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Timber Frame Insulation
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. In this respect timber frame performs much better than standard masonry construction. Timber frame offers unique advantages to home owners, builders and contractors:
- Construction is faster
- A wide range of U-values can be achieved depending on Building Regulations requirement
- 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
- Relatively light weight requiring reduced footings and foundations compared to masonry construction
Timber frame construction is the developed world’s most widely used residential building method. It fulfils a 21st century agenda, offering a method of construction which is engineered, energy efficient, sustainable and quality assured. With a huge supply of plantation timber readily available in the UK and Ireland this form of construction is very environmentally friendly.
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. The vapour control layer may be incorporated within the plasterboard or installed separately.
Joints should be as few as possible and sealed, with special care taken around penetrations for services.
A breather membrane on the outside of the sheathing is also necessary to protect against 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.
In some timber framed systems, such as the Twin Insulated, the insulation in the cavity maintains the timber frame above the dewpoint temperature thus reducing the condensation risk even further.
Timber frame and fire performance
A half hour fire resistance in domestic external walls is required by the Building Regulations. Timber frame walls with mineral wool insulation are ideal for meeting this requirement. 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. In the Twin Insulated system, cavity barriers are not necessary because the cavity is completely filled with non-combustible mineral wool insulation.
Twin Insulated Crown FrameTherm and Crown DriTherm Cavity Slab
This system is unique to Knauf Insulation and has been developed to meet the demand for higher insulation values in timber frame construction. It consists of a standard timber frame wall on the inside, a cavity fully or partially filled with Crown DriTherm Cavity Slab and an outer leaf of brickwork cladding. The system can be used in any type of building.
