Knauf Earthwool Loft Roll 44 Insulation is available in 100mm, 150mm and 200mm thicknesses. Pre cut rolls of 400mm and 600mm strip are produced by Knauf. It has a thermal conductivity of 0.044 W/mK. Earthwool is usually laid in two layers, the first layer should be put between the joists and the second layer should be laid over the joists at a right angle to the first layer. It is wrapped in a polythene packaging for short term protection.