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Wall Insulation: Insulating solid walls with internal dry lining – insulation boards fixed to battens

Solid stone wall

Existing plaster finish

Battens on a strip of DPC

Mannok Therm Wall / MW or Mannok Therm Laminate-Foil / MLF PIR insulation boards

Plasterboard

Internal finish

  • Solid stone wall

  • Existing plaster finish

  • Battens on a strip of DPC

  • Mannok Therm Wall / MW or Mannok Therm Laminate-Foil / MLF PIR insulation boards

  • Plasterboard

  • Internal finish

Insulating existing solid walls can vastly improve the energy efficiency of the building, giving greater comfort and living conditions and reducing heating costs resulting in lifetime energy bill savings. With a large percentage of a building’s heat loss occurring through the walls, it is important to combat this by installing appropriate insulation. Internal dry lining of solid walls is particularly effective for retrofit projects where there is a requirement to improve the U-values of the building. The addition of internal wall insulation may have a small impact on the internal floor space, but will help significantly reduce heat loss and improve the structure’s U-value.

The type of wall structure will determine the insulation installation method used. For uneven wall -surfaces, the fixing of timber battens to provide an even surface for the insulation boards is best in order to achieve a uniform layer of insulation and prevent thermal bridging issues.

PIR wall insulation boards will provide excellent thermal performance with simple installation. Mannok Therm Wall / MW insulation boards can be used for this application, and with a double foil facing will provide superior thermal performance.

Alternatively, Mannok Therm Laminate-Foil / MLF PIR insulation boards may be used to eliminate the requirement for an additional layer of plasterboard for the internal finish. These insulation boards are also foil faced on the inner side and have a plasterboard facing on the other side.

The low emissivity foil facings on each of these insulation boards increase the thermal resistance and improves the overall thermal performance of the wall. It also minimises the board thickness required to achieve the design U-value, which is an important consideration when applying internal insulation.

How to install solid wall internal insulation: internal dry lining fixed to battens

1. Ensure the surface of the existing wall is prepared correctly for the fixing of the timber battens. This includes removal of skirting boards, cupboards and other fixings, picture rails and window boards, as well as any wall coverings with high vapour resistance, such as vinyl wallpaper or gloss paint.

2. Fix the treated timber battens to the wall, ensuring they are isolated from the wall surface by a strip of DPC material. Uneven wall surfaces should be packed out to give a true surface for installing the wall insulation boards. Fix additional battens to support cupboards, radiators, shelves and any other fittings.

3. Fit the Mannok insulation boards to the timber battens at 400mm centres, ensuring the insulation boards are butted tightly together to form a continuous layer of insulation.

4. Fix the insulation boards using screws which have been selected to minimise heat loss. U-value calculations for the wall should account for the additional heat loss resulting from mechanical fasteners.

5. If using Therm Wall insulation, tape the boards with metalised tape to form an AVCL which will prevent moisture from the building interior condensing on the cold side of the insulation.

6. If using Mannok Therm Wall / MW insulation boards, fit a separate plasterboard lining to the surface of the boards and fix this to the timber battens. If using Mannok Therm Laminate-Foil / MLF insulation, the plasterboard finish on the external surface means a separate layer of plasterboard is not required.

Insulation thickness and U-values

To calculate the required thickness of wall insulation, refer to our online U-value calculator or reference the tables below.

Required thickness of Mannok Therm Wall / MW

Mannok Therm Wall / MW insulation fixed to timber battens @ 400mm centres:

Masonry Type
215mm Brick 500mm Stone 215 Dense Block 215mm Aircrete Thermal Block (B5)
Thickness (mm) U-value (W/m2K)
37.5 0.44 0.43 0.47 0.32
42.5 0.41 0.40 0.43 0.30
50.5 0.35 0.34 0.37 0.27
62.5 0.29 0.29 0.30 0.24
72.5 0.26 0.26 0.27 0.21
82.5 0.23 0.23 0.24 0.19
92.5 0.21 0.21 0.22 0.18
102.5 0.19 0.19 0.20 0.17
112.5 0.18 0.17 0.18 0.15

U-value results above based upon wall construction shown:

Masonry (see table); 15mm plaster; 25mm cavity; Mannok Therm Wall / MW with 12.5mm plasterboard or Mannok Therm Laminate-Foil / MLF insulated plasterboard. Calculations performed to BS EN ISO 6946, taking account of repeating thermal bridges

Required thickness of Mannok Therm Laminate-Foil / MLF

Mannok Therm Laminate-Foil / MLF insulation fixed to timber battens @ 400mm centres

Masonry Type
215mm Brick 500mm Stone 215 Dense Block 215mm Aircrete Block (B5)
Thickness (mm) U-value (W/m2K)
37.5 0.44 0.43 0.47 0.32
42.5 0.41 0.40 0.43 0.30
50.5 0.35 0.34 0.37 0.27
62.5 0.29 0.29 0.30 0.24
72.5 0.26 0.26 0.27 0.21
82.5 0.23 0.23 0.24 0.19
92.5 0.21 0.21 0.22 0.18
102.5 0.19 0.19 0.20 0.17
112.5 0.18 0.17 0.18 0.15

U-value results above based upon wall construction shown:

Masonry (see table); 15mm plaster; 25mm cavity; Mannok Therm Wall / MW with 12.5mm plasterboard or Mannok Therm Laminate-Foil / MLF insulated plasterboard. Calculations performed to BS EN ISO 6946, taking account of repeating thermal bridges.

Need technical support?

For help and advice on any of our products and how they might fit your needs please contact our Technical by Mannok team.

  • Floor Insulation
  • Pitched Roof Insulation
  • Flat Roof Insulation
  • Wall Insulation