Insulation materials in timber framed structures

Insulation materials in timber framed structures

Timber-framed structure systems are a fast-growing construction technique thanks to quick installation and the possibility of prefabricating the panels.

This construction system is for erecting vertical load-bearing walls in new and renovated buildings. It consists of solid wood studs; bracing panels; semi-rigid insulation material made of fibrous material in one or two layers placed between (front and rear) the studs; a vapor barrier on the inner side of the insulation material; an outer rainscreen; and inner and outer coatings.

The most commonly used insulation materials are panels and semi-rigid mineral wool rolls, although other types are acceptable (polystyrene, polyurethane, cellulose wadding, etc.).
The thermal performance of this system depends on the thermal resistance of the insulation material as well as the section and frequency of structural frame elements. These thermal bridges can deteriorate to varying degrees depending on the position of the insulation material. However, this system has the advantage of permitting installation of insulation material with wide thicknesses between 120 and 200 mm.

Rules to follow

The construction of walls with timber framed structures must be performed in accordance with the detailed guidelines in the NF DTU 31.2 standard for the construction of timber framed houses and buildings. Special care is required to minimize the risk of condensation. For this, it is essential to ensure good water vapor tightness on the inner side to limit the ingress of moisture generated in rooms through the wall.

Durability and performance during use

Insulation material may be exposed to rain during its use. It must therefore have suitable water resistance. Although it does not affect the mechanical resistance of the system, the insulation material used must also support its own weight during installation and remain fixed by insertion between timber frames. Its natural size variations added to the moisture and temperature effects must be limited based on the type of insulation material used.

The durability of the structure depends on maintaining the continuity of the moisture sealing plane during installation and throughout the life of the structure.

For an insulator to be certified by ACERMI for use in timber framed walls, its performance under the stress conditions listed above are checked by ACERMI. The search engine on the ACERMI website (www.acermi.com) includes a use criterion for selecting certified insulation materials for use in timber framed walls. So far, 67 ACERMI certificates for this use are available and downloadable from the website.

Once the insulation product has been selected, all that remains is to follow the installation guidance (Building Code of Practice (DTU), Technical Appraisals, etc.) to achieve effective and durable thermal insulation.

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