Cross laminated timber, depending on the moisture content and the type of bonding, has a water vapour resistance factor between μ=30-80, whereby, as a result of usual element thickness, diffusion inhibiting building element components emerge. Depending on the diffusion resistance of the outside insulation and facade additional interior vapour barriers can be dispensed with. At the same time the large, surface active and moisture retaining, interior surfaces in relation to the hygric tolerance of the entire structural element offers considerable advantages as compared to other construction methods.
Depending on the constructional structure, for planed cross laminated timber elements, electric power sealed surfaces and the corresponding necessary airtightness for the building component has already been achieved, in addition follows, manufacturer specific, the formation of panel materials or side glued board layers in the floor layers. As an alternative to this, open to high diffusion, airtight channels can be used. In the area of priority butt joint element seams, simple mountable and at the same time elastic deformable compression bands and sealing tubes on the basis of their operational principles ensure a permanent air seal between the construction components, whereby electric power sealed building shells are developed and heat loss as well as building damage is minimised.
Under the exclusion of convective leakage for the thermal protection technical aspect a thermal conductivity λ= 0,13 W/(m·K) for the uninsulated element can be assumed. Cross laminated timber elements can be combined on the exterior, free of a thermal bridge, with the most variable insulation materials (wood, mineral or glass fibre insulation materials and systems (ETICs, ventilated facades). Additional interior located installation planes lead to further improvements of the insulation standard. Elements constructed to the passive house standard are not uncommon.
U-value of an exemplary wall construction
Additional interior located installation planes lead to further improvements of the insulation standard. As a result of the available specific high heat capacity of wood, c = 2100 J/(kg·K), the cross laminated timber construction method in space limited areas offers a clear advantage in comparison to the light building constructions. With comparable U-values a, close to, three-fold thermal mass can be achieved which leads to a greater phase displacement and amplitude suppression and therefore simultaneously increasing the comfort especially in the summer months.