern building techniques and materials have contributed greatly to indoor air problems. The introduction of 'toxic' materials indoors has increased our exposure to compounds that are detrimental to our health. This case study was selected to demonstrate how easy it can be to build or modify a house to have better overall indoor air quality. The case study mainly focuses on VOCs, but many of the indoor air quality management techniques outlined refer to other indoor air factors as well (e.g. ventilation, reduction of inorganic pollutants and site selection). This case study relates to both residences and commercial buildings because many of the techniques used (for source control) can apply to the majority of buildings regardless of their function. The modern building techniques and materials present today introduce harmful pollutants into the indoor air, therefore a project was undertaken to see whether it was possible to build a house without using conventional materials and techniques (Mesaros 2003). The aim of the project was to reduce the amount of indoor pollutants significantly, so that any individual, particularly those with a predisposition to react to pollutants (e.g. asthmatics and multiple chemical sensitivity sufferers), can live in an environment that eliminates or greatly reduces exposure to offending pollutants/allergens. There is overwhelming evidence to demonstrate that the best way to achieve good indoor air quality is source control. A first practical step toward this goal has been undertaken by the Council of the European Communities who have issued a council directive on construction products (CEC 1993). The directive, among other requirements, states that:
The project outlined in this case study, has taken these directives into account in both the construction and maintenance of the house. A variety of pressures have contributed to the development of indoor air quality strategies used to improve the indoor environment. Pressures such as the importance of indoor air quality, the types of pollutants commonly found and their implications to health, and the increase in population susceptibility, have all indicated the need to formulate better, more chemically sound building techniques and materials. Pressures to use more conventional products are increasing, mainly because of economic reasons. Many of the conventional products are cheaper and less labour intensive, therefore they are usually preferred to the more expensive alternatives, particularly in the building industry. Because of the cost, many individuals have no choice except to use materials known to be 'toxic'. For example, solid wood doors are four times more expensive than their plywood counterparts (which contain formaldehyde resins). Emphasis on source control is currently growing in Australia (Brown 1997), in response to pressures by organisations, researchers and the community. Formaldehyde emission limits in pressed-wood products are one such example, where voluntary initiatives by industry have been undertaken. But what is also needed is a community education program outlining how individuals can themselves undertake their own source control. The benefit of this would be that individuals can have some “control” over their own indoor environment, and make informed decisions over what products they will and won't use in the construction and maintenance of their homes. This case study is an example of a response to all of these pressures. In response to the indoor air quality pressures, particularly source control, a project was undertaken examining improved building design. A house was built using materials that were known to have very low or no 'outgassing' properties. To date, there has been no house in Australia that has been built with these objectives in mind. Materials with the lowest outgassing levels are hardwood, steel, ceramic and stone, therefore these materials were used extensively in the house. Overall, no glues, paints, foams, additives and synthetics of any kind were used. Materials with the highest outgassing rates Level of outgassing Material High level Polyester Polyethylenes Silicones Epoxy resins Medium level Polyurethanes Flurocarbons Aluminium Copper Low level Hardwood Iron Steel Ceramic Stone Source: NASA, American spacecraft substance grading 1990 Site selection was of primary importance in the construction of this home. Efforts were made to locate the house well away from air contamination sources (e.g. traffic and smog (inorganic compounds)), and regional/local factors that affect air quality (e.g. plant odours, agriculture, and industry). The house faces a northerly aspect to gain maximum sunlight and warmth. Large windows were used to encourage as much natural sunlight and ventilation into the home as possible. The increased ventilation also helped reduce dampness and mould growth to a minimum. The house is a double brick construction (rendered internally), using hardwood floors, hardwood roof supports, and a tiled roof. All wood was kiln dried to accelerate outgassing of terpene compounds, and nailed, rather than glued to any supports. Ceramic tiles were used extensively throughout the house on the floors and walls of the bathrooms. They were set in untreated cement that contained no additives and glues. The advantage of having a tiled wall in the bathroom area is that it is waterproof (doesn't require additional mould treatment) and easy to keep clean (simple to wet wipe). The bathrooms have high ventilation rates (large opening windows), to reduce dampness and mould growth. Areas with solid hardwood floors were sealed using a home-made preparation of organic waxes and oils. Rendered walls were painted with a lime wash and the ceiling was painted with a similar home-made preparation. The kitchen is fitted out with American oak timber which has a lower terpenes content than Tasmanian hardwood. A solid stone benchtop (bolted into place rather than glued), was used in the kitchen area rather than a laminated surface. A large window was placed in the kitchen to increase ventilation and eliminate cooking odours (volatile oils).
Heating was achieved through the use of electrical wall panels. These panels have no moving parts therefore any dust is not blown around the room. The panels themselves are out of aluminium and baked ceramic, therefore when heated they have the minimum level of outgassing currently possible for a heating device. Furniture was also selected with their outgassing properties in mind. There is an extensive use of glass, stone and brass, all of which have very low-levels of outgassing. Every material used in the house is untreated cotton (including mattresses and rugs) or silk, and dark colours have been avoided to reduce the introduction of harmful chemicals that are commonly used in dyes. Pollution absorbing plants are also a feature, and serve as an absorbing mechanism for any low-levels of pollutants. Maintenance of the house is relatively simple. Avoidance of any commercial products was the key, including the introduction of simple “old fashioned” cleaning techniques. Most cleaning is achieved through the use of sodium bicarbonate, lemon juice, olive oil, unscented soap, and vinegar. When construction was finished, a quantitative assessment was undertaken to determine TVOC levels. Results showed that TVOC levels were barely detectable. In most cases, materials used were not as expensive as the commercially available products. Possible reasons are that many of the materials were in their raw form, without any other additional processing required, such as the introduction of additives, special treatments, fungicides, colours etc. This case study can be an example of how a few simple changes to building changes can make a difference to the indoor air quality. It is understood that many individuals do not have the opportunity to start building a low VOC house from the beginning (although this is preferable to ensure the greatest reduction of sources), but some or all of the elements outlined can be used in any existing dwelling or office. For example, the photo below highlights the successful use of pollution absorbing plants in a Hobart office building. Just a few simple changes (e.g. the use alternative cleaning products and the introduction of pollution absorbing plants) can make a significant difference to the indoor environment and to everyone's health.
Case Study compiled by Dr Desiree Mesaros, DM Research and Consulting. |
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