Overview
Insulated external timber frame walls can provide better insulation performance than masonry walls of comparable thickness. Timber frame is also widely recognised as the most environmentally friendly construction method – a construction with extremely low ‘embodied energy’. This is the energy required to manufacture a building component or material, deliver it to site and install or construct it. In this respect timber frame performs much better than standard masonry cavity wall construction. Timber frame offers unique advantages to home owners, builders and contractors:
- Reduced construction time
- A wide range of U-values can be achieved depending on the required level of thermal performance
- Excellent thermal efficiency
- Potential for easy future renovation
- Pre-fabrication enhances quality control due to off site manufacture, thereby reducing the risk of on-site workmanship problems
- Light weight requiring reduced footings and foundations compared to masonry construction
The importance of condensation control
A vapour control layer is essential on the ‘warm’ side of the insulation to reduce the risk of condensation forming within the timber frame. Joints should be as few as possible and sealed, with special care taken around penetrations for services.
A vapour permeable membrane on the outside of the sheathing board is also necessary to protect the timber frame from water penetration whilst allowing water vapour to escape.
As a rule of thumb, the vapour resistance of the materials on the ‘warm’ side of the insulation should have at least five times the vapour resistance of the materials on the ‘cold’ side of the insulation. Alternatively, calculations should be carried out to assess the risk of interstitial condensation by referring to BS 5250 : 2011.
Timber frame and fire performance
In most timber frame constructions, cavity barriers must be used to divide up the external cavity in order to reduce the risk of fire spread.
Timber Frame Walls
TF01: Single Layer Between Studs
TF02: Single Layer Between Studs with Service Void
Tf03: Between Studs with Insulated Plasterboard
Tf04: Blown in Insulation, Between Studs
Tf05: Built in between studs with partially filled cavity
Solution Optimiser and Pathfinder
| Application | Product(s) | Achievable U-value Range |
| Single layer - between studs | Knauf Insulation FrameTherm® Rolls and Slabs | 0.22-0.30 W/m²K |
| Single layer - between studs with service void | Knauf Insulation FrameTherm® Rolls and Slabs | 0.19-0.30 W/m²K |
| Between studs with insulated lining | Knauf Insulation FrameTherm® Rolls and Slabs & Knauf Insulated Plasterboard | 0.17-0.30 W/m²K |
| Blown in, between studs |
Supafil® Frame |
0.14-0.29 W/m²K |
| Built in between studs with partially filled cavity | Knauf Insulation FrameTherm® Rolls and Slabs & Rocksilk® Rainscreen Slabs | 0.08-0.24 W/m²K |