Internal wall insulation is commonly used in existing buildings and in retrofit projects. The thermal performance of insulated cavity walls can be significantly improved by adding a layer of PIR insulation boards on the internal face of the walls. For masonry walls, the fixing method used will be dependent on the internal finish of the existing wall. In order for the wall insulation to be fitted correctly and achieve maximum performance, preparation of the internal surface is essential.
For walls with a very uneven surface, it is unlikely that dot and dab application of the insulation boards will be suitable, so using mechanical fixings will give the best result. This could include the fixing of timber battens on the wall surface to provide an even surface for the fixing of insulation.
For walls that are in good condition with an even surface, adhesive fixing of the wall insulation boards can be used.
For masonry surfaces with cracked or damaged plaster, it is important to ensure the damage is repaired prior to the installation of the internal insulation boards. For brick or block walls, pointing with mortar should be completed in order to prevent any air gaps and minimise thermal bridging issues.
All walls should be assessed to determine if they are suitable for dry lining prior to works commencing.
Mannok Therm Laminate-Kraft / MLK insulation boards are recommended for internal dry lining of masonry cavity walls. These high performance PIR insulation boards are faced on one side with a kraft paper facing which is suitable for adhesive or mechanical fixing methods, and plasterboard bonded on the other side to give a suitable internal wall finish.
The thickness of wall insulation required will be dependent on the U-values you wish to achieve. Installing internal insulation impacts on the floor space of the internal rooms, so careful detailing can help minimise thickness of insulation to minimise the impact on floor space whilst achieving excellent thermal performance. See the below table for U-value results based on the wall construction shown. For project specific U-values use our free U-value calculator.
Required thickness of Mannok Therm Laminate-Kraft / MLK:
Cavity wall with internal drylining
Mannok Therm Laminate-Kraft / MLK | Partial fill cavity insulation (mm) | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
50 | 60 | 75 | 80 | 100 | ||||||
Thickness (mm) | U-value (W/m2K) | |||||||||
37.5 | 0.22 | 0.20 | 0.17 | 0.17 | 0.15 | |||||
42.5 | 0.21 | 0.19 | 0.17 | 0.16 | 0.14 | |||||
50.5 | 0.19 | 0.18 | 0.16 | 0.15 | 0.13 | |||||
62.5 | 0.17 | 0.16 | 0.14 | 0.14 | 0.12 | |||||
72.5 | 0.16 | 0.15 | 0.14 | 0.13 | 0.12 | |||||
82.5 | 0.15 | 0.14 | 0.13 | 0.12 | 0.11 | |||||
92.5 | 0.14 | 0.13 | 0.12 | 0.12 | 0.11 |
103mm brick outer leaf; 40 - 50mm low emissivity residual cavity; Mannok Therm Wall / MW; 100mm concrete block (conductivity as shown); 12mm plaster with dry wall adhesive; Mannok Therm Laminate-Kraft / MLK insulated plasterboard on plaster dabs. Calculations performed to BS EN ISO 6946, taking account of repeating thermal bridges.
For help and advice on any of our products and how they might fit your needs please contact our Technical by Mannok team.
Cavity Wall Insulation
Solid Wall Insulation
Dormer Wall Insulation