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in the valley of the blind

Architect's memo 90: February 2008

The enthusiastic manner in which local businesses are embracing sustainable practices is compelling evidence that we really do want to do the right thing. And why not? Sustainability makes good sense. While it may mean somewhat different things to different people, the definition from the American Heritage dictionary 'Capable of being continued with minimum long-term effect on the environment' seems to encapsulate the nub of it.

When Environmental Choice NZ was set up, industry was given the opportunity to input into the criteria. The paint industry presented a strong case that any paint considered must first pass a recognised quality standard. The thinking was that, first and foremost, the paint must be able to do its job. There was, at that time, evidence from overseas that poorly performing paints, sold as environmentally friendly, had, in fact, a greater environmental footprint because of the need for more frequent repaints.

To their great credit, ECNZ heeded this advice, ahead of several overseas jurisdictions who are only now adding actual performance to their criteria.

Given the performance requirements, the main thrust of Environmental Choice was to lower heavy metal content, the use of hazardous materials and VOCs.

Rarely is anything completely straightforward, even in the case of heavy metals. There are several heavy metals including copper, chromium and zinc which, although toxic, are considered, at low levels, to be essential to human health. Selenium which, because of the high levels in grass in some of the mid-western states of the USA, causes toxicity in grazing animals, needs to be added to animal feed here because our low levels can cause deficiency problems.

VOCs are also a contentious subject as discussed in Memo 81. The rational facts of the matter are that the small levels of the relatively low toxicity solvents, especially the sort that are used in waterborne paints, are never going to be the cause of any serious environmental problems either short or long-term. Further, there is no waterborne paint - even zero VOC paint - that would not form a better film with the addition of a little solvent. And yet the paint issues in sustainability seem to have come down to a Dutch auction over VOC levels.

Even the quasi-regulators seem to have lost direction, or, at least, not to have kept up with technology. A low sheen acrylic is restricted to a very low VOC per litre under some green programmes, whether it be a conventional latex type or whether it be a waterborne enamel. The former are relatively mature technology while the latter are actively replacing high VOC alkyd enamels. The anomaly is that a 200gm solventborne enamel is happily accepted by the green legislators while a 55gm VOC low sheen waterborne enamel replacement with nearly a quarter of the VOCs is not! Crazy.

There should be no discrimination between solvent and waterborne systems. A set of performance parameters should be laid down for a paint and a target VOC set. Paints must firstly meet the performance requirements and, only then can they be selected on VOC.

The use of renewable resources is seen as an important element in achieving sustainability. For the paint industry, if this is able to be achieved from materials or byproducts that would otherwise go to waste, then this would be very desirable. The reality is, however, that the major renewable resource used by the paint industry are vegetable oils, which would otherwise be used for human consumption or animal feed.

There is a certain moral dilemma here. The major swing in America to using maize as a raw material for bio-fuel has already seen a tightening of supply (and hence a rise in prices) to the animal feed market. Further shifts in this direction could produce profound distortions in the agriculture industry.

Resene's stance is unequivocal. We believe that our best contribution to sustainability is to offer longevity and thus reduce the need for repainting. Reducing toxicity has always been a way of life at Resene but quality remains paramount.

If you will forgive the use of brand names, the following example fully illustrates our stance:-

A wall on a public convenience is to be coated with a gloss finish.

System A is Resene Quick Dry undercoat and Resene Hi-Glo. The wall gets tagged regularly and, because the graffiti bites deeply into the Resene Hi-Glo, repeated cleaning fails to remove it and the wall must be repainted. This is a monthly occurrence.

System B replaces the Resene Hi-Glo with Resene Uracryl, a two-pack acrylic urethane. The tagging gets wiped off easily and, because of this, after a while the tagging stops. The system is still performing in the second half of its second decade.

Does Uracryl have a high VOC? - yes. Is the VOC toxic? - somewhat but not very. Does the system continue 'outgassing' during its life? - no. Can uncured isocyanates be dangerous if sprayed? - yes. Is the cured film toxic in any way? - no. Is this a sustainable system? - oh yes indeed.

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differences between primers, sealers and undercoats

Architects memos
The Resene architect's memo section provides technical information on a variety of topics relating to paints, finishes and coatings.

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