Paints
Paints have three constituents: pigments for colour, a binding substance to hold the particles of pigment together and a solvent to enable the mixture to flow freely. It is the solvents which are the main problem since they are designed to evaporate. Most of the solvents used come into the category of volatile organic compounds (VOCs) and are aggressive pollutants. It has been calculated that over 500 000 tonnes of solvent are released into the atmosphere globally each year. (Eco-Renovation, Edward Harland, Chelsea Green Publishing Company, Vermont, USA, Revised edition 1999). Another statistic is that organic solvents are responsible for 20 per cent of the hydrocarbon pollution in the atmosphere and second only to motor vehicles (Berge, 2000).
It is the solvents deriving from the petrochemical industry which are the most toxic and which are implicated in the phenomenon of off-gasing. This may continue for a considerable time with sometimes serious health consequences. (A comprehensive list of surface treatments and their solvents is to be found in Berge, 2000: 405.In their finish they appear much the same as conventional petrochemical emulsions and are as easy to apply. They are solvent-free and do not have the pervasive smell of chemically based paints. They are also biodegradable. An example for interior walls is Aquamarijn Maril matt emulsion class 2.
A traditional paint system for walls and ceilings is one which is supplied in powder form to which water is added just before use. It is made from natural substances and comes in a variety of colours. It contains no harmful chemicals and is washable after curing. A proprietary brand is Holzweg Cassein wall paint. The Holzweg colour range includes 21 natural earth pigments and 15 mineral pigments.
Holzweg also produces benign paints for exterior use, as well as varnishes for timber and waxes for floor treatment. Exterior timber preservative paints come in Scandinavian Iron Oxide Red ideal for weather-boarding and garden timber. Aquamarijn Garol garden furniture oil class 1 is ideal for the treatment of exterior hardwood, penetrating the timber protecting it from weathering.
All the above products are available from Construction Resources Ecological Building Supplies, 16 Great Guildford Street, London SE1 0HS, Tel: 0207 450 2211.
A natural paint collection is available from The Green Building Store. Its emulsion paints Primasol and Ecosol are solvent-free. Ingredients include chalk, linseed oil, talcum, earths and bergamot oil (www.greenbuildingstore.co.uk).
Natural Building Technologies uses paint formulae with ancient origins. Its range includes Scandinavian Red Paint, a water-based timber preservative using only natural materials. Information from www.oldhousestore.co.uk
Auro Organic Paint Supplies offers water-based gloss and eggshell paint finishes which avoid VOCs, They are quick drying and can be thinned with water (www.auroorganic.co.uk).
Ecosil from Keim is also VOC-free. It is alkaline and totally inert and prevents algae and mould growth without the use of plasticizers and biocides. It is durable and easy to clean. Its water-solvent, interior, silicate-based paints use organic fillers and pigments (www.spec-net.com.au/company/keim.html).
Nutshell Natural Paints are derived from natural materials, such as plant oils and minerals. Its interior emulsion includes linseed oil and beeswax (www.nutshellpaints.com). Other ecological paints products are:
• Livos natural paints
• Casa paints
• Ecos organic paints from Lakeland Paints Ltd
• Solvent-free paint strippers include ‘Homestrip’ and ‘Eco-Solutions’.
Many of these products can be obtained from Green Choices DIY section (www.greenchoices.org). Some of these products may also be found in Homebase and B&Q stores. Further advice can be obtained from the Ecological Design Association, www.edaweb.org.
Humidity
The choice of paints and varnishes can have an impact on the level of humidity within the home. Temperature is the key factor in determining how much moisture the air can hold. At 20°C air can hold 14.8 g/m3; at 0°C it can only hold 3.8 g/m3. On average, a living room contains 5-10 g/m3. Fluctuations in temperature will alter the carrying capacity of the air and may result in condensation. It is important take up moisture. Such materials act as a stabilizing agent, keeping the humidity level reasonably constant. In other words, hygroscopic materials have a damping effect on moisture fluctuations just as thermal mass regulates temperature (Berge, 2000: 251-253).
It is recommended that internal walls should be finished in hygroscopic emulsion paint over plaster. This ensures that excess moisture can be absorbed by the plaster and masonry wall, releasing it when the internal humidity level creates imbalance. A further benefit is that water vapour carries some gas contaminants, such as nitrogen oxide and formaldehydes. When the water vapour enters the hygroscopic materials these chemicals may be deposited and broken down giving these materials a degree of air cleansing capacity. However, the transfer of moisture will not happen if wall surfaces have impermeable finishes, such as oil-based paints or varnishes, plastic wallpaper or even wallpaper fixed with plastic-based pastes. Internal walls need to breathe, otherwise condensation is virtually inevitable.
