between studs in a stud frame wall. Most manufacturers provide custom sizes as well and batts and ropes are easy to cut once on site. Wool insulation costs significantly more than conventional fiberglass insulation, but does not require the use of protective gloves, and may have significantly lower health risks to both the building occupants and the installation crew. It can be used in the roof, walls and floors of any building type as long as there are spaces to put the insulation in. Installing wool insulation is very similar to installing conventional insulation batts; it can be held into place with staples or it can be friction-fit, which involves cutting the insulation slightly bigger than the space it occupies, using friction to hold it in place. Environmental considerations Some wool used to manufacture insulation is the wool discarded as waste by other industries due to its colour or grade. As a controlled waste product it cannot be disposed of until it is cleaned. Hence the energy footprint of washing the wool is attributed to the livestock industry under PAS2050. There are some primary environmental factors that need to be considered when looking for a source of wool, such as the way the flock is treated for pesticides, the chemicals used in the treatment of the wool after shearing, and the distance from the source to its final destination. Sheep are often treated with insecticide and fungicide in a process called dipping. This leaves a residue on the fleece and can result in groundwater contamination if used improperly. These residues are often washed off once the fleece is sheared, but this results in three byproducts: grease, liquor, and sludge. The first two can be safely disposed of, but the third contains remnants of the pesticides which cause a concern for disposal. Sheep wool insulation is often treated with borax to enhance its fire retardant and pest repellent qualities. The level of Borax is relatively low only 4% dry weight although the scouring baths have a higher load of 8–9%. Borax mining employs one of the cleanest mining techniques available but borax is increasingly coming into focus as a suspected reproductive toxin having been considered relatively safe for many years; animal ingestion studies in several species, at high doses, indicate that borates cause reproductive and developmental effects. The most significant exposure route for humans is inhalation which raises questions over whether