Pitched Roof Rafter Level (Warm Roof)

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APPLICATION OVERVIEW

Our insulation solutions for warm roofs maximise both space and thermal efficiency, whilst also  contributing to acoustic performance.

Insulation is friction-fitted between rafters, with the option to underline the rafters with a layer of thermal laminate to further enhance thermal performance.

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RECOMMENDED PRODUCTS

Why Mineral Wool?

  • Mineral wool offers the best all-round thermal, fire and acoustic performance when compared to rigid foam boards to insulate between rafters.

  • Mineral wool friction fits between rafters, providing an optimum seal and preventing gaps associated with rigid foam boards, which can otherwise lead to unwanted heat loss.

Download our Solutions Guide    Download our Pitched Roofs Rafter Level PDF

Typical U-values
Using batten and counter batten with Earthwool Rafter Roll (between rafters) and Knauf insulated plasterboard (below rafters) - with draped membrane and 50mm air gap.

 Knauf Insulated Plasterboard thickness (mm)
Rafter Roll Thickness (mm)35506575
150 (2 x 75)0.180.160.150.14
100 (1 x 100)0.240.210.180.17

Note: Rafter sizes assumed to be 38mm wide at 600mm centres (6.3% bridging) and the same depth as the insulation. Knauf Insulated Plasterboard comprised of 9.5mm of plaster board at λ=0.19 where the remainder is the thickness of the thermal laminate

Typical U-values
Using Earthwool Rafter Roll (between rafters) and Knauf insulated plasterboard (below rafters) - with LR underlay pulled taught and insulation to fully depth of rafters

 Knauf Insulated Plasterboard thickness (mm)
Rafter Roll Thickness (mm)35506575
50 (100 + 2 x 75)0.120.110.110.10
225 (3 x 75)0.130.120.110.11
200 ( 2 x 100)0.150.130.120.12
175 (100 + 75)0.160.150.130.13
150 (2 x 75)0.180.160.150.14
100 (1 x 100)0.240.210.180.17

Note: Rafter sizes assumed to be 38mm wide at 600mm centres (6.3% bridging) 10mm deeper than the insulation to account for the draped membrane. Knauf Insulated plasterboard comprised of 9.5mm of plaster board at λ=0.19 where the remainder is the thickness of the thermal
laminate.

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For any U-value calculations for alternative construction build-ups, please contact our Technical Support Team on 01744 766 666.
For written U-value calculations, please email details of your full through construction build-up to technical.uk@knaufinsulation.com and we will respond accordingly to meet your requirements
We are a fully accredited member of the industry leading British Board of Agrément (BBA) U-value and Condensation Calculation Competency Scheme which promotes and assists accurate, objective and consistent calculations of U-values and condensation calculations within the UK construction industry. As part of our ongoing participation in the scheme, we are required to maintain written records for audit trail purposes.