Materials for the near future
Saving energy is one thing, buildings as carbon sinks is another. Yet this is the destiny of buildings according to John Harrison, a technologist from Hobart, Tasmania. He has produced a magnesium carbonate-based ‘eco-cement’. In the first place it only uses half the energy for process heating required by calcium carbonate (Portland) cement. The roasting process produces CO2 but most of this is reabsorbed by a process of carbonation as the cement hardens. Using eco-cement for such items as concrete blocks means that nearly all the material will eventually carbonate resulting in an absorption rate of 0.4 tonnes of CO2 for every tonne of concrete. The ultimate eco-credential of this material is the rate of carbon sequestration. According to Harrison, ‘The opportunities to use carbonation processes to sequester carbon from the air are just huge. It can take conventional cements centuries or even millennia to absorb as much as eco-cements can absorb in months’, (‘Green Foundations’, New Scientist 13 July 2002: 40). This means that an eco-concrete tower block can perform the same function as growing trees as it steadily fixes carbon. Harrison estimates that a shift to eco-cement could ultimately cut CO2 emissions by over one billion tonnes, since it could replace 80 per cent of uses currently served by Portland cement.
There is one further attribute to this material. Being less alkaline than Portland cement it can incorporate up to four times more waste in the mix than conventional cement to provide bulk without losing strength. This could include organic waste which would otherwise be burnt or added to landfill, sawdust, plastics, rubber and fly ash.
Eco-cement is not unique in its pollution absorbing properties. Mitsubishi is producing paving slabs coated with titanium dioxide which remove most pollutants from the air. In Japan, 50 towns are already using them and in Hong Kong it is estimated that they remove up to 90 per cent of the nitrogen oxides that create smog. Magnesium-based concrete coated with titanium dioxide could be the basis for eco-cities of the future.
Timber
A basic principle in using timber is to ensure it originates from a sustainable source, such as a managed forest. The problem is the degree of confidence one can place on a label. There have been numerous cases of timber being given this guarantee that have proved to be fraudulent. An inherent problem is that wood from, say, tropical rainforests, passes through any number of intermediaries before it gets to the UK market. At any one stage the authenticity of the sustainability mark can be compromised. There are reliable guides like The Good Wood Guide produced by Friends of the Earth or the National Green Specification (www.greenspec.org.uk). Similarly, Construction Resources is a reliable guide to ecologically reliable timber.
The officially recognized certification scheme for sustainably managed timber is operated by the Forest Stewardship Council (FSC). The council runs a global forestry certification scheme based on two key principles: forest management and chain of custody certification. The FSC label is claimed to indicate that the wood comes from a well-managed forest/wood and guarantees that its place of origin has been independently verified.
In the UK over one million hectares of forest and woodland are FSC certified which represents 38 per cent of total forest cover. Some certificates cover groups of woodland under single management, such as the UK Woodland Trust. Certification covers European and North American hardwoods and softwoods and certain tropical hardwoods. Unfortunately, there have been questions raised about the efficacy of FSC certification in South East Asia in a report by the UK-based Rainforest Foundation Trading in Credibility (November 2002) which states, ‘The public cannot be assured that wood products carrying the FSC logo comes from a well-managed forest’. It cites numerous instances of certification granted in doubtful circumstances. Nevertheless if the FSC as the internationally recognized body with a certification scheme takes account of the criticism levelled against it, confidence should be restored (www.fsc-uk.info).
There is a wide range of temperate hardwoods which are an alternative to the tropical variety. Native hardwoods tend to have greater resistance to weathering and pests than the tropical varieties.
Examples are oak, beech, ash, elm, birch and sycamore. Their sustainability credentials are also usually impeccable. The UK has embarked on an ambitious reforestation programme with a mix of deciduous and coniferous trees. Pine is a good all-purpose softwood available in large quantities from managed forests.
In replacing timber doors and windows, the two things to remember are:
• Ensure that they have FSC certification, preferably from a temperate source. DIY stores are not always all that discriminating.
• They conform to the current building regulations.
The same applies to windows where timber is the ecological material of choice, rather than products from the petro-chemical industry.
Finally, with all materials, there is a degree of embodied energy, that is, energy expended in the processes of production and transportation. This is a huge subject which is being tackled by the Building Research Establishment. However, it certainly helps to use materials that are from a nearby source and therefore have the minimum of so-called carbon miles. As another example of reducing the ecological impact of production and transport, architects Robert and Brenda Vale used bricks from a local works fired by methane from a landfill site for their zero energy house in Southwell, Nottinghamshire.
Main points
• Paints and varnishes should be free from volatile organic compounds.
• Various brands of water-based paints are suitable for both internal and external use.
• For internal walls emulsion paints with hygroscopic characteristics reduces condensation.
• Wood should be certified by the Forest Stewardship Council as coming from a sustainable source.
• Timber from such a source is the ecological choice for window frames.
