such as insulation for flooring. Minor damages to cork surface can make the material more prone to staining. Sheep's wool insulation Sheep's wool insulation is a very efficient thermal insulator with a similar performance to fiberglass, approximately R13-R16 for a 4-inch-thick layer. Sheep's wool has no reduction in performance even when condensation is present, but its fire retarding treatment can deteriorate through repeated moisture. It is made from the waste wool that the carpet and textile industries reject, and is available in both rolls and batts for both thermal and acoustic insulation of housing and commercial buildings. Wool is capable of absorbing as much as 40% of its own weight in condensation while remaining dry to the touch. As wool absorbs moisture it heats up and therefore reduces the risk of condensation. It has the unique ability to absorb VOC gases such as formaldehyde, nitrogen dioxide, sulphur dioxide and lock them up permanently. Sheep's wool insulation has a long lifetime due to the natural crimp in the fibre, endurance testing has shown it has a life expectancy of over 100 years. Wood fiber Wood fiber insulation is available as loose fill, flexible batts and rigid panels for all thermal and sound insulation uses. It can be used as internal insulation : between studs, joists or ceiling rafters, under timber floors to reduce sound transmittance, against masonry walls or externally : using a rain screen cladding or roofing, or directly plastered/rendered, over timber rafters or studs or masonry structures as external insulation to reduce thermal bridges. There are two manufacturing processes: a wet process similar to pulp mills in which the fibers are softened and under heat and pressure the ligin in the fibres is used to create boards. The boards are limited to approximately 25 mm thickness; thicker boards are made by gluing (with modified starch or PVA wood glue). Additives such as latex or bitumen are added to increase water resistance. a dry process where a synthetic binder such as pet (polyester melted bond), polyolefin or polyurethane is added and the boards/batts pressed to different densities to make flexible batts or rigid boards. Cotton batts Cotton insulation is increasing in popularity as an environmentally preferable option for insulation. It has an R-value of around 3.7 (RSI-0.65), equivalent to the median value for fiberglass batts. The cotton is primarily recycled industrial scrap, providing a sustainability benefit. The batts do not