Insulation FAQs

Technical support FAQ

Can Loft Roll be used in my stud wall or in between rafters?

No, Loft Roll is only designed for use on horizontal applications i.e. as ceiling insulation in cold ventilated roofs.  Loft Roll is a lightweight product designed for optimum thermal performance and ease of application, as such it will not withstand the forces of gravity when installed vertically, nor does it offer any “friction fit” properties.

How do I cut Loft Roll?

Knauf Insulation Loft Rolls are available as “Combi Cut” for ease of application, however if sizes do not match requirement then the whole roll can be cut when in the pack using an insulation saw or sharp knife with a plain or serrated edge.

What is the thermal conductivity of Acoustic Roll?

Acoustic Roll is not assigned a discrete thermal conductivity as it is produced to meet the min 10kg/m3 as per building regulations. If a thermal requirement is also requisite other Knauf Insulation products that meet the minimum density requirements can be used. Contact our Technical Services Team for further information on 01744 766 666

Note: for Robust details certain density criteria above the minimum may be required to achieve compliance.

Can any Loft Roll product be used in applications where acoustic absorbance is needed?

Only Loft Roll 40 can be used in horizontal applications where acoustic absorbance is required in relevant Approved Documents  where a product with a  minimum density of 10kg/m3 is deemed to supply the required acoustic absorbence.

Note: for Robust details certain density criteria above the minimum may be required to achieve compliance.

How does the density of Glass Mineral Wool insulation affect its acoustic performance, and is there an optimum?

In acoustic terms virtually all glass and rock mineral wool products are relatively low in density, this means that unless there are specific frequency’s to be damped, products in the range of 10 – 60kg/m3 will as a rule of thumb give similar results.

Note: Insulation products alone do not give a sound reduction value, only systems or construction elements give this value. Therefore any sound reduction numbers quoted will be in reference to a built system e.g. a partition wall or separating floor not a slab or roll of insulation.

Why do you not declare the density of some of your products?

Knauf Insulation products purposed primarily for thermal insulation are manufactured to meet the requirements of the relevant harmonized standard, and as such density is not declared characteristic. In the case of thermal performance density alone is not a parameter that will relate directly to R or K value. This is the case as each product is designed not only for thermal performance but also for suitability in the application intended, where a product is like to be used for Acoustic insulation as well as thermal we do confirm the minimum density. Please contact our Technical Services Team for further information on 01744 766 666

Does density relate directly to thermal performance?

As above; not directly in many cases as products are manufactured to meet application demands as well as thermal performance. Select your product in accordance with the intended application in the first instance and match up to the required thermal performance or R value, finally you may need to take into account density from the point of view of acoustic absorption.

What is meant by reaction to fire?

REACTION TO FIRE is the inherent combustibility of a material.  

What does Euroclass A1 mean?

Euroclass A1 means that products meet the highest possible level of non-combustibilty for thermal insulating products when classified to BS EN 13501-1, this classification is a requirement of the relevant harmonized standard as a part of CE marking. A1 means that the product has an extremely low amount of combustible material within it and therefore will not contribute to a developing fire in terms of adding fuel

What is the difference between reaction to fire and fire resistance?

REACTION TO FIRE is the inherent combustibility of a material  

Fire resistance relates to the ability of a built system or element of a building to resist the effects of a developed fire, fire spread and more importantly allow occupant escape and safety. It takes into account how; the system maintains its structure as a loadbearing elements prevents the spread of the fire and provides protects adjacent spaces or buildings from the heat of the fire.

Do you offer a service to collect waste mineral wool?

We do not accept waste mineral wool at present. Although we have investigated and continue to investigate several possibilities for accepting waste mineral wool insulation back into our facilities and so diverting it from landfill, there are several challenges that we have yet to overcome:

  • Mineral wool insulation is a relatively low-density material. Transporting large quantities uncompressed is relatively inefficient in energy and emissions terms. That's why we compress the new product as much as we can when we pack it in the factory. 
  • Our glass mineral wool already contains around 80% recycled materials. One lorry can bring some 20 tonnes of the recycled materials to the Veolia glass recycling facility adjacent to our St. Helens plant; but a large articulated truck wouldn't hold more than 3 or 4 tonnes of waste mineral wool insulation.
  • Differentiating rock mineral wool insulation from glass mineral wool insulation can be difficult, especially if the product is older. However, rock mineral wool and glass mineral wool are made in quite different processes and couldn't be reprocessed together. 
  • Any contamination can cause serious damage to our production equipment. Cleaning recovered waste erodes the environmental benefits of recovering.

As technology improves and segregation at building sites and refurbishment projects improves, so may our ability to accept and recycle the waste. As such this is an area which we are monitoring very closely so that we hope to offer this service to our customers in the future.

Can DriTherm® Cavity Slab be used below DPC level?

DriTherm® Cavity Slabs are a non-hygroscopic, glass mineral wool slab that incorporates a silicon enhanced Ecose® binder designed for use in masonry cavity walls. DriTherm® Cavity Slabs can be used in situations where they bridge the DPC in walls. Tests by the British Board of Agrément confirm that DriTherm® Cavity Slabs will not transmit water to the inner leaf, nor will they transmit moisture by capillary action across the cavity or from below damp proof course level.

Does full filling with DriTherm® Cavity Slab eliminate the need for cavity barriers?

A full fill cavity with KDriTherm® Cavity Slabs will meet the requirements of the Building Regulations 2010 Approved document B (Part 6), therefore cavity barriers will not be required. DriTherm® Cavity Slabs have the highest Euroclass Classification, Euroclass A1 Reaction to Fire Classification, in accordance with BS EN 13501-1 : 2007 as the insulation fully fills the cavity, no cavity barriers are required. (For more details please see: BBA Certificate 95/3212)

What do the numbers on some of your product names mean?

The numbers on our product names are related to the thermal conductivity of the product. So the lower the number, the better thermal performance that product will give. For example Loft Roll 40 will give a better thermal performance than Loft Roll 44.