Paint is used in the construction of homes for purposes of decoration, protection (I.e. painted metal surfaces to prevent corrosion) or functionality (painting a surface white to reflect heat). The use of paint in construction can pose problems for green building as paint itself often contains toxic elements, releases fumes and is made in ways not beneficial to the environment
Paint consists of three main parts, the pigment, the binder and the solvent. The pigment is the part of paint that gives it the colour that is required. This used to be made from materials such as lead which proved to be a health risk and as such has been banned from modern paints. These days paint manufacturers are using different materials to create the pigment with a common one being titanium dioxide which is a much less toxic and is even found in food colourant
The binder of paint is the component responsible for it forming as a film and its adhesion to the painted surface. The binder is also responsible for the finish of the paint affecting things such as glossiness and durability. Binder can be made from natural and synthetic sources such as acrylic, polyurethane and oil based substances.
The main purpose of the solvent in paint is to alter the viscosity. The solvent is volatile and does not form part of the paint film often evaporating away causing the fumes associated with painting. The types of solvent used varies, whilst not technically a solvent water cab be used as well as other materials such as petroleum distillate, ethers, ketone's and glycol ethers.
The main pollutant paint gives off when in use is Volatile Organic Compounds (VOC's). VOC's are released from the paint often while drying from the solvent used. VOC's can have a huge effect on the internal air quality of a building and the environment and are a major contributor to sick building syndrome (a feeling of unwell caused by polluted internal air from various sources such as fumes leaving occupants with head aches and generally feeling ill). In Britain the coatings industry has come up with a labelling system to warn consumers of the VOC content of materials such as paint, these consist of 5 bands and a warning that VOC's are an atmospheric pollutant. The bands are Minimal - VOC content 0% to 0.29%, Low - VOC content 0.3% to 7.99%, Medium - VOC content 8% to 24.99%, High - VOC content 25% to 50% and Very High - VOC content more than 50%. When considering which paint to use in an environmentally friendly build it is always best to look for the lower VOC rating as these often contain less synthetic materials and will increase the internal air quality of a building reducing the load on ventilation systems.
Organic paints are the ideal choice for the green builder. These often contain Zero VOC's or solvents, They don't contain heavy metals as pigment and do not use other environmentally unfriendly materials such as vinyl chloride. These types of paints use water as there solvents and although they do contain some synthetic ingredients such as binders (due to natural oil based binders taking days to dry and others such as rosins requiring solvents like turpentine to be of any use) they are still non toxic. Organic paints often tend to be more breathable then synthetic paints, this is important as painting surfaces with modern paints which have low breathability can seal in dampness. Using a breathable paint is important on new walls and plaster, which can take a number of years to dry thoroughly. Low breathable paints will also result in increased condensation which encourages mould growth.
Recycled paint is also an option for the green builder. Paint can be recycled using two methods re blending and reprocessing. Re blended paint is manufactured from left over paint handed into recycling centres this is then screened and remixed using little new materials, however colour choice is limited to some neutral colours (I.e. white's). Reprocessed paint takes the same recycled paint and mixes it with new materials allowing a much wider choice of colours. Reprocessed paint should be used for exterior painting with re blended used internally, this is because reprocessed is a higher quality then re blended. Recycled materials can also be used in paint, for example glass can be recycled into paint with some recycled paints containing up to 30% glass.
Paint no longer needs to be thought of as a toxic but necessary part of the build, low VOC, organic and recycled paint are now readily available to the green builder and can cut the environmental impact of the structure as well as improving the air quality for its occupants.
