External Masonry Cavity Walls
EXTERNAL MASONRY CAVITY WALLS

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APPLICATION OVERVIEW

Our recommended full-fill cavity wall systems not only provide the best U-value to wall-width ratio, but are also highly cost effective when compared with alternative solutions.

Full-fill built-in solutions are installed as the walls are built and can be installed in all types of buildings across the built environment, as detailed in their British Board of Agrément (BBA) Certificates.

The walls of a home represent the largest surface through which heat can escape, and are consequently responsible for around 60 per cent of the heat lost from a typical un-insulated house*.

Supafil Blowing Wool is blown into the cavity through a series of small holes drilled in the outer wall by professional approved installing technicians.
*Energy Savings Trust

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RECOMMENDED PRODUCTS

Why Mineral Wool?

  • Mineral wool slabs are sized to fit between wall ties without the need for retaining discs, reducing costs and increasing installation efficiency.

  • Fully filling the cavity prevents mortar snots and other debris falling into the cavity, preventing bridges that can serve as a path for water to track from the outer to inner leaf.

  • Blown-in mineral wool provides a full-fill solution, even if walls are built out of tolerance, reducing the risk of unwanted heat loss.

  • Installed by approved technicians, with no need for product storage on site, improving site efficiency and removing the risk of theft.

Download our Solutions Guide       Download our Masonry Cavity Wall PDF

Typical U-values
Built-in using Earthwool Dritherm Cavity Slab 32 Ultimate

Earthwool DriTherm Cavity Slab 32 Ultimate thickness (mm)Medium block (0.45W/mK)High strength aircrete (0.19 W/mK)Standard aircrete (0.15 W/mK)Lightweight Aircrete (0.11 W/mK)
300 (2 x 150mm)0.110.100.100.10
200 (2 x 100mm)0.150.150.140.14
1500.190.180.170.17
1250.220.210.200.20
1000.260.250.240.23


NOTE: The U-values have been calculated assuming that all walls are lined with 12.5mm standard plasterboard on dabs on standard blocks with 10mm mortar joints. Wall ties assumed to be stainless steel at 2.5 per m2 with a cross-sectional area of no more than 12.5mm2 for structural cavities up to 100mm wide. For cavities greater than 100mm up to 150mm, the cross sectional area of wall ties is assumed to be 24mm2. For cavities above 150mm, the cross sectional area of wall ties is assumed to be 60mm2. Air gap correction level is zero. Multiple layers are required for several of the solutions detailed above.

Typical U-values
Built-in using Earthwool Dritherm Cavity Slab 34 Super

Earthwool DriTherm Cavity Slab 34 Super thickness (mm)Medium block (0.45W/mK)High strength aircrete (0.19 W/mK)Standard aircrete (0.15 W/mK)Lightweight Aircrete (0.11 W/mK)
300 (3 x 100mm)0.110.110.110.10
200 (2 x 100mm)0.160.150.150.15
150 (7 x 75mm)0.200.190.180.18
1250.230.220.210.20
1000.270.260.250.24

NOTE: The U-values have been calculated assuming that all walls are lined with 12.5mm standard plasterboard on dabs on standard blocks with 10mm mortar joints. Wall ties assumed to be stainless steel at 2.5 per m2 with a cross-sectional area of no more than 12.5mm2 for structural cavities up to 100mm wide. For cavities greater than 100mm up to 150mm, the cross sectional area of wall ties is assumed to be 24mm2. For cavities above 150mm, the cross sectional area of wall ties is assumed to be 60mm2. Air gap correction level is zero. Multiple layers are required for several of the solutions detailed above.

Typical U-values
Built-in using Earthwool Dritherm Cavity Slab 37 Standard

Earthwool DriTherm Cavity Slab 37 Standard thickness (mm)Medium block (0.45W/mK)High strength aircrete (0.19 W/mK)Standard aircrete (0.15 W/mK)Lightweight Aircrete (0.11 W/mK)
300 (2 x 150mm)0.110.110.110.11
200 (2 x 100mm)0.160.160.150.15
1500.210.200.200.19
1250.250.230.230.22
1000.290.270.270.26

NOTE: The U-values have been calculated assuming that all walls are lined with 12.5mm standard plasterboard on dabs on standard blocks with 10mm mortar joints. Wall ties assumed to be stainless steel at 2.5 per m2 with a cross-sectional area of no more than 12.5mm2 for structural cavities up to 100mm wide. For cavities greater than 100mm up to 150mm, the cross sectional area of wall ties is assumed to be 24mm2. For cavities above 150mm, the cross sectional area of wall ties is assumed to be 60mm2. Air gap correction level is zero. Multiple layers are required for several of the solutions detailed above.

Typical U-values
Blown-in (injected) using Supafil 34

Cavity width thickness (mm)Medium block (0.45W/mK)High strength aircrete (0.19 W/mK)Standard aircrete (0.15 W/mK)Lightweight Aircrete (0.11 W/mK)
3000.110.110.110.10
2000.160.150.150.15
1500.200.190.180.18
1250.230.220.210.20
1000.280.260.250.24




Note: The U-values have been calculated assuming that all walls are lined with 12.5mm standard plasterboard on dabs on standard blocks with 10mm mortar joints. Wall ties assumed to be stainless steel at 2.5 per m2 with a cross-sectional area of no more than 12.5mm2 for structural cavities up to 100mm wide. For cavities greater than 100mm up to 150mm, the cross sectional area of wall ties is assumed to be 24mm2. For cavities above 150mm, the cross sectional area of wall ties is assumed to be 60mm2. Air gap correction level is zero.

Typical U-values
For fully filled masonry cavity walls - existing - using Supafil 40 (brick outer leaf / cavity / 100mm inner leaf as detailed below)

Cavity Width (mm)Brick (λ - 0.56)Block (λ - 0.1.13)Block (λ - 0.51)Block (λ - 0.34)
1000.320.330.320.31
850.360.370.360.35
750.400.410.390.38
650.440.460.440.42
500.520.560.520.50

Note: The U-values have been calculated assuming that all walls are lined with 12.5mm standard plasterboard on dabs on standard blocks with 10mm mortar joints. Wall ties assumed to be stainless steel at 2.5 per m2 with a cross-sectional area of 100mm - 12.5mm2, >100 - 150mm - 24mm2, >150mm - 60mm2. Air gap correction level is zero.

Typical U-values
For fully filled masonry cavity walls - existing - using Supafil Carbon Plus (brick outer leaf / cavity / 100mm inner leaf as detailed below)

Cavity Width (mm)Brick (λ - 0.56)Block (λ - 0.1.13)Block (λ - 0.51)Block (λ - 0.34)
1000.280.280.280.27
850.320.330.320.31
750.350.360.350.34
650.390.400.390.37
500.470.490.470.45

Note: The U-values have been calculated assuming that all walls are lined with 12.5mm standard plasterboard on dabs on standard blocks with 10mm mortar joints. Wall ties assumed to be stainless steel at 2.5 per m2 with a cross-sectional area of 100mm - 12.5mm2, >100 - 150mm - 24mm2, >150mm -  60mm2. Air gap correction level is zero.

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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.