Alternatives for moth treatment in woolCopy Link

Wool Insulation Wales

Wool Insulation Wales (WIW) aims to develop, manufacture and supply Welsh sheep’s wool thermal and acoustic insulation products on a large scale. These are both rolled loft insulation and insulation for use in wall panels.

WIW predominantly will serve housing associations and industrial or commercial property owners that when buying wool insulation, gain an extra metric by which they can measure their ESG goals. Large scale users of WIW products can also boast green supply chain credentials because the primary producers of wool are located in local rural economies. WIW has ambitious future volume targets for its product.

Moths

Species of moths that attack wool are commonly called ‘clothes’ or ‘carpet’ moths depending on where they are found and what fabrics they target. The moths are looking for animal-based fibres to lay their eggs because the larvae feed on keratin, a protein found in animal fibres, and also in dust. There are two main moth species that cause most of the damage to clothing and home textiles - the Webbing (or Common) Clothes Moth and the Case-bearing moth. 

The transition from winter to spring triggers pupation and the move to the next lifecycle stage. Flying clothes moths are usually seeking to mate. As the adult webbing clothes moths mature, they will be less active and prefer dark, undisturbed areas, where they will lay their eggs. They target areas that will leave them undisturbed and on the animal fibre based food source that will be needed by the larvae to survive after they hatch. The eggs are mostly under 1 mm long and barely visible. A female will lay several hundred during her lifetime.

The eggs are attached with a glue-like substance and can be quite difficult to remove. After the egg hatches, the clothes moth larva will immediately look for food. Webbing moth larvae can obtain their required food within two months to progress to the next stage of their life-cycle, but if conditions are unfavourable they will feed intermittently for a long time. Whether it takes two months or two years, each larva will eventually spin a cocoon in which it will pupate and change into an adult Webbing Clothes Moth.

Case-bearing moths are also widespread. Again it is only the larvae which eat keratin. The Case-bearing moth builds itself a portable case out of debris such as fibres and hairs, in which it can hide.

Both species have a similar life cycle. The adults do not live long and the mated adult female lays hundreds of eggs in her short life time. The eggs will be laid in the quieter, darker and undisturbed areas of materials and lay dormant for approximately 4 to 10 days before hatching. The larvae can live for up to 2 years, which accounts for continued damage as they eat through the winter months, but in warmer periods they will pupate within 2 months of hatching, resulting in a number of cycles through the Spring to Autumn months. The pupation stage will last up to 2 weeks before the adults emerge. The adults are relatively harmless and only live 2-3 months.

Wool insulation and anti-moth treatment

Using wool for building insulation enables the construction industry to meet its carbon targets in a safe and sustainable way, as part of the circular economy. It has a short value chain, with most wool production coming from the same places. 70% of UK Wool is traded through British Wool.

Raw wool is first of all scoured by major scouring plant operators before arriving to WIW for production of insulation. Scouring involves the following stages:

• 5 washes at temperatures ranging from 55-73C with a total immersion time of 7 minutes
• The First three tanks are charged with a biodegradable alcohol ethoxylate detergent and sodium carbonate
• The final tank is controlled to a neutral pH by the addition of formic acid
• The wool is then passed through a dryer at temperatures ranging from approximately 65-95 degrees centigrade for a period of approximately 3 minutes.

During the last stage of washing, the material is treated with anti-moth agents (typically borax or permethrin) in the coolest of a series of washes. The final wool material is provided to WIW, that creates its final product (see figure 1), in a similar way to felt matting.

Borax is the main anti-moth treatment used for wool insulation, with different treatments being appropriate for different use cases (e.g. clothing). Borax works by desiccating the moth larvae within the wool. Historically, many different types of chemicals were used for moth treatment, but many cannot be used now due to Health, Safety and Environmental (HSE) regulations. 

Figure 1: Final wool insulation product