100mm Knauf Loft Roll 44 Combi-Cut Insulation - 13.89m²

One of the most common variety of loft insulation is loft roll insulation. Often made from glass mineral wool or fibreglass, it is designed to prevent the loss of heat by trapping air within the fibres, and is installed between joists at ceiling level, i.e the “floor” of the loft. This prevents heat from within the living areas of the home from being lost via thermal bridging into the loft. 

Knauf Loft insulation roll consists of 1 roll of mineral wool with a total width of 1140mm. They are “combi-cut” which means that the roll is perforated along the length of the roll at various points to allow you to split it into either two rolls at 570mm wide, or three rolls at 380mm wide. Each roll measures 12180mm (12.18m) long, and can be cut to size using a sharp utility knife. Typically, when installing Loft Insulation, 100mm roll is used as the first initial layer laid between the joists, and thicker insulation is added on top to reach the minimum thickness required by building regulations (270mm/350mm in Scotland).

Knauf Loft Insulation roll is a thermal insulation designed for use for insulating against heat loss through thermal bridging in lofts. It is made from a glass mineral wool, which is created by spinning molten glass into fibres, which are then compressed to create a soft and flexible wool-like batt or blanket. Being made from glass, it is a highly non-combustible material, achieving the highest “Euroclass A1” Resistance to Fire rating, and is bound with a patented ECOSE® binder which avoids added formaldehyde or phenol.

Knauf Loft Roll 44 is designed to be easy to install within lofts to prevent loss of heat through loft spaces. It is placed at “ceiling level” within the loft (between and on-top of joists of the ceiling below) and is typically layered to take advantage of the space at loft level to achieve high levels of thermal insulation. Typically, a thinner thickness (100mm) is installed between the joists, and then thicker rolls are laid in a perpendicular direction on top of the joists to achieve an overall thickness that meets building regulations.

Loft roll 44 is “pre-cut” (perforated) in various places to allow it to be split into either two 570mm width rolls, or three 380mm width rolls. If neither of these widths suit the joist spacing, it is recommended to cut the entire roll to size with an insulation saw whilst still in the packaging.

Knauf Loft Roll is easily cut using a sharp utility knife. 

Read: How to Insulate and Board a Loft.

Building regulations dictate that loft insulation should be a minimum of 270mm (350mm in Scotland) which can be achieved even with just two layers of insulation. However, increasing the thickness of the loft insulation roll maximises the energy efficiency achieved through your loft insulation, so it is advised to make the insulation as thick as space and budget will allow, with new build properties tending to reach 400mm - 500mm depth. 

The U-value (thermal transmittance) of a building component such as a wall, roof, or window, measures its thermal conductivity or how easily heat can pass through it. The lower the U-value, the better the insulation. To calculate the U-value, you typically need to consider several factors, including the materials used, their thicknesses, and any air gaps. A general formula for calculating the U-value:

U = 1 over R

Where:

U = U Value

R = The total thermal resistance of the building component, including all layers of materials and air gaps.

Use the Knauf U Value Calculator.