Product Description:

Knauf Loft Roll 44 Combi-Cut is a flexible glass mineral wool insulation roll, 170mm thick and covering 6.49m². It is used for thermal insulation of pitched roofs at ceiling level, laid between and over ceiling joists, and is equally suitable for insulating suspended timber floors.

The Combi-Cut format is what makes the roll quick to work with in a loft. It is partially cut along its length so it can be separated by hand into narrower widths to fit between standard joist centres, or left whole and rolled out full width across the joists for the top layer, which removes most of the cutting from the job.

The 44 designation refers to the material's thermal conductivity of 0.044 W/mK, which at 170mm gives an R-value of around 3.86 m²K/W. The 170mm thickness is the one most commonly laid as the upper layer over a 100mm roll between the joists, because the two together come to 270mm — the depth currently recommended for loft insulation. Rolled out at right angles across the joists, the top layer covers the timbers themselves and removes the cold bridging that would otherwise run through them. Glass mineral wool is lightweight, resilient, and non-combustible, and sits snugly without slumping or leaving gaps, which is where most of the performance is lost in a poorly laid loft. Wear gloves, a dust mask, and long sleeves when handling, keep the insulation clear of downlighters and flues, and do not block eaves ventilation.

